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This is to certify that the

dissertation entitled

TRIPLET ENERGY TRANSFER IN
PHOTOEXCITED DIKETONES

presented by

James V. DeFrancesco

has been accepted towards fulfillment
of the requirements for

phoDo degree in ChemiStrl

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TRIPLET ENERGY TRANSFER IN PHOTOEXCITED DIKETONES
By

James Vincent DeFrancesco

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Chemistry

1992

Copyright by
James Vincent Defiancesco

1992

i'l

ABSTRACT

TRIPLET ENERGY TRANSFER IN PHOTOEXCITED DIKETONES
by

James Vincent DeFrancesco

The rate at which excitation energy transfers between chromophores

of diketones was investigated. Energy transfer (ET) was induced by

irradiation of the diketones with 313nm and 366nm ultraviolet light.
The most significant aspect of this work is the assignment of rates for

both exothermic and endothermic ET between the chromophores of a

diketone molecule. By varying the most influential factors which

determine ET rates, the difference in energy between the triplet excited

states of each chromophore (AE) and the length of the alkyl tether

linking the chromophores, two trends emerged. First, as the AE

increased between two interacting chromophores within a given
bichromophoric series of compounds, exothermic ET increased and

endothermic ET decreased. Second, as the alkyl tether length connecting
the two chromophores increased, both the exothermic and endothermic ET
rates decreased. Intramolecular ET rates were derived by fitting the

experimental photokinetic data with mathematical models.

I"

“‘1

5.!

ACKNOWLEDGMENTS

I would like to express my gratitude to Dr. Peter J. Wagner and the

1480 Department of Chemistry for financial support and use of the fine

facilities. A special thanks to all of my Wagner group friends, past

and present, for the many stimulating talks about photochemistry and

politics. Thanks to the support staff in the NMR facility,

electronics,

glass,

and machine shops along with the stock clerks and

secretaries, all of whose efforts are a bigger part of this type of

degree than most people realize.

A big thanks to my many friends at MSU, the chemheads in

particular, for their constant friendship and support.

I would also like to acknowledge my undergraduate professors at

Elmhurst College, especially Dr. Eugene Losey, whose enthusiasm for

teaching organic chemistry prompted me to pursue this degree.

Last but not least, I would like to thank my family who, even

though they could never really understand just what I did in the lab for

all of those hours, provided me with love and guidance. Yes mom, I'm

really done !

ii

- To Linda, my sea of love -

P.
P.
P.

T‘A.BJL‘E (717 (TCIAIT‘EIAVT'S

Page!
LIST OF TABLES ................................................ ...viii
LIST or IIGURES .................................................. xiii
INTRODUCTION......... ............................................. 1
I. Objectives...... ...... ...... ................................... 1
II. Previous Work in Energy Transfer ............................... 2
III. Deriving ET Rates from Photochemical Reaction Products ........ 17
A. The Norrish Type II Photoelimination Reaction .............. 17
B. The Photoenolization Reaction .............................. 19
IV. Photokinetics of Bichromophoric Systems ....................... 21
A. Energy Transfer in System with Two Interacting Triplets.... 23
1. Mechanism (two triplets) ....................... . ....... 23
2. Equations (two triplets) ............................... 23
3. Definition of Terms (two triplets) ..................... 24

B. Energy Transfer in System with Three Interacting Triplets.. 25

1. Mechanism (three triplets) .............................. 25

2. Equations (three triplets) .............................. 26

3. Definition of Terms (three triplets) .................... 27

RISULTS ........................................................... 28
I. Preparation of Diketones and Ketones .......................... 28
II. Techniques Used in Energy Transfer Study .................... .. 34
A. Stern-Volmer Quenching and Quantum Yields... .............. 34

B. Ultraviolet and Phosphorescence Spectroscopy ............... 40

III. Energy Transfer Analyses ....................................... 47
A. The Benzoyl-t3-methyl—4-alkanoylphenoxy) Diketones ...... ...48

B. 1-82-4-(2-Me-4-An)Bt and 1—82-4-(o-TliBt ................. ..66

C. The Benzoyl-(4-benzoylphenoxy) Diketones........ ........ ...74

D. The Benzoyl-(2'methyl—4-benzoylphenoxy) Diketones..........86
E. Related Diketones Studied by E.W. Frerking and B.P. Giri...92
Iv. Miscellaneous Quenching Experiments ............................ 104

A. Intermolecular Quenching .................................. 104

8. Measurement of Syn and Anti Triplet Lifetimes ............. 106

1. Stilbene Sensitization ................................. 106

2. Stern-Volmer Quenching of 4-MeO-2-MeVP ................. 109
DISCUSSION ...... ..... ............................................ 111
I. Interchromophore Energy Gap (AE) ............................. 111
II. Interpretation of Quantum Yields .............................. 114
III. Energy Transfer Rates ......................................... 117
A. A” The Benzoyl-(3-methyl-4-alkanoylphenoxy) Diketones ..... 117

E. 1-Bz-4-(2-Me-4-An)Bt and 1-Bz-4-(o-Tl)Bt .................. 126

C. The Benzoyl-(4-benzoy1phenoxy) Diketones .................. 132

D. The Eenzoyl-(2'methyl-4-benzoylphenoxy) Diketones ......... 139

IV. Conclusions ................................................... 146
V. Future Work ................................................... 150
EXPERIMENTAL ..................................................... 152
I. Chemicals ....................................................... 152
A. Solvents .................................................. 152

8. Internal Standards ........................................ 153

C. Quencher .................................................. 153

D. Ketones and Diketones ..................................... 154

1” 7-(3-Me-4-AcPhO)BP ..................................... 154

a. vbCIBP ............................................. 154

b. y—IBP ................................. V .............. 155

c. ybIBP ketal ......................................... 156

d. 4-NaO-2MeAP ........................................ 156

2 . 7- (3-He-4- (y—MeVal) Ph0)BP. .......................... . . .158

a. Sodium.salt of mrcresol ............................ 158

b. y-m-cresleP ...... . . . . ............................ . . 158

. 15(4-BzPhO)BP .......................................... 160

. 7- (3-Me-4-BzPhO) sp .................................... 161

a. mrcresyl benzoate .................................. 161

b. 4-OH-2-MeBzP ..................................... .. 161

c. 4-NaO-2-MeBzP ...................................... 162

5. 5- (3-Me-4-AcPhO)VP . .................................... 164

a. 5-C1VP .............................................. 164

10.
11.
12.

13.
14.

15.
16.

17.
18.

19.

20.
21.

vi

b. 5-va ............................................... 164
5-(3-Me-4—ValPhO)VP .................................... 166
5-(3-Me-4-(beeVal)PhO)VP .............................. 167
a. 4-OH-2-Me-1-MeVP .................................... 167
b. 4-NaO-2-Me-1-MeVP .................................. 168
5-(4-BzPhO)VP ..... . ................................. ...169
8-(3-Me-4-BzPhO)VP ..................................... 17o
5-(2'-Me-4-BzPhO)VP .................................... 171
5-(4-CNPhO)VP .......................................... 173
£-(2'-Me-4-BzPhO)HxP ................................... 174
a. E-BrflxP ............................................. 174
b. e-IHxP .............................................. 174
c. e-IHxP ketal ........................................ 175
d. e-Phonxp ............................................ 17s
€-(4-CNPhO)HxP ......................................... 177
(-(2'-ne-4-szph0)npp ................................... 177
a. c-srnpp ............................................. 177
b. C-Brnpp ............................................. 178
c. C-IHpP ketal ........................................ 178
d. C-PhOHpP ............................................ 178
C-(4-CNPhO)HpP ........................................ .180
n-(2'-Me-4-szph0)0tp .................................. 181
a. n-BrOtP ............................................ 181
b. n-IOtP ............................................. 181
c. n-IOtP ketal ....................................... 182
d. fl-PhOOtP ........................................... 182
n-(4-CNPhO)OtP ........................................ 183
1-Bz-4-(2-Me-4-An)Bt .................................. 184
a. 4-neo-2-Me-8-c1vp .................................. .184
b. 4-MeO-2-Me-5-C1VP ketal ............................. 185
c. 4-Meo-2-Me-8-CNVP ketal ............................. 185
1-Bz-4-(o-T1)Bt ....................................... 187
a. 8-C1VP ketal ....................................... .187
b. 6-CNVP ketal ........................................ 187
4-MeO-2-MeAP .......................................... 188
4-MeO-2-EtAP ..... . ...................... . ........... .. 189

a. m-ethylphenyl acetate .............................. 189

vii

b. 4-0H-2-EtAP ........................................ 189

c. 4-NaO-2-EtAP ....................................... 189

22. 4-MeO-2-MeVP .......................................... 190

23. 4-MeOBzP .............................................. 191

24. 4-MeO-2-MeBzP ......................................... 191

25. 4-MeO-2'-MeBzP ........................................ 192

26. EP .................................................... 193

27. VP..... ............................................... 193

28. 2—MeVP ................................................ 193

29. 2-MeAP ................................................ 194

30. AP .................................................... 195

II. Column Chromatography ......................................... 195
III. Instrumentation ............................................... 196
IV. 1HNMR Spectral Characteristics ................................ 197
V. UV SpectrosCOpy ............................................... 197
VI. Phosphorescence Spectroscopy .............. I .................... 197
VII. Photokinetic Data ............................................. 198
A. Glassware ................................................. 198

B. Weighings.... ............................................. 198

C. Irradiation Tubes ......................................... 198

D. Degassing Procedure ....................................... 199

E. Irradiation Chambers ...................................... 199

F. Sample Analysis ........................................... 199

1. Quantum Yields... ..................................... 201

2. Stilbene Sensitization Experiments .................... 201

3. Type II Quantum Yields (451) .......................... 203

RA! DATA........... .............................................. .204

LIST OF RIIIRINCIS..... ......................................... 272

lLI’S T 10 F' T.A B'L.E'S

Page!
Table 1: Quantum Yields of Diketones at 313nm in Benzene .......... 38
Table 2: Quantum Yields of Diketones at 313nm in Methanol ......... 39
Table 3: Quantum Yields of Diketones at 366nm .................... 39

Table 4: Extinction Coefficients of Diketones and Model Ketones... 41

 

Table 5: Phosphorescence Data of Diketones and Model Ketones ...... 45 I
Table 6: Flash and Steady State Decays of Diketones

and Model Ketones at 313nm .............................. 55
Table 7: Photokinetic Values of Model Ketones at 313nm ............ 56 t}
Table 8: Photokinetic Data of Diketones Studied by

Prerking and Giri in Benzene at 313nm .................... 101
Table 9: Parameters of Diketones with Three Interacting

Triplets at 313nm... ..................................... 102

 

Table 10: Parameters of Diketones with Two Interacting
Triplets at 313nm and 366nm .............................. 103

Table 11: Actual and Calculated Quantum Yields of Diketones ........ 143
Table 12: Energy Transfer Values Derived for Diketones.............144

Table 13: Energy Transfer Values Derived for Diketones
Studied by Frerking and Giri in Benzene..... ............. 145

Table 14: Stern-Volmer and 0 Data of y—(S-Me-4-AcPhO)BP
at 313nm in Benzene............................. ...... ...204

Table 15: q,“ Data of 7-(3-Me-4-AcPhO)BP at 313nm in Benzene. . . . . .205

Table 16: Stern-Volmer and O Data of 1-(3-Me-4-AcPhO)BP
at 313nm in Methanol.. .............. ........ ........ .....206

viii

 

 

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Stern-Volmer and O Data of 7-(3-Me-4-(y—MeVal)PhO)BP
at 313nm in Benzene ...................................... 208

45,,“ Data of 1-(3-Me-4-(Y—MeVal)PhO)BP
at 313nm in Benzene ...................................... 210

Stern-Volmer and O Data of y—(3-Me-4—(y-MeVa1)PhO)BP
at 313nm in Methanol ..................................... 211

Stern-Volmer and O Data of y—(4-BzPhO)BP
at 313nm in Benzene ...................................... 212

Stern-Volmer and O Data of y—(4-BzPhO)BP
at 313nm in Methanol ..................................... 213

Stern-Volmer and O Data of y—(4-BzPhO)BP
at 366nm in Benzene ...................................... 214

Stern—Volmer and O Data of 7-(4-BzPhO)BP
at 366nm in Methanol ..................................... 215

45““ Data of 7-(4-BzPhO)BP at 366nm in Benzene
w/added Dioxane .......................................... 216

Stern-Volmer and O Data of y—(3-Me-4—BzPhO)BP
at 313nm in Benzene ...................................... 217

OM“ Data of y-(3-Me-4-BzPhO)BP at 313nm in Benzene ...... 219

Stern-Volmer and O Data of y-(3-Me-4-BzPhO)BP
at 313nm in Methanol ..................................... 220

Stern-Volmer and O Data of 1-(4-CNPhO)BP
at 313nm in Methanol... ..... ......

Stern-Volmer and O Data of 8-(3-Me-4-AcPhO)VP
at 313nm in Benzene ................. . .................... 223

dfiux Data of 5-(3-Me-4-AcPhO)VP at 313nm in Benzene ...... 224

Stern-Volmer and O Data of 5-(3-Me-4-AcPhO)VP
at 313nm in Methanol... ............. .......... ........... 225

Stern-Volmer and O Data of 8-(3-Me-4-Va1PhO)VP
at 313nm in Benzene ...................................... 227

 

 

 

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Stern-Volmer and O Data of 5-(3-Me-4-(y—MeVal)PhO)VP
at 313nm in Benzene ...................................... 228

ON“ Data of 8-(3-Me-4—(7-MeVa1)Ph0)vp
at 313nm in Benzene ...................................... 230

Stern-Volmer and O Data of 8-(3-Me-4-(7—MeVal)PhO)VP
at 313nm in Methanol ..................................... 231

Stern-Volmer and o Data of 5-(4-BzPhO)VP
at 313nm in Benzene ...... . ............................... 232

Stern-Volmer and O Data of 5-(4-BzPhO)VP
at 313nm in Methanol ..................................... 234

Stern—Volmer and O Data of 5-(4-BzPhO)VP
at 366nm in Benzene ...................................... 236

Stern-Volmer and O Data of 8—(4-BzPhO)VP
at 366nm in Methanol ..................................... 237

Stern-Volmer and O Data of 5-(3-Me-4-BzPhO)VP
at 313nm in Benzene ................... . .................. 238

OM“ Data of 5-(3-Me-4-BzPhO)VP at 313nm in Benzene. ..... 239

Stern-Volmer and O Data of 8-(3-Me-4-BzPhO)VP
at 313nm in Methanol ..................................... 240

Stern-Volmer and 4» Data of 5-(2'-Me-4-BzPhO)VP
at 313nm in Benzene... .......... . ........................ 241

OH“ Data of 8-(2'-Me-4-BzPhO)VP at 313nm in Benzene ..... 242

Stern-Volmer and O Data of 8-(4-CNPhO)VP
at 313nm in Methanol. .................................... 243

Stern-Volmer and O Data of e-(2'-Me-4-BzPhO)HxP
at 313nm in Benzene..... ........... .......... ............ 244

On" Data of e-(2'-Me-4-BzPhO)HxP at 313nm in Benzene. . . . 246

Stern-Volmer and O Data of e-(4-CNPhOH-ixP
at 313nm in Benzene ........... . . . . . . . .................... 247

 

 

 

 

 

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OH“ Data of 8-(4-CNPhOH-ixP at 313nm in Benzene ......... 248

Stern-Volmer and O Data of C-(2'-Me-4-BzPhO)HpP
at 313nm in Benzene ...................................... 249

OMam Data of {-(2'-Me-4-BzPhO)HpP at 313nm in Benzene. . . . 250

Stern-Volmer and O Data of C-(4—CNPhO)HpP
at 313nm in Benzene ...................................... 251

OMax Data of (-(4-CNPhOHipP at 313nm in Benzene .......... 252

Stern-Volmer and O Data of n-(2'-Me-4-BzPhO)OtP
at 313nm in Benzene ...................................... 253

OMax Data of 11-(2'-Me-4—BzPhO)OtP at 313nm in Benzene. . ..254

Stern-Volmer and O Data of n-(4-CNPhO)OtP
at 313nm in Benzene ...................................... 255

OMax Data of ‘n-(4-CNPhO)OtP at 313nm in Benzene .......... 256

Stern-Volmer Data of BP Quenched w/4—MeO-2-MeBzP
at 313nm in Benzene ...................................... 257

Stern-Volmer Data of BP Quenched w/4-Me0-2'-MeBzP
at 313nm in Benzene ...................................... 258

Stern-Volmer Data of 4-MeO—2-MeVP at 313nm in Benzene....259
OM“ Data of 4-MeO-2-MeVP at 313nm in Benzene ........... 260

Stern-Volmer and O Data of 4-MeO-2-MeVP at 313nm
inMethanol.............. ................................ 262

Stern-Volmer and O Data of 1-Bz-4-(2-Me-4-An)Bt
at 313nm in Benzene ........ . ............................. 264
OM“ Data of 1-Bz-4-(2-Me-4-An)Bt at 313nm in Benzene....265
Stern-Volmer and O Data of 1-Bz-4-(2-Me-4-An)Bt
at 313nm in Methanol ........... ..... .......... 266

Stern-Volmer and O Data of 1-Bz-4-(o-T1)Bt
at 313nm in Benzene ................. . .................... 267

 

 

 

 

 

 

xii
Table 67: OMax Data of l-Bz-4-(o-Tl)Bt at 313nm in Benzene ......... 268

Table 68: Stern-Volmer and O Data of 1-Bz-4-(o-Tl)Bt
at 313nm in Methanol ..................................... 269

Table 69: Stilbene Sensitization of 4-MeO-2-MeAP at 366nm
in Benzene .......................... . .................... 270

 

 

 

 

 

 

L.I'S'1‘ (9 F‘ 171143 £71815 S

Page!
Figure 1: Benzoyl- (p-alkanoylphenoxy), 1-Bz-4-(2-Me-4-An)Bt,
and 1-Bz-4-(o-Tl)Bt Diketones .......................... 31
Figure 2: Benzoyl-(p-benzoylphenoxyl) Diketones ................... 32
Figure 3: Model Ketones ........................................... 33
Figure 4: Effect of Added Dioxane on the Quantum Yield of

1-(3-Me-4-AcPhO)BP at 313nm in Benzene (eAP observed). . .36

Figure 5: Effect of Added Dioxane on the Quantum Yield of
7-(3-Me-4-(y-MeVal)PhO)BP at 313nm in Benzene
(aAP observed; 0 7-(3-Me-4-AcPhO)BP observed) ......... 36

Figure 6: Effect of Added Dioxane on the Quantum Yield of
7-(3-Me-4-BzPhO)BP at 313nm in Benzene (eAP observed). ..37

Figure 7: Effect of Added Dioxane on the Quantum Yield of
e-(2'-Me—4-BzPhO)HxP at 313nm in Benzene (eAP obsv'd) . ..37

Figure 8: Phosphorescence Spectra of 4-MeO-2-MeAP,
1- (3-Me-4-AcPhO) BP, 1- (3-Me-4— (y-MeVa1)PhO)BP,
5-(3-Me-4-AcPhO)VP, 5-(3-Me-4-ValPhO)VP,
5-(3-Me-4-(y-MeVal)PhO)VP, and 1-Bz-4-(2-Me-4-An)Bt
(_ in 2-MeTHF; ------ in MeOH/EtOI-I) ..... . ......... 42

Figure 9: Phosphorescence Spectra of 1-Bz-4-(o-T1)Bt
(— in 2-MeTi-IF: ------ in MeOH/Eton) ............... 42

Figure 10: Phosphorescence Spectra of 4-MeOBzP,

15(4-BzPhO)BP, and 5-(4-BzPhO)VP
(___ in 2-MeTi-1F; ------ gin MeOH/EtOH) ............... 43

xiii

 

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Phosphorescence Spectra of 4-Me0-2-MeBzP,
1-(3-Me-4-BzPhO)BP, and 5-(3-Me-4-BzPhO)VP
(in 2-MeTMF and in MeOH/EtOH) ........................... 43

Phosphorescence Spectra of 4-MeO-2'-MeBzP,
5-(2'-Me-4-BzPhO)VP, e-(2'-Me-4-BzPhO)HxP,
C-(2'-Me-4-BzPhO)HpP, and n-(2'-Me-4-BzPhO)OtP

in 2-MeTHF .............................................. 44

Phosphorescence Spectra of VP and 4-MeO-2'-MeBzP
in 2-MeTHF .............................................. 44

Stern-Volmer Plots of y—(3-Me-4-AcPhO)BP at 313nm
in Benzene (oAP observed; A. k‘,_,a and ka_,s varied,

B. 1:341. and ka-n varied, C. kr_,s and kr_M varied) ...... 57

Stern-Volmer Plots of 7-(3-Me-4-(1-MeVal)PhO)BP at 313nm
in Benzene (oAP observed: A. k,_NI and ka_,s varied,

B. RP” and ka-n- varied, C. kr_,s and qua varied) ...... 58

Stern-Volmer Plots of 5-(3-Me-4-AcPhO)VP at 313nm
in Benzene (eAP observed: A. k$_,a and ka_,s varied,

B. ks-tr and kam,r varied, C. qus and kr_,‘,,l varied) ...... 59

Stern-Volmer Plots of 8-(3-Me-4-ValPhO)VP at 313nm
in Benzene (oAP observed; A. ksqa and ka_,s varied,

B. k,_,r and kaar varied, C. it,_.__,_,3 and kr__,il varied) ...... 60

Stern-Volmer Plots of 5-(3-Me-4-(y-MeVal)PhO)VP at 313nm
in Benzene (oAP observed: A. k,_,a and k._” varied,

B. k,_,r and ka_,r varied, C. kr_,s and qua varied) ...... 61

Stern-Volmer Plots Of y—(3-Me-4-AcPhO)BP at 313nm
in Methanol (oAP observed: A. k,_,‘I and ka-ts varied,

B. k,_,r and km»r varied, C. kr_,s and qua varied) ...... 62

Stern-Volmer Plots of y—(3-Me-4-(y—MeVal)PhO)BP at 313nm
in Methanol (oAP observed: A. k,_,a and ita_,s varied,

B. it,_,r and k3”,r varied, C. kr_,s and kw”I varied) ...... 63

 

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Stern-Volmer Plots of 5-(3-Me-4-AcPhO)VP at 313nm
in Methanol (oAP observed: A. k$_,a and kfim,S varied,

B. k,_,r and key,r varied, C. kr_,s and kl._,a3 varied) ...... 64

Stern-Volmer Plots of 8-(3-Me-4-(y-MeVal)PhO)VP at 313nm
in Methanol (oAP observed; A. k‘,_,£I and kaqs varied,

B. k,_,r and kw,r varied, C. kt.” and qua varied) ...... 65

Stern-Volmer Plots of 1-Bz-4-(2-Me-4-An)Bt at 313nm
in Benzene (oAP observed: A. k._m and ka—n varied,

B. k,_,r and ka_,r varied, C. kr_,, and qua varied) ...... 69

Stern-Volmer Plots of 1-Bz-4-(2-Me-4-An)Bt at 313nm
in Methanol (oAP observed: A. ksqa and Rik,s varied,

B. k,_,r and ka_,, varied, C. k1._,s and kr_,a varied) ...... 70

Stern—Volmer Plots of 1-Bz-4-(o-T1)Bt at 313nm
in Benzene (oAP observed: A. k_,‘_,‘‘ and ka_,53 varied,

B. k:,_,r and ka_,r varied, C. kr_,s and kt.” varied) ...... 71

Stern-Volmer Plots of 1-Bz-4-(o-T1)Bt at 313nm
in Methanol (eAP observed: A. ksqa and k‘!|_,s varied,

B. kw,r and kw,r varied, C. kr_,s and kr_,a varied). . . . . . 72

Stern-Volmer Plots of 1-Bz-4-(o-T1)Bt at 313nm
(oAP observed; 0 2-MeAP observed; A. in benzene,
B. in methanol) ................................ ... ..... 73

Stern-Volmer Plots of y-(4-BzPhO)BP in Benzene

at 313nm and 366nm (0 AP observed at 366nm:

eAP observed at 313nm: kexo - 40::10'7s'1

and ken“ - 0.1x107s’1). ........... . ..................... 78

 

Stern-Velma: Plots of y—(3-Me-4-BzPhO)BP at 313nm
in Benzene (oAP observed; A. kw” and kw”i varied,

B. k._,r and kaq, varied, C. kr_,s and ktqa varied) ...... 79

 

 

 

 

 

~31.

 

 

 

 

xvi

Figure 30: Stern-Volmer Plots of 5-(4—BzPhO)VP in Benzene
to AP observed at 366nm; oAP observed at 313nm;
km, - 20x107s'1 and kendo - 0.050x107s'1) ......... so
Figure 31: Stern-Volmer Plots of 5-(3-Me-4-BzPhO)VP at 313nm
in Benzene (eAP observed; A. k,,_,,I and ka_,, varied,

B. k,_,r and ka_,r varied, C. kr_,s and kr—m varied) ...... 81

Figure 32: Stern-Volmer Plots of y-(4—BzPhO)BP in Methanol
to AP observed at 366nm; eAP observed at 313nm,-

- 40x107s'1 and kendo - 0.10x107s'1) ........... 82

 

kBXO

Figure 33: Stern-Volmer Plots of 7-(3-Me-4-BzPhO)BP at 313nm
in Methanol (eAP observed; A. ks“,al and kam,s varied,

B. k,_,r and ka_,r varied, C. kr_,s and qua varied) ...... 83

Figure 34: Stern-Volmer Plots of 8-(4—BzPhO)VP in Methanol
(0 AP observed at 366nm; eAP observed at 313nm:

- 20x107s'1 and kendo - 0.050x107s'1) .......... 84

 

k0860

Figure 35: Stern-Volmer Plots of 5-(3-Me-4-BzPhO)VP at 313nm .
in Methanol (oAP observed; A. ks_,a and ka_,,s varied,

B. k,_,,_. and ka_,r varied, C. kr_,s and kr_,a varied) ...... 85

Figure 36: Stern-Volmer Plots of 5-(2'-Me-4-BzPhO)VP at 313nm
in Benzene (eAP observed; A. k,_M and k?” varied,

B. k,_,r and kaqr varied, C. k,_.__,,3 and kn” varied) ...... 88

Figure 37: Stern-Volmer Plots of e-(2'-Me-4-BzPhO)RxP at 313nm
in Benzene (-AP observed; A. kw” and it?” varied,

B. k...” and kaqr varied, C. k,_,, and kr_.nI varied) ...... 89

Figni'e 38: Stern-Volmer Plots of (-(2'-Me-4-BzPhO)MpP at 313nm
in Benzene (oAP observed; A. it,_,a and kaq, varied,

B. k,_,, and km.”r varied, C. k,_,. and kr_"l varied) ...... 90

Figure 39: Stern-Volmer Plots of n-(2'-Me-4-BzPhO)OtP at 313nm
in Benzene (oAP observed: A. k,_,‘I and ka_,, varied,

B. k,__,r and kid, varied, C. kP” and kw” varied) ...... 91

 

 

 

eta.
e

 

 

 

 

Figure

Figure

Figure

Figure

Figure

Figure

Figure

lPigure

F igure

Ffiigure

Figure

40:

41:

42:

43:

44:

45:

46:

47:

48:

49:

50:

Diketones Studied by H.W. Frerking and B.P. Giri ........ 94

Stern-Volmer Plot of y—(4-ValPhO)BP at 313nm
in Benzene (o propene observed: oAP observed) ......... 95

Stern-Volmer Plot of 1-(3-Me-4-(beeVal)PhO)BP
at 313nm in Benzene (o y-(3-Me-4-AcPhO)BP observed:
oAP observed) .......................................... 95

Stern-Volmer Plot of 8-(4-ValPhO)VP at 313nm in Benzene
(o 1—(3-Me-4-AcPhO)BP observed; eAP observed) ......... 96

Stern-Volmer Plot of 5-(3-Me-4-(beeVa1)PhO)VP at 313nm
in Benzene (o 5-(3-Me-4-AcPhO)VP observed;
oAP observed). ................. ....... ..... . ........... 96

Stern-Volmer Plot of 1b(3-Me-4-(yHMeVal)PhO)BP at 313nm
in Methanol (o y—(3-Me-4-AcPhO)BP observed;
oAP observed) ........................ .. ............. ... 97

Stern-Volmer Plot of 5-(3-Me-4-(7-MeVal)PhO)VP at 313nm
in Methanol (o 8-(3-Me-4-AcPhO)VP observed;
oAP observed) ........................ . ................. 97

Stern-Volmer Plots of y—(4-BzPh)BP in Benzene
(0 AP observed at >340nm; oAP observed at 313nm;
km, - 97x107a'1 and kendo - 0.20x107s’1) .......... 98

Stern-Volmer Plots of 5-(4-BzPh)VP in Benzene
(0 AP observed at >340nm; eAP observed at 313nm;
km, - 48x107s'1 and xendo - 0.10x107s'1) .......... 98
Stern-velmer Plots of y—(2'-Me-4-BzPh)BP at 313nm
in Benzene (oAP observed; A. k,_,a and kaq, varied,

B. k,_,r and k._,r varied, C. kt.” and kr_,a varied). . . . . . 99

Stern-Volmer Plots of 5-(2'-Me-4-BzPh)VP at 313nm
in Benzene (eAP observed: A. kw», and krd‘ varied,

B. k,_,r and ka_,r varied, C. kr_,s and qua varied). . . . . .100

 

 

 

 

 

Figure

kare

Figure

Figure

Figure

FiQUre

Pig‘ure

E“Silure

Pigure

Figure

51:

52:

53:

54:

55:

56:

57:

xviii

Quenching of Butyrophenone by 4-MeO-2-MeBzP
at 313nm in Benzene (oAP observed) ..................... 105

Quenching of Butyrophenone by 4-MeO-2'-MeBzP
at 313nm in Benzene (oAP observed) ..................... 105

Sensitization of Trans-Stilbene by 4-MeO-2-MeAP
at 366nm in Benzene (ecis-stilbene observed) ........... 108

Stern-Volmer Plot of 4-MeO-2-MeVP at 313nm
(4-MeO-2-MeAP observed; A. in benzene:
B. in methanol).. ...................................... 110

Stern—Volmer Plots of y-(B-Me-4-AcPhO)BP and
y-(3-Me-4-(1HMeVal)PhO)BP in Benzene at Various

ET Rates (OAP observed for 7-(3-Me-4-AcPhO)BP,-

oAP observed for yb(3-Me-4-tbeeVal)PhO)BP) ............ 122

Stern-Volmer Plots of 5-(3-Me-4-AcPhO)VP,
5-(3-Me-4-Va1PhO)VP, and 5-(3-Me-4-(7-MeVal)Ph0)VP in
Benzene at Various ET Rates (0 AP observed for 8-(3-
Me-4-AcPhO)VP; A AP observed for 5-(3-Me-4-ValPhO)VP;

oAP observed for 5-(3-Me-4-(beeVal)PhO)VP) ............ 123

Stern-Volmer Plots of 7-(3-Me-4-AcPhO)BP and
y-(3-Me-4-(beeVal)PhO)BP in Methanol at Various

ET Rates (OAP observed for 1-(3-Me-4-AcPhO)BP;

oAP observed for y-(3-Me-4-415MeVal)PhO)BP)... ......... 124

Stern-Volmer Plots of 5-(3-Me-4-AcPhO)VP and
5-(3-Me-4-(beeVal)PhO)VP in Methanol at Various

ET Rates (OAP observed for 8-(3-Me-4-AcPhOWP:

an observed for 5-(3-Me-4-(y—MeVal)PhO)VP) ......... 125

Stern-Volmer Plots of 1-Bz-4-(2-Me-4-An)Bt
in Benzene at Various ET Rates (oAP observed) .......... 130

Stern-volmer Plots of 1-Bz—4-(2-Me-4-An)Bt
in Methanol at Various ET Rates (eAP observed) ......... 130

 

 

 

 

PHI

 

 

 

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Pigure

F igu re

Fitgure

Enigure

61:

62:

63:

64:

65:

66:

67:

68:

69:

70:

71:

xix

Stern-Volmer Plots of 1-Bz-4-(o-T1)Bt
in Benzene at Various ET Rates (oAP observed) .......... 131

Stern-Volmer Plots of l-Bz-4-(o-Tl)Bt
in Methanol at Various ET Rates (oAP observed) ......... 132

Stern-Volmer Plots of 7-(3-Me-4-BzPhO)BP
in Benzene at Various ET Rates (oAP observed) .......... 137

Stern-Volmer Plots of 5-(3-Me-4-BzPhO)VP
in Benzene at Various ET Rates (OAP observed) .......... 137

Stern-Volmer Plots of 7-(3-Me-4-BzPhO)BP
in Methanol at Various ET Rates (oAP observed) ......... 138

Stern-Volmer Plots of 5-(3-Me—4—BzPhO)VP
in Methanol at Various ET Rates (eAP observed) ......... 138

Stern-Volmer Plots of 5-(2'-Me-4-BzPhO)VP
in Benzene at Various ET Rates (oAP observed) .......... 141

Stern-Volmer Plots of c-(2'-Me-4-BzPhO)HxP
in Benzene at Various ET Rates (oAP observed) .......... 141

Stern-Volmer Plots of C-(2'-Me-4-BzPhO)HpP
in Benzene at Various ET Rates (oAP observed)..... ..... 142

Stern-Volmer Plots of n-(2'-Me-4—BzPhO)OtP
in Benzene at Various ET Rates (eAP observed) .......... 142

Plot of k,exo vs. Interchramophore Distance in Benzene...149

 

 

 

 

‘EZZ-

 

 

 

MAW

AP (acetophenonel
31’ {WWW}
VP (vaiaophaione)
1-(3oMe-4-AcPhO)BP [‘7-(3-methyl-4-aoetyiphenoxy)butyrophenonel
y-(J-Me-lt-(y-MeVaDthBP (y-(3-mcthyi-4-(y~mcthylvaleryi)phenoxy)butyrophenone)
H4-BzPhO)BF (H4-benzoyiphenoxy)butymphcnone)
y-(3—Me-4-BzPhO)BP [y-(3-methyl-4-benzoylphcnoxy)butyrophenonc}
5—(3-Me-4-AcPhOWP I5-(3-methyi-4-acetylphenoxy)vaierophenonc}
5—(3-Me-4-VaiPhOWP [H3-mcthyl-4-vaierylphenoxy)vaiaophenone]
5-(3-Me-4-(y-MeVal)PhO)VP [5—(3-methyl-4-(y-methyivaieryl)phcnoxy)valerophenone]
8-(4-ltzPhO)VP (8-(4-benzoylphenoxy)valemphcnone]
5-(3-Me-4-BzPhOWP {5-(3-methyi-4-benzoyiphenoxy)vaicrophcnonel
8’(2'-Itp‘le-4-le’h0)VP (5-(2'-mcthyi-4-bcnzoyiphcnoxy)valerophenoncl
5'(4-CNPhO)VP {5—(4-cyanophenoxy)valcrophenone)
e'(Z'JMeat-le’hO)HxP [8-(2'-mcthyl-4-benzoylphenoxy)hexanophcnone}
e‘(4-CNPh O)HxP [e-(4-cyanophcnoxy)hexanophenone)
C-(2'-Me.4.nzphompp {C-(2'-methyi-4-benzoylphenoxy)heptanophcnone}
C‘(4-CNPh 0)HpP {C-(4—cyan0phcnoxy)hcptanophcnone)
II‘(2'-Tvie-4oltzl’h0)OtP {n-(2'-mcthyl-4-benzoylphenoxybctamphenone)
“‘(4~CNPhO)OtP (n44-cyanophenoxy)octanophenone]
1‘32-4-(mTi)Bt (l-benzoyi-4-(o-toluoyi)butane]
1:8z4.(2.Me-4.An)8: Il-bcnzoyl-4-(2-methyi-4-anisoyl)butanel
2‘NleAl’ {2-methyiacctophenone] .
“Have (Z-methyivalctophenom)
*MeO-z-MeAP {4-mcthoxy-2-mcthyiaoetophenone]
4‘R‘leO-z-EtAP (4-methoxy-2-ethylacetophenone}
*MeoeMevr [4.mothoxy-2-mcthylvaierophcnone}
*Meoazr (ll-methoxybenwphcnmc}
*MeO-z-MeBzP {4-methoxy-2-methylbcnzophenone]
4JtieO-ZSMeBzP [kmcthoxy-Zflmcthylbcnmpheoone]

XX

 

 

INTRODUCTION

I . Object ivea

The subject of this dissertation is the intramolecular triplet

energy transfer (ET) between the lowest lying excited states of two

ketone chromophores. In this research, I'chose to study how ET rates
change as a function of interchromophore distance, interchromophore

energy gap, and type of triplet-triplet interaction. This was

accomplished by systematically increasing the length of the alkyl tether

Which joins the two chromophores, changing the orientation of the lower

energy chromophore, changing the solvent, and altering the nature of the

lcnver energy chromophore. The photokinetic behavior of the diketones

twat; monitored by measuring the chemical yield of photocleavage products.

TTIis photochemical probe acted as an “internal clock" in deriving ET

rates.

There were a number of reasons for selecting the systems in this
“Hark. As in most research endeavors, I wanted to build upon the

fiindings of previous researchers in our group. They demonstrated that

tll'iese systems were easy to synthesize and purify, the photoproducts
Slould be readily analyzed by common chromatographic methods, and their

Sixcited states could be conveniently accessed via irradiation at 313 and

366nm. It was their initial efforts in discovering the unusual behavior

of simpler diketones which laid the groundwork for this investigation.
Also, diketone systems have gained recent attention because of their

ability to serve as models to elucidate ET processes which occur in

larger, polymer systems. Examples of how the knowledge gained

 

 

 

 

from diketone ET studies could be used to combat polymer photodegrada-
tion will be covered later in this introduction.

When considering ET, it is necessary to define the specific type of
Emeraction involved. It is generally accepted that the transfer of
excitation from one triplet ketone to the ground state of another moiety
to produce a new triplet proceeds via the exchange mechanisnu1'7
Triplet-triplet ET is 'spin-allowed' by the exchange mechanism, however
it is 'forbidden' by the dipole-dipole mechanism."’ The exchange

mechanism can be visualized as the transfer of excitation from an

electronically excited donor (D*) to a ground state acceptor (A)

(LUMQ) ___'__. /\\—_ __ __'_

————>
O
(HOMO) —' A 00 _' ° __
13* A D A*

tllrough a simultaneous two electron exchange.1° One electron from the
llvwest half-occupied n* orbital (LUMO) of the excited donor is
t:r‘ansferred to the empty LUMO of the acceptor, and one electron from the
highest occupied molecular orbital (HOMO) of the acceptor is transferred
t:othe HOMO of the donor. Since ET in diketones is reversible, the
E>rocess of D*/A going to D/A* can be viewed as the exothermic component

tbf ET, and the reverse, D/A* to D*/A, as the endothermic component.

II. Previous Work in Energy Transfer

One of the earliest examples of intermolecular ET between nearly

isoenergetic phenyl ketones with similar lifetimes was reported by

 

 

 

 

 

Wagner and coworkers11 in 1972. They found that the quantum efficiency

for photocleavage of valerophenone did not decrease until conversion to

the photoproduct acetophenone reached 75%. This is significant because

it means that acetophenone, which absorbs light equally as well as

valerophenone, transferred triplet energy back to the valerophenone with

a rate constant of at least 109 M'ls'l.

One of the earliest reports of intramolecular triplet ET is from

Leer-makers, Byers, Lamola, and Hammond2 in systems which contained

benzophenone and naphthalene chromophores separated by alkyl tethers. A

dilute, rigid-glass matrix of 1 at 77°K irradiated at 366nm (a wave—

length where only the benzophenone absorbs) produced a phosphorescent

emission characteristic of only the naphthyl chromophore. Similar

irradiation of an equimolar mixture of l-methylnaphthalene and 4-

methylbenzophenone gave a phosphorescent emission characteristic of only

the 4-methy1benzophenone chromophore. This clearly indicated that the

Phosphorescence of the naphthyl chromophore observed in 1 resulted from

intramolecular ET from the benzophenone chromophore. In order to

determine whether ET was singlet or triplet in nature, experiments were

c(inducted to detect the presence of triplet benzophenone. Sensitization

of the cis—>trans isomerization of piperylene by 1 at 366nm revealed

that about 10% of the benzophenone triplets could be quenched. It was

 

 

 

 

H

a
...e'

 

r...
e

 

'e.

 

Q...
a

-..

 

a

Le
a

o

concluded that irradiation of 1 at 366nm initially populates the singlet
state of the benzophenone, which then intersystem crosses to the triplet
and finally transfers its excitation energy to the naphthyl chromophore.
Triplet ET was believed to proceed at a rate of >109 5’1 with 100%
Irradiation of 1 at 313nm, a wavelength where naphthyl

efficiency.
absorbs 70-80% of the light, produced a decreased fluorescence from the
naphthyl which was offset by enhanced phosphorescence of the
benzophenone group (based on the emission spectrum of an equimolar
mixture of l-methylnaphthalene and 4-methylbenzophenone) . This led to

the conclusion that singlet ET from the naphthyl to the benzophenone

grottp occurs. Singlet ET was believed to proceed at a rate of ~107 to

108 s'l‘with 75 to 90% efficiency.

Further work was carried out by Lamola12 on the temperature
dependent phosphorescence of a bichromophoric system which consisted of
a lbenzophenone and a triphenylene chromophore (2) in a polymethyl—

methacrylate film over the range of 82-298°K. Excitation of 2 with

 

313nm light (a wavelength where both chromophores absorb) at 82%(

produced an emission spectrum which was a combined phosphorescence of

the independent chromophores, triphenylene and benzophenone, in a 2:3

ratio. However, at higher temperatures, the phosphorescence looked less

 

 

 

 

like the triphenylene and more like that of the higher energy benzo-
phenone. At room temperature, only emission from the benzophenone
cfluomophore was observed. Based on these phosphorescence findings along
vuth lifetime measurements, Lamola concluded that reversible triplet ET
cmcurred in the bichromophoric system 2 over the entire temperature
range studied. Triplet ET from the benzophenone to the triphenylene was
believed to proceed at a rate >>104 5‘1, and ET from triphenylene to
benzophenone at a rate of 1 5’1.

The means of separating chromophores within a single molecule has
inspired some fascinating research into the effects of interchromophore
distance and molecular flexibility on ET. The control of interchromo-
Ffiuore distance is straightforward since it can only be achieved through
true placement of various tether lengths or spacers between chromophores.
chvever, molecular flexibility can be controlled from outside the
n\Olecule by solvent and temperature or from within the molecule by
stmacer rigidity. In the preceding examples, both Hammond, et al.,3 and
I«imrnolau studied the ET of bichromophoric systems possessing flexible
allkyl tethers in rigid solvent matrices. Filipescu, DeMember, and Minn‘
<=hose to control molecular flexibility from within the molecule. They
?fcmnd that triplet ET between a tetralin-1,4-dione chromophore and a
fluorene separated by a norbornane framework (1) was efficient, but not

complete. Based on the phosphorescence and fluorescence spectra, it was

 

 

determined that triplet energy migration from the teralin-dione to the
fluorene was about 83% efficient.

Zimmerman and McKelvey‘ also studied ET in a bichromophoric system
with a rigid spacer. In 1, benzoyl and 1-naphthy1 chromophores are held
at opposite bridgehead positions of a rigid bicyclol2.2.2]octane
framework. Their experiments and findings are very similar to those of
Hammond, et al.,2 in the bichromophoric system 1. Irradiation of A at
350nm (where only the benzoyl absorbs) gave a phosphorescent emission
identical to that of 1-methylnaphthalene, which served as a model for

the naphthyl chromophore. Irradiation of 1 at 295nm (where the

naphthyl absorbs 95% of the light) gave only a weak fluorescent emission
from the naphthyl, compared to the emission spectrum of an equimolar

mixture of the model compounds l-methylnaphthalene and pivalophenone.

 

 

 

They reasoned that naphthyl phosphorescence observed when the benzoyl
was selectively excited at 350nm was a result of triplet ET from benzoyl
to naphthyl. Likewise, the reduced naphthyl fluorescence observed when
the naphthyl was selectively excited at 295nm was the result of singlet
ET from naphthyl to benzoyl.

In a more recent investigation by Zimmerman and Lynch,13 the
bichromophoric system 5 underwent photoinduced rearrangements,
competitive with ET between the dienone and aryl chromophores. The a-

naphthyl system gave only the phenol product under both direct and

 

 

OH
hN'
Ar = (It-naphthyl a-naphthyl
C)
a—naphthyl
B-naphthyl
OH B-naphthyl
.Ar Ar
IIV
a = +
Ar = fl-naphthyl
B-naphthyl
B-naphthyl O

sensitized irradiation whereas the B-naphthyl system gave the phenol and
bicyclic products. The ratios of products from the B-naphthyl system
was very dependent on the means of irradiation; direct irradiation gave
a phenol/bicyclic ratio of 1.6/1 and sensitized irradiation gave a
phenol/bicyclic ratio of 24/1. This dependence of product distribution
on the means of irradiation indicated that two excited species were

involved. Furthermore, Stern-Volmer quenching experiments on the

 

B-naphthyl system gave dual-sloped plots for phenol formation,
indicative of excited state interconversions. It was concluded that two
triplets, n,x* of the dienone and x,n* of the B-naphthyl, each with
different lifetimes, were responsible for phenol product formation.
Kellerl‘ reported that both triplet and singlet excitation energy
was completely transferred between anthrone and naphthalene chromophores
separated by a spiro linkage. he observed that selective excitation of
the naphthalene chromophore in 5 and 1_at 77°K in a rigid—glass matrix
produced phosphorescence from the anthrone chromophore. Likewise,

selective excitation of the anthrone produced phosphorescence from

O

 

the naphthalene. This behavior could only be due to intramolecular ET.
Keller arrived at the same conclusions about ET in 5 and 1 as Hammond,
et al.,2 did in 1. Initial excitation of the naphthalene chromophore
populates the singlet state which undergoes exothermic ET to populate
the lower energy singlet of the anthrone chromophore followed by
intersystem crossing to the triplet that produces phosphorescence from
the anthrone chromophore. Conversely, initial excitation of the

anthrone chromophore populates the singlet state which intersystem

 

 

 

crosses to the triplet and then undergoes exothermic ET to populate the
lower energy triplet of the naphthalene chromophore and produces
phosphorescence from the naphthalene chromophore. Perhaps the most
intriguing aspect of this work was that ET occurred despite the fact
that the two chromophores are held perpendicular to one another, which
should preclude the orbital overlap needed for ET. However, Keller
reasoned that only a small deviation from orthogonality was necessary to
achieve transfer.

Closs and coworkers,7 in an extension of investigations into long
distance intramolecular electron transfer and hole transfer, studied ET
-in bichromophoric systems consisting of a B-naphthyl and a 4-benzoyl-
phenyl chromophore connected by cyclohexane and decalin ring spacers
(fl). Triplet-triplet ET was measured by monitoring the decay of the 4-
benzoylphenyl triplet or the buildup of the naphthalene triplet upon

flash excitation of the 4-benzoylphenyl chromophore. ET rates decreased

,0" .

A A

A = B-naphthyl D = 4-benzoylphenyl

by nearly three orders of magnitude as the interchromophore distance
increased in going from a cyclohexane to a decalin spacer. ET rate
constants ranged from 1.3 x 109 s'1 for the 1,4-di-equatoria1
cyclohexane system to 3.1 x 106 3’1 for the 2,6-di-equatorial decalin
system. The dependence of ET rates on interchromophore distance was

illustrated in a logarithimic plot of ET rate constants versus the

 

 

10

number of sigma bonds separating the two chromophores (both in
equitorial ring positions) which gave a nicely defined linear
relationship. Closs identifies a number of similarities between the
processes of electron transfer and ET. Among these, he points out that
ET, as described by the Dexter mechanism, can be simply regarded as a
simultaneous two electron transfer. Closs found that both electron and
energy transfer rates were highest for systems having chromophores in
equitorial positions. In assessing the merits and drawbacks of studying
the two, Closs admits that given the limitations of electron transfer
(i.e., the effect of solvent reorganization on electron exchange rates
as a result of changing solvent polarity), investigations into ET may
provide more useful information about electronic coupling interactions
than electron transfer.

Ito and Matsuura15 studied intramolecular ET in a large number of
substituted poly-carbonyl systems. Those of relevance to this
dissertation were bichromophoric, containing two benzophenone moieties,
one of which had a sterically congested triisopropyl benzoyl group (2).
These chromophores were joined at the para position by alkyl tethers of

one, two, and three methylenes in length. The results from steady state

0

n = 1 - 3

quenching experiments indicated that ET was fastest in the longest

tethered system, n = 3. It was concluded that the optimum sandwich

 

 

ll

conformation needed for ET via the exchange mechanism is geometrically
prevented when n < 3. They also made the unlikely contention that
excitation preferentially resides at the most sterically hindered
carbonyl group based on the entropy factor. Weak phosphorescence of the
bichromophoric system was attributed to efficient ET from the
benzophenone to the sterically hindered triisopropyl benzophenone, which
undergoes rapid triplet reaction. However, arguments in favor of the
notion that excitation preferentially resides at the more sterically
hindered site remain unconvincing. It is unclear just exactly what the
data indicate. This matter warrants further investigation.

One of the most significant studies into the effect of interchromo-
phore distance on ET was done by Cowan and Baum5 with the benzoyl-styryl
bichromophoric systems 19. By systematically increasing the tether
length from two to four methylenes, a marked decrease in the rate of ET

was observed. Selective excitation of the carbonyl led to a transfer of

O ”~\v/J:::]
12
\

(012),,

energy to the styryl chromophore, resulting in a trans-ecis styryl
isomerization. On the basis of quenching experiments, they derived ET
rate constants of 7.2x1010, 1.0x1010, and 3.3x109s‘1 for the series n =
2-4, respectively.

An investigation into the photochemistry of a-benzoyl—mwazido~

6

alkanes by Wagner and Scheve1 revealed that selective excitation of the

 

 

12

benzoyl chromophore (l = 365nm) resulted in photochemistry typical of
excited triplet azides in addition to type II from the ketone. The
results of steady state quenching experiments led them to conclude that
triplet ET from the benzoyl chromophore to the azide decreased from 3.7
to 0.29 to <0.03 x 1083’1 as the interchromophore tether length
increased from three to five methylenes, respectively.

Wagner and Nakahira17 studied the steady-state photochemistry of 6-
(4'-methoxyphenyl)-1-pheny1hexane-1,6-dione (11). By monitoring type
II reaction products from both ends, they found that the triplet state

lifetimes of these chromophores were nearly identical. Since the

 

 

 

 

O
O ocn3 11
0
3nm*
ann*
3 * 1i 4-MeOAP
A tYPe 11 11,1! energy
AP ‘ ‘X transfer 3
NJ!"
“

 

lifetimes of these chromophores when in separate molecules are quite
different, they concluded that an ET equilibrium must exist between the
lowest triplet states of the two. The kinetics for such a bichromo-
phoric system were worked out independently by Shetlar18 and
Wagner/Nakahira.19

In a follow-up to their intramolecular mixed chromophore study,

 

 

 

13

Wagner and Nakahira19 investigated the intermolecular photokinetics of
nonanophenone (NP) and p—methoxynonanophenone (p-MeONP). They found
that in the presence of p-MeONP, the quenching plot of NP exhibited a
curvature which it did not have alone. It was concluded that curvature
was due to ET between the two ketones. The steep initial slope of the
mixed system reflected reaction of the usually short lived NP triplet
caused by ET from the longer lived p-MeONP. Likewise, a similar
quenching experiment on p-MeONP in the presence of NP gave a lifetime
much shorter than that of p-MeONP independently. This showed that NP
could influence the lifetime of p-MeONP in the same way that p-MeONP
could influence that of NP. On the basis of the quenching studies, they
determined that the rate of exothermic ET from NP to p-MeONP was 5x108
tf'ls’l and the endothermic ET rate from p-MeONP to NP was 2.3x1061qu'1.

Continuing work in this area conducted by the Wagner group clearly
showed that in certain systems an ET equilibrium between chromophores
existed and could be measured. Frerkingzo attempted to quantify the
rates of the two components of intramolecular ET in diketones similar to
that studied by Wagner and Nakahira. The systems in this study (12)
contained the same two chromophores as in 11, however they differed in
that their anisoyl chromophore was turned around. It was determined
that in the case of the y-(4-AcPhO)BP (n = 3, R - methyl) and 5-(4-
AcPhO)VP (n = 4, R = methyl) diketones, where only the benzoyl

chromophore is reactive, ET was nearly equilibrated with rates of

 

 

 

 

14

O O
orK “
(Cflzi'n—O R
n = 3,4
R = methyl,n-butyl

~1033”1 exothermic and ~107s’1 endothermic. There were also systenm
studied which could react at both chromophores, 7—(4-ValPhO)BP (n - 3,
R = n-butyl) and 5-(4-ValPhO)VP (n - 4, R - n-butyl). The quenching
plots for these systems exhibited downward curvature for the benzoyl
chromophore and upward curvature for the anisoyl. These bi-reactive
systems perturbed the ET equilibrium, but not to the point of totally
eliminating the endothermic component. They did, however, provide
lifetimes and quantum yields for both chromophores which proved useful
in determining the extent of equilibration and size of the inter-
chromophore energy gap. It was found that the energy gap at ambient
temperature was smaller than that measured from phosphorescence data
taken at 773(. ‘The conclusion of this study was that in systems where
ET in both directions occurs faster than the decay of either chromo-
phore, it is impossible to determine actual rates of ET; only limits can
be given.

In 1979, Scaianoz1 studied the flash kinetics of several methyl
substituted 1,5-diketones (13) as models for poly(pheny1-vinyl ketone)
in an attempt to account for photodegradation in the polymer. By
placing a methyl group on the ring ortho to the carbonyl of one
chromophore, the yields of type II products from both chromophores were

reduced. He concluded that energy migration, occurring at a rate of

 

 

(Scaiano‘s polymer systems)

>109 s’l, was faster than any other energy decay pathway. The fast
photoenolization of the o-methyl chromophore22 suppressed ET to the
other carbonyl and acted as an energy sink. As a result, the total
amount of energy available for the type II process was reduced.

Dr. B.P. Giri in the Wagner group also studied ET in bichromophoric
systems similar to the benzoyl-anisoyl systems, but with the anisoyl

3 Irradiation of these

chromophore replaced by a benzophenone.2
benzoyl-(4-benzoylphenyl) diketones (11) at >340nm led to a significant
amount of photocleavage product from the benzoyl chromophore. In fact,
enough acetophenone was formed to obtain a quenching plot for the
benzoyl chromophore. Since the benzophenone chromophore absorbs light
almost exclusively at this wavelength and the phenyl alkyl ketone
triplet lies ~4 kcal/mole higher in energy (according to phosphorescence
measurements of model compounds), it was concluded that excitation of

the alkanophenone chromophore occurred via endothermic ET from the 4-

 

 

 

l6

benzoylphenyl triplet. This is totally plausible given that benzo-

phenone has a very long-lived triplet‘1 which, in the absence of any

 
   

energy
\\\\£::nsfer

1hv,>340nm

other decay route, would readily transfer its excitation energy to the
nearest possible acceptor, in this case the alkanophenone chromophore.
To prove that the observed photokinetic behavior was indeed due to
ET from the 4-benzoylphenyl to the benzoyl chromophore, an o—methyl was
placed on the 4-benzoylphenyl chromophore. This alteration provided the
4-benzoylphenyl triplet with an energy sink through a very rapid
enolization reaction which was expected to compete effectively with
endothermic ET, thus reducing the influence of endothermic ET on the
kinetic scheme. Even upon prolonged irradiation of the o-methyl analog
of 11 at >340nm, type II product was not detected. This indicated that
endothermic ET was virtually noncompetitive with decay of the 2‘-

methyl-4—benzoylphenyl triplet.

 

 

 

 

17

III. Deriving ET Rates from Photochemical Reaction Products

The study of ET can be conducted in one of two ways, either
spectroscopically or photochemically. Most of the studies summarized
earlier in this chapter made use of fluorescence, phosphorescence, and
UV by measuring the growth or disappearance of an excited state signal.
This method is well suited to systems possessing very different
chromophores whose excited state emissions and absorptions do not
overlap. But, in this investigation, the two chromophores within each
system were too similar to make any reasonable distinctions in the
spectroscopy of their excited state triplets. ‘Therefore, the approach
used in this work of monitoring the formation of various photoproducts
to determine interchromophore ET rates was the best method available.

A. The Norrish Type II Photoelimination Reaction
The photochemical means of monitoring ET in this work was provided

by the Norrish Type II reaction.2“'25

Excitation of a phenyl ketone
group produces a triplet excited state which tends to abstract a 7-
hydrogen from its alkyl group to form a 1,4-biradical.26'27 This

biradical then collapses to form a smaller ketone and an olefin. In

this work, measurement of acetophenone formation by gas chromatography

was used to derive ET rates.

hV

 

Two measurements of phenyl ketone photochemistry provide the most

18

insight into understanding their behavior: the quantum yield (On and
the excited triplet lifetime (I). The quantum yield of the reaction is a
direct measurement determined by the ratio of product molecules to the
number of photons absorbed. The use of actinometers in determining
light quanta absorbed is detailed in the Experimental chapter. The

quantum yield for the type II reaction can be expressed as:33

4’11 = d’isc kBP. T PII (1)

where dfisc is the quantum yield for intersystem crossing from singlet to
triplet, kBR is the rate constant for biradical formation, 1 is the
lifetime of the triplet state, and PII is the probability that the
biradical will collapse to give product. The triplet lifetime (I) is an
indirect measurement extracted from a steady state kinetics quenching
experiment which generates a Stern-Volmer plot.““9'31 When known amounts
of an excited state quencher (Q) are present, a plot of O°/O versus [Q]
gives a straight line whose slope = kqt,'where d” is the quantum yield
at [Q]=0 and kq is the quenching rate constant.

Quantum yields and triplet lifetimes are influenced by the presence
of various functional groups on the phenyl ring32 or the alkyl group33
and by solvent polarity. The impact of these factors on O and t can be
explained in terms of reactivity (kBR). For instance, relative to
hydrogen, an electron donating group such as alkoxy in the para position
of the ring can change the lowest lying triplet in a ketone from an n,n*
toia.x,n*. Since y-hydrogen abstraction occurs only from an equilibrium

concentration of an upper n,n* state, this change reduces 451 by

l9

decreasing km.32 A further decrease in reactivity and quantum yield
occurs when solvent polarity increases. Polar solvents widen the energy
gap between the reactive n,u* and the non-reactive n,n*.33 Since n,n*
states do not decay directly by the type II reaction, the placement of
an electron donating group in the para position and an increase in
solvent polarity tend to increase 1.

Electron donating and withdrawing groups placed at various
positions of the alkyl group of a phenyl ketone impact I by influencing
y-hydrogen lability. The effect of substituents at the 5, E, C, and n
positions on reactivity of the y-hydrogen is purely inductive and
decreases as the substituents get farther away.33 An inductively
electron withdrawing methoxy group in the 8-position decreases kBR.33
The same effect is found with an electron withdrawing group such as
cyano at the 5-position.3‘ An increase in solvent polarity causes a
decrease in kBR which increases 1; however, 45; will be enhanced due to
biradical solvation and a subsequent increase in 1311.32

B. The Photoenolization Reaction

The work detailed in this dissertation represents the first
extensive study into ET in diketones that uses the photoenolization
reaction to isolate ET in a single direction. At the outset of this
project, it was hoped that the placement of an o-methyl onto the p-
alkanoylphenoxy and p-benzoylphenoxy chromophores would eliminate
endothermic ET. The reasoning was that the lower energy chromophore
would have a very fast decay path of photoenolization which would render
the relatively slow process of endothermic ET noncompetitive. This
would create a one way ET situation with straightforward photokinetics.

However, the photoenolization reaction added another triplet to the ET

 

. .-.-.-

 

 

 

20

scheme which somewhat complicated kinetic analyses.

Phenyl ketones containing an o—methyl actually have two different
conformers, syn and anti, which interconvert via bond rotation about the
C-C bond connecting the carbonyl to the benzene ring. The geometry of
the syn and anti forms have been described by Wagner and Chen22 as
"rotational minima in which the ortho methyl and the carbonyl oxygen
are either on the same side or on opposite sides of the plane
perpendicular to the benzene ring and bisecting the para-carbon and the

carbonyl carbon" rather than two planar conformers.

(syn triplet) , (anti triplet)
0* 0*
bond
fl
<.——————————-
rotation
R0 R0
photo-
enolization

' HO HO O
, /
-4>~ -q>-
R0 no R0

Photokinetic studies have shown that photoenolization introduced by
an o-methyl competes significantly with type II cleavage.22 The effect
on OHI is dramatic in a ketone like valerophenone where addition of an
o-methyl reduces €51 by a factor of 20. Isolation of the syn form by
virtue of measuring the triplet lifetime of the tetralone indicated that

the rate of H-abstraction from the o—methyl is on the order of 5x109s"1

 

 

 

 

 

21

in benzene.22 This rapid enolization rate is due to the proximity of
the o-methyl benzylic hydrogens. Since the anti conformer rotates into

the syn at a rate of 3x107s‘1

, virtually all type II cleavage in a
ketone like o—methylvalerophenone must come from the anti.22

The complication to the photokinetics was not due to the short
lived syn triplet which decays almost exclusively by photoenolization,
but rather to the anti triplet which is long-lived enough to participate
in endothermic ET. However, this new dimension was not as large of a
stumbling block as originally thought since there was ample information

in the literaturezz'a‘ to provide values for the kinetic parameters

needed to interpret the photokinetics.

IV. Photokinetics of Bichromophoric Systems

Flash kinetic analyses were performed on two of the diketones and
several model ketones studied (results are listed in Table 6). However,
it was the steady state quenching experiments conducted on all of the
diketones and model ketones which proved to be the most useful tool in
interpreting photokinetic behavior. In this work, it is imperative to
understand the impact of ET on the Stern-Volmer quenching plots of the
diketones. Stern-Volmer quenching will give a straight line plot in
three cases: 1) when there is only one triplet present, 2) when ET
between two triplets occurs at a rate faster than triplet decay (i.e.,
equilibrium), and 3) when ET between two triplets occurs in only one
direction. The plot will be curved when quenching competes with ET
between two triplets, each having distinctively different

lifetimes.13'1"1"35 Quenching of discrete triplets affects the energy

 

 

 

22

migration between chromophores which in turn causes curvature

m; reflects shon-lived
tn'plet component

\ [11:qu 4,0 /¢

 

O°/O

 

\

in0 reflects long-lived
tn'plet component

 

 

 

[Q] [Q]

of the normally straight plot. The photokinetics of bichromophoric
systems are considerably more complicated than those of simple ketones.
Kinetic expressions for systems possessing two interacting triplets have
been derived by Wagner35 and are described below. Wagner has also
derived kinetic expressions for systems with three interacting triplets,

which are also described in the following section.

 

 

A. Energy Transfer in System with Two Interacting Triplets

1. Mechanism.(two triplets)

hv 1 . ISC 3 .
Ro ——————e>- R -—————i> R
3 1' kr
R ———-> Acetophenone
hV l 9 ISC 3 t
Uo -—————e> [J ---*> L]
. UT
3 " ku--—)r 3 *
R0 + [J -——————e> I? ‘+ UO
3 ' kr—w 3 "
R + UO ———_—_.. R0 + U
3 * kq
R + Q ———> RC
3 * kq
U + Q .____—.. U

R is the benzoyl triplet which can react to give acetophenone.
U is the unreactive triplet.
Q is a triplet quencher.

2. Equations (two triplets)

The Stern-Volmer relationship of two interacting triplets can be written

as:

¢°/¢= (1 + A101 + 819121/11 + c1911 (2)

The quantum yield in the absence of quencher is:

4’0 = [(Br 4’ fluku—trtu)krtr]/D (3)
where,
A = kqur + tul/D (4)
B -

(kq‘trkq‘tu) /D (5)

 

24

C = (Bylaw/(Br + Bukusr‘ru) (6)
D = 1 (krautrku—brtu) (7)
The light fractions absorbed by the reactive and unreactive chromophores
are:
Br = Er/(Er + Eu) (8)
Bu = Eu/(Er + Eu) (9)
3. Definition of Terms (two triplets)
kr_,._l = rate constant for reactive triplet ET to unreactive triplet.
ku-n» = rate constant for unreactive triplet ET to reactive triplet.
l/g = kr = decay of reactive triplet in the absence of ET.
l/‘t =

u decay of unreactive triplet in the absence of ET.

 

25

B. Energy Transfer in System with Three Interacting Triplets

1. Mechanimm (three triplets)

hv= BIA

 

 

So hv= a.
R.—< sw—<1:i—~R*—<Z:Z
A hv= __

 

S k 3s
3R'—/ o ——>r'*s RO—/

3
R —\ ———> R0 “3A

3 i
< So kegs < s
-—-——!>
3A’ A0
38' ——-1/—Ts——> S + enol
~ . 1 't
’A —/—a——> A0
k
3R + Q ———q.—» R0
k
3S + Q —q——-> sO
. k
3A + Q ——3-—> A0
3R‘ —-r—-> Acetophenone

()3’U123

is a triplet quencher.

 

 

exothermic
energy
transfer (kexo)

endothermic
energy
transfer (kemkfi

anti to syn
interconversion
via bond rotation

photoenolization + decay

decay

bimolecular
quenching
by triplet
quencher
(diene)

type II reaction (l/Tr)

is the benzoyl triplet which can react to give acetophenone.
is the syn triplet of the o-methyl chromophore.
is the anti triplet of the o-methyl chromophore.

 

26

2. Equations (three triplets)

The main equation which describes the Stern-Volmer relationship of three

interacting triplets can be written as:

d>°/¢ = (1 + Am] + BIO]?- + C(QJ3)/(l + me] + EIQJZ)

The quantum yield in the absence of quencher is:

4’0 = kr'trtflrm‘ - kaasks-éa) + fia(ka-)r + ka—>sks->r)
+ Bs(ks—)r + ks-§aka—)r)]/z

where,

{9'
I

- kqur<l " ka—isks—m) + 15(1 ' ka—Mkr-m) + Ta(l - ks-nrkr—ésH/z

2

B = kq (11,125 + 1516 + tatr)/Z
c - T t 1 k 3/z

‘ a s r q
D = kc;[Br(Tr + Ta) + Baka-nts + Bsks—mtaJ/R
E - B I T k 2

‘ r s a q
R = [31.1141 ' ka—-)sks—t)a) + BaTrU‘a—n 4’ ka-asks—H)

4' Bstr(ks—)r + ks—baka—n)

Z = 1 ' ka-ésks-aa ' ka—nkr—m ‘ kr—bsks—n'

' kresksaaka-er ' ks—nkr-baka-bs

(10)

(11)

(12)

(13)

(14)

(15)

(15)

(17)

(18)

The light fractions absorbed by the reactive, syn, and anti chromophores

are :

Br
35
Ba

er/(er + xaea + 1585)
1525/“): + xaea + 1585)
Xaea/ (er + Xaea + 1568)

(19)
(20)
(21)

27

Extinction coefficients of the syn and anti chromophores are assumed to

be the

same.

Light fractions for these two chromophores are expressed

as population-weighted fractions of the o-methyl chromophore's

extinction coefficient:

3.

Br "
Ba -
5s "
kr-->s
k:s-M:
kr-ba
ka—br

ks—n

ka-M:

Bo-methyl - 1555 + Xaca (22)

Definition. of Termm (three triplets)

light fraction absorbed by reactive chromophore.

light fraction absorbed by anti conformer.

light fraction absorbed by syn conformer.

- rate

- rate

- rate

- rate

- rate

3 rate

constant for reactive triplet ET to syn triplet.
constant for syn triplet ET to reactive triplet.
constant for reactive triplet ET to anti triplet.
constant for anti triplet ET to reactive triplet.
constant for syn triplet bond rotation to anti triplet.

constant for anti triplet bond rotation to syn triplet.

1/1r - decay of reactive triplet by type II reaction in the absence
of ET.

l/t. - decay of syn triplet by photoenolization in the absence of ET.

1/1:a - decay of anti triplet in the absence of ET.

kr - rate constant for type II reaction.

I; ‘ 1 ’ I, ' [Al/([3] + [8])

 

RESULTS

Correlation of the photokinetic results with the curve-fitting
plots is covered in this chapter. This chapter provides a detailed
analysis of how the non-linear quenching plots were used to derive rates
of interchromophore ET in the various diketone systems studied. The
analyses involved curve-fitting the Stern-Volmer quenching data with

computer generated quenching plots.

I. Preparation of Diketones and. Ketones

The various diketones and model ketones (Figures 1-3) were prepared
via acylations, etherifications, and nucleophilic substitutions. The
diketones 7-(3-Me-4-AcPhO)EP, 1-(3-Me-4-(1bMeVal)PhO)EP, y—(4-EzPhO)BP,

and 7—(3-Me-4-BzPhO)EP were prepared in the following way:

0 r-\
O O

O f“
MCI fl 0 0
Cl I
© Cl :GJKN HO OH WC) N31. ©></\4
slug 3* -
R 0
oh
,. NaO

 

 

R C)
0
RI
(:3JK~,A\,.O‘E::JL

R" CH3, C32CH2CH (CH3) 2' C685

28

. ’l'li.‘

 

 

29

The diketones 5-(3-Me-4-AcPhO)VP, 5-(3-Me-4-ValPhO)VP, 5-(3-Me-4—
(7HMeVal)PhO)VP, 5-(4-BzPhO)VP, and 5-(3-Me-4-EzPhO)VP were prepared in

the following way:

0

aJk~/~\/”\ O 0
© c1 c_1- GJWCI NaI 6W1
AlCl3
R 0
oh.
NaO

 

 

0 3°
' -
Mafia

R" CH3,CH;CH2C52CH3, CH2CHzCH (CH3) 2, C5145

The diketones 5-(2'-Me-4-BzPhO)VP, £-(2'-Me-4-BzPhO)HxP, C-(2'-Me-4-

EzPhO)HpP, and n-(2'-Me-4-BzPhO)OtP were prepared in the following way:

0

r-\
O
O O
C 1M Er W ROI—‘0“ W Na I
(:5 4.» Br.______., Br
AlCl3 3* l
['1
O O
©>K~v I
NaOIZD

 

 

0 I_\
O o CIJltfij O 0
<1 O‘LZD
G’K/w o—G Eb AlCl3 G

30

The diketones l-Bz-d-(Z-Me-4-An)8t and 1-Bz-4-(o-Tl)Bt were

prepared in the following way:

 

 

o r—\
)w 0 r1 0 0
C1 C1 HO OH
AlCl > c1 '——;—> (:1
CH30 3 C830 H C1430
NaCN

MgBr r'\

o oca3 1) cf 0 0
M ‘ WC}!

0

 

(:3 CH.M Rom +OH
AlCl3

NaCN
éugBr

61M“

‘2) H3O

 

GJKA, (DA/v.0
7-(3-Me-4-AcPhO)BP 8-(3-Me-4-AcPhOWP
1—(3-memyl-4-acetylpbonoxy)butymphenom 5-(3-mcfl1ylmylphcn0XYWEMthonc

O
0
0M 0
7-(3-Me-4-(y-MeVaIWhO)BP
7-(3-mcthyl«Hy-mothylvaleryl)phenoxy)but)mphcnonc

[5wa

5- (3- Me-d-VslPhOWP
6-(3-methyl-4-valerylphenoxy)valerophenone

O
O
W OM
5-(3-Mc-4-(7—MeVaIH’hO)VP
5—(3~medlyl-4-($mothylvaleryl)phenoxy)valanphenone

ocn3

   

l-Bz-4-(2-Me-4-An)!!! l-Bz-4-(o-Tl)Bt
l-bmwyl-4-(2-medmyI-4-m1isoymumne l-benzoyM-(o-toluoylwum

rigure 1: Benroyl-(p-alhanoylphenory), l-Er-e-(Z-ue-e-An)8t,
and l-Er-e-(o-Tl)3t Diketones

 

32

O
0
° so C] ° “
©J\/\I dwo Q Q
y-(s-Bzrhomr 8-(2'-Me-4-BzPhOVP
+(4-bcnzoylphcmxy)bmyrophwmc 8-(2'4nodnyl4bemoylphenoxywalcmphcnonc

0 o
O * -\ ' o
W W0“
7—(3-Me-4-BzPh0mP e-(2'-Me-4-BzPhO)HxP
7—(3-memyl-4-benznylphmoxy)butymphenone e-(2'-methyl4-buuoylphenoxy)hexanophemne

8-(4-BsPh0)VP {-(2'-Mc-4-BzPhO)HpP
5—(4-bcnzoylphenoxy)valanphwonc C—(2'4nMy14-bcnmylphenoxy)heptanophenonc
O
O O 0 “
dud 0% 01w. e 0
O
5-(2'-Me-4-BzPh0)VP n-(2'-Me-4-BzPhO)OtP

8-(2'-mod:yl-4-bcnmylpbmxy)valaophmonc nfl'mothyH—bmzoylphonoxynmnplrnme

Figure 2: Benroyl- (p-benroylphenory) Diketones

33

y-(A-CNPhO)!!!’
1-(4-cymphenoxy)butyrophenmc

6-(4-CNPhO)VP
5-(4«cymophanoxy)valaophunle

e-(4-CNPhO)HxP
t-(4-cyanophmoxyfllcxanophcnonc

‘JLANo—O cu

C-(4-CNPhO)HpP
C—(Wnplmnxyfiwpmnpmnone

n-(4-CNPhO)OtP
n-(4-cysnophenoxy)ocmnopham

Figure 3 : nodal Ketones

O

4-Me0-2-MeAP
Lmefioxy-Z-methylacotophenom

O

4-MeO-2-MeVP
4-methoxy-2-memylvalaophenme

c1130

0

ago

 

4-MeOBzP
4-mcthoxybenzophenone

O
4-MeO-2-MeBzP
4-medmxy-2-medwlbcnmphcnme

c1130

 

4-MeO-2'-MeBzP
Wry-Z‘wcfiylbmwpham

34

II. Techniques Used in Energy Transfer Study

Interpretation of the ET behavior of the diketones was done by
fitting the steady state quenching data to mathematical models which
represent the photokinetics involved. This section presents the
acquisition of quenching and other pertinent physical data required to
make such fits. Section III describes the application of these data to
the models in the derivation of ET values. The photokinetic parameters
and ET results of all diketones are summarized at the end of this
chapter in Tables 9 and 10.

A. Stern-Volmer Quenching and Quantum Yields

Stern-Volmer steady state kineticsa‘ were used to study ET in the
diketone systems. The sole quencher used was 2,5-dimethyl-2,4-
hexadiene, which quenches triplets at a rate of 6x109 M‘ls”1 in
benzene37'39 and 7.5x109 M’ls'1 in methanol.32 Special care was taken to
insure that only pure, sublimed quencher was used. Even nicely
crystalline material present at the frozen liquid surface contains large
amounts of polymeric impurities which could adversely affect the results
of a quenching experiment. Quenching experiments were conducted by
preparing benzene and methanol solutions containing 0.01M diketone,
internal standard, and quencher at various concentrations. The methanol
used was only 80% methanol with 20% benzene (v/v) added to avoid tube
cracking during degassing. The solutions were placed in irradiation
Pyrex or Kimax tubes, degassed, and irradiated at 313 or 366nm. Type II
product formation was measured by gas chromatography. Conversion of the
zero quencher (always the tube of highest conversion) was kept below 10%

since photoproducts often act as internal filters, quenchers, and in

 

 

35

some cases, quantum yield enhancers.11

Quantum yields (dn were measured in parallel with SV quenching runs
and in separate quantum yield maximization experiments. Actinometry was
provided by degassed benzene solutions of 0.1M valerophenone33 for
irradiations of less than 8 hours and 0.1M 2-methylvalerophenone22 for
irradiations greater than 8 hours. Type II formation of acetophenone
from valerophenone and 2-methylacetophenone from 2-methylvalerophenone
was measured by gas chromatography.

Quantum yields for type II product formation at their maximum
levels (dfij'nax) were determined in benzene with the addition of
purified 1,4-dioxane. It is well known that the addition of Lewis bases
such as 1,4-dioxane will maximize the quantum yield of the type II
reaction by complexing with the biradical and suppressing its reversion
back to starting ketone.11 The dfil'uax values reported in Table 1 were
reached at ~2M dioxane (representative Chum“ plots are given (in
Figures 4-7). Quantum yields for some ketones and diketones rose higher
at dioxane concentrations >2M. However, these were generally
disregarded because at >2M, dioxane becomes the major solvent component
and the °II.Max values measured cannot be considered valid data
reflective of photokinetic behavior in benzene. Besides, the maximized
quantum yield experiments were internally consistent for the series of
diketones studied and generally gave maximum values which were 1.5 - 2.0
times greater than the quantum yields in the absence of dioxane. The
conversion of the highest quantum yield tube in each run was kept to a
minimum (usually ~l%) to eliminate any quenching or light filtering

effects from photoproducts.

 

0.11"

0.10"

0.09"

 

(b 0.08-
0.07

0.06

 

0.05'TV' ‘ I ' I ' I ' I ' I ** I ' ’1
7

[Dioxane],M

figure 4: Effect of Added Dioxane on the Quantum Yield of
7-(3-lle-4-AcPhO)BP at 313nm in Benzene (sAP observed)

 

 

 

0 . 15
0 . 10
(I)

T

0 . 05 '
J O

a. U... - -‘=° -.°.-.-.-- .----.--°

l,-------.°---.- ‘

0 00 v 1 V I V I v 1 v I j 1 v ' v I v I
0 1 2 3 4 5 6 7 8 9

[Dioxane],M

figure 5: Effect of Added Dioxane on the Quantum Yield of
y-(3-lte-4-(y-ueVal)PhO)BP at 313nm in Benzene
(oAP observed; 0 7-(3-Me-4-AcPhO)BP observed)

 

 

 

37

 

 

 

 

 

 

(D
[DioxanclM
figure 6: Effect of Added Dioxane on the Quantum Yield of
7-(3-ue-4-BzPhO)BP at 313nm in Benzene (e AP obsv'd)
0.03 "
‘ ——-.-——_.‘
0.02 "
q) .
0.01
0.00 I ‘ I ' I ' I j I ' I ' j V l ‘ 1
0 2 4 5 6 7 8
[Dioxane],M
figure 7: Effect of Added Dioxane on the Quantum Yield of

e- (2 ' -l(e-4-Bth0) Bx?
(eAP observed)

at 313nm in Benzene

 

 

Table 1: Quantum

Diketone or Ketone

Yields

 

Y'(3-Me-4-ACPhO)BP

Y-(3-Me-4-(7—MeVal)PhO)BP

5-(3-Me-4-AcPhO)VP

8-(3-Me-4-ValPhO)VP

8-(3-Me-4—(y—MeVa1)PhO)VP

Y-(4-BzPhO)BP
Y-(B-Me-4-82PhO)BP
8-(4-BzPhO)VP
8-(3-Me-4-azph0)vp
5-(2'—Me-4-BzPhO)VP
€-(2'-Me-4-BzPhO)HxP
C-(2'-Me-4—azph0)npp
n-(2'-Me-4-BzPhO)OtP

1-Bz-4-(2—Me-4—An)Bt

1-Bz-4-(o-Tl)Bt

4-MeO-2-MeVP

 

* . . . .
The prec1510n of 431 values was determined by multiple runs.

values was determined by either multiple runs or by visual inspection of the C)

vs.[Dioxane] plot.

(1)
on

of Diketones at

313nm in Benzene *

 

‘DII d>II,MaX
0.066 $0.006 .10 $0.01
0.069 $0.001 (82) .13 $0.01
0.011 $0.0007 (An) .020 $0.002
0.031 $0.001 .037 $0.002
0.028 $0.001 (82)
0.0017 $0.0001 (An)
0.029 $0.001 (Bz) .036 $0.003 (82)
0.010 $0.001 (An) .021 $0.003 (An)
0.041 $0.002
0.0053 $0.0002 .0093 $0.0003
0.0057 $0.00002
0.0023$0.0001 .0043 $0.0004
0.0045 $0.0002 .0075 $0.0005
0.0094 $0.0002 .020 $0.001
0.017 $0.007 .040 $0.005
0.011 $0.002 .030 $0.002
0.071 $0.002 (82) .080 $0.005

0.

.0017 $0.0001 (An)

.053 $0.004 (82)
.0061 $0.0002 (Tl)

0011 $0.0001

The precision of d)

.0023 $0.0001

.072 $0.003 (B2)
.0083 $0.0004 (Tl)

.0022 $0.0002

ll,max

II,msx

 

‘U‘LIQE .1."

Table 2: Quantum Yields of

Diket one or Xetone

 

1~(3-Me-4-Acph0)ap

7- (3-Me-4-(1—MeVal)PhO)BP

5-(3-Me-4-AcPhO)VP

5-(3-Me-4-(1bMeVa1)ph0)VP

Y-(4-BzPhO)BP
7-(3-Me—4-BzPhO)BP
5-(4-BzPhO)VP

5-(3-Me-4-BzPhO)VP

1-Bz-4- (2-Me-4-An) Bt

1-82-4- (o-Tl) Br.

4 -MeO-2 -MeVP

 

39

Diketones at 313nm in Methanol*

(>11

 

0.15 $0.007

0.11 $0.005 (Bz)
0.026 $0.002 (An)

0.041 $0.002

0.030 $0.001 (82)
0.043 $0.001 (An)

0.054 $0.003
0.0057 $0.0005
0.029 $0.001
0.0017 $0.00005

0.076 $0.001 (82)
0.0029 $0.0001 (An)

0.067 $0.001 (82)
0.0054 $0.0001 (T1)

0 .0065 $0.000?

1"The precision of $11 values was determined by multiple runs.

Table 3: Quantum Yields of Diketones at 366nm*

Diketone

 

 

Y-(C-BzPhO)BP
T-(3-Me-4-BzPhO)BP
5-(4-BzPhO)VP

5-(3-Me-4-BzPhO)VP

 

¢II(1.n benzene) d’II(in MeOH)
0.043 $0.001 0.040 $0.001
0.0081 -

0.019 $0.001 0.016 $0.0005
0.0046 -

*The precision of $11 values was determined by multiple runs.

. L": !‘«.-.-r- '

 

 

40

B. Ultraviolet and Phosphorescence Spectroscopy

Ultraviolet (UV) spectra of diketones and model compounds were
taken in benzene and methanol/benzene (4:1, v/v) for the purpose of
measuring their extinction coefficients at 313nm and 366nm. These data
are listed in Table 4. It was particularly important to obtain the
extinction coefficients for the model compounds so that the light
percentage garnered by each chromophore (B) in the diketone systems
could be known. This information was necessary for proper analysis and
programming of the curve-fits. These spectral data were also used to
correct for light absorption differences in the 366nm irradiation
experiments and the butyrophenone quenching experiments.

Phosphorescence spectra were measured at 779K in two solvents, 2-
methyltetrahydrofuran (Z—MeTHF) and a 5:1 methanol/ethanol (v/v)
mixture. These data are summarized in Table 5 and example spectra are
provided in Figures 8-13. The spectra of most diketones do not differ
significantly from that of the model ketone representing the lowest
energy triplet in each system. The spectra of 1-(3-Me-4-AcPhO)BP, 7-
(3-Me-4-(‘y-MeVal)PhO)BP, 5-(3-Me-4-AcPhOHfP, 8-(3-Me-4-ValPhO)VP, 5-(3-
Me-4-(15MeVal)PhO)VP are similar to that of the model ketone 4-MeO-2—
near. The spectra of 7-(4-BzPhO)BP and 5-(4-BzPhO)VP are identical to
that of the model ketone 4-MeOBzP. The spectra of y-(B-Me-d-BzPhO)BP
and 8-(3-Me-4-BzPh0)VP are identical to that of the model ketone 4-Meo-
2-MeBzP. The spectra of 5-(2'-Me-4-BzPhO)VP, £-(2'-Me-4-BzPhO)HxP, C-
(2'-Me-4-BzPhO)HpP, n-(2'-Me-4-BzPhO)OtP are identical to that of the

model ketone 4-HeO-2'-MeBzP.

 

P7

 

41

Table 4: Extinction Coefficients of Diketones and Model Eetones

 

€3l3nm' M'lcm'l 8366“”, M‘lcm'1
Ketone or Diketone (Benzene) (MeOH) (Benzene) (MeOH)
Y-(B-Me-4-AcPhO)BP 236 527 5.0 -
1-(3-Me-4-(yeMeVa1)ph0)BP 245 530 5.3 -
Y-(4-BzPhO)BP 1143 5261 126 91
1*(3-Me-4-BzPhO)BP 1716 3940 172 177
5-(3-Me-4-AcPhO)VP 235 546 6.4 -
5-(3-Me-4-ValPhO)VP 237 - 7.0 -
6—(3-Me-4-(y-MeVa1)ph0)VP 254 564 6.7 —
5-(4-BzPhO)VP 1295 5560 129 92
5-(3-Me-4-BzPhO)VP 1790 4043 172 188
5-(2'-Me-4-BzPhO)VP 548 - 68 -
£-(2'-Me-4-BzPhO)HxP 547 - 68 —
C-(2'-Me-4-B2PhO)HpP 565 - 7o -
n-(2'-Me-4-szpn0)0tp 573 - 70 -
y-(4-CNPhO)BP 60* 71 - _ 2.2
5-(4-CNPhO)VP 57* 73 - 2.5
€-(4-CNPhO)HxP 54 - 4.3 -
C-(4-cnph0)npp 53 - 3.9 -
fl-(4-CNPhO)OtP 51 - 4.2 -
4-MeO-2-MeAP 163 367 - -
4-MeOBzP 797 3988 113 77
4-MeO-2-MeBzP 1314 3057 158 157
4-MeO-2 ' -MeBzP 339 2780 62 34
l-Bz-4-(o-T1)Bt 136 196 7.9 -
l-Bz-4-(2-Me-4-An)Bt 241 476 8.4 -
vs 47 67 3.8 2.0
Z-MeAP 82 134 4.1 -

 

* From Ph.D. dissertation of H.W. Frerking, p41.

 

 

 

 

 

 

 

Intensity
’ I I I
350 400 450 500 550
1mm
figure 8 : Phosphorescence Spectra of 4 -MeO-2-MeAP ,

y-(3-Me-4-AcPhO)BP, y-(3-Me-4-(‘y-MeVal)PhO)BP,

8- (3-Me-4-AcPhO) VP, 5-(3-14e-4-Vaiphowp ,
5-(3-Me-4-('y-MeVal)PhO)VP, and l-Bz-4-(2-Me-4-An)Bt
(____. in 2-MeTHF; ----- in MeOH/EtOH)

 

Intensity

 

 

 

 

350 400 450 500 550

figure 9: Phosphorescence Spectra of 1-Bz-4-(o-T1)Bt
(— in Z-MeTHF; ------- in MeOH/EtOH)

 

Intensity

 

 

 

 

figure 10: Phosphorescence Spectra of 4-MeOBzP, y-(4-BzPhO)BP,
and 8-(4-BzPhO)VP in 2-xeTns and neon/tron

 

Intensity

 

 

 

 

' I l
350 400 450 500 550

figure 11: Phosphorescence Spectra of 4-MeO-2-lleBzf,
7-(3-ue-4-BthO)BP, and 8-(3-ue-4-szph01w
in 2-lleTHf and neon/stall

 

Intensity

 

 

 

' I
350 400 450 500 550
1mm

figure 12: Phosphorescence Spectra of 4-ueO-2'-ueBzP,
8- (2 ' -xe-4-szph0)VP, s- (2 ' -Me-4-BzPhO) exp,
z;- (2 ' -Me-4-BzPhO) HpP, and n- (2 ' -Me-4-BzPhO) or?
in 2-MeTnf

 

    
     

4-MeO-2'-MeBzP

 

Intensity

Equimolar mixture of
VP + 4-MeO-2'-MeBzP

 

 

 

figure 13: Phosphorescence Spectra of VP and C-MeO-Z'd‘eBzP
in Z-KeTnf

45

Table 5: Phosphorescence Data of Diketones and model Ketones

Diketone or Ketone Solvent 0,0 band AE,kcala
(nm) (kcal)

 

 

Y-(3-Me-4-AcPhO)BP Z-MeTHf ~398 71.8 2.3
MeOH/EtOH,S:1 ~410 69.7 3.6
7-(3-Me-4-(beeVa1)Pn0)BP Z-MeTHF ~398 71.8 2.3
MeOH/EtOH,5:1 ~410 69.7 3.6
5-(3-Me-4-AcPhO)VP 2-MeTHF ~398 71.8 2.3
MeOH/EtOfl,5:1 ~410 69.7 3.6
5-(3-Me-4—Va1ph0)VP Z-MeTHF ~398 71.8 2.3
5-(3-Me-4-(7-MeVal)PhO)VP Z-MeTHF ~398 71.8 2.3
MeOH/EtOH,5:1 ~410 69.7 3.6
l—Bz-4-(2-Me-4-An)Bt Z-MeTHF ~398 71.8 2.3
MeOH/EtOH,5:1 ~410 69.7 3.6
1-Bz-4-(o-Tl)Bt 2-MeTHF 389 73.5 0.8
MeOH/EtOH,5:1 393 72.7 0.6
1-(4-BzPhO)BP 2-MeTHF 419 68.3 4.6
MeOH/EtOH,5:1 419 68.3 5.0
1‘(3-Me-4-BzPhO)BP 2-MeTHF 428 66.8 5.9
MeOH/EtOH,5:1 428 66.8 6.5
5-(4-BzPhO)VP 2-MeTHF 419 68.3 4.6
MeOH/EtOH,5:1 419 68.3 5.0
5-(3-Me-4-BzPhO)VP 2-MeTHF 428 66.8 5.9
MeOH/EtOH,5:1 428 66.8 6.5

5-(2'-Me-4-BzPhO)VP 2-MeTHF 414 69.1 3.6

46

Table 5 (cont'd)

£-(2'-Me-4-BzPhO)HxP Z-MeTHF 414 69.1 3.6
C-(2'-Me-4-szph0)app Z-MeTHF 414 69.1 3.6
n-(2'-Me-4-BzPhO)OtP 2-MeTHF 414 69.1 3.6
4-MeO-2-MeAP Z-MeTHf 398 71.8 -

MeOH/EtOH,5:l ~408 70.1 -

 

4-MeOBzP 2-MeTHF 419 68.3 - 5
MeOH/EtOH,5:1 419 68.3 - -
4-MeO-2-MeBzP Z-MeTHF 428 66.8 - i
MeOH/EtOH,5:1 428 66.8 - '
4-MeO-2'-MeBzP 2-MeTHf 414 69.1 - E
MeOH/EtOH,5:1 419 68.3 - '
vp 2-MeTHF 393 72.7 -
MeOH/EtOH,5:l 390 73.3 -
7—(4-CNPhO)BP 2-MeTHF 393 72.7 -
MeOh/EtOH,5:l 390 73.3 -
5-(4-CNPhO)VP 2-MeTHF 393 72.7 -
MeOH/EtOH,5:l 390 73.3 -
£-(4-CNPhO)HxP Z-MeTHF 393 72.7 -
C-(4—CNPh0)HpP 2-MeTHF 393 72.7 -
n-(4—CNPh0)0tP Z-MeTHF 393 72.7 -
2-MeAP Z-MeTHf 389 73.4 -
MeOH/EtOH,5:1 393 72.7 -

 

aInterchromophore energy gap determined from phosphorescence of model ketones at 77°K.

47

III. Energy Transfer Analyses

Two types of diketones were studied in this work, those with two
triplets and those with three. The photokinetics of the two-triplet
systems, 1—(4-BzPhO)BP and 5-(4—BzPhO)VP, are presented in the Intro-
duction chapter and described by Equations 2-9. The two triplets
involved in ET in these systems are the benzoyl and the p-benzoyl-
phenoxy. The three-triplet systems are 7-(3-Me-4-AcPhO)BP, 7—(3-Me-4-
(7-MeVa1)PhO)BP, 1-(3-Me-4-szhomp, 5-(3-Me-4—AcPhO)VP, 8-(3-Me-4-
ValPhO)VP, 8-(3-Me-4-(y-MeVa1)Ph0)VP, 5-(3-Me-4-BzPhO)VP, l-Bz-4-(2-Me-
4-An)Bt, 1-Bz-4-(o-T1)Bt, 5-(2'—Me-4-BzPh0)VP, e-(2'-Me-4-szph0)axp, C-
(2'-Me-4-BzPhO)HpP, and n-(2'-Me-4-BzPhO)OtP. (The photokinetics of
these are also presented in the Introduction chapter and described by
Equations 10-22. Since these diketones have an o-methyl chromophore,
they have three triplets involved in ET: benzoyl, and the syn and anti
conformers of the o-methyl chromophore.

The following sections detail the derivation of ET rate constants
through the fitting of experimental quenching results with the
mathematical models for the various systems. The sources of all
necessary parameters (lifetimes, type II rate constants, etc.) are also
provided. The figures show the fit of quenching data obtained experi-
mentally with those generated by the mathematical models. Each figure
is broken down into three parts, A, B, and C. Each part illustrates the
impact that changing different rate constants has on the predicted
quenching curves. The three processes varied in the analysis are
syn/anti interconversion (krea and qus in part A), endothenmic ET

(kendo - kw,r or ka-n in part B), and exothermic ET (kexo - kr_,s + kr_,a

 

48

in part C). The best fit of the data for each diketone is represented
by a solid line; deviations from the best fit are represented by dashed
and bolded lines.

The significance of the plots which result from changes in the
above mentioned rate constants and what each indicate about the photo-
kinetics is discussed to a limited degree in the following sections.
However, a general interpretation of the ET results in light of other ET

studies is covered in the Discussion chapter.

A. The Benzoyl-(3-methyl-4-alkanoy1phenoxy) Diketones

The diketones in this series contain a benzoyl chromophore attached
by an alkyl tether of three or four methylenes in length to the oxygen
of a 3-methyl-4-alkanoylphenoxy chromophore. Those with tethers of
three methylenes in length are 7-(3-Me-4-AcPhO)BP and 1*(3-Me-4-(7—
MeVal)PhO)BP. Those with tethers of four methylenes in length are 5-(3-
Me-4-AcPhO)VP, 5-(3-Me-4-ValPhO)VP, and 5-(3-Me-4-(Y-MeVal)PhO)VP.

The lifetimes and interconversion rate constants of the syn and
anti triplets are obtained from the photokinetics of model ketones
representing the o-methyl chromophore. for the systems with a 3-
methyl-4-a1kanoylphenoxy chromophore, ksas - 6.4x105s'1 in benzene and
2.2x105s”1 in methanol. These are the triplet lifetimes of 4-methoxy-2-
methylacetophenone which were measured by flash kinetics by Dr. P.J.
Wagner at the NRC in Ottawa, Canada in 1987 (listed in Table 6). Since
the flash method (under these conditions) is only able to detect the
longest lived triplet species which absorbs at 420nm, the lifetime

measured must be the rate at which the anti triplet bond rotates into

1.

 

49

its syn conformer. The syn and anti populations, Is and 16, are assumed
to be 0.79 and 0.21 in benzene. This is taken from the values reported
by Wagner and Chen for 2-methylvalerophenone.22 Similarly, x5 and xa in
methanol are assumed to be 0.89 and 0.11, the same values reported for
2-methylvalerophenone in t-butanol.22 The value of kw,a is calculated
from qug and the populations of each conformer (see Equation 23

below); It,”M - 1.‘7xlO‘s‘1 in benzene and 0.27x1053'1 in methanol.

k's-ea ' ka-9s (la/15) (23)

The rate of photoenolization of the syn triplet, 1/15, is 1x10%‘1
in benzene. This was measured by steady-state sensitization of the
trans-acis stilbene isomerization by 4-MeO-2-MeAP. A decay of 1x1083‘1
for the syn triplet in benzene is indicated by the double reciprocal
plot shown in figure 53 which has an initial slope of $0.015 and y-
intercept of 1.45. In methanol, a 1/15 of 7x105s"l was estimated based
on the decays of the model ketones 2-methylacetophenone,22 valero-
phenone,33 and p-methoxyvalerophenone,32 and on the best fit of the
quenching data to the predicted curves. The decay of the syn triplet of
2-methylacetophenone was measured as 52:109s’1 by Wagner and Chen.22
Since the p-methoxy group reduces triplet decay of p-methoxyvalero-
phenone by a factor of ~50 relative to valerophenone32 and the switch
from benzene to methanol further reduces the triplet decay of p-
methoxyvalerophenone by a factor of ~5,32 the rate of decay of the syn-
3-methyl-4-a1kanoylphenoxy triplet was initially estimated at ---10"s"1
(i.e., 5x109s"1 + 50 + 5). However, curve-fitting of the quenching data

with the mathematical model demanded that l/‘ts be <107s'1 and 7x1053’1

 

 

50

gave the best fit for all diketones containing this chromophore.

The decay of the anti triplet in the absence of interconversion to
the syn, l/ta, was calculated from model ketones. for 7-(3-Me-4-
AcPhO)BP and 5-(3-Me-4-AcPhO)VP, 1/1a is 3x105s'1 in benzene and
methanol. This is based on the decay of p-methoxyvalerophenone.32 The
1/1a value for 8-(3-Me-4-ValPhO)VP in benzene of 7x105371 is based on the
model ketones p-methoxyvalerophenone32 and 2-methylvalerophenone.22
This value was arrived at by multiplying the 1/1 for p-methoxyvalero-
phenone32 of 2.2x1053’1 by a factor of 0.3 to account for the reduction
in reactivity introduced by the o-methyl group."’2 A similar estimation
process was applied to yield 1/1a values of 1.5x1063’1 in benzene and
3x105s"1 in methanol for 7-(3-Me-4-(7—MeVal)PhO)BP and 5-(3—Me-4-(y—
MeVal)PhO)VP. In benzene, l/‘ta was calculated by multiplying the 1/1
for p-methoxy(ybmethyl)valerophenone32 of 5x106s‘1 by 0.3 to account for
the reduction in reactivity caused by the o-methyl group.22 In
methanol, l/‘ra was calculated by dividing the llta in benzene of
1.5x105s’1 by 5 to account for the reduction in reactivity caused by the
switch to methanol.32

The light fractions absorbed by the benzoyl, syn, and anti chromo-
phores in benzene are Br - 0.22, B, - 0.32, and Ba - 0.16. These values
are calculated from the extinction coefficients of the model ketones
valerophenone and 4emethoxy-Z-methylacetophenone and from the syn/anti
ratio of 79/21 found for 2-methylacetophenone22 (see Equations 19-22).
The benzoyl chromophore absorbs 22% of the light and the 3-methyl-4-
alkanophenoxy chromophore absorbs 78%. This 78% of the light is shared
by the syn and anti conformers. Since 21% of the 3-methyl-4-alkano-

phenoxy chromophore is in the anti fornuzz Ba - 0.16 (0.78 x 0.21). for

 

 

51

the syn, the light fraction is calculated based on the fact that only
52% of the syn singlets intersystem cross to form syn triplets:
therefore, 3, - 0.16 (0.78 x 0.79 x 0.52). In methanol, the light
fractions absorbed by the benzoyl, syn, and anti chromophores are Br -
0.15, BS - 0.39, and Ba - 0.094. These are also calculated from the
extinction coefficients of valerophenone and 4-methoxy-2-methylaceto-
phenone in methanol and from the syn/anti ratio of 89/11 found for 2-
methylacetophenone in t-butanol.22 In methanol, the benzoyl absorbs 15%
of the light and the 3-methy1-4-alkanophenoxy chromophore absorbs 85%.
Since 11% of the 3-methy1-4-alkanophenoxy chromophore is in the anti
form,22 Ba - 0.094 (0.85 x 0.11). for the syn, it is assumed that the
percentage of singlets which intersystem cross is the same as in
benzene; therefore, BS - 0.39 (0.85 x 0.89 x 0.52).

The decays and type II rate constants of the 7- and B-benzoyl
triplets in benzene were derived by H.W. frerking; these are l/tr -
8.8x107s’1 and k, - 4.9x107s‘1 for the ‘y-benzoyl,” 1“: - 1.4x107s'1 and
kr = 0.80x107s'1 for the 5-benzoyl.‘° frerking reasoned that the most
appropriate models for the 7- and 5-benzoyl chromophores would have a
moiety on the phenoxy ring with resonance and inductive properties
similar to an acyl group, but would not absorb light. The reactivities
of these "ideal" models were extrapolated from Hammett plots based on
the reactivities of the model ketones 1r(CNPhO)BP, 1%(PhO)BP, 5-
(CNPhO)VP, and 5-(PhO)VP. The decays and type II rate constants in
methanol were taken directly from the model ketones 7-(CNPhO)BP and 8-
(CNPhO)VP; these are 1/1r - 4.01:10'7s’1 and kr - 2.1111073"1 for the 7-

benzoyl, l/‘tr - 1.0x10"s"1 and kr - 0.60x107s'1 for the 8-benzoyl.

52

for 1—(3-Me-4—AcPhO)BP, quenching data was obtained by monitoring
the acetophenone (AP) type II product coming from the benzoyl chromo-
phore. Rates of ET derived for this system are kexo'- 17x107s'1 and
kemk>- 0.50x1073"1 in benzene. figure 14 illustrates the correlation of
the dual-sloped experimental quenching data with the predicted quenching
data generated by the mathematical model. As shown in part A, a two
fold increase and decrease in the syn/anti interconversion rate has a
moderate effect on the fit. Increasing the rate of interconversion
eliminates some of the initial steep slope and shifts the curve downward
by shortening the lifetime of the anti triplet. This behavior can be
explained in terms of the competition between ka_,s and kendo (ka_,r and
kyqr) for anti triplet excitation. As competition increases, kenclo
becomes less of a factor and the system approaches a one-way ET scheme
with a linear quenching plot. Changes to kyaa can be ignored due to
the extremely short lived syn triplet (1/1s - 1083'1). Parts B and C
show that changes in the ET rate constants have a significant impact on
the fit.

The diketone T-(3-Me-4-(15MeVal)PhO)BP was designed to measure type
II product from.both the benzoyl and anisoyl chromophores, however,
curve-fitting analyses were performed only on the benzoyl quenching data
because the mathematical model used assumes that only the benzoyl
triplet is reactive. A model capable of curve-fitting quenching data
from a system where two of the three triplets form product is currently
under development by Dr. P.J. Wagner. figure 15 shows that the
quenching slope for benzoyl type II is lower with a diminished initial

slope compared to 1—(3-Me-4-AcPhO)BP. Rates of ET derived for this

53

system are kexo - 17x1073'1 and kendo - 0.20x107s‘1 in benzene. The
decreased sensitivity of the quenching plot to changes in the syn/anti
interconversion and endothermic ET rates, compared to the acetyl system,
indicates that ET in this system is closer to a one-way process. This
could be due to the increased competition for anti triplet excitation
introduced by the VHMeVal sidechain type II. The quenching plot appears
to have the same sensitivity to changes in the exothermic ET rate as the
acetyl system.

The diketones 5-(3-Me-4-AcPhO)VP, 8—(3-Me-4-ValPhO)VP, and 5-(3-Me-
4—(15MeVa1)PhO)VP have an alkyl tether which is one methylene unit
longer than the y-diketones. for 5-(3-Me—4-Acth)VP, ET rates of kexo-=
7.7x107s'1 and kendo" 0.30x10"s'1 in benzene were derived. The
quenching plot of this diketone does appear to have an initial steep
slope, which suggests the presence of a long lived triplet involved in
endothermic ET (figure 16). The sensitivity of the quenching plot to
changes in the syn/anti interconversion and ET rates is similar to that
of 7-(3-Me-4-AcPhO)BP.

The diketones 8-(3-Me-4-ValPhO)VP and 5-(3-Me-4-(7—MeVal)PhO)VP
were designed to measure type II from both chromophores, but only
quenching of the benzoyl was used in the curve-fitting analyses for the
same reasons as 15(3-Me-4-115MeVal)PhO)BP. ET rates of kexo" ‘7.7x107s'1
and kendo" 0.10xlO7s‘1 in benzene were derived for both diketones.
figures 17 and 18 show that the linear quenching plots of these
diketones are less sensitive towards changes in the syn/anti
interconversion and endothermic ET rates than the y-diketone analogs.
The sensitivity of these curves to changes in the exothermic ET rates is

similar to that of the y-diketones.

54

The photokinetics of the benzoyl-(3-methyl-4-alkanoy1phenoxy)
diketones were also studied in methanol. for 7-(3-Me-4-AcPhO)BP, ET
rates of kexo - 18x10"s"1 and kendo - 1.5x107s'1 were derived. figure 19
shows that the quenching plot is insensitive to factor of ten changes in
the syn/anti interconversion rates, but very sensitive to factor of two
changes in the ET rates. figure 20 shows that similar results are
obtained for 7-(3-Me-4-(15MeVal)th)BP in methanol. Rates of ET derived
for this diketone, based on the analysis of the benzoyl type II
quenching data, were kexo - 18x107s"1 and kendo - 0.50x107s’1. The dual-
sloped benzoyl quenching plots of 1—(3-Me-4-AcPhO)BP and y—(3-Me-4-(7—
MeVal)PhO)BP have greater steep initial slope components in methanol
than in benzene. This reflects a lengthening in triplet lifetimes
caused by the increase in solvent polarity.

for 5-(3-Me-4-AcPhO)VP and 8-(3-Me-4-(7—MeVal)PhO)VP, the quenching
plots in methanol are dual-sloped with a steep initial slope component
not present in benzene. The rates of ET derived for 5-(3-Me-4-AcPhO)VP
in methanol were kexo - 18x107s“1 and kendo - 1.0x107s'1. figure 21 shows
that the quenching plot of 5-(3-Me-4-AcPhO)VP, like that of 1-(3-Me-4-
AcPhO)BP, is relatively unaffected by changes in the syn/anti intercon-
version rates, but extremely sensitive to changes in the ET rates. for
5-(3-Me-4-(Y-MeVal)PhO)VP, ET rates of km, - 18x107s‘1 and kendo -
0.60::107s'1 were derived. figure 22 shows that the quenching plot
responds to syn/anti interconversion and ET rate changes similarly to

the acetyl analog.

55

Table 6: flash and Steady State Decays of Diketones and Model
Eetones at 313nm

.JLLaJJL_EJULLaixJIJa ..Jlir1u11_SlAUJL_.

 

 

Diketone or Ketone lltbenzene, 1/TMeOH, l/Tbenzene, b l/TMeOH,
106 s’1 106 3'1 106 3'1 1o6 3'1
y-(4-AcPhO)BP 7.0 1.2 9.1 -
7-(4-ValPhO)BP 7.0 1.2 14.0 -
15(3-Me-4-AcPhO)BP 11.0 3.0 - -
8-(4-AcPhO)VP 2.0 0.7 2.5 -
5-(4-ValPhO)VP 2.2 0.5 4.4 -
5-(3-Me-4-AcPhO)VP 5.0 2.0 - -
4-MeO-2-MeAP 6 . 4 2 . 2 - -
Y-(4-CNPhO)BP 23.0 20.0 62.0 42.0
5-PhOVP 24 .0 12.0 246.0 -
5-(4-CNPhO)VP 17.0 10.0 12.0 10.0

 

‘ flash data collected by Dr. P.J. Wagner at the NRC in Ottawa, Canada (1987).

b Data from the Ph.D. dissertation of H.W. frerking, p 70.

Table 7: Photokinetic Values

56

of model Eetones at 313nm‘

 

 

Ketone Solvent (bu 01m“ qu,M-1 l/t,1075’1 kn,107S‘1

Hecmomp numb 0.40 0.56 - - .
Methanol 0.53 $0.01 - 186 4.0 2.1

8-(4-CNPhO)VP Bandwb 0.38 0.53 . - -
Methanol 0.55 $0.01 - 734 1.0 0.55

£-(4-CNPhO)1-IXP 861128116 0.23 $0.03 0.36 $0.01 77 7.8 2.8

C-(4-CNPhO)HpP Benzene 0.11 10.01 0.23 10.01 46 13.0 3.0

n-(4-CNPhO)OtP Balzac 0.17 $0.02 0.30 $0.02 38 15.7 4.7

a The precision was determined by multiple runs.

b Data from the Ph.D. dissertation of H.W. frerking, p 33.

0V4)

d>°ld>

¢°l¢

figure 14:

57

 

   
  
   
 

 

 

 

 

 

 

 

 

   
 
  
  
 
 

 

 

 

6
. ......... A
5..
4. ......
a- """
2" 7 7
0.0851110 , If“, - 0.32x10
1 ._ 11H, - 0.1711107, 11“, - 0.6411107
—— x._,. - 0.3411107, 11“, - 1.311107
0 I ' I If I ' j r I ' I ' I ' I 1 fl ' I . I 1
0.00 0.01 0.02 0.03 0.04 0.05 0.05 0.07 0.08 0.09 0.10 0.11
6 ”r
. ....... ' B
5. .........
4" .....
a- """"
2" 7 7
...... 11H, - 1.0x10 , 11H, - 1.0x10
1 —— 11H, - 0.5011107, 11“, - 0.501110"
—x,_., - 0.2511107, 11“, - 0.2511107
0 I fi I tfi 1 I v I 1 I ' j 'fi ' I 1 I V 1 '
0.00 0.01 0.02 0.03 0.04 0.05 0.05 0.07 0.08 0.09 0.10 0.1 1
6 ...?
. ....... .. c
5'1 ......
1
4-
3d
2" 7 7
...... kt... - 6.5810 ' kr4 - 1.83610
1 — 11H, - 1311107, x,_,. - 3.51110"
—k,_,. - 2631107, 1:“. - 7.011107
0 I ‘ I ' I ' I ' I 1 I ' I ' I j I ' I ' I V
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.1 1
[01M

Stern-Voile: Plots of 7-(3-ue-4-Acth)Bf at 313nm
in Benzene (oAP observed:

varied, C. k,_,s and kt“,a varied)

A. 11”,. and k._” varied,

s. 1:“, and k“,

0°ld>

¢°l<b

¢°l¢

figure 15 :

58

 

  

 

.,

...... x._,. - 0.0853110 , 11H, - 0.3211107
7

—_ 11H. - 0.171110 , 11H, - 0.6411107

__ 11H, - 0.341110 , 11H, - 1.311107

 

 

 

 

 
   

 

   
  

 

 

 

 

 

 

o I ' I ' I ' I ' I 1 I ' I ' I ' I i I '
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
4
....""/./' B
3- ..........
2-
1 ...... 1:“, 0.4011107, x._,, - 0.4011107
— 11H, - 0.202110", 11“, - 0.202110"
— 11H, - 0.101110", “...: - 0.1031107
01 . I V I v I ' I V I v I ' I ' 1 j I '
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
4
C
3..
2-
1 ...... k,_,. - 6.51110", x,_,. - 1.821107
— k,_,, - 13x10 , x,_,. - 3.511107
_x,_,, - 26x10 , k,_,, - 7.011107
01 w I v I v 1 1 I v I v I ' I 1 I V I '
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
[01M

Stern-Voile: Plots of 1-(3-ue-4-(y-WeVal)PhO)BP
at 313nm in Benzene (01).? observed:

varied, B. k,_,r and ka-br varied, C. qus and qua varied)

A. 11H, and kr”

59

 

   
   
  

 

 

 

 

 

 

 

 

 

 

 

 

7 7
A
6
5
4
0°10 '
3
2 ...... 11“,, - 0.08511107, )1“. - 0.3211107
1 11“. - 0.1711107, 11“, - 0.6411107
_ 11M,I - 0.341110 , k1..- - 1.311107
0 I ' I ' I ' fi 3 I I I fi I T
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
7 ,u
. ----- B
6- '
5-
4a-
¢°l¢ 1
3-
2' ...... 11,_,, - 0.6011107, 11h,r - 0.6011107
1 —— 11H, - 0.3011107, 11,», - 0.3011107
_)1,_,r - 0.1511107, “...: - 0.151110"
0 1 1 I f j fi I t I 7 I V I ‘
0.00 0.01 0.02 0.03 0.04 0.05 0.06. 0.07
7 ,.
1 " C
6- e
5d
4-
¢°l¢ 3
3-
2- ------ x“, - 3.01110". )1,_,. - 0.05111107
1 11,4. - 6.011107, 11,_,. - 1.711107
—-11,_,, - 121110 , k,_,. - 3.41110"
0 I ' j T I ' I ' I V j ' T j
0 00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
[011M

figure 16: Stern-Valuer Plate at 8-(3-ue-4-AcPhO)VP at 313nm
in Benzene (oAP observed; A. 11”,, and RP” varied,

B. k,_,r and 11.41. varied, C. 111.43 and kph varied)

¢°ld>

0‘70

¢°l0

Figure 17 :

6O

 

 

   

 

 

 

   

 

 

 

 

   

 

 

..... ' A
5. ........
4- """"
an:
2- 7 7
...... 11H, - 0.0431110 , 11._,, - 0.161110
1 — 11,_,. - 0.1711107. 11“. - 0.641110"
_. 11H. - 0.6011107, 11“, - 2.611107
0 I I v I v i - I ' I f I ' I '
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.00
5 ,.
.,o‘.. B
5. .....
4- """
3- .........
2" 7 7
...... 11HJr - 0.201110 , 11Hr - 0.201110
1 —— 11H, - 0.1011107, 11“, - 0.1011107
_x,_,, - 0.05011107, :1“, - 0.0501110"
o T I ' I ' I v I ' I ' I ' I '
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
6
' C
5-
4d
3-
2' 7 7
...... x,_,, - 3.01110 . 11,_,. - 0.001110
1 —— 11H, - 6.011107, 11“,. - 1.71110"
__ 11,_,, - 121110 . 11,_,, - 3.211107
0 I ' ' I ' I ' I ' I ' l ' I '
0.00 0.01 0.02 0.03 0.04 0.05 0.05 0.07 0.08
[0].”
Stern-Valuer Plots of 5-(3-ue-4-Va12h0)VP at 313nm

in Benzene (on? observed:

8. 11,." and kip,r varied, C. hr», and Rh” varied)

A. k,_,a and k?” varied,

61

 

   
   
 
   

 

 

 

 

 

 

 

 

 

 

 

 

4
...... A
3. ............
¢°l¢ 2- ..........
1 ...... 11,_,. - 0.04311107. 11._,, - 0.1611107
— 11“,. - 0.1711107. 11._,. - 0.6411107
— 11Ha - 0.631110 , 11H. - 2.611107
01 . I ' I V I I
0.00 0.01 0.02 0.03 0.04
4 .....
. ....... B
3- ..........
«mo 2- ........
7 7
1 ...... 11H, - 0.2011107, k1.“ - 0.2011107
— 16“., - 0.10x10 , Rh“ - 0.10x10
_..11,_,1r - 0.05011107, )1,_,r - 0.05011107
01 1 I 1 I t I '
0.00 0.01 0.02 0.03 0.04
4
0"" C
3"
0°l¢ 2"
7 7
1 ...... krd' - 3.0810 ' kr4 - 0.85X13
— 11H, - 1211107, x,_,. - 3.211107
0 . . , . , . , ,
0 00 0.01 0.02 0.03 0.04
[01M

Figure 18: Stern-Voiler Plotz of 8-(3-Ile-4-(‘y-ueVa1)PhO)VP
at 313nm in Benzene (oAP observed; A. ks-m and kl”,s

varied, B. ksq, and kid, varied, C. kr_,s and kr-n varied)

62

 

    

 

 

 

 

 

 

 

 

24
A
20
16
¢°I¢b 12
8 7 7
...... 11H. - 0.00271110 , 11H, - 0.0221110
4 — 11H, - 0.02711107. 11H, - 0.221110"
_. 11H, - 0.2711107, 11“, - 2.211107
01 v I ' I I I 1 I v I I
0.00 0.01 0.02 0.03 0.04 0.05 0.06
24 ..r
O'.". B
20
16 ..e'.'.'.
«mo 12 ..o;
8 I”. 7 7
...... 11,_,, - 3.01110 , 11H, - 3.01110
4 ._ 11H, - 1.511107, )1“, - 1.1511107
—k1..1 - 0.751110", 11“, - 0.7511107
0 1 i I ' l ' I 1 I f I fi
0.00 0.01 0.02 0.03 0.04 0.05 0.06
24 ‘
a....'. C
20
16 ........ '
mo 12 .w'”
a ' 1 1
...... 11,_,. - 0.01110 , 11H. - 1.01110
4 ’ — 11“, - 161110 , 11,_,. - 2.011107
— 11“, - 321110 , 11,_,. - 4.01110"
0T I I ' T ' I ' I I 1 I
0.00 0.01 0.02 0.03 0.04 0.05 0.06
[01M

Figure 1 9 :

Stern-Vomr Plots of y- (3-3‘e-4-AcPhO)BP at. 313nm
in IIethenol (oAP observed:

B. 11,.” and k?” varied, C. k,_,, and RP” varied)

A. k...” and kn.“I varied,

63

 

 

 

 

 

 

 

 
  
 

 

 

11 ..v
10 ----- . A
9 """"""
a . ..... '
7 .....
6 ...".
«mo 5
3 - ...... 11H, - 0.002711107. 11H, - 0.02211107
2 ...—— )1“. - 0.02711107, )1“, - 0.2211107
1 ...... 11H, - 0.271110", *1.» - 2.21110"
0 f I I ' r 1 I ' I ' I '
0.00 0.01 0.02 0.03 0.04 0.05 0.05
11 * ,.
1° ' a
9 a"...
a
7 '00"...
0°10 6
5 e
4 0'
3 ...... 11H, - 1.01110", 11“, - 1.011107
2 — ks.“ - 0.501110 , 11H, - 0.5011107
1 —11,,_,r - 0.2511107, 11,_,, - 0.251110"
0 1 I I ' I ' I I I i I v
0.00 0.01 0.02 0.03 0.04 0.05 0.06
11 ‘
10 . C
9
8
7
O°l0 6
5
4
3 - ----- 11,_,. - 0.011107, )1“. - 1.011107
2 — 11H, - 161110 , 11H. - 2.011107
1 —11,_,, - 321110 , 11,_,_ - 4.01110"
0 I V 1 1 I j I T j 1 1 V
0.00 0.01 0.02 0.03 0.04 0.05 0.05
[OI-M
Figure 20: Stern-Voile: Plot. of 1— (3-ue-4- (y-ueVe1)PhO)BP

at 313nm in Methanol (oAP observed; A. ks—n and 11.4,

varied, B. k,_, and kaqr varied, C. qus and k?" varied)

I

64

 

 

 

 

 

 

 

 

 

 

25 ,.-I
........ A
20 _, ......
15 '
¢°l¢
10
7 ...... 11,_,, - 0.002711107, k...- - 0.0221110"
5 / — 11H, - 0.02711107, 11h. - 0.2211107
_ 11H, - 0.271110 , k1.» - 2.211107
0 I I I I I I I I I I I I fi I
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
25
0'... B
20 ""000.
15 ...o"'. .
0°70 '
1o 'OO'O' .
" 7 7
.0 ------ 11“,, - 2.02110 , 11.4r - 2.020107
5 y —11,_.,-1.01110, 11“,: 1.01110
— 11._,, - 0.5011107, 11Mr - 0.5011107
0" ' I ' 1 ' I ' I ' I ' j '
0.00 0.01 0.02 0.03 0.04 0.05 0.05 0.07
25
"""" C
20 """"
15 "..oooo
0°10
10 ....ee
' ------ 1‘2.» - 6.01110", 11,_,. - 1.01110"
5 — 11,_,, - 161110", 11,_,. - 2.01110"
—11,_,, - 321110 , 11,”, - 41.011107
0 1 ' 1 ' '— ' 1 ' U ' I 7 r V
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
[01M
l'igure 21: Stern-Volaer Plots of 5- (3-fle-4-AchO)VP at 313nm

in uethenol (oAP observed;

B. ks»r and ka_,

A. 11”” and had; varied,

varied, C. k and k varied)
1' {-98 I43

65

 

 

 

 

 

  
  
 
 
 

 

 

 

    

 

 

 

a
‘ ........ A
7 ......... o
6 ,. ............
5 ...
«mo 4
3 ',0".'.'.
2 ' / ...... 11,_,. - 0.002711107, 11._,, - 0.02211107
' — 11H. - 0.0271110", 11._,, - 0.2211107
‘ — 11H, - 0.2711107, 11“,, - 2.211107
0 I I I I I T I I I I I
0.000 0.003 0.006 0.009 0.012 0.015 0.018
a
. ...... B
7" """"
‘ .".".
6- ......
s-
¢°l0 4"
3-
7 7
2d ------ 11“,, - 1.2x10 , kaqr - 1.21110
1 — 11H, - 0.6011107, 11“,, - 0.603110:
—k._.r - 0.301110 , 11“., - 0.302110
0 1 I I I I I I I I f I
0.000 0.003 0.006 0.009 0.012 0.015 0.018
3
C
7
6
5
¢°l¢ 4
3
7 7
2 ...... kt... - BQOXIO ' ktfi‘ - 1.01110
‘ — )1,_,. - 161110 , 11,_,. - 2.01110:
—x,_,, - 321110 . 11“. - 4.01110
0 I I ‘ 1 V U ' I ' ' 1
0.000 0.003 0.006 0.009 0.012 0.015 0.018
[011M

figure 22 :

Stern-Vain: Plots of 5-(3-Ie-4-(7-XeVa1)PhO)VP
at 313113 in Methanol (0119 observed; A. 11,_,a and 11.."

varied, B. 11$“,r and 11”,, varied, C. 11,45 and kr—n varied)

66

B. 1-3:-4-(2-fle-4-An)8t and l-Bz-‘-(o-Tl)8t

The photokinetics of 1-Bz-4-(2-Me-4-An)8t was studied in benzene
and methanol. Since this diketone contains essentially the same
chromophores as the 7b and S-diketones presented in the previous
section, most of the parameters are the same. The only parameters which
differ are the decays of the benzoyl and anti triplets. The decay of
the benzoyl triplet in benzene, 1/‘tr - 41.611107!”1 and k, - 3.93107s‘1, is
taken from the model ketone 5-oarbomethoxyvalerophenone.33 The decay in
methanol, 1/11r - 2.8x107s’1 and )1, - 2.3111073-1, was estimated‘by
nmltiplying the ljkr and kr values in benzene by 0.6 to account for the
reduction in reactivity caused by the switch to maethanol,.33'3‘2 The
decay of the anti triplet in benzene was calculated from the model
ketones 2—methylvalerophenone,22 p-methoxyvalerophenone,32 and 5-
carbomethoxyvalerophenone.32 The value of 3.011105s'1 for l/ta in
benzene was estimated by first dividing the 1/1 for 5-carbomethoxy-
valerophenone32 of 4.6311075'1 by 50 to account for the reduction in
reactivity due to the p-methoxy group, and then multiplying this
quotient by 0.3 to account for the reduction in reactivity caused by the
o-methyl groupz2 (i.e., 4.611107s’1 + 50 x 0.3 - 3.0x105s’1). The 1/1a
value in methanol is also assumed to be 3.0x105s’1.

The ET analysis of l-Bz-4-(2-Me-4-An)Bt was performed using only
the benzoyl type II quenching data. A quenching plot of anisoyl type II
product was not possible because of the low chemical yield. Rates of ET
for this diketone of km.o - 1221107s'1 and heme - 0.2211107s’1 were derived
in benzene. Figure 23 shows that the response of the nearly linear

benzoyl quenching plot to changes in the syn/anti interconversion and ET

 

 

67

rates is similar to 7-(3-Me-4-AcPhO)BP and 5-(3-Me-4-AcPhO)VP. The
quenching plot in methanol has a much more distinct steep initial slope
which reflects the lengthening of triplet lifetimes in the polar
solvent. The ET rates derived in methanol are kexo- 1811107s‘l and kendo
- 0.30x107s'1. Figure 24 shows that the quenching plot in methanol is
much less sensitive to changes in the syn/anti interconversion rates
than in benzene, but extremely sensitive to changes in the ET rates.
This behavior is similar to that of the 7— and 5-diketones.

The diketone l-Bz-4-(o-Tl)8t is simdlar to 1-Bz-4-(2-Me-4-An)Bt,
but differs in one respect; the o-methyl chromophore has no 4-methoxy
group. Because of this structural difference, most of the parameters
governing the photokinetics of this system are different. The following
triplet populations, decays, and rate constants are based on the model
ketone 2-methylvalerophenone.3"2 The anti-)syn interconversion rate
constant, qum, is assumed to be 3x107s“1. The populations of syn and
anti in benzene and methanol, which are taken from the the model ketone
Z-methylvalerophenone22 in benzene and t-butanol, are the same as those
previously given for the 3-methy1—4-alkanoy1phenoxy chromophore. A
ksqa value of 0.80111073'1 was calculated from ka-Is and the populations
of each conformer (Equation 23). Decay of the syn triplet by photo-
enolization, 1/1,, is .‘111109s’1 in benzene and 1:1109s"1 in methanol. The
anti triplet decay in benzene, 1/1:a - 1.4x107s’1, was derived from.the
model ketones 2-methylvalerophenone22 and S-carbomethoxyvalerophenone.32
This was estimated by multiplying the 1/1 for 8-carbomethoxyvalero-
phenone32 of 4.611107s’1 by 0.3 to account for the reduction in

reactivity due to the presence of the o-methyl group.22 The anti

68

triplet decay in methanol, 1/1a - 0.28x107s'1, was estimated by dividing
the 1/1:a value of 1.41110'75’1 in benzene by 5 to account for the
reduction in reactivity caused by the switch to methanol.32

The light fractions absorbed by the benzoyl, syn, and anti chromo-
phores are 5, - 0.36, Bs - 0.26, and Ba - 0.13 in benzene and Br - 0.33,
B; - 0.31, and Ba - 0.074 in methanol. These values were calculated
from the extinction coefficients of 2-methylvalerophenone and valero-
phenone and from the same populations of syn and anti used for the 3-
methyl-4-a1kanophenoxy chromophore (see Equations 19-22). The decay and
type II rate constant of the benzoyl triplet are the same as 1-Bz—4-(2-
Me-4-An)Bt.

Type II product in this diketone can be generated from both the
benzoyl and toluoyl ends of the molecule, however, the ET analysis is
based only on the benzoyl type II for the same reasons as 15(3-Me-4-(7-
MeVa1)PhO)BP and 5-(3-Me-4-(1IMeVal)PhO)VP. The ET values derived are

k - 20111073'1 and kendo - 1.0211075‘1 in benzene and Item - 11x107s'1 and

8)“)
kendo - 0.5021107s’1 in methanol. Figures 25 and 26 show that the
quenching plots are relatively insensitive to changes in the syn/anti
interconversion and endothermic ET rates, but very sensitive to changes
in the exothermdc ET rate. The Stern-Volmer plots of type II quenching

from the toluoyl end of the molecule in benzene and methanol are shown

in Figure 27.

0°11!)

0°l¢

¢°l¢

Figure 23 :

69

 

   
   
   

 

 

 

 

 

 

 

 

 

 

 

6
. ........ a
5.
4.:
an .......
2‘ ...... 7 7
........ )1._,. - 0.0051110 , 11H, - 0.321110
1 — 11H. - 0.171110", 11“, - 0.541110"
_ 11Ha - 0.3411107, 11“. - 1.311107
01 V I ' I 1 I ' I '
0.00 0.02 0.04 0.06 0.08 0.10
5
. ....... B
5- ,,,,,,,,,
4- ..........
3-
2" 7 7
...... 11H, - 0.441110 , 11H, - 0.441110
1 — 11“, = 0.2211107, 11“, - 0.2211107
_11,_,, - 0.111110 , 11Mir - 0.111110"
0 I i I ' I 1 I 1 j 1
0.00 0.02 0.04 0.06 0.08 0.10
6 ',e'
. ....... c
5.. ........
4-
3.:
2.: 7 7
...... 11,_,, - 4.01110 , k1.“ - 1.31110
1 — 11,_,. - 9.51110 , 11,_,. .. 2.51110"
_x,_,, - 1911107. 11“. - 5.011107
0 I 7 I T j Y I ' I '
0.00 0.02 0.04 0.06 0.08 0.10
[01M
Stern-Velmr Plots of I-Bz-l- (2-ue-4-An) at

at 31321:: in Benzene (0111? observed; A. )1,_,‘I and 11,43

varied, B. 11...”. and 11”,, varied, C. k,_,s and kr_,a varied)

H

I
i

0°l0

¢°l¢

¢°l<b

'70

 

   
   
   

 

 

 

 

 

 

 

 

 

 

 

 

12
........ A
10 1
8-1
5- .......
4" 7 7
...... x“, - 0.00271110 , 11H, - 0.0221110
2 11“, - 0.02711107, )1“, - 0.2211107
— 11._,. - 0.271110", k._,, - 2.21110"
of I I I I I I I I I
0.00 0.02 0.04 0.06 0.08 0.10
12 .I
4 B
10 "
8-
q
6-
4' 7 7
...... 11HIr - 0.501110 . 11H, - 0.501110
2.. — )1Hr - 0.3011107, 11Hr - 0.3011107
—k...1 - 0.1511107, 11“, - 0.1511107
0T w I ‘ I ' I Y I '
0.00 0.02 0.04 0.05 0.08 0.10
12 .-
. , ,,,,, c
10 "
8-
W
6‘
4' 7 7
...... 11,4, - 5.01110 , 11,4. - 1.01110
2. — 11H, - 151110", 11,_,, - 2.011107
_11,_,, - 321110 . 11,_,, - 1.01110"
0 r I I I I I I I I I
0.00 0.02 0.04 0.06 0.08 0.10

[OI-M

”our. 24: stern-Vein: Plots of i-az-I—(z-ue-4-An)st

at 313m in uethanol (oAP observed; A. k,_,a and Rags

varied, B. 11”" and 11,4, varied, C. k,_,s and RPM varied)

0V0

¢°l0

(If/d)

Figure 25 :

71

 

  
 
   
 
   
 

 

 

 

 

 

 

 

 

 

 

 

5
....... A
4-1 .............
3-1 ...........
2d
----- 7 7
......... 11,_,. - 0.051110 , 11H, - 0.301110
1 — 11,4. - 0.501107, )1._,. - 3.01110"
_ 11H, - 5.011107, “1.11 - 3011107
0 T v 1 I y y I I I I I I I I I
0.00 0.03 0.06 0.09 0.12 0.15
5
......... B
4- ...........
5- ..........
2-1 ..........
...... 11,_,, - 2.011107. 11“, - 2.01110"
1 —— 11,_,, - 1.011107, “1...: - 1.011107
—-k....1 - 0.511107, “1.1: - 0.511107
0 1 I I ‘ I I I I I I I I I I I
0.00 0.03 0.06 0.09 0.12 0.15
5 ..-
''''' C
4- """""""
3.
2.:
------ 11,4. - 5.011107. 11,_,. - 2.211107
1 — 11,4. - 1511107, 11,_,, - 4.311107
—11,_,, - 321110 , k,_,, - 5.51110"
0 I ‘ j j 1 t 1 V ' I ' v I ' U
0.00 0.03 0.06 0.09 0.12 0.15
[01M

Stern-Volur Plots of l-Ez-l-(o-Tl)8t at 3132115
in Benzene (oAP observed:

8. l1,_,r and 1134: varied, C. kr_,s and kr_,a varied)

A. 118m,a and ka-os varied,

0°l¢

0V0

(”/0

Figure 2 6 :

72

 

   
 

 

 

 

 

   

 

 

 

 

   

 

 

 

6 .
1 ------- 1.
5-
4-1
3' fl
2- ...... ., ,
------------ 11.... - 0.0074x10 . k._,. - 0.0501110
1 ' — 11,_,. - 0.07411107, )1“, - 0.511107
_ “1.11 - 0.741110", 11“, - 5.011107
0 1 I I fl I I I I ' I I I I I I I I
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
6 ‘
0‘... B
51
4.
3.:
2 ‘ ....... 7 7
............ 11...: - 1.01110 . 11H, - 1.01110
1 " _11.5_,, - 0.5011107, 11,_,, - 0.5011107
_11,_., - 0.2511107. k1.“ - 0.251110"
0 I I I I I I I I I I i I I I I I
0.00 0.01 0.02 0.03 0.04 0.05 0.05 0.07 0.08
6 'or
. ..... c
57
4.
31
2' 7 7
...... 11,4, - 5.01110 , 11,_,. - 0.501110
1 — 11,4, - 1011107, )1,_,. - 1.21110"
—)1,_,, - 201110 , k2..- - 2.411107
0 I I I I I I I I I I I I i I r I
0.00 0.01 0.02 0.03 0.04 0.05 0.05 0.07 0.03
[01.35

in Methanol
B. l1,_,r and kw,r varied, C. 111.4, and RP” varied)

(e AP observed:

Stern-Volta": Plots of l-Bz-C-(o-Tl)3t at 313nm
A. )1,_,a and )1...” varied,

73

 

 

 

 

 

 

 

7
A
6
5
4
0°10
3 O
2
1 .
O 1 I I I I I
0.00 0.05 0.10 0.15
[01M
8
O B
0°l¢
0.08

 

[01M

Figure 27: Stern-Valuer Plot. of 1-8:-4-(o-1‘1)Bt at. 313nm
(oAP observed,- 0 2-MeAP observed,- A. in benzene, B. in

methanol)

74

C. The Benzoyl-(l-benzoylphenoxy) Diketones

These diketones, which include y—(d-BzPhO)BP, 1-(3-Me-4-BzPhO)BP,
5-(4—BzPhO)VP, and 5-(3-Me-4-BzPhO)VP, were studied to measure the
effect of increasing the interchromophore energy gap on ET rates. The
parameters used in the ET analysis for the p-benzoylphenoxy chromophore
are based on the model ketones 4-MeOBzP, 4-Me-2-MeOBzP, and 4-Me-2'-
MeOBzP.

For 1-(4-BzPhO)BP, the benzoyl type II rate constants in benzene
and methanol are the same as in 1—(3-Me-4-AcPhO)BP. The light fractions
absorbed by the benzoyl and p-benzoylphenoxy chromophores (Br and Bu)
were calculated from the extinction coefficients of the model ketones
valerophenone and 4-methoxybenzophenone (see Table 4 and Equations 8 and
9). In benzene, the light fractions are 3, - 0.056 and Bu - 0.94 at
313nm, and fir - 0.033 and Bu - 0.97 at 366nm. In methanol, the light
fractions are B, - 0.0165 and an - 0.983 at 313nm, and B, - 0.0253 and 1311
= 0.975 at 366nm. The decays of the p-benzoylphenoxy triplet in the
absence of endothermic ET, l/Iu, are assumed to be the 1/1 values
measured for benzophenone; 3x1055‘1 in benzene and 1x1053'1 in
methanol.‘1

The ET values derived for y-(4-BzPhO)BP in benzene are kaxo -
40x107s’1 and kendo" 0.10x107s'1. Figure 28 shows the benzoyl quenching
plots obtained in benzene at 313 and 366nm. The large difference in the
decays of the two triplets is manifested in the curvature of the 313nm
plot. At low quencher concentrations, ET occurs faster than any decay
process and the slope reflects the long lived p-benzoylphenoxy triplet.

However, at higher quencher concentrations, quenching of the p-benzoyl-

 

75

phenoxy triplet competes with endothermic ET and the slope reflects the
decay of the shorter lived benzoyl plus the additional decay of
exothermic ET. In the 366nm plot, the high quenching slope is similar
to the initial slope of the 313nm plot. This is due to the fact that at
366nm, the p-benzoylphenoxy chromophore absorbs nearly all of the light
and the process which dictates the quenching behavior is endothermic ET.
This plot must contain a low slope component at higher quencher concen-
trations which exists well outside of our experimental window.

The diketone 7-(3-Me-4-BzPhO)BP has basically the same two chromo-
phores as the previous system, however, the added o-methyl group on the
phenoxy ring of the p-benzoylphenoxy means that both syn and anti
conformers exist. The 1/1r and RI for the benzoyl chromophore are the
same as in y—(d-BzPhO)BP. The light fractions absorbed by the benzoyl,
syn, and anti chromophores are based on the model ketones VP, 4-MeO-2-
MeBzP, 2-methylbenzophenone, and on a syn/anti ratio of 62/383‘ (see
Equations 19-22). These are 3, - 0.035, BS - 0.60, and Ba - 0.37 in
benzene and Br - 0.021, BS - 0.61, and Ba - 0.37 in methanol. The rate
constants for anti-+syn interconversion, ktqm, are 2.0x107s'1 in benzene
and 0.6'7x10"s'1 in methanol. The rate constant for syn-oanti inter-
conversion, krfim, is l.2x10"s'1 in benzene and 0.40x107s“1 in methanol.
These values are calculated from Equation 23 and a syn/anti ratio of
62/38." Decay of the syn triplet by photoenolization, 1/1s - 6.0x109
s’l, is assumed to be the same as measured in 2-methylbenzophenone.3‘
Decays of the anti conformer, l/ta, are assumed to be the same as l/tu
in y—(4-BzPhO)BP; 1/1a - 3.0x105s'1 in benzene and 1.01:105s'1 in

methanol.

 

76

The ET rates derived for 7-(3-Me-4-BzPhO)BP in benzene are kéxo =
44x107s’1 and kendo" 0.050x107 s'l. Figure 29 shows that the quenching
curve is nearly linear with just a small steep initial slope component.
The curve is fairly sensitive to changes in the syn/anti interconversion
and endothermic ET rates and very sensitive to changes in the exothermic
ET rate. The lack of any significant steep initial slope indicates that
endothermic ET does not compete with decay of the p-benzoylphenoxy
triplet introduced by the o-methyl (law,s and llrs).

In the diketones 5-(4-BzPhO)VP and 8-(3-Me-4-BzPhO)VP, the alkyl
tether is one methylene longer than in the previous two Vbdiketones.
Most of the ET parameters which fit the ybdiketones apply to these two,
except for l/‘tr and RI of the benzoyl triplet which are the same as in
8-(3-Me-4-AcPhO)VP. The ET values derived for 5-(4-BzPhO)VP in benzene
are kexo - 20x107s"1 and kéndo" 0.050x107s'1. Figure 30 shows the
benzoyl quenching plots obtained in benzene. The quenching behavior is
similar to 1-(4-BzPhO)BP; the dual-sloped 313nm curve has a steep
initial slope which is roughly equivalent to the slope of the 366nm
curve. The ET values derived for 5-(3-Me-4-BzPhO)VP in benzene are kexo
- 21x107s’1 and,k‘ndoz- 0.10x107s'1. Figure 31 shows that the benzoyl
quenching curve obtained in benzene is similar to that of y-(3-Me-4-
BzPhO)BP with a small degree of steep initial slope. The curve also
repsonds similarly to changes in the syn/anti interconversion and ET
rates.

In methanol, the ET rates derived for 1-(4-BzPhO)BP are kexo -
410x107s"1 and kendo" 0.10x107s'1. Figure 32 shows that the benzoyl

quenching curves at 313 and 366nm are identical. For y-(B-Me-4-BzPhO)BP

 

77
in methanol, ET rates of kexo - 47x107s'1 and.kéndol- 0.10x107s’1 are
derived. Figure 33 shows the dual-sloped quenching plot which is very
sensitive to changes in syn/anti interconversion and ET rates.

The ET rates derived for 5—(4-BzPhO)VP in methanol are kexo -
20x107s‘1 and kendo - 0.050x107s'1. Figure 34 shows that the benzoyl
quenching curves at 313 and 366nm have similar, but not identical
slopes. As was the case with y—(4-BzPhO)BP, the switch to methanol
greatly alters the shape and slope of the quenching curve by reducing
benzoyl decay to the point where endothermic ET determines the photo-
kinetic behavior. For 8-(3-Me-4-BzPhO)VP in methanol, ET rates of kexo
- 37111073'1 andkendo - 0.10111073"1 are derived. Figure 35 shows that
the benzoyl quenching curve has a steep initial slope component which is
much more pronounced than in benzene. Once again, the switch to

methanol has allowed endothermic ET to become competitive with benzoyl

type II decay.

 

78

121

 

 

 

 

V

*T

1 I I
0.02 0.03 0.04

[OI-M

Figure 28: Stern-Volume: Plots of 7-(4-EzPhO) EP in Benzene
(0 AP observed at 366nm; oAP observed at 313nm:
km“, - 410x107s"1 and kendo - 0.10x107s’1)

 

79

 

    

 

 

 

  
   

 

 

 

  
 

 

 

 

1o 7 .....
9 """ e A
8
7
6
090 5
4
3 ------ x,_,. - 0.6011107, 11“, - 1.011107
2 — x,_,. - 1.211107, )1“. - 2.011107
1 — k1... - 2.41110 , k“, - 4.011107
0 r I I I I I I fi I I I
0.0 0.1 0.2 0.3 0.4 0.5 0.6
10 ...-I
9 " e B
0
7
6
090 5
4
3 ------ 11H, - 0.1011107, 11._,, - 0.1011107
2 — )1“, - 0.05011107, )1“, - 0.0501110"
1 —- x,_,, - 0.02511107, )1“, - 0.0251110"
0 I I I I I I I I I I I
0.0 0.1 0.2 0.3 0.4 0.5 0.6
10
9 7 e C
8
7
6
¢°I0 5
4
3 ------ 11H. - 141110", )1,_,. - 0.51110"
2 )1,_,. - 2711107, k,_,. - 1711107
1 — 11,4, - 541110 , k,_,, - 3411107
0 I I I I I I I r I I I
0.0 0.1 0.2 0.3 0.4 0.5 0.5

Figure 2 9 :

[OI-M

ltern-Vol-er Plots of 7-(3-ue-4-BzPhO)BP at 313nm
in Benzene (uAP observed: A. lt,,_m and 11.43 varied,

B. k._,r and kaqr varied, C. kr_,s and Rh” varied)

 

80

 

 

0 j ' I
0.000 0.002

V V 1 V

I I
0.006 0.008

[011M

1 I
0.004 0.010

Figure 30: Btern-Volner Plots of 8-(4-BzPhO)VP in Benzene

(0 AP observed at 366nm; oAP observed at 313m:

11“., - 20111075'1 and xendo - 0.05111073'1)

 

Obie I“

 

81

 

 

 

 

 

 

 

 

 

 

11 .7
1o A
9 -----
a
6 .o'”.
0°10 S
3 ------ 11H, - 0.601110", )1“, - 1.011107
2 “.1" — x,_,, - 1.21110 , 11H, - 11.011107
1 — 11,_,. - 2.41110 . 11H, - 4.01110"
0T I I I f I I I I I
0.00 0 05 0.10 0.15 0.20 0.25
11 ' ..-
1o .. ..... -' s
9
a """
o 6 O '''' .
0/0 5 .-
4
3 " ------ 11H, - 0.2011107. 11“, - 0.2011107
2 —— 11H, - 0.101110 , “1.1: - 0.1011107
1 — 11H, - 0.05011107, )1“, - 0.0501110"
0 T I I I I I I I I I
0.00 0.05 0.10 0.15 0.20 0.25
11 7 ,.
1o C
9
a 00"...
6 ..I”
0°10 5
4
a ------ x,_,. - 5.51110", 11,_,, - 4.01110"
2 " — 11H, - 1311107, 11“, - 13.011107
1 — 11,_,, - 26x10 , 11,_,. - 161110"
0 I ' fl ' I V I V I '
0.00 0.05 0.10 0.15 0.20 0.25
[OLM
figure 31: Stern-Vol“: Plots of 6-(3-ue-4-BzPhOHrP at 313nm

in Benzene (oAP observed: A. 11,.” and kaqs varied,

E. k,_,r and 11”,, varied, C. qus and qua varied)

'"fl-Lfl.

82

20'

 

 

 

T

1 i

0.002 0.003 0,004

[01M

1
0.000 0001

Figure 32: Stern-Voller Plots of 1—(4-EzPhO)BP in Hethanol
(o AP observed at 366nm,- oAP observed at 313nm:

kexo ' 4031078.1 and kendo .1 0.10x107s'1)

 

 

83

 

 

 

 

 

 

 

  

 

 

 

10 ......
9 ........... A
a ..........
7 .. .........
a
0°10 S ..o""
4 ’1‘
3 0:" ------ 11,_,. - 0.2011107, *9-1: - 0.3411107
2 — 11,_,. - 0.401110", 11“, - 0.571110"
1 — 11H, - 0.801110". 11“, - 1.311107
0 I I I I I I I I I I I I I
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
10
9 . ........ B
a ........
7 g .....
5
0°10 5
4 '
3 ------ 11,_,, - 0.201110", 11._,, - 0.201110"
2 - — 11Hr - 0.101110", 11“, - 0.1011107
1 — )1,_,, - 0.05011107, )1“, - 0.0501110"
0 I I I I I j I I I I I I I
0.00 0.02 0.04 0.06 0.08 0.10 0.121 0.14
10
9 C
8
7
6
0°10 5
4
3 ------ 11,_,. - 1511107, 11,_,, - 9.011107
2 — 11,_,. - 291110 , x,_,. - 1911107
1 — 11,4, - 591110 , 11,_,, - 351110"
0 T j j I v I j I ' I ' I '
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
[011M

Figure 33 :

Stern-Voller Plots of y-(3-lh-4-BzPhMBP at 313nm
in lethenol (oAP observed; A. 10"."I and he.” varied,

B. k,_,r and had, varied, C. k,_,s and k,_,a varied)

 

84

 

 

 

I _ I
0.0000 0.0005 0.0010 0.0015

Figure 34: 8tern-Volner Plots of 8-(4-BzPhO)VP in Methanol
(0 AP observed at 366nm; oAP observed at 313nm:

 

M111. - 20111075’1 and kendo - 0.050111073'1)

-"° he}. 1“ v‘ '

 

“‘1 ‘3-«

85

 

 

 

 

   
    

 

 

 

 

 

 

 

 

7 .'
..... A
5 ...... '
0°/0
3
2 ------ 11,_,. - 0.201110", 11,_,, - 0.3111107
7
‘ — 1th.. - 0.4011107, Rh“ - 0.673110
— 11,_,, - 0.901110 , k1.» - 1.31110
0 I I I I I I I I I I I I I I
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
7 ..0'
. B
6.1
5-
4-
0°l0
3.1
2- ------ 11H, - 0.2011107, 11.__,, - 0.2011107
1 -— 11H, - 0.101110",7 11H, - 0.101110" 7
— 11H, - 0.0501110 , 11H, - 0.0501110
o I ' I ' I j I 1 I ' T j j '
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
7
C
6
5
4
0°l0
3
2 ...... k2.» - 1211107. 11,_,. - 7.01110"
1 — x,_,. - 2311107, 11,_,. - 141110:
— kt”. " 46810 , kF—a " 28X10
o I ' I I I V I I I ' I 1 I fl
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
[011M

Figure 35: Stern-Voller Plots of 5-(3-Ile-4-EzPhOHtP at 313nm
in Methanol (9AP observed; A. RF“ and Rh” varied,

B. It”, and hr” varied, C. kt_,s and kr_, varied)

I a

86

D. The Benzoyl-(2'-nethyl-l-benzoylphenozy) Diketones

These four diketones, 5-(2'-Me-4-BzPhO)VP, e-(2'-Me-4-BzPhO)HxP, (-
(2'-Me-4-BzPhO)apP, and n-(2'-Me-4-BzPhO)OtP, were studied to measure
the effect on ET of lengthening the alkyl tether from four to seven
methylenes. These are very similar to the preceding benzoyl-(B-methyl-
4-benzoylphenoxy) diketones, the only difference being the length of the
tether and placement of the o-methyl group on the 4-benzoylphenoxy
chromophore.‘ In 7-(3-Me-4-BzPhO)BP and 8—(3-Me-4-BzPhO)VP, the o-methyl
is on the phenoxy ring, but in the these four systems it is on the other
ring.

For 8-(2°-Me-4-szpr10)VP, e-(2'-Me-4-szpn0)éxp, c-(z'-Me-4-szph0)app,
and n-(2'-Me-4-BzPhO)OtP, the light fractions of the benzoyl, syn, and
anti in benzene are 5, - 0.12, BS - 0.55, and Ba - 0.33. These are based
on the model ketones VP and 4-MeO-2'-MeBzP. The values of kmqs, keaa'
l/ta, and 1/1:s were the same as for 7-(3-Me-4-BzPhO)BP and 5-(3-Me-4-
BzPhO)VP. The benzoyl decays and type II rate constants for the these
diketones were measured from the models 5-(CNPhO)VP, e-(CNPhO)HxP, (-
(CNPhO)HpP, and n-(CNPhO)OtP and are listed in Table 7.

Figures 36-39 show that the quenching plots of the four diketones
are linear. The 1111' rates derived for 5-(2'-Me-4-BzPhO)VP, e-(2'-Me-4-
BzPhOHixP, C-(2'-Me-4-szphompp, and 11-(2'-Me-4-BzPhO)OtP are km, -
21111075-1 and 11,mdo - 0.10111073-1, 11m, - 21111075-1 and hem - 0.10111075-1,
kexo - 211x107s’1 and kendo - 0.50x107s’1, k9,“, - 24x107s"1 and kendo -
0.050x107s'1, respectively. All of the quenching plots display little
sensitivity to an increase in the syn/anti interconversion rate, but

greater sensitivity to a decrease in this rate. The plots also all show

 

87

little sensitivity to a decrease in the endothermic ET rate, but greater
sensitivity to an increase in this rate. The fact that all quenching
plots are very sensitive to changes in kpes and kpfia indicates that

exothermic ET is an important contributor to the benzoyl decay in all

four diketones.

 

 

88

 

    
   
   

 

 

 

 

 

 

 

 

10
9 A
8
7
6
0°10 5
4
3 ------ x._,. - 0.3011107, 11“, - 0.5011107
2 — 11H. - 1.21110 . 11._,. - 2.01110"
1 —11,__,, - 4.51110 , 11H, - 9.01110"
OI I 1 V I ' 1 t I 1 I '
0.00 0.05 0.10 0.15 0.20 0.25 0.30
10 ’
9 a
8
7
6
0°10 S
4
3 ...... 11,_,, - 0.2011107, 11“, - 0.2011107
2 —— “3.1: - 0.1011107, 11.4, - 0.1011107
1 — 11,_,, - 0.05011107, )1“, - 0.0501110"
o I I I ‘ I 1 I j I 1 I 1
0.00 0.05 0.10 0.15 0.20 0.25 0.30
10 ’
9 C
8
7
6
0°l0 5
4
3 ...... 11,4. - 5.511107. 11“. - 41.011107
2 —— 11,_,, - 1311107, 11,_,. - 9.011107
1 — 11H, - 251110 , 11,_,. - 151110"
0 1 i I I I ' I r I j 1 '
0.00 0.05 0.10 0.15 0.20 0.25 0.30

[01M

Figure 36: 8tern-Volner Plots of 8-(2'-ue-4-IzPhO)VP at 313nm
in Eenzene (oAP observed; A. 15",. and Rh” varied,

B. k._,r and had, varied, C. RF” and k?” varied)

 

0°10

0°10

0°10

89

 

 

   

 

 

 

 

  

 

 

 

 

  
  

 

 

6 _,
. ....... A
5- .........
4- .........
3-1
2" "' 7 7
------ k1... - 0.31110 . 11._,, - 0.51110
1 — 11H. - 1.21110 , 11._,. - 2.011107
—11,_,. - 4.91110 . 11H, - 9.011107
0 1 f T 1 I I I v
0.00 0.05 0.10 0.15 0.20
6
. . s
5- .........
4- .........
3- .........
2" ........ 7 7
------------ 11H, - 0.201110 . 11H, - 0.201110
1 — 11H, - 0.1011107, 11“, - 0.1011107
—x,_,, - 0.05011107, )1“, - 0.05011107
0 T T I I j I j f
0.00 0.05 0.10 0.15 0.20
6 ,.- '
e ..e"' C
5? ..... '7
4.1 ' """"""
3-
2. '7 7
...... qu' - 6.5810 ' qu‘ - 4.07010
1 — k,_,, - 1311107. 11,_,. - 9.011107
-—11,_,, - 251110", 11,4 - 151110"
0 I I I ' I j I '
0.00 0.05 0.10 0.15 0.20
[011M

Figure 37: Stern-Voila: Plots of e- (2'-lle-4-BzPhO) nzP

at 31311111 in Benzene (oAP observed: A. k,_,a and k._”
varied, E. k,_,r and kaqr varied, C. kt”, and k?" varied)

0°/0

0°/0

0°l0

Figure 38 :

9O

 

   
   
   
 

 

 

 

 

 

 

 

 

 

 

5
A
1 .......
4- ..........
3'1 . ......
2-
------ 11,_,. - 0.3011107. 11“. - 0.5011107
1 — 11H. - 1.21110 , 11H, - 2.011107
— k1... - 4.91110 , 11H, - 9.011107
01 I I I I I I I
0.00 0.05 0.10 0.15 0.20
5
‘ B
41 ............
31 ............
2- ............
,,,,,, 7 7
--------- 11._,Jr - 0.101110 . 11._,, - 0.101110
1 — 11H, - 0.05011107, )1“, - 0.05011107
—11,_,, - 0.02511107, 11Hr - 0.0251110"
o I ' I ' I 1 I '
0.00 0.05 0.10 0.15
5
1 ........ c
4- ........ '
3" .........
2-1
- 7.511107, 11,_,, - 4.511107
1 11,_,, - 1511107. 11,_,. - 9.01110"
—11,_,, - 301110", 11,_,, - 191110"
0 I I I ' I ' I '
0.00 0.05 0.10 0.15 0.20
[011M
Stern-Volner Plots of C- (2 ' -ue-4-BzPhO) BpP
at 313nm in Benzene (cAP observed; A. k,_,a and ka-n

varied, 8. RF” and k?” varied, C. RP” and k?” varied)

 

 

0.20

0‘70

¢>°/¢

0°l¢

riqure 39:

91

 

   
  

 

 

 

   
   

 

 

 

 

 

8
A
7
6
5
4
3
7 7
2 ------ 11H, - 0.121110 , 11H, - 0.21110
—— 11,_,,l - 1.21110 , 11H. - 2.01110
1 — 11H. - 121110 . 11H, - 201110"
0 I ‘ I 1 I V t ' j V
0.0 0.1 0.2 0.3 0.4 0.5
3
B
7
6 .........
5 ........
4 ....... .
3
7 '7
2 ------ 11H, - 0.101110 .7 11M, - 0.101110 7
— 11H, - 0.0501110 , 11H, - 0.0501110
1 —11‘_,1r - 0.0251110". 11“, - 0.0251110"
0 j ' I ' I ' I ' I '
0.0 0.1 0.2 0.3 0.4 0.5
8 _
C
7
6
5
4
3
7 7
2 ...... krfi. - 7.5X13 ' ktd. - 0.5X12
— k1..- - 151110 . 11H. - 9.01110
‘ —11,_,. - 3011107. 11“. - 101110"
0 I ' T f I ' I V I '
0.0 0.1 0.2 0.3 0.4 0.5
[01M

Stern-Valuer Plots of n-(Z'dle-l-Brvhmou’
at 313nm 1n Benzene (oAP observed; A. h... and k._,,
varied, B. k,_,r and 11”,, varied, C. qus and qua varied)

92

2. Related Diketones Studied by 8.17. Frerking and B.P. Giri

Curve-fitting analyses were also applied to quenching data acquired
by H.W. Frerking‘z and B.P. Giriz‘ on a number of diketones related to
the diketones covered in the preceding sections. The structures of
their diketones are presented in Figure 40.

Frerking studied the photokinetics in benzene of diketones similar
to the benzoyl-(3-methyl-4-alkanoylphenoxy), but without the o-methyl.
For 15(4-AcPhO)BP and 1-(4-ValPhO)BP, he derived ET rates of kexo" 12-
15x107s'1 and k‘ndOI- l-3x107s‘1. Figures 41 and 42 show the quenching
plots of type II reaction from both ends of the molecule for 7-(4-
ValPhO)BP and the analogous o-methyl diketone T-(3-Me-4-(15MeVal)PhO)BP,
respectively. For the longer tethered diketones, 8-(4-AcPhO)VP and 8-
(4-ValPhO)VP, Frerking derived ET rates of Item - lO-l.‘3:~c10"s'1 and kendo -
1-3x107s’1. Figures 43 and 44 show the quenching plots of type II
reaction from both ends of the molecule for 5-(4-ValPhO)VP and the
analogous o-methyl diketone 6—(3-Me-4—(15MeVal)PhO)VP, respectively.
The quenching plots of type II reaction from the anisoyl end of both the
1— and 8-diketones have higher slopes than the quenching plots of the
benzoyl. In methanol, the anisoyl quenching plots for 1-(3-Me-4—(y—
MeVal)Ph0)BP and 5-(3-Me-4-11HMeVal)PhO)VP exhibit upward curvature, as
shown in Figures 45 and 46.

The diketones studied by B.P. Giri were 7-(4-BzPh)BP, 75(2'-Me-4-
BzPh)BP, 8-(4-BzPh)VP, and 5-(2'-Me-4-BzPh)VP. These are similar to the
benzoyl-(4-benzoylphenoxy) diketones, but have no oxygen at the end of
the alkyl tether. The photokinetic behavior of these diketones is

similar to that of the benzoyl-(4-benzoylphenoxy) diketones. Figures 47

93

and 48 show that the quenching plots of 7—(4-BzPh)BP and 8-(4-BzPh)VP at
313nm in benzene have a steep initial slope and a low final slope. The
quenching plots at >340nm are linear with slopes similar to the initial
slopes of the 313nm plots. The ET rates derived for 7—(4-BzPh)BP are

11 - 97111075'1 and )1endo - 0.20111073-1- The 131' rates derived for 6-(4-

exo
BzPh)VP are kexo - 4182:1073’1 and kendo - 0.10x107s'1.

For 7-(2'-Me-4-BzPh)BP and 5-(2'-Me-4-BzPh)VP, the quenching plots
are linear. The absence of any steep initial slope is due to the o-
methyl on the 4-benzoylphenyl chromophore which, as in the benzoyl-(3-
methyl-4-benzoylphenoxy) diketones, makes endothermic ET noncompetitive
with the rapid photoenolization decay. The ET rates derived for 7-(2'-
Me-d-BzPh)BP are 11am - 971110711:1 and kendo - 0.20111073'1. Figure 49
shows that the quenching curve is fairly insensitive to changes in the
syn/anti interconversion and endothermic ET rates, but very sensitive to
changes in the exothermic ET rate. The ET rates derived for 5-(2'-Me-4-
BzPh)VP are kexo - 48111073’1 and kendo - 0.10x107s'1. Figure 50 shows

that the quenching curve responds similarly to 7-(2'-Me-4-BzPh)BP toward

variations in the syn/anti interconversion and ET rates.

[fend

‘y-(4-AcPh0)BP

y-(4-acetylphenoxy)butyrophenone
H.F. Frerking

O

o
WO—G/k
8-(4-AcPhO)VP

5-(4-acctylphcnoxy)valcmphenone
H.F. Frerking

O

o
O C
0
744.32%)”

H4-benzoylphenyl)butyrophcnone
B.P. Giri

O
O
, 0 O
Q
8-(4-BzPh)VP

8—(4-benzoylphenyl)valaophcnonc
B.P. Giri

94

o
O W
©xuxA/O
'y-(4-ValPhO)BP

7.(4-valerylphenoxy)butyrophcnone
HF. Frerking

O
O
Wo—O/lk/v
5-(4-ValPhO)VP

5—(4-valerylphcnoxy)valaophenone
B.P. Frerking

o
o
0 o
0
“roam-4.321111)”

y-(2'-methyl-4-benzoylphenyl)butyr0phcnone
B.P. Giri

 

8-(2'-Me-4-BzPh)VP
8-(2'-mcd|yl-4-benzoylphcnyl)valemptmone
B.P. Giri

Figure 40: Diketones Studied by HJI. Frerking and B.P. Giri

95

 

0°l0

 

 

 

 

o 1 . . . . - . , 1
0.000 0.002

I I
0.006 0.008 0.010 0.012

[0].“!

I
0.004

Figure 61: Stern-Velmr Plot of y-(l-ValPhO)BP at 313nm

in Benzene (0 propene observed; ' an? observed)

 

¢°l¢

 

 

 

 

0.10

[01M

Figure 42: Stern-Volner Plot of 7-(3-Me-4-(y-ueVal)PhO) B? at
313nm in Benzene (0 1-(3-Me-4-AcPhO)BP observed,-
0119 observed)

96

 

 

 

15
10 c
we
0
5 o
0 f . r . 1 . a .
0.000 0.002 0.004 0.006 0.008
[01M

Figure 43: Stern-Volner Flot of 8-(4-ValPhO)VP at 313nm
in Benzene (O propene observed; 011? observed)

 

O°l¢

 

 

 

 

. .
0.03 0.04

I
0.02
[01M

l'igure 44: 8tern-Volner Plot of 8-(3-fle-d-(1-fleVal)PbO)VP at
313nm in Benzene (0 5-(3-Me-4-AcPhO)VP observed:
oAP observed)

97

 

20’

15

«we 10

 

 

1
0.00 0.01 0.02 0.03 0.04 0.05
[01M

Figure 45: Stern-Voller Plot of 'y-(3-ue-4-(y-ueVal)PhO)BP at
313nm in “ethanol (0 y-(3-Me-4-AcPhO)BP observed;
.13? observed)

 

so
40 4

30 1
WM) .

 

  

 

 

 

 

I I I
0.000 0.005 0.010 0.015 0.020

[01M

Figure 46: Stern-Volmr Plot of 5-(3-ue-4-(1-ueVal)PhO)VP at
313nm in Bethanol (O 8-(3-Me-4-AcPhO)VP observed:
oAP observed)

GPKD

Figure

dfflb

Figure

 

 

 

 

I I
002 003

[011M

I
001 004

47: Stern-Volur Plots of y-(l-BzPh)BP in Benzene

(0 AP observed at >340nm; oAP observed at 313nm;
k - 97111073"1 and k - 0.2031073'1)

exo endo

 

 

 

 

' —" V j j

0.002 0.003
[01M

0xm4

48: Stern-Velma: Plots of 5-(4-BzPh)VP in Benzene

(0 AP observed at >340nm; eAP observed at 313mm;
11 - 48x107s'1 and k - 0.10111073'1)

exo endo

99

 

   
   
   

 

 

 

 

 

 

 

 

 

 

 

 

6 ..O'
..... A
5-
4.:
0% 3.1
2" 7 7
------ 11._,, - 0.601110 , 11H, - 1.01110
1 -— )1,_,. - 1.21110". )1“, - 2.01110"
— 11H, - 2.41110 . 11H, - 4.01110"
0 I I 1 1 I I j 1 1 v
0.0 0.2 0.4 0.6 0.8 1.0
0 ?
B
5'!
4d
0‘70 3" """"""
2" """" 7 7
------ ks.» - 0.401110 , 11._,, - 0.401110
1 — 11H, - 0.201110". 11“, - 0.201110"
—— 11H, - 0.101110 , 11H, - 0.101110"
0.0 0.2 0.4 0.5 0.8 1.0
s o,
... C
54-:
4-1
¢°l¢ 3"
2" 7 7
------ 11,4. - 301110 . 11,_,. - 191110
1 11,_,. - 601110". 11,_,. - 371110"
— 11,_,, - 1201110", )1“, - 741110"
0 1 f I ' j ' I j I i
0.0 0.2 0.4 0.6 0.8 1.0

[011M

Figure 49: Btern-Volner Plots at 7- (2'-lle-4-Bsz)BP at 313nm
in Benzene (CAP observed; A. 11”,. and RP” varied,

B. k,_,r and 11“, varied, C. RP” and kn” varied)

lOO

 

   
   
   

 

 

 

 

 

 

 

 

 

 

 

 

 

4
A
4 ._.,
3.. .............
41°10 24 ...............
""""""" 7 7
1 ------ 11H, - 0.601110 , 11H, - 1.01110
-— )1Ha - 1.21110 . 11H, - 2.01110
— 11Ha - 2.41110 , 11H, - 4.01110"
0 I I I I I I I I
0.00 0.05 0.10 0 15 0.20
4
B
3.1 ..............
0‘74) 2" ............
"""""""""" 7 7
1 ...... ksqr ‘ 0.20X107, kaqr - 0.20X107
—— k3.“ = 0.101110 , Rad, - 0.101110
— 11H, - 0.0501110". 11“, - 0.0501110"
O T t 1 I r 1 1 1'
0.00 0.05 0.10 0.15 0.20
4 "r
..e". C
1 ----- "
3.1
¢°l¢ 2"
7 7
1 ...... krfl' - 15X10 ' krda - 9.0)(10
11,4, . 301110". kt-fl - 101110"
—— 11H, - 601110 . 11,4, - 361110"
01 i 1 r I ‘ I 1
0.00 0.05 0.10 0.15 0.20

[01M

Figure 50: Stern-Vohner Plots of 8-(2'-ue-4-BzPh)VP at 313nm
in Benzene (eAP observed,- A. kw” and kinds varied,

B. ksqr and k?” varied, C. kr_,s and qua varied)

100

 

   
   
  

 

 

 

4
A
3-
090 2"
""""""""""" 7 7
1 ....... kI—el - o'soxlo I kaq. ' 1.0X10
— 11Ha - 1.21110 , 11H, - 2.01110"
— )1,_,, - 2.41110 . k1.» - 4.01110"
oT . . . . r , .
0.00 0.05 0.10 0.15 0.20

 

&
Wfiw

 

0°ld> 2 "'

‘T-v-Lu 1'4““

 

 

.....
.....
e...
0‘.
.0
.0

7
------ )1“, -= 0.201110". k,_,, -= 0.201110

7 7
— 11H, - 0.101110 , 11H, - 0.101110

7 7
—— 11HJr - 0.0501110 . 11HJr - 0.0501110

 

 

 

0 T I I I I I I I
0.00 0.05 0.10 0.15 0.20
4 O. ......... C

0°10 2 "‘

 

...... kt”, - ISXIOZ' kr* - 9.0)‘137
11H. - 3011107, 11,4, - 1811107
- 601110 , 11“,, - 361110

 

— kt—p‘

 

‘ 1 T

I
0.00 0.05 0.10 0.15 0.20
[01M

Figure 50: 8tern-Volner Plots of 5-(2'-lle-4-BzPh)VP at 313nm
in Benzene (oAP observed; A. )c,_,a and Rags varied,

B. 168%: and ka—n varied, C. qus and qua varied)

101

Table 8: Photokinetic Data of Diketones Studied by Frerking
and Giri in Benzene at 313nm

 

 

Diketone d’n $11,113,, SV slope,M'1 AE,kcala
7-(4-AcPhO)BPb 0.29 0.53 510 2.3
7-(4-ValPhO)BPb 0.33 (82) 0.49 (82) 400 (82) 2.3
0.039 (An) 0.065 (An) 509 (An)
5-(4-AcPhO)VPb 0.34 ' 0.42 2031 (mo) 2.3
1196 (mi)
5-(4—ValPhO)VPb 0.21 (82) 0.31 (82) 1230 (1110,82) 2.3
567 (mf'BZ)
0.075 (An) 0.16 (An) 1743 (1110,1111)

Y‘M-szmspc 0.053 0.055 1835 (mo) 4.6
23 (mf)

(at >340nm) - - 1870
Y-(2'-Me-4-szh)spc 0.018 0.019 6 4.6
8-(4-szh1vpc 0.051 0.072 3070 (mo) 4.6

55 (mf)

(at >340nm) 0.051 0.052 4600
5‘(2'-Me-4-82Ph)VP° 0.017 0.029 12 4.6
\

 

b The interchromophore energy gap measured by phosphorescence of model ketones at 77°K.

C

H.w. Frerking data
B-"- 6111 data

102

so ...... 3 Beam .

 

 

 

 

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....n e .. ...... ...... .... a... .... ...... 2... ea... en... 886.. nu 5.56.11...
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... e e ...... 2 ... «a... n a «a... e... ...... an... «a... 9056.. 2 5.5.7.2-“.-75.

...... ...u a. ...... e ...... ..n en... en... 5.... 836.. ..n ..5..Emi»2-.~.e

...... e.« a. ea... ..N... .... en... an... S... 83.6.. 3 Leeanmiozéx

...... ...u a. ..n..... e8... 2 an... an... 2... 28.6.. en 3050:7623"...

...... ...a a. 91...... one... 2 an... an... N... 835m ..n eez.o.:£.voz-.~..u

...... a... ...u a. ...... ...... 2 an... an... N... 93.6.. ..n sagavozévu

...... z. ...u e. ...... ...... n. 2... we... 2... 888.. en magniozaz

...... .... S... ...... nee... 2e... 2 R... ...... .8... .655»: 2

...... .... ...u u. ...... ...... 2 ..n... ...... nae... 888.. .m 9.95miozée

e... e... S... ...... ...... ...... en ...”... S... .8... .655»: an

...... e... ..." «... ewe... ewe... a 2... ...... 3.... 88.6.. ea 3.9597630...
...... .... 2... 5.... ...... ...u ...... e. 2...... on... 2... .655»: 2

... .... 3.... ...... ...... ... ...... .... ...... 2... «u... 835.. 2 §.Q§=>ez¢voz.0e

... .... 3... ...... ...... .... ...... .... ...... «n... «a... 88.8.. 2 9.05.2130).
2... .... 2... 8e... .... ...N .... e. 3e... ...“... 2... .2256: S

... e... 3.... ...... en... .... en... .... ...... 2... «a... 835.. ... 96.82.762.01.
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... a... we... ...... en... 2 ea... 2 ...... an... an... 836.. 2 am.o§._.>oz¢e.oz.c+
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... a... 3.... ...... ..n... n... ea... 2 2... an... «a... 88.0.. I 3.223.139.
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7.5...

Human an euedmduh uaduueueuaH Genera flue! eoaoueflfln no Queues—INCA ..m OHQQH

63

10

 

 

 

 

Eamon Una

 

EH? 1 .. 1 n...
§.3.=333we
5......333...
w... we... .... .... ... we... ew... 665...... w.w we .1355;er
ee we... w.w ...w N. we... «w... 659.3. w.w .w we...o.:..>.w.e
...e ..w..... ...w ...... we we... we..... 95...... w.w w..
...e ..w..... e... ...... we we... we... 92...... w.w we 25.53.33
...... ..w..... .....e ..e... e we... we..... 6.656.. w.w ..w
...... ewe... .....e ee... ee 8... we... “55:... w.w 2. Eugene...
...... ...... .... ewe... 8 we... 2...... .2256: wee we
...... ...... .... ..e..... e. we... 2.... .6556: w.w 3
S... ..w..... .... ewe... ..e ee... 2.... 6.626.. w.w ..w
..w... ewe... .... ..w..... ..e we... .2... 9690.. w.w ..w .5658.wa
..w ...... ...w ...... .... we... 2.... .6556: w.w we
..e ...... e... ...... .... we... 2.... .6556: w.w ew
e... ..w..... w.w ...... ee ee... wee... n.59.... w.w we
e... ..w..... w.w ...... ..e ee... .8... 2.69.... w.w we $65.83;
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.3 .3:

 

104

Iv. uiacellaneouz Quenching Experiments
A. Intermolecular Quenching

Intermolecular quenching of the benzoyl triplet of one diketone
molecule by the p-benzoylphenoxy chromophore of another in benzene was
measured as a control experiment by steady-state quenching of the type
II reaction of butyrophenone with 4-MeO-2-MeBzP and 4-MeO-2'-MeBzP
(Figures 51 and 52). Butyrophenone was chosen because of its fairly
long lived and readily quenched triplet. This is important to minimize
the competitive light absorption correction factor. Since both butyro-
phenone and the two quenchers absorbed light at 313nm, a correction for
competitive light absorption was necessary. The fact that the butyro-
phenone triplet is long lived meant that a relatively small amount of
quencher was needed to generate a Stern-Volmer plot and the amount of
light absorbed by the quencher was minimized. Equation 24 shown below

was used to correct for competitive absorption:
¢°/¢corr 7 ¢°/¢uncorr x EBPlapl/(sBPIBP]+€Q[Q]) (24)

where 53? and.eQ are the extinction coefficients of BP and Q (B? -
butyrophenone and Q - 4-MeO-2-MeBzP or 4-MeO-2'-MeBzP).

Intermolecular quenching rates were obtained by dividing the slope
099) of the quenching plot by the triplet lifetime of butyrophenone
“butyrophenone - 1.1x10‘7s 33) . The slopes of butyrophenone quenching by
4-Me0-2-Meszp and 4-14eo-2'—Meszp are 223 W1 and 295 ml, respectively.
These results translate into bimolecular quenching rate constants of

2.0x109s’1M'1 for 4-MeO-2-MeBzP and 2.‘7x109s'1M’1 for 4-MeO-2'-MeBzP.

 

"’. 12.11,. .‘ n.3-

105

   
    
 
     

 

 

 
  
    

 

 

12 -
d
10 _ uncorrected for para'al .
‘ light absorption by Q
8 '1
T
41% 6 -
‘ correctedfor partial
4 - light absorption by Q
1
2 .J
0 j . 1 v j I I I I I I
0.000 0.002 0.004 0.006 0.008 0.010
[01M
Figure 51 : Quenching of Butyrophenone by 4-ueO-2 -IleBzP
at 313nm in Benzene (0 AP observed)
6 -
5 - uncorrected for partial
. light absorption by Q
4 J
ool¢ 3 u
‘ corrected forme
2 - light absorption by Q
1
o 1 ‘ I ‘ I f I fl j ' I
0.000 0.002 0.004 0.006 0.008 0.010
[OLM
Figure 52 : Quenching of Butyrophenone by 4-ueO-2 ' -IleBzP

at 313nm in Benzene (oAP observed)

 

106

B. Measurement of Syn and Anti Triplet Lifetimes

The triplet lifetimes of the syn and anti conformers of the 3-
methyl-4-alkanoylphenoxy chromophore were measured by sensitization of
stilbene by 4-MeO-2-MeAP and Stern-Volmer quenching of 4-MeO-2-MeVP
(Figures 53 and 54). These steady-state measurements complement flash
kinetic data presented earlier in this chapter.

1. Stilbene Sensitization

As shown in Figure 53, the sensitization of trans-stilbene by 4-
MeO-Z-MeAP in benzene at 366nm yields a dual-sloped curve characteristic
of a system where two distinct triplets of the sensitizer (syn and anti
conformers of 4-MeO-2-MeAP) are quenched by trans-~stilbene.‘3 The range
of data collected was limited by the solubility of quencher at high
concentrations (<10 M’l) and by the detection limit of the gas chromato-
graph at low concentrations (>150 M‘l).

The short lived syn triplet is responsible for the steep initial
slope and the long lived anti triplet is responsible for the relatively
low final slope. Extrapolations to lower trans-stilbene concentrations
(represented by the dashed line) were made based on supporting inform-
ation about this provided by flash photokinetic data presented in Table
6. Triplet decays (II!) are derived from the plot with the following
equationz‘30“

kg; - intercept/slope (25)

An initial slope of $0.015 with a y-intercept of 1.45 indicates a
decay of 108 s'1 for the syn triplet. This decay represents photo-
enolization of the syn triplet with the o-methyl (1/13). The final

slope of ~0.0004 with a y-intercept of 2.5-3.0 indicates a decay of

I ...u: lei...“..-e’ 1'.

 

‘rl

107

~106 s"1 for the anti triplet. This decay represents interconversion of

the anti triplet to the syn by bond rotation (kafis) .

 

 

 

108

 

 

 

possible
final
intercepts
41.1

1.0 ‘

0.5 '

0.0 ' I I I I I I I I I I ‘l

0 50 100 150 200 250 300

[tt'ans-stilbene],M‘l

Figure 53: Sensitization of Trans-Stilbene by 4-lleO-2-lleAP
at 366nm in Benzene (o cis-stilbene observed)

 

 

 

109

2. Stern-Volmer Quenching of 4-ueo-2-BeVP

Figure 54 shows the quenching plots of 4-MeO—2-MeVP in benzene and
methanol. These experiments were designed to measure the syn and anti
triplet decays of this model ketone, however since interconversion from
one conformer to the other competes with type II decay, the lifetime of
neither triplet could be isolated solely from the quenching slopes.
Although proper kinetic analysis of the plots is difficult because the
curves represent the composite quenching of two interconverting triplets
(syn and anti), the decays derived from the slopes generally agree with
those obtained by other steady-state and flash means.

Curvature in the benzene plot arises from the bimolecular quenching
of two triplets, syn and anti, each with significantly different
lifetimes. The final slope, which indicates a decay on the order of
~108 s'l, reflects the influence of the short lived syn triplet on
quenching and is the same value measured for 1/1:s in the sensitization
of stilbene by 4-MeO-2—MeAP. The steep initial slope reflects the
influence of the longer lived anti triplet on quenching.

In methanol, the quenching plot is nearly linear with a slope of
~700 M‘1 which indicates a decay of ~10" s'l. Since the raw data show
that there exists a small, but much steeper initial slope, the slope of
~700 Mflzmust be reflective of the syn triplet decay. Coincidentally,
this final slope decay of ~10" s’licorresponds to the calculated l/Ts
value used in the ET analyses of diketones which contain this

chromophore.

110

 

 

 

 

 

[01M

0A

 

30

20

¢DV¢> 15

1O

 

 

1
0.00 0.01 0.02 0.03
[01M

l'igure 54: Stern-Veins: Plots of 4-ueO-2-IleVP at 313nm
(ll-MeO-Z-MeAP observed; A. in benzene, B. in methanol)

0.04

DISCUSSION

This chapter discusses the significance of the experimental results
and presents the conclusions of the ET study. Comparisons are made with
the findings of other studies conducted on related systems. Even though
it is difficult to compare results of data collected at different times
and under different circumstances, it must be done for these systems,
since relatively little is known about actual rates of two-way ET in P
diketones. Any significant experimental disparities which could affect

the outcome of such comparisons are acknowledged. ;

 

I. Interchromophore Energy Gap ME)

The intramolecular ET rates of diketones depend on many factors.
This research focused on the effect of interchromophore distance and
interchromophore energy gap (AB) on ET rates. The interchromophore
distance for the diketones of this investigation can only be measured by
the length of the tether connecting the chromophores. Of course, the
distance is not the same for all molecules of a given diketone since the
flexible tethers allow the molecules to coil upon themselves and assume
a number of conformations. The actual distance between the chromophores
differ for each conformation. The issue of using tether length as a
means of measuring interchromophore distance and how this relates to the
ET values derived for the various diketones will be addressed later in
this chapter.

The AE can be measured in two ways, from the phosphorescence

spectra of model ketones representing the independent chromophores

111

112

within the diketones and from the ET rate constants. Theoretically,
these measurements should arrive at the same AB values, but they do not
always correlate. Frerking concluded that the AE values derived from
phosphorescence spectra in his diketone study were generally higher than
those derived from ET rate constants.‘5 Wagner, Thomas, and Harris were
first to recognize that AE values in phenyl ketones measured at 77%(
changed upon warming.‘6 Therefore, two AE values for each diketone are
considered in this chapter. The first, described by Equation 26, is the
difference in the 0,0 phosphorescent band energies of the lowest lying
triplets of each chromophore.

AE - E - E (26)

triplet,chromophore A triplet,chromophore B

The second, described by Equations 27-30, is derived from the ratio of

k and k

endo

exo values reported in the Results chapter for each diketone.

The ratio of kmto/kendo (Ket) can be derived from AE using the Gibbs

function:

AG - AH - TAS (27)
where, at conditions of constant pressure, volume, and temperature,‘7
AE - AH (28)
The process of ET occurs without any change in multiplicity,

structure, or solvent reorganization, however AS at 0.“"5° Although the

influence of the entropy change on ET has not been addressed in this

IL'JTJI

'—

 

'q‘l:‘

study, it is acknowledged. Therefore, the following approximation has

been assumed:
AG - AB (29)

The ratio of ET rate constants should then follow a Boltzman

distribution.
AB - -RT anet (30)

Besides providing some indication about the magnitude of AE, the
phosphorescence spectra of the diketones and model compounds contain
evidence of the existence and extent of ET in the diketones studied. As
mentioned in the previous chapter, the only observable phosphorescent
emission in the diketones was that of the lowest energy triplet. For
example, the emission spectra of the benzoyl-(2'-methyl-4-benzoyl-
phenoxy) systems are identical to that of 4-MeO-2'-MeBzP, the model
ketone for the 2'-methyl-4-benzoylphenoxy chromophore. This can be
compared to the emission spectrum of an equimolar mixture of VP and 4-
MeO-2'-MeBzP, which is simply a combined spectrum of the two independent
chromophores. The absence of any alkanophenone emission in the diketone
spectrum indicates that the vast majority of excitation resides at the

2'-methyl-4-benzoylphenoxy chromophore.

 

114

II. Interpretation of Quantum Yields

The quantum yields measured for type II product formation
complemented the quenching data in the derivation of intramolecular ET
rate constants and were of most use when compared to quantum yields
calculated assuming different degrees of ET reversibility in the
diketones. Table 11 summarizes both measured and calculated quantum
yields of the diketones studied. The dkahyd is the quantum yield for
type II product formation calculated from the mathematical models
(Equations 3 and 11) . The °Calc"d,EQ is the quantum yield calculated
based on the assumption that ET is completely equilibrated (i.e., kexo
and kemk>>> triplet decays). When ET is equilibrated, the population
of each excited state, x, is determined by the kexo and kéndo values
derived for each diketone (see Results chapter). The dkalcuhnoso is the
quantum yield calculated based on the assumption that endothermic ET
does not compete with decay of the lower energy triplet.

For the diketones containing two interacting triplets, 7-(4-

BzPhO)BP and 5-(4-BzPhO)VP, equations 31 - 33 apply:

kr xr PER
- (31)

xr/‘r + Xu/Tu

¢Calc'd, EQ

 

Br kt PBR
d’Calc'dmoEQ - (32)
kr + kexo
where,
x1? - 1 - x“ - kendo/ (kexo + kendo) (33)

Equations 34 - 44 apply to the diketones containing three

TAR.” —

|\‘ _.

 

\PO

115

interacting triplets. For 7-(3-Me-4-BzPhO)BP, 8-(3-Me-4-BzPhO)VP, 5-
l(2'-Me-4-BzPhO)VP, £-(2'-Me-4-BzPhO)HxP, C-(2'-Me-4-szh0)HpP, and n-

2'-Me-4-BzPhO)OtP:

 

 

kr X: PBR
¢Calc'd,EQ 3 (34)
xr/Tr + xs/Ts + (l/Ia + ka—95)xa
Br kr PER
¢Ca;c'd,noEQ 3' (35)
kr + k
exo

Although the parameter ke in the three-triplet diketones is actually

TACC

k$6r and ka_fl, it is treated as a single parameter in the following

calculations for the sake of simplicity.

X? = Reno‘s/(keno + kerdo) (36)
x3 = [kexc/(kexo + ker1do)] x 0'62 (37)
Xe = [kexc/(kexc + kendej] x 0'38 (38)

Equations 34 and 35 apply to the benzoyl chromophore of Y—(3-Me-4-
AcPhO)BP, yr(3-Me-4-(Y—MeVal)PhO)BP, 5-(3-Me-4-AcPhO)VP, 5-(3-Me-4-
ValPhO)VP, 5-(3-Me-4-(75MeVal)PhO)VP, l-Bz-4-(2-Me-4-An)Bt, and l-Bz-4-

(o-Tl)Bt. For the anisoyl chromophore, Equations 39 and 40 apply:

kr(anisoyl) xa PBR

¢Calc'd,£Q = (39)
xr/tr + XS/ts + (1,18 + ka-as’Xa

 

 

F I
*4
(W

 

 

PER kr(aniscy1) kexo Br
Ca1c'd,noEC = (Ba + ) (40)
l/Ta + REV—)5 kCXC + l/TI
where the populations of syn and anti in benzene are,
x5 = [kexo/(kexo + kendo)] x 0-79 (41)
Xa = [kexo/(kexo + kendo)J X 0-21 (42)
P
and in methanol are, 7
x. = [km/(kg... + keno-a] x 0.89 <43)
~ )
Xa = [keXO/(kexc + kendo)J X 0'11 (44)
i
h

 

Interpretation of the quantum yields requires an understanding of
the relationship between the measured and calculated values. One would
expect that the quantum yield in a given system is highest when ET is
reversible and equilibrated, and lowest when ET is irreversible and
occurs in only one direction. However, this does not hold true for all
diketones because many factors must be considered. Careful scrutiny of
the kinetics involved reveals thatthe highest quantum yield occurs at
the point where the product of reactive triplet population (either fir,
Xx! or a combination of the two) and the rate constant for reaction is
greatest and the sum of all triplet decays is least. The lowest quantum
yield occurs when the above described situation is reversed.

For example, consider the two diketones 5-(4-BzPhO)VP and 8-(2'-Me-
4-BzPhO)VP. In 5-(4-BzPhO)VP, the highest possible quantum yield occurs

if one assumes that ET is totally reversible (i.e., d) ) because

Calc'd,EQ

117

km, + xu/Iu - 3 x 105 3'1 (denominator on right side of Equation 31)
which is much smaller than kr + kexo - 2 x 107 s"1 (denominator on right
side of Equation 32), despite the fact that fit > 1r. However, in 5-(2'-
Me-4-BzPhO)VP, the highest possible quantum yield occurs when one
assumes that ET is not reversible (i.e., ¢Ca1c'd,noso) because xr/‘rr +

xu/tu - 6 x 108 s‘1 which is greater than kr + kmo - 2 x 109 3’1,

and Br > xx.

III. Energy Transfer Rates

As stated in the Introduction, the two most influential factors
governing intramolecular ET rates are the physical separation of the
chromophores and the energy difference between triplet excited states of
each chromophore. This study investigated the effect of these two
factors on ET rates. In addition, the fact that the diketones have
either an n,n* +9 n,n* or n,n* +9 n,n* ET interaction provided the
opportunity to compare the relative ET efficiencies of each interaction
type. The ET rate constants (k.exo and kendo) for each diketone are
summarized toward the end of this chapter in Table 12.

A. The Benroyl-(3-nethyl-4-alkanoylphenoxy) Diketones

In these diketones, the effect of lengthening the alkyl tether from
three to four methylenes on the magnitude of ET rates was investigated.
The photokinetic behavior and especially the response of quenching
curves to changes in the various parameters (see Figures 14-22 in
Results chapter) suggest that ET in the shorter tethered Y-(3-Me-4-
AcPhO)BP and 7-(3-He—4-(15MeVal)PhO)BP diketones is more reversible than

in the longer tethered 5-(3-Me-4-AcPhO)VP, 8-(3-Me-4-ValPhO)VP, and 8-

 

118

(3-Me-4-(7bMeVal)PhO)VP diketones. Also, the increase in solvent
polarity from benzene to methanol appears to make ET more reversible in
both the 1— and 5-diketones.

In benzene, the quenching curve of 15(3-Me-4-AcPhO)BP has a steep
initial slope component which is diminished, but still present, in y-
(3-Me-4-(1eMeVal)PhO)BP. The steepness reflects the anti triplet's
involvement in the ET kinetic scheme as it repopulates the benzoyl
triplet with excitation energy. The anti triplet must be the source of
endothermic ET because it is long lived enough and of significant
population to allow endothermic ET to be competitive with other decay
paths. The syn triplet cannot contribute to endothermic ET because it
is too short lived and decays rapidly through photoenolization. Similar
behavior is seen in the S-diketones where the steep initial slope found
in the quenching curve of 5-(3-he-4-AcPhO)VP is not present in the
curves of 5-(3-Me-4-ValphowP and 6-(3-Me-4-(y—MeVa1)Ph0)vp.

AE for the 7* and 5-diketones should be the same because the
chromophores are identical. Since the ratio of kem/kendo is determined
by AE, this ratio should remain constant for diketones with identical
chromophores. The ET rate constants which best fit the data of 7-(3-
Me-d-AcPhO)BP and.7—(3-Me-4-(15Meval)PhO)BP in benzene are kexo -
l7xlO7s‘1 and kendo - 0.30x107s’1. For 5-(3-Me-4-AcPhO)VP, 5-(3-Me-4-
vupnowp, and 8-(3-Me-4-(7-MeVal)PhO)VP in benzene, the ET rate
constants which best fit the data are kexo - 7.’7x10"s'1 andkzendo -
0.14x107s’1. Lengthening the alkyl tether by one methylene unit causes
ET to decrease by a factor of two. Figures 55 and 56 show the fit of
the raw data of the 1- and 5-diketones with the calculated curves and

the response of the curves to changes in both kexo and kendo. The

' ' P. .‘hl—“q—y

 

l. .

responsiveness of the curves to changes in the ET values reflects the
extent to which ET is equilibrated. The y-diketones are not nearly as
sensitive to changes as the 5-diketones.

The ET rate constants of the 7- and B-diketones indicate a AE of
2.4 kcal. This correlates well with the AE of 2.3 kcal calculated from
phosphorescence spectra. The quantum yields (listed in Table 11)
indicate that ET is reversible, but not equilibrated for both the 7- and
5-diketones in benzene. The GHIJMX and dkakfld values correlate better

with ¢ than with d)

Calc'd,noEQ Calc'd,EQ’ ;

The photokinetic behavior of the 7- and 8-diketones can be compared

to that of Frerking's 7-(4-ValPhO)BP and 5-(4-ValPhO)VP diketones.‘2

 

'F-

The benzoyl and anisoyl chromphores are very similar, the only
difference being the o-methyl on the anisoyl. Unfortunately, the ET
values derived by Frerking for 7—(4-ValPhO)BP and 5-(4-ValPhO)VP did not
differ significantly from one another and the quantum yields indicate
that ET in Frerking's diketones is nearly equilibrated. The benzoyl and
anisoyl chromophore ¢31me values for y-(4#ValPhO)BP of 0.49 and 0.065
correlate much better with the ¢ka1chEQ values of 0.48 and 0.029 than
with the d%31c%anEQ values of 0.051 and 0.20, respectively. For 8-(4-
ValPhO)VP, the benzoyl and anisoyl ¢ILMax values of 0.31 and 0.016
correlate much better with the ¢ka1cuLEo values of 0.19 and 0.015 than
with the «kalcwhnoto values of 0.018 and 0.21, respectively.

The photokinetic behavior of the benzoyl-(3-methyl-4-alkanoyl-
phenoxy) diketones in methanol indicates that the switch from benzene to
methanol causes ET to become more reversible. This is evident in the

quenching plots which have a pronounced steep initial slope in methanol

120

compared to the nearly linear plots in benzene. The steep initial slope
reflects the influence of the long lived anti triplet on the kinetic
scheme. Ironically, the increase in solvent polarity was designed to
make ET irreversible by stabilizing the n,n* triplet of the 3-methyl-4-
alkanoylphenoxy chromophore32'51'53 which would increase AE and the
kexo/kendo ratio.

Fitting the quenching data of these diketones to the mathematical
models was considerably more difficult in methanol than in benzene. As
evident in Figures 57 and 58, it is impossible to maintain a constant
kexo/kendo ratio and achieve a good fit of the data, even within each set
of 7- and 5-diketones. The best fit of the data for each individual
diketone gives the same value of kexo, but kfindo‘varies. In the two 1-
diketones, kexo - l8x10"s'1 and kendo - 1.5x107s’1 and 0.50x10"s’1 for 7-
(3-Me-4-AcPhO)BP and 7-(3-Me-4-(1-MeVal)PhO)BP, respectively. In the
two 5-diketones, km, - 18x107s'1 and kendo - 1.0x107s'1 and 0.60x107s'1
for 8-(3-Me-4-AcPhO)VP and 5-(3-Me-4-(75MeVal)PhO)VP, respectively. If
one assumes that ET in all four of these diketones occurs at nearly the
same rate and an average of the ET rate constants is taken, a kendo
value of ~1.0x107s'1 is obtained. A kexolkendo ratio of 18/1 would
indicate a AE of 1.7 kcal which compares poorly with the 3.6 kcal
calculated from phosphorescence spectra. A AE of 1.7 kcal is somewhat
smaller than one might predict in a system where ET occurs between the
lowest alkanophenone triplet (either n,n* or n,u*) and the n,n* of the
alkanophenoxy triplet which lies ~3 kcal/mole below the alkanophenone.

The poor correlation of the predicted to derived AE values and the

fit of the quenching data with the calculated curves suggest that our

 

121

model may not accurately depict the photokinetics involved. Perhaps the
assumption that ET occurs only between the n,n* or n,u* of the alkano-
phenone and the n,n* of the alkanophenoxy is faulty. Given the effect
that methanol has on the relative energies of the alkanophenone
triplets, ET might actually occur between the n,x* or x,x* of the
alkanophenone and the n,u* of the alkanophenoxy. In a polar solvent
such as methanol, stabilization of the alkanophenone u,x* accompanied by
a destabilization of its n,n* would give nearly isoenergetic
triplets"’1“3’3 which would be close enough in energy to participate in ET
with the n,n* of the alkanophenoxy chromophore.

The quantum yields are consistent with the assessment that ET in
these 7- and 5-diketones in methanol is reversible and nearly

equilibrated. The (DH and ¢Calc,d values correlate better with ¢Calc'd,£0

than with ¢Ca1c'd,noEQ°

0V0

0°/¢

¢°l¢

Figure 55:

122

 

 

 

 

 

 

   
 

 

 

 

 

 

 

 
  

 

 

 

6
‘ 0
5d
' o
4 o . e
e
3" o .
. .e
2- 3
« 9
14)
0 v I 1 I ' j V I V
0.00 0.02 0.04 0.06 0.08 0.10
6 ...0'
5- ..........
4..
3- ......
2" 7 7
...... km - 1.7x10 , xendo - 0.030x10
1 — km, - moo", km” - 0.30::107
—— km, - 170x107, km“, - 3.0x107
0 1 ' 1 V I 1 I ' fl '
0.00 0.02 0.04 0.06 0.08 0.10
6 ,,,,,
5n ........ ..
4 ........
4- .........
a- ,,,,,,,,,
2' 7 7
...... kexo - 1.7810 ' k.nd° - 0.030X10
1 —— km, - l7x107, xmdo - 0.30x107
— x." - 170x107, km“, - 3.0x107
0.00 0.02 0.04 0.06 0.08 0.10

[01M

Stern-Velmer Elots of 7- (3-ue-4-AcPhO)BP and y- (3-
lIe-l-(y-IteVaIH’hmaP in Benzene at Various ET
Estes (OAP observed for 1-(3-Me-4-AcPhO)BP; oAP
observed for 7- (3-Me-4- (1-MeVal)PhO) BP)

123

 

 

 

 

 

   
 

 

 

 

 

  

   

 

 

 

 

 

 

 

7:
o
6 cl 0 A
5.
‘ A.
¢°l¢ 4.: o O l
3‘ O
. o
2‘ .0. e 8
11) '
o [7 i I v I T I v
0.00 0.02 0.04 0.06 0.08
7
6
5
4 i...
one 3 °
2 ...... km, - 0.77x107, kmdo - 0.014x107
— km, - 7.7x107, km“, - 0.14x107
1 — km, - 7mm", kwdo - 1.4mm7
o 1 . . . u . u .
0.00 0.02 0.04 0.06 0.03
7
6
5
4 ,._.
CVIO
3 7 7
2 ...... km, - 0.77x10 , km“, - 0.014x10
It.” - 7.7x107, kendo - 0.14x107
1 — km, - 77x107, xendo - 1.4x107
0.04 0.05 0.08
¢WW1
...... x.“ - 0.77x107, km“, - 0.014x107
— k.” - 7.7x107, km“, - 0.14x107
—— km, - 77x10 , km“, - 1.4x107
I ' I '
0.04 0.06 0.08
[0].“)

Figure 56:

Stern-Volmer Plots of 8-(3-ue-4-AcPhOHrP, 5-(3-
ue-l-ValPhOHIP, and 8-(3-ue-4-(7-ueVal)PhO)VP in
Benzene at Various ET Rates (0 AP observed for 5-(3-
Me-4-AcPhO)VP; A AP observed for 5-(3-Me-4-ValPh0)VP;

oAP observed for 8-(3-Me-4-(y—MeVal)PhO)VP)

124

 

18
16
14
12

10
dwo

 

 

0.05

 

0°l<b

    

.,
...... km, - 1.8x10 , km“, - 0.1x107
7 7
— kexo ' 18x10 ' kendo " 1.0x10
-—x.,,° - 180x107, km“, - 10x107

.
O.
o
.0
o
,e
o
,0
O
O
o.
O
O
.0
0".
o
o
o
o
o
O
.0
o
O
.0
o
.0
.0
.0

 

 

T f

I I
0.03 0.04 0.05

 

0°l¢

   
 

...... kexo - 1.3,‘107' kendo - 0.1x107
7

— kexo " 18x10 ' kendo ' 1'0x107

—x.,,° - 180x107, km“, - 10x107

 

 

Figure 57:

1 ‘U

V j U I V

I I
0.03 0.04 0.05

[0].“)

Stern-Velmer Plots of 7- (3-ue-4-AcPhO) BF and 1-(3-

, ue-l- (y-ueValu’hO) BB in methanol at Various ET

Bates (GAP observed for 7-(3-Me-4-AcPhO)BP; oAP

observed for 7- (3-Me-4- (y-MeVal) PhO) BP)

 

 

 

 

 

   
 

 

 

 

 

125
20
15 " O
‘ o
(”/0 10! O
l o .
0 ° 0
5" 00. 0
j {.0
0 T ' 1 ' I v ' '
0.00 0.01 0.02 0.03 0.04
20 a
15 "
0°/¢ 10"
5. ........... km, - 1.8x107, km“, - 0.10x107
" — x.“ - 18x107, kw“ - 1.0x107
—x.,,° - 180x107, xmdo - 10x107
0 T I I 1 I j I fl
0.00 0.01 0.02 0.03 0.04
20

...... km, - Leno", km“, - 0.10x107
k.‘° - 18810 ' k.nd° - 1.08107
— kOXO - IBOXIO , kOBdO ' 103(10

 

 

 

 

 

v v

I I
0.02 0.03 0.04

[01M

Figure 58: Stern-Volmer Plots of 8-(3-Ile-4-AthO)VP and 6-(3-
ue-l-(y-ueVal)PhO)VP in nethanol at Various ET
Bates (0 AP observed for 8-(3-Me-4-AcPhO)VP; oAP
observed for 8- (3-He-4- (y-MeVal) PhO) VP)

126

B. l-Bz-C-(Z-fle-l-An)8t and 1-Bz-4-(o-Tl)Bt

These two diketones are different from the preceding diketones
because the carbonyls of both chromophores are bonded directly to the
alkyl tether and therefore are treated separately.

The photokinetics of 1-Bz-4-(2-Me-4-An)8t indicate that ET is
reversible, but not equilibrated. This diketone can best be compared to
the l-Bz-4-(4-An)Bt system studied by Wagner and Nakahira.17 They
believed that ET in l-Bz-4-(4-An)Bt was completely equilibrated because
the lifetimes of the two chromophores were nearly the same (kqtbenzoyl -
240 M‘1 and kqtanisoyl - 370 M’l) . However, upon closer analysis of the
photokinetic data, Frerking determined that ET was actually not
equilibrated and derived ET rates of kexo - 20x107s’1 and kendo -
4.0x107s'1. These differ significantly from the ET rate constants
derived for 1-Bz-4-(2-Me-4-An)8t in benzene of kexo" 12x107s"1 and k.endo
- 0.22x107s’1. This disparity in ET rates between the two systems
reflects the fact that it becomes more difficult to assign keno and k,mdo
values as ET approaches equilibrium. Figure 59 shows the response of
the l-Bz-4-(2-Me-4-An)8t quenching curve to changes in kexo and.k§nd°.
The sensitivity of the quenching curve to changes in the ET rates lies
between that of the 1- and 8-diketones. This is consistent with the ET
values and interchromophore distance, both of which fall somewhere
between the 1- and 5-diketones.

Since l-Bz-4-(2-Me-4-An)Bt contains essentially the same chromo-
phores as the benzoyl—(3-methyl-4-alkanoylphenoxy) diketones, the AE
predicted by phosphorescence is 2.3 kcal in benzene. This correlates

very well with the AE of 2.4 kcal derived from the ET values. The

 

127

quantum yields for type II from both the benzoyl and anisoyl chromo-
phores indicate that ET is not equilibrated. The 615nm“ and °Ca1c'd
values correlate better with 0Ca1c'd,noEQ than with 0C.1c.d’go.

The switch from benzene to methanol caused a change in the
quenching curve of 1-Bz-4-(2-Me-4-An)Bt similar to that in the benzoyl-
(3-methyl-4-alkanoylphenoxy) diketones. The initial slope is steeper
and more pronounced in methanol than in benzene which indicates an
increase in ET reversibility. This would most likely be due to the same
factors as in the benzoyl-(3-methyl-4~alkanoylphenoxy) diketones. Also,
similar to the benzoyl-(3—methyl-4-alkanoylphenoxy) diketones, it proved
difficult to curve-fit the quenching data of 1-Bz-4-(2-Me-4-An)Bt in
methanol and maintain the same keno/item,o ratio of 18/1 used in the
benzoyl-(3-methyl-4-alkanoylphenoxy) diketones (Figure 60). The best
fit of the data gives ET rate constants of kexo - 18x107s'1 and kendo -
0.30x107s’1. Since the chromophores are the same as in the benzoyl-(3-
methyl-4-alkanoylphenoxy) diketones, it is reasonable to conclude that
Item/km,o is also the same (i.e., km, - 18x107s’1 and kendo ~1.0x107s"1).

The quantum yields also reflect that ET is more reversible in
methanol than in benzene. The Qum‘x and Ogle“, values correlate better
with °Ca1e'd,r—:o “a“ "it“ °Ca1e'd,noso°

The diketone l-Bz-4-(o-Tl)Bt is most similar to 1,4-dibenzoylbutane
(DiBth) studied by Frerking.5‘ Unfortunately, since Frerking concluded
that extensive self-quenching prohibited the assignment of ET rates in
DiBth, a quantitative comparison cannot be drawn between the two. The

photokinetics of 1-Bz-4-(o-Tl)Bt indicate that ET is reversible, but not

equilibrated.‘ The ET values derived for this diketone in benzene are

""q
._--

 

”1

 

128

kexo - 20x1073‘1 and kendo - 1.0x107s‘1. These ET values indicate a AE
of 1.8 kcal compared to 0.8 kcal predicted from the phosphorescence
spectra. The difference in AB measurements may be due to the
difficulty in assigning the 0,0 emission band from the phosphorescence
spectrum of 2-methylvalerophenone, the model for the toluoyl
chromophore. As observed in other o-methylphenyl ketones,ss the
phosphorescence spectrum of 2-methylvalerophenone is poorly resolved.
Figure 61 shows the response of the quenching curve to changes in the ET
rates. The sensitivity of the curve to ET rate changes, which is
greater than that of 1-82—4-(2-Me-4-An)Bt and 7-(3-Me-4-(vbMeVal)Ph0)BP
and similar to that of 5-(3-Me-4-(vbMeVal)PhO)VP, indicates that ET is
nearly irreversible. The ¢II,Max and °Ca1c'd values correlate better with

d)

Ca1c'd,noEQ than With ¢Ca1c’d,EQ'

The increase in solvent polarity from benzene to the methanol does
not appear to change the degree to which ET is equilibrated in 1-Bz-4-
(o-Tl)Bt, however, the phosphorescence spectra of model ketones suggest
that the relative energies of the benzoyl and toluoyl triplets are
inverted. According to the phosphorescence spectra, the toluoyl triplet
lies 0.6 kcal above the benzoyl in methanol. This compares with a AE
of 1.8 kcal indicated by the derived ET values of kexoa- llxlOVs"1
(benzoyl-)toluoyl) and kendo - 0.50x10"s’1 (toluoyl—)benzoyl) . Figure 62
shows the response of the quenching curve to changes in the ET rates.
The sensitivity of the curve to ET rate changes is about the same as in
benzene which indicates a similar degree of ET reversibility. This is
further supported by the type II quantum yields of both chromophores.
The ¢)

and d’c .d values correlate better with 0c.1c.d'nogo than with

II,Hax alc

 

129

¢Calc'd,£0°

It is difficult to ascertain the ET situation in 1-82-4-(o-Tl)Bt
because of conflicting data, in both solvents. Phosphorescence
measurements indicate that ET from the benzoyl chromophore to the
toluoyl in methanol is 0.6 kcal endothermic, however, the ET values
indicate that this process is 1.8 kcal exothermic. Also, there is a
large discrpency between the AE predicted by phosphorescence and that

by the ET values in benzene. Perhaps the inconsistencies are due to the

relatively small AE values in both solvents.

130

 

¢°l0 3-

 

 

  

 

...... k.x° - 1.2X107, k.nd° - 0.022X107

 

 

 

1 km, - lleo7, km“ - 0.22x107
—x.,,,, - 120x107. km“, - 2.2xlo7

Oi ' I i I ' I ' I i

0.00 0.02 0.04 0.06 0.08 0.10

[Cl-M

Figure 59: Stern-Volmer Plots of l-Bz-4-(2-ue-4-An)Bt in
Benzene at Various ET Bates (oAP observed)

 

 

 

e
e
e
0°/¢
...... km - Lexie", km“ - 0.10xlo7
—— km - 18x107, kw“ - 1.0x107
o —x.,,, - 180x107, km“ - 10x10?
0.00 0.02 0.04 0.06 0.08

[0].“)

Figure 60: Stern-Volmer Plots of I-Bz-4-(2-ue-4-An)Bt in
Ilethanol at Various ET Rates (0 AP observed)

 

131

 

  
 

 

 

 

 

5 0,1
q a
4 " '0'
d o,"
31
¢°/¢ " .0"
2. 0'
7 7
------ k.“ - 2.0x12 , kwdo - 0.103210
1 — x.” - 20x10 , kmdo - 1.0x10
0 —— km, - 200x107, km", - 10x10?
I 1 1 I 1 1 I fi 1 I 1 1 I fl 1
0.00 0.03 0.06 0.09 0.12 0.15

[0].”

Figure 61: Stern-Velma: Plots of 1-Bz-4-(o-Tl)Bt in
Benzene at Various ET Bates (oAP observed)

 

  
 

 

 

 

 

6 7

5 u

4 -

¢°/¢ 3 J O..."

2 7 _- 7
...... k.xo . 1.1810 , k.nd° - OoOSOXIO

1 .—_. km, - llxlo7, km“, - 0.50x107
—k.,,o - 110x107, km“, - 5.0x107

0 1 1 I 1 I 1 I 1 I 1 I 1 I 1 I 1

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

[01M

Figure 62: Stern-Volmer Plots of 1-Bz-4-(o-T1)Bt in
lethanol at Various ET Bates (oAP observed)

132

C. The Benzoyl-(4-benzoylphenoxy) Diketones

In these diketones, the effect of changing AE and the inter-
chromophore distance on the magnitude of ET rates was investigated. For
7-(4-BzPhO)BP and 5-(4-BzPhO)VP, the photokinetics indicate that ET is
reversible and nearly equilibrated. This is possible because kendo
competes effectively with the slow decay of the 4-benzoylphenoxy
triplet. However, in 1—(3-Me-4-BzPhO)BP and 5-(3-Me-4-BzPhO)VP,
photoenolization increases the 4-benzoylphenoxy triplet decay to the
extent that kendo becomes noncompetitive.

Since 7-(4-BzPhO)BP and 5-(4-BzPhO)VP contain the same two
chromophores, they should have the same Item/Mmo ratio. In benzene,
the derived ET rate constants for Y-(4-BzPhO)BP of k.exo - 40x107s'1 and

k - 0.10x10"s’1 indicate a AE of 3.5 kcal. The same AE value is

endo
indicated by the derived ET rate constants of kexo - 20x107s"1 and kendo
- 0.050x10"s’1 for 5-(4-BzPhO)VP in benzene. This AE compares to the
4.6 kcal predicted from the phosphorescence spectra.

The diketones 1-(3-Me-4-BzPhO)BP and 8—(3-Me-4-BzPhO)VP differ
structurally from.1-(4-BzPhO)BP and 8-(4-BzPhO)VP in only one respect,
the o-methyl on the phenoxy ring. The ET rate constants derived for y-
(3-Me-4-BzPhO)BP and 5-(3-Me-4-BzPhO)VP compare well with those of 7-(4-
BzPhO)BP and 5-(4-BzPhO)VP. This would be expected since the chrome-
phores are actually very similar. The only ET rate constant in this set
of four diketones which appears to be inconsistent with the others is
the kando of ‘y-(B-Me-4-BzPhO)BP. The value of 0.050x107s’1 derived by

the best fit of the data appears to be a factor of 2 to 4 lower than

expected based on the other ET rate constants. Since the kexolkend,>

133

ratio should be the same in 7-(3-Me-4-BzPhO)BP and 8-(3-Me-4-BzPhO)VP, a

k in the range of 1.0x1073‘1 to 2.0x10"s'1 would be expected for y-

endo
(3—Me-4-BzPhO)BP. One must conclude that khndo is approximately

1.0x107s’1 in both y-(3-Me-4-BzPhO)BP and 5-(3-Me-4-EzPhO)VP. Figures
63 and 64 show the fit of the ET rate constants of kexo - 44x107s'1 and

k - 0.10x107a'1 for 7-(3-Me-4-BzPhO)BP and kw, - 21x107s'1 and kendo

endo
- 0.10x10"s'1 for 8-(3-Me-4-BzPhO)VP. These ET rate constants indicate

a AE of ~3.4 kcal compared to the 5.9 kcal predicted from the phosphor-
escence spectra. The difference between the AE values derived from the
ET rate constants and those predicted from the phosphorescence spectra

of model ketones appears to be greater when the acceptor chromophore is
4-benzoylphenoxy than when the acceptor is 4-alkanoylphenoxy.

The degree to which ET is equilibrated in these four systems is
evident in the quenching plots and the quantum yields. In benzene, the
313nm quenching plots of both Y-(4-BzPhO)BP and 5—(4-BzPhO)VP are dual-
sloped with a steep initial slope similar to the slope of the 366nm
quenching plots. This steepness, which reflects participation of the
long lived p-benzoylphenoxy triplet in ET, is almost completely
eliminated in 7-(3-Me-4-BzPhO)BP and 5-(3-Me-4-BzPhO)VP by introduction
of the photoenolization reaction. The only source of endothermdc decay
available in 7b(3-Me-4-BzPhO)BP and 5-(3-Me-4-BzPhO)VP is the anti
triplet, which is much lower in population and has a shorter lifetime
than its p-benzoylphenoxy counterpart in 1—(4-BzPhO)BP and 8-(4-
BzPhO)VP. Therefore, ET is more reversible in 1-(4-BzPhO)BP and 5-(4-

BzPhO)VP than in 7-(3-Me-4-BzPhO)BP and 5-(3-Me-4-BzPhO)VP. This is

also borne out in the quantum yields. The d’u flax and @cudd values of

134

1—(4-BzPhO)BP and 6-(4-szphowp correlate better with o than with

Ca1c'd,EQ

d)

Calc'd,noEQ' where the ¢ILMM and ¢Ca1c,d values of 7-(3-Me-4-BzPhO)BP and

5-(3-Me-4-BzPhO)VP correlate better with ¢Ca1c‘d,ncEQ than with °Ca1c'd,so°

When the solvent is switched from benzene to methanol, ET becomes
more reversible in the four diketones because of the reduced benzoyl
decay. This is evident in the 313nm quenching plots of 1—(4-BzPhO)BP
and 5-(4-BzPhO)VP, where the methanol plots are nearly linear compared
to the benzene plots which have pronounced curvature. Methanol has the
opposite effect on the shape of the quenching plots of 7-(3-Me-4-
BzPhO)BP and 5-(3-Me-4-BzPhO)VP, where the benzene plots are nearly
linear and the methanol plots are curved. Although the effect of
methanol on the quenching curves of the two sets of diketones may appear
contradictory, it is actually quite consistent with the ET photokinetics
and can be rationalized in the following manner. In 1-(4-BzPhO)BP and
8-(4-BzPhO)VP, the change in the quenching curve from benzene to
methanol happens because decay of the benzoyl is slowed down to the
point where the lifetime measured in the experimental window becomes
dominated by the long lived p-benzoylphenoxy triplet. Only at high
quencher concentrations does the plot begin to reflect the lifetime of
the shorter lived benzoyl triplet by curving downward. In y-(3-Me-4—
BzPhO)BP and 5-(3-Me-4-BzPhO)VP, the decrease in benzoyl decay provides
a much better opportunity for endothermdc ET to compete with anti
triplet decay. Thus, the influence of the anti triplet in the ET
scheme, which manifests itself as a steep initial slope in the quenching
plot, is more prominent in methanol than benzene.

For y—(4-BzPhO)BP and 8—(4-BzPhO)VP, the ET values derived in

135

methanol are the same as those in benzene. This is consistent with the
small change in the AE value predicted from phosphorescence, from 4.6
kcal in benzene to 5.0 kcal in methanol. Any increase in ET reversi-
bility caused by the switch to methanol is difficult to detect from the
quantum yields because ET is nearly equilibrated in benzene already and
the differences sought may be within the experimental error of the
measurement. However, an increase in ET reversibility caused by
methanol is evident in the quenching curves of 1-(3-Me-4-BzPhO)BP and 5-
(3-Me-4-BzPhO)VP. Figures 65 and 66 show that the quenching curves have
a steeper initial slope in methanol compared to benzene. This steep
initial slope reflects the influence of the long—lived anti triplet on
quenching and the participation of endothermic ET in the kinetic scheme.
The ET values derived in methanol of kexo - 47x107s’1 and k.endo -
0.10x107s'1 for y—(3-Me-4-azph0)sp, and kexo - 37xlo7a'1 and kendo -
0.10x107s'1 for 5-(3-Me-4-BzPhO)VP indicate a AE of 3.5 kcal. This
compares poorly to the AE of 6.5 kcal predicted by phosphorescence.

The quantum yields agree with the assertion that ET in the diketones is
more reversible in methanol. The 45me and 41mm.d values of 1-(3-Me-4-
BzPhO)BP and 5-(3-Me-4-BzPhO)VP correlate better with °Calc'd,noEQ in
benzene than in methanol.

In comparing these diketones to the benzoyl-(3-methyl-4-alkanoyl-
phenoxy) diketones, the increase in interchromophore distance from three
to four methylenes reduces the rate of ET in both sets of diketones.
Furthermore, the increase in AB as the acceptor chromophore goes from
4-alkanoylphenoxy to 4-benzoylphenoxy causes the Rum/km“,o ratio to
increase. The benzoyl-(4-benzoylphenoxy) diketones can also be compared

to Giri's Y-(4-BzPh)BP, 1*(2'-Me-4-BzPh)BP, 5-(4-BzPh)VP, and 5-(2'-Me-

136

4-BzPh)VP diketones. Taken as a group, ET rates decrease as the

interchromophore distance increases. If the oxygen at the end of the

tether in the 4-benzoy1phenoxy diketones is considered roughly
equivalent to a methylene as a spacer, then kexo decreases consistently

by a factor of ~2 as the interchromophore distance goes from three to

five units (either methylenes or oxygens).

 

 

090

45°10

137

 

    

 

 

 

    

 

 

10

9 e

8

7

5

5

4

Z ------ k.x° - 4.4x107, km“, - 0.010xlo"

— It.“ - 44x10 , km“, - 0.10x10
1 — kw, - 440x107, km", - 1.0x107
0 I 1 I 1 I 1 I 1 j 1 I 1
0.0 0.1 0.2 0.3 0.4 0.5 0.6
[0].”
Figure 63: Stern-Volmer Plots of y-(3-ue-4-BzPhO) BP in
Benzene at Various ET Bates (- AP observed)

11
1O

9

8

7

6

5

4

3 2.1xlo7, km“, - 0.010x107

2 — It.” - 21xlo7, tum - 0.10x107

1 — km - 210x107, km, - 1.0xlo7

0W 1 I 1 I 1 I 1 I 1

0 00 0.05 0.10 0.15 0.20 0.25

[0].”)

Figure 64: Stern-Volmer Plots of 5-(3-ue-4-BzPhO)VP in

Benzene at Various ET Rates (oAP observed)

one

138

 

  
 

 

 

10 ,a’

9

8

7

6

5

4

3 ------ km, - 4.7x107, xmdo - 0.010;th7
2 ,. — It,“ - 47x107, km“, - 0.10x107

1 — k.” - 470x107. hem. - 1.0x107
0 I 1 I 1 I 1 I 1 1 v r a U 1
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14

[0].“)

Figure 65: Stern-Volmer Plots of 1-(3-ue-4-BzPhO)BP in

¢°I<b

lethanol at Various ET Bates (oAP observed)

 

 

 

2- ...... x.” - 3.7xlo7, It...“ - 0.010;:107
1 — km - 37x107, km, - 0.10x107
—- It.” - 370x107, km, - 1.0xlo7

 

V 1 V i V T

I I I I I
0.02 0.03 0.04 0.05 0.06

[0].“)

Figure 66: Stern-Volmer Plots of 5-(3-Ile-4-BthO)VP in

lethanol at Various ET Rates (oAP observed)

 

0.07

139

D. The Benzoyl-(Z'-methyl-4-benzoy1phenozy) Diketones

In these diketones, the effect on ET of increasing the interchromo-
phore distance from four to seven methylene units was investigated. The
fact that the quenching plots of each are linear and relatively
insensitive to decreases in kendo, but very sensitive to increases in
kindo, indicates that ET is effectively irreversible.

The most curious aspect of these systems is that the magnitude of
ET does not appear to change significantly as the interchromophore
distance increases from four to seven methylenes. The k.exo values
derived for the 5, c, C, and n diketones range from 21x107s’1 to
24.0x107s'1. These are probably within experimental error of one
another given that the bimolecular quenching rate of BP by 4-MeO-2'-
MeBzP is 2.7x109s"1M"1 which translates into a pseudounimolecular
benzoyl decay of 2.7x107s'1 at 0.01M diketone (see Results chapter).
The kendo values, which range from.0.10x107s'1 to 0.050x107s'1, are also
probably within experimental error of one another. The ET rate
constants derived for the four diketones indicate a A8 of ~3.4 kcal.
This correlates well with the 3.6 kcal predicted by phosphorescence.

The finding that ET rates do not decrease as the tether length
increases supports a “through space” mechanism for ET as opposed to a
“through bond" mechanism. A reasonable explanation for this behavior is
that the tether's effectiveness at dictating interchromophore distance
is negated by the ability of the molecules to coil upon themselves. If
ET occurred through the bonds which link the two chromophores, the
magnitude of It”,o and kmdo would be expected to decrease as the number

of spacer units increase.

140

The response of the quenching curves to ET rate changes is shown in
Figures 67-70. The quantum yields agree with the steady-state quenching
results and indicate that k.nd° is a relatively insignificant
contributor to ET. The 011.)!“ and fibula“, values of 8-(2'-Me-4-BzPhO)VP,
e-(2'-Me-4-BzPhO)HxP, C-(2'-Me-4-BzPhO)HpP, and n-(2'-Me-4-BzPhO)OtP
correlate better with 0C.1c.d'n°m than with flaunt”.

The fact that the chlnux values in the e-, C-, and n-diketones are
considerably lower than unity is a point of concern. Whether this is
due to either: 1) a lack of basicity of the Lewis base used in the
quantum yield maximization experiments (dioxane) which gave only partial
biradical solvation and incompletely suppressed reversion of the
biradical back to ground state ketone or 2) some other triplet reaction
competing for benzoyl excitation is unclear. Although the source cannot

be identified at this point, the discrepency must be acknowledged.

 

1i!

141

 

   
 

 

 

 

10

9

8

7

6

0WD 5

4 ,__..

3 ...... It,” - 2.1x107, km“, - 0.010x107
2 — It.“ - 21x10 . kn,“ - 0.10x107

1 — kn“, - 210x107, xmdo - 1.0x107

0 1 1 I 1 I 1 I 1 I 1 I 1
0.00 0.05 0.10 0.15 0.20 0.25 0.30

[Q],M

Figure 67: Stern-Volmer Plots of 5-(2'-ue-4-BzPhO)VP in
Benzene at Various ET Rates (- AP observed)

 

d>°l<b 3 "

 

 

   
 

 

...... km, - 2.1xlo7, x.,,,,,, - 0.010x107

 

 

1 — It.“ - 21x107, kn“ - 0.10x107
—k.,,o - 210x10 , nude - 1.0x107
0 1* 1 I 1 fi fi I 1
0.00 0.05 0.10 0.15 0.20
[01.1“

Figure 68: Stern-Voller Plots of c-(2'-I(e-4-BzPhO)ExP in
Benzene at Various ET Rates (0 AP observed)

142

 

 

   
 

 

 

 

 

    
 

 

 

 

s
4- "
3J
0'70
2.)
7 7
------ km, - 2.4x10 , kmdo - 0.0050x10
‘ — km, - 24xlo7, km“ - 0.050:th7
—k,xo - 240x107, km“, - 0.50x107
0 i j 1 v I V U '
0.00 0.05 0.10 0.15 0.20
[01.1“
Figure 69: Stern-Velma: Plots of C- (2 '-ue-4-BzPhO) BpP in
Benzene at Various ET Rates (0 AP observed)
a l
7
6
5
¢°l¢ 4
3 ____-
7 7
2 ...... k.x° - 2.43610 ' k.ndo - OoOOSOXIO
1 — km, - 24x107, km“, - 0.050x107
—k.,,° - 240x107, k...“ - 0.50xlo7 ‘
o I Y I ' t j I v 6 '
0.0 0.1 0.2 0.3 0.4 0.5

Figure 70:

[01M

Stern-Volmer Plots of n-(2'-ue-4-BzPhO)OtP in
Benzene at Various ET Rates (oAP observed)

143

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144

Table 12: Energy Transfer Values Derived to: Diketones

Diketone

 

 

Y‘(3-Me-4-AcPhO)BP

Y-(B-Me-4-115MeVal)Ph0)BP

5-(3-Me-4-AcPhO)VP

5-(3—Me-4-ValPhO)VP

5-(3-Me-4-(y-MeVal)PhO)VP

1-Bz-4-(2-Me-4-An)Bt

1-Bz-4-(o-Tl)Bt

7-(4-BzPhO)BP

Y‘(3-Me-4-BzPhO)BP

5-(4-BzPhO)VP

5-(3-Me-4-BzPhO)VP

5-(2'-Me-4-BzPhO)VP
£-(2'-Me-4-BzPhO)HxP
C-(2'-Me-4-szh0)npp

fl-(2'-Me-4-BzPhO)OtP

Solvent lce,‘¢,.107a'1 kendwlouz’1
Benzene 17 0.30
Methanol 18 1.0
Benzene 17 0.30
Methanol 18 1.0
Benzene 7. 0.14
Methanol 18 1.0
Benzene 7. 0.14
Benzene 7. 0.14
Methanol 18 1.0
Benzene 12 0.22
Methanol 18 1.0
Benzene 20 1.0
Methanol 11 0.50
Benzene 40 0.10
Methanol 40 0.10
Benzene 44 0.10
Methanol 47 0.10
Benzene 20 0.050
Methanol 20 0.050
Benzene 21 0.10
Methanol 37 0.10
Benzene 21 0.10
Benzene 21 0.10
Benzene 24 0.050
Benzene 24 0.050

145

Table 13: Energy Transfer Values Derived for Diketones
Studied by 8.“. l'rerking and B.P. Girl in Benzene

Diketone Item, 1073"1 kendo, 107s"1

 

 

‘y- (4-AcPhO) BP and
y—(4-ValPhO) 8?a 15 3.0

5-(4-AcPhO)VP and
5-(4-Valphowpa . 10 1.0

75(4-BzPh)BP and
1*(2'-Me-4-BzPh)BPb 97 0.20

5-(4-BzPh)VP and
5-(2'-Me-4-BzPh)VPb 48 0.10

 

a H.W. Frerking
b B.P. Giri

146

IV. Conclusions

The three major findings of this investigation into the intra-
molecular ET in diketones are: 1) kexo and kendo decrease as the
interchromophore tether length increases from three to five atoms, but
neither k9,“, nor kendo change significantly beyond five atoms, 2) the
ratio of kexo/kendo increases as A3 increases, and 3) the nature of
triplet-triplet interaction (n,u* 6+ u,u* or n,n* +9 n,n*) does not
affect ET rates.

The interchromophore tether'length, up to five units, has a
significant impact on the ET rates of diketones. When the donor
chromophore is alkanophenone and the acceptor is acylphenoxy, a tether
length increase of one methylene unit causes a factor of two decrease in
kexo from.17x107s‘1 to 7.7::1073’1 which is accompanied by a decrease in
kéfldo from3.0x10"s'1 to 1.4x107s'1. Similar decreases occur when the
acceptor chromophore is either benzoylphenyl or benzoylphenoxy for
tethers up to five atoms in length. As the tether length increases from
three to five atoms, kexo decreases from 97x107s"1 to 21::107s‘1 and kendo
decreases from 0.20x107s'1 to 0.10x107s‘1. The difference in hem/ken“
ratios between the two sets of systems can be attributed to a larger AB
when the acceptor chromophore is either benzoylphenyl or benzoylphenoxy.

The apparent leveling off of khxo as the tether length exceeds five
units, illustrated in Figure 71, is the most curious finding of this
investigation. These results favor a “through space” mechanism for ET
in diketones over the ”through bond” mechanism proposed by Closs and
coworkers in related bifunctional systemm.7'5° However, one notable

difference between the diketones of this investigation and the systems

147

studied by Close is the rigidity of the interchromophore spacer. The
cyclohexane and decalin ring spacers used by Closs are considerably more
rigid than the alkyl tethers in the diketones. Perhaps neither
mechanism precludes the existence of the other and the path which ET
follows is determined by the structure of the molecule. In flexible
systems, the through space mechanism may dominate, but in rigid systems,
the through bond mechanism may dominate.

The increase in solvent polarity from benzene to methanol
definitely made ET more reversible. Although, the increase in
complexity of the ET scheme caused by methanol makes it difficult to
ascertain all of the orbital interactions involved, the reduced benzoyl
type II reactivity is certainly the most obvious factor which affected
ET reversibility.

The type of triplet-triplet interaction in the diketones, either
n,n*++n,n* or n,n*++n,n*, did not appear to have a bearing on the ET
rates. The benzoyl donor chromophore in all diketones had an n,u*
lowest energy triplet. The acceptor chromophore had a n,n* lowest
triplet when the chromophore opposite the benzoyl donor was anisoyl or
toluoyl and an n,n* lowest triplet when the chromophore opposite the
benzoyl donor was benzophenone. Given that the type of triplet-triplet
interaction was not an independently controlled variable and the ET
rates ranged within one order of magnitude, one cannot conclude that the
triplet-triplet interaction type had any significant effect on ET rates.

The effect of interchromophore distance on ET is similar to other
studies, however the magnitude of the effect in this work is smaller.

ET rates in the diketones of this investigation decreased by a factor of

148

4 as the tether length increased from three to five atoms. This effect
is mild when compared to the factor of 20 decrease found by Cowan and
Baum; in benzoyl-styryl systems as the tether length increased from two
to four atoms, the factor of 100 decrease found by Wagner and Schevel‘
in benzoyl-azido systems as the tether length increased from three to
five atoms, and especially the factor of ~10,000 decrease found by Closs
and coworkers7 in benzoylphenyl-naphthyl systems as the number of
intervening spacer atoms increased from three to six.

And finally, it must be concluded that since the method of deriving F
ET rate constants used in this work focused primarily on the decay of
the donor alkanophenone chromophore, k.exo values were more easily and

accurately isolated than ken” values.

 

”T

149

 
 
  
 

 

 

 

1°° “2254:4131th
so -
1
It... 5° " samusmwp
107 .1 ‘ y-(3-Me-4-BzPhO)BP
S 40 q
l e-(2'-Mc4-BzPh0)HxP n-(2'-Me-4-BlPhO)OlP
20 1 0 o . 4’ '
‘ 5-(3-Me-4-BzPhOWP HZ-MM-le’hompl’
o I I I I I
a 4 s a 7 a

Intachromophore Distance (# of spacer units in tether, either CH2 or 0)

Figure 71: Plot of 1:.“ vs. Interchromophore Distance in

Benzene

 

150

V . l'uture lork

During the course of this research project, a number of parameter
values used in the ET analyses were approximated. Among these are the
ratio of syn/anti triplets in the o-methyl chromophores, lifetimes of
the syn and anti triplets, the exact triplet energies of the 4-methoxy-
2-methylketones, and the extinction coefficients of the syn and anti
conformers (they may be different). Further studies into ET should
address this issue by measuring and better quantifying these values. ?

Perhaps the easiest way to progress this research is to simplify 1
the photokinetics through elimination of the anti triplet from ET

scheme. This could be accomplished by changing the anisoyl chromophore

 

HF

of the benzoyl-(4-alkanoylphenoxy) diketones into a tetralone or maybe
an indanone. The same idea could work in the benzoyl-(4-benzoylphenoxy)
systems where the 4-benzoylphenoxy chromophore could be converted to a

fluorenone or anthrone. This would lock-out the anti form and insure

Gijo‘éé 0'1,st ®.©

(Diketones with only two triplets, no anti triplet!)

 

that ET proceeded in only the exothermic direction (from the benzoyl to
the anisoyl). There would be no long lived anti triplet through which
endothermic ET could occur: any relatively slow endothermdc ET would
have to compete with the rapid photoenolization decay. The photo-

kinetics of such systems would truly be irreversible. ‘However, it

151
should be noted that these tetrasubstituted aromatic compounds are
difficult to synthesize. My attempts to prepare phenolic precursors to
the tetralone and indanone analogs of the 4-alkanoylphenoxy and 4-
benzoylphenoxy chromophores via Friedel-Crafts chemistry proved to be
fruitless.

Other avenues of future study could focus on solid state
photochemistry. These systems would be perfect candidates for a solid
state photochemical study. Depending on the results of x-ray crystal
structures, the solid state behavior could give some valuable insight
into the effect of tether length on ET. Quite possibly the same trend
could be seen in the solid state as was evident in solution.

Another interesting path could be the addition of a few more
chromophores into the system. If the triplets were of different
energies, ET could be observed as it cascades down a string of chromo-
phores, starting at the highest energy triplet and eventually residing

on the lowest.

 

EXPERIMENTAL

1. Chemicals

This section describes the preparation, purification, and identifi-
cation of all chemicals used in this work. All solid diketones,
ketones, and internal standards were dried under vacuum in a desicator
in the presence of P205 overnight, following final recrystallizations.

a. Solvents

Benzene

Reagent-grade benzene was stirred over conc. HZSO4 until the acid
washing remained colorless (usually 3 x 300mL portions). The benzene
was washed with distilled water (2 x 300mL), saturated NaHCO3 (3 x
300mL), distilled water (2 x 200mL), saturated NaCl (1 x 300mL), and
then dried over anhydrous M9304. The filtered benzene was refluxed
overnight over P205 (~200g/4L of benzene), then distilled through a one
meter column packed with stainless steel helices. The middle fraction
(~80%) which boiled at 80.0°C was saved.

1,4-Diorane

This was purified by refluxing overnight with LiAlH4 or CaH2 and
distilling through a one foot column packed with glass rings. The
middle fraction (~80%) which boiled at 1019C was saved.

Ethanol

Ethanol (200 proof) was refluxed over Na metal (~4g/2L) overnight,
then distilled through a one foot column packed with glass rings. The

middle fraction (~80%) which boiled at 78.09C was saved.

152

153

Methanol

Spectral grade methanol was purified in the same way as ethanol
(bp=65.0°C).

2-Methyltetrahydrofuran

This was refluxed overnight over CaHZ, then distilled through a one
foot column packed with glass rings. The middle fraction (~80%) which
boiled at 78.0°C was saved.

B. Internal Standards

n-hexadecane (C16)

This was used as received from Aldrich Chemical Co.

n-eicosane (C20)

This was recrystallized twice from ethanol.

n-tetracosane (C24)

This was recrystallized twice from ethanol.

phenylnonadecane (Clg'Ph)

This was recrystallized twice from ethanol.

C. Quencher

2,5-dimethyl-2,4-hexadiene

This was used as received from Aldrich Chemical Co. The container
was kept in the freezer and pure diene was obtained by collecting

sublimed crystals at the top of the jar and weighing them out in liquid

form.

154

D. Ketones and Diketones
1.7-(3-Me-4-AcPhO)BP )b(3-methyl-4—acetylphenoxy)butyrophenone
a. y-ClBP 7—chlorobutyrophenone

The first preparation was from the Grignard reaction of 4-chloro-
butyronitrile (1 equivalent, 669, 0.64mol, Eastman Chemicals) and
phenylmagnesium bromide (1 equivalent, 1159) in dry ether. This was
allowed to stir overnight. The resulting mixture was poured into a
beaker containing lSOOg of ice/200mL of cone. HCl and warmed on the
steam bath for 2 hours in order to hydrolyze the ketimine'HCl. (NOTE:
Cold ether extraction, usually performed before warming to remove
unreacted starting material and coupling biproduct, was not done because
the ketimine'HCl hydrolyzed too quickly which resulted in loss of the
product ketone to the ether solution.) The mixture was then extracted
with ether (4 x 300mL) and the combined ether extracts were washed with
distilled water (2 x 500mL), saturated NaHCO3 solution (2 x 250mL),
distilled water (2 x 500mL), saturated NaCl solution (1 x 500mL), and
dried over anhydrous Mgsoq. All solvent was removed to yield 559 (47%
yield) of a brown oil. This oil was distilled (120-125°C at 0.8 torr)
to give a clear, light-green liquid.

The second preparation was the following. Under a N2 atmosphere,
one equivalent of anhydrous aluminum chloride (9.5g, 0.071mol) in 100mL
of CHZCl2 was stirred and cooled to 0%: for 10 minutes. To this was
added one equivalent of 4-chlorobutyryl chloride (10g, Aldrich
Chemicals) and stirring continued for another 10 mdnutes at 09C. One
equivalent of benzene (5.59) was added slowly and the mixture allowed to

warm to room temperature, then stirred overnight. The mixture was

155

poured into a beaker containing 1009 of ice/20g of cone HCl and the
aqueous layer was extracted with ether (3 x 200mL). The organic layer
and the ether extracts were combined and washed with distilled water (2
x 200mL), saturated NaHCO3 solution (2 x 200mL), distilled water (1 x
200mL), saturated NaCl solution (1 x 200mL), and dried over anhydrous
M9304. All solvent was removed on the rotavap to yield 9.0g (70% yield)
of a yellow oil. EI-MS m/e 185 (0.45%), 184 (1.2%), 183 (1.5%), 182
(M+,3.5%), 120 (31%), 105 (100%), 77 (64%); IHNMR (60MHz,CDCl3) 82.2
(quintet,2H,PhCOCHZCBZCHZCl), 83.2 (triplet,2H,PhCOCfiz), 83.7 (triplet,
ZH,CHZC1), 57.5 (triplet,2H,m-Ar), 57.6 (triplet,lH,p-Ar), 88.0
(doublet,2H,o-Ar).

b. y-IBP yriodobutyrophenone

(NOTE: It was very important to perform this procedure in
relative darkness. The amount of room light exposure was kept to a
minimum. The product becomes darker the longer it is exposed to light.)
Under a N2 atmosphere, 10 equivalents of anhydrous NaI (839, 0.55mol)
was dissolved in 500mL of dry acetone. One equivalent of erlBP (10g)
was added and the mixture was refluxed overnight. The acetone was
removed on the rotavap and the resulting solid was diluted with 200mL of
distilled water then extracted with ether (3 x lSOmL). The ether
extracts were combined and washed with distilled water (3 x 200mL),
saturated NaCl solution (1 x 200mL), and dried over anhydrous Mgsoq.
All solvent was removed on the rotavap. The crude product was
decolorized with norit in hexane and recrystallized from ethyl
acetate/hexane to give 12g (80% yield) of slightly brown—white crystal,
mp=51.0-52.0WZ. EI-MS m/e 275 (M+1,0.05%), no M+ found, 148 (5.3%), 147

(55%), 146 (18%), 120 (17%), 105 (100%), 77 (65%); 1HNMR (250MH2,CDC13)

156

52.28 (quintet,2H,J=7Hz,PhCOCH2C52CH2I), 53.16 (triplet,2H,J=7Hz,
PhCOCHZ), 53.35 (triplet,2H,J=7Hz,CHZI), 57.49 (triplet,2H,J=8Hz,m-Ar),
57.60 (triplet,1H,J=7Hz,p-Ar), 57.99 (doublet,ZH,J=7Hz,o-Ar); IR (CClq)
1690 cm-1.
c. y-IBP ketal ethylene glycol ketal of yriodobutyrophenone

In the dark, one equivalent of y—IBP (209, 0.073mol) and 6.6
equivalent of ethylene glycol (309) were refluxed in benzene along with
a catalytic amount of p-toluenesulfonic acid (~0.Sg) under a dean-stark
trap overnight. When the stoichiometric amount of water (1.39)
collected in the trap, the reaction mixture was cooled to room
temperature and washed with distilled water (3 x 200mL), saturated NaCl
solution (2 x 300mL), and dried over anhydrous M9504. All solvent was
removed on the rotavap to yield 179 (74% yield) of crude product which
was recrystallized from ethyl acetate/hexane to give white crystals,
mp=70.0-72.0°C. EI-MS m/e 300 (0.07%), 241 (1.1%), 197 (0.1%), 150
(3.1%), 149 (45%), 147 (47%), 120 (14%), 105 (100%), 77 (56%); 1HNMR
(c0c13) 81.92 (multiplet,4H,Cfl2CHQCH2I), 83.15 (triplet,2H,J=7Hz,CflZI),
53.74 (multiplet,2H,CHz ketal), 53.99 (multiplet,2H,CH2 ketal), 57.24-
7.98 (multiplet,5H,Ar); IR (CClq) no C=O present.

d. 4-NaO-2MeAP sodium salt of 4-hydroxy-2-methylacetophenone

One equivalent of NaOH (4.09, 0.1mol) was dissolved in 100mL of
MeOH/water (85/15) as N2 was bubbled through the solution. One
equivalent of 4-hydroxy-2-methylacetophenone (Aldrich Chemicals) was
added and this was allowed to stir for 1/2 hour. Most of the solvent
was removed on the rotavap, the remaining solvent was removed on a

mechanical pump overnight at 1.0 torr. The resulting white crusty solid

(100% yield) was not purified. EI-MS m/e 176 (2.9%), 149 (31%), 135
(79%), 107 (31%), 91 (15%), 77 (40%).

The diketone was prepared as follows. Under a N2 atmosphere, one
equivalent of 4-NaO-2-MeAP (119, 0.065mol) was dissolved in 100mL of dry
DMF (dried over 4A molecular sieves). One equivalent of y—IBP ketal
(179) was dissolved in SOmL of dry DMF and added slowly. (NOTE: The
ketal had to be used because the ketone gave only the result of an
enolate attack on the Yemethylene. This was confirmed by the fact that
the only isolable product was phenyl-cyclopropyl ketone which was
identified by 1HNMR) This mixture was heated to 60°C and allowed to
react overnight in the dark. The reaction mixture was diluted with
SOOmL of water and this was extracted with ether (4 x 500mL). The ether
solution was washed with distilled water (3 x 500mL), 1M NaOH (3 x
500mL), distilled water (3 x 500mL), and saturated NaCl solution (1 x
500mL), and dried over M9804. All ether was removed on the rotavap to
give a product (89, 50% yield, white crystals from ethyl acetate/hexane,
mp=54.0-56.0°C) identified by EI-MS (m/e 340,M+) as the monoketal of the
desired diketone. This monoketal was dissolved in ~50mL of
acetone/water (1:1), 29 of 82804 was added, and the mixture was warmed
on a steam bath for 10 minutes in order to hydrolyze the ketal. The
acetone was removed on the rotavap and the resulting solid was diluted
with 150mL of ether, washed with distilled water (2 x 200mL), saturated
NaHCO3 solution (1 x 100mL), and dried over M9804. All ether was
removed on the rotavap and two recrystallizations from hexane gave white
cotton-like crystals, mp=67.0-67.5W3. EI-MS m/e 296 (M+,0.36%), 177

(2%), 161 (4%), 147 (96%), 105 (100%), 77(59%): IR (cc14) 2925 cm‘l,

158

1680 cm'1 (c=0), 1690 cm-1 (C=O,sh), 1603 cm'l, 1569 cm‘l, 1452 cm'l,
1358 cm‘l, 1320 cm'l, 1295 cm'l, 1250 cm'1 (sh), 1242 curl; 13CNMR
(300MHz,CDCl3) 8199.25, 8199.18, 8161.15, 8142.03, 8136.72, 8133.01,
8132.43, 8129.82, 8128.50, 8127.88, 8117.93, 8110.87, 866.90, 834.60,
828.93, 823.52, 822.45; 1HNMR (300MHz,CDCl3) 82.25 (quintet,2H,
J=6.5Hz,Ha), 52.53 (singlet,3H,Hb), 52.55 (singlet,3H,Hc), 53.19
(triplet,ZH,J=7.le,Hd), 84.11 (triplet,ZH,J=6.SHz,He), 86.73 (singlet,
1H,Hf), 86.74 (doublet of doublet,18,J=8.3&2.7Hz,Hf.), 87.45
(triplet,ZH, J=7.7Hz,Hg), 87.56 (triplet,1H,J=7.1Hz,Hh), 87.73 (doublet,
1H,J=8.3Hz,Hi), 57.98 (doublet,2H,J=6.9Hz,Hj); see pg 197 concerning

the resolution of Hf and Hf..

 

9 'y-(3-Mc-4-AcPhO)BP

2. Y-(3-Me-4-(YHMeVal)PhO)BP )~(3-methyl-4-(7Bmethylvaleryl)-
phenoxy)butyrophenone
(1. Sodium salt of m-cresol
Prepared from m-cresol in the same manner as 4-NaO-2-MeAP.
b. y-m-cresleP y-m-cresylbutyrophenone
Prepared from.y-IBP ketal (1 equivalent, 209, 0.06mol) and the
sodium salt of m-cresol (2 equivalents, 169) in the same manner as 7-
(3-Me-4-AcPhO)BP to yield 109 of a yellow oil (67% yield) which was

recrystallized from hexane to give white crystals, mp=32.0-33.0°C.

159
1HNMR (300MHz,CDCl3) 52.22 (quintet,ZH,J=6.SHz,PhCOCHZCHQCHz-m-cresyl),
82.30 (singlet,3H,CH3), 83.19 (triplet,ZH,J=6.9Hz,PhCOCflz), 84.05
(triplet,ZH,J=6.OHz,CH2-m-cresyl), 56.67-6.75 (multiplet,3H,Ar), 57.14
(triplet,lH,Ar), 87.43 (triplet,ZH,Ar), 87.55 (triplet,1H,Ar), 87.98
(doublet,2H,Ar).

The diketone was prepared frontybm-cresleP (1 equivalent, 3.59,
0.012mol) and 4-methylvaleryl chloride (1 equivalent, 2.09, Eastman
Chemicals) in the same manner as YbClBP (Friedel-Crafts reaction). One
decolorization with norit in hexane and three recrystallizations from
hexane gave 2.59 (61% yield) of white crystals, mp=88.5-89.0W3. EI-MS
m/e 296 (1.4%), 281 (0.7%), 147 (100%), 135 (13%), 105 (41%), 77 (18%);
IR (cc14) 2960 cm’l, 1690 cmfl (c=0), 1684 cmfl (c=0), 1601 cmfl, 1568
cmfl, 1449 cmfl, 1314 cm’l, 1248 cm’l, 1208 cm'l, 1175 cm'l, 1119 cm'l;
13CNMR (300MHz,CDCl3) 8202.59 (Q=O,4-acylphenoxy), 8199.25 (g=o, '
benzoyl), 8160.86, 8141.65, 8136.78, 8133.05, 8131.29, 8130.29, 8128.54,
8127.94, 8117.91, 8110.89, 866.91, 838.84, 834.66, 833.59, 827.79,
523.58, 822.39, 822.18; 1HNMR (300MHz,CDCl3) 80.923 (doublet,6H,
J=6.0Hz,Ha), 81.55—1.65 (complex,3H,Hb&Hb.), 82.26 (quintet,2H,
J=6.SHz,HC), 52.51 (singlet,3H,Hd), 52.86 (triplet,2H,J-7.5Hz,He), 53.20
(triplet,ZH,J=7.IHz,Hf), 54.11 (triplet,ZH,J=6.0Hz,Hg), 56.73 (singlet,
lH,Hh), 56.74 (doublet of doublet,lfl,J-8.3&2.7Hz,Hh.), 57.46 (triplet,
28,J=7.4Hz,Hi), 87.57 (triplet,1H,J=7.22,Hj), 87.79 (doublet,1H,
J89.682,Hk), 57.98 (doublet,2H,J=7.ZHz,Hl); see pg 197 concerning the

resolution of Hh and “5'-

160

    

1 y-(3-Me-4-(y-MeVal)PhO)BP

3. 1-(4-BzPhO)BP yr(4-benzoylphenoxy)butyroPhenone
4-NaOBzP sodium salt of 4-hydroxybenzophenone
Prepared from 4-hydroxybenzophenone (Aldrich Chemicals) in the same
manner as 4-NaO-2-MeAP.
The diketone was prepared from one equivalent of y-IBP ketal
(4.39) and one equivalent of 4-NaOBzP (3.09) in the same manner as y-
(3-Me-4—AcPhO)BP (ethyl acetate had to be added to the ether solution
during the work-up to keep the product from falling out of solution).
The crude product (49 of a yellow solid, 85% yield) was decolorized with
norit in ethyl acetate/ether and recrystallized twice from ethyl
acetate/ether to give white, cotton-like crystals, mp=90.0—91.0°C. EI-
MS m/e 225 (1.1%), 147 (100%), 105 (82%), 77 (9.9%); IR (CCl4) 2943
cm'l, 1692 cm”1 (C=O,benzoyl), 1655 cm."1 (C=O,4-benzoylphenoxy), 1603
cm‘l, 1576 cm’l, 1559 cmfl, 1541 cmfl, 1506 cmfl, 1473 cm‘l, 1449 cmfl,
1317 cm'l, 1306 cm'l, 1279 cm‘l, 1254 cm’l, 1172 cm‘l, 1149 cm'l; 13CNMR
(300MHz,CDCl3) 5199.04 (C=O,benzoyl), 5195.18 (C=O,4-benzoylphenoxy),
5162.36, 5138.08, 5136.62, 5132.93, 5132.32, 5131.66, 5129.89, 5129.48,
8128.42, 8127.98, 8127.80, 8113.85, 867.07, 834.50, 823.41; lawns
(300MHz,CDCl3) 52.24 (quintet,2H,J-6.682,Ha), 53.17 (triplet,ZH,

J=7.1Hz,Hb), 54.11 (triplet,ZH,J=6.2Hz,Hc), 56.92 (doublet,2H,

161

J=9.0H2,Hd), 87.41 (triplet,4H,J=7.5Hz,He), 87.51 (triplet,2H,
J=7.2Hz,Hf), 87.71 (doublet,2Hg,J=8.3Hz,Hg), 87.77 (doublet,2H,

J=8.7Hz,Hh), 87.95 (doublet,2H,J=8.0Hz,Hi).

 

e y444hdfiK»BP

4. 7-(3-Me-4-BzPhO)BP 7~(3-methyl-4-benzoylphenoxy)-
butyrophenone
a. mrcresyl benzoate
One equivalent of m-cresol (59,0.046mol) was dissolved in 75mL of
10% NaOH solution and stirred. One and a half equivalents of benzoyl
chloride (109) was added and the solution stirred for half an hour at
room temperature. The reaction mixture was extracted with ether (3 x
100mL). The combined ether extracts were washed with 10% NaOH (3 x
100mL), distilled water (2 x 200ml), saturated NaCl solution (1 x
100mL), and dried over Mgsoq. All solvent was removed on the rotavap to
yield ~109 of a yellow oil which was recrystallized from hexane to give
79 (71% yield) of yellow crystals, mp - 51.0-54.0W3. EI-MS m/e 212
(M+,0.7%), 119 (100%), 91 (43%), 65 (30%).
b. 4-OH-2-MeBzP 4-hydroxy-2-methylbenzophenone
Two equivalents of anhydrous A1C13 (7.59) was dissolved in 100mL of
nitrobenzene at 0%:. One equivalent of mrcresyl benzoate (69) was

dissolved in 40mL of nitrobenzene and added over a 10 minute period.

162

The reaction was heated to 50%: and allowed to react overnight. The
reaction mixture was poured into a beaker containing 2009 of ice/SOmL
conc HCl and extracted with ether (3 x 200mL). The combined ether
extracts were washed with saturated NaHCO3 solution (4 x 200mL) to get
rid of any benzoic acid and extracted with ether (4 x 100mL). The NaOH
solution was acidified with cone HCl and extracted with ether (3 x
200mL). The combined ether extracts were washed with distilled water (1
x 300mL), saturated NaCl solution (1 x 300mL), and dried over anhydrous
M9504. All solvent was removed to yield 49 (67% yield) of a light brown
solid which was dissolved in a minimum amount of ether and loaded onto a
silica gel column (12" x 2" diam., hexane/ethyl acetate, 85/15). The
p-hydroxy product precipitated as a white solid on the top of the column
and was collected after one column volume of solvent was passed through
to flush out any o-hydroxy byproduct. The desired p-hydroxy product was
recrystallized once from ether/hexane, once from ethyl acetate/hexane,
and once from MeOH/water to give 29 (33% yield) of yellow-white
crystals, mp=127.0-129.0°C (lit. 129°C“). EI-MS m/e 212 (M+,41%), 211
(86%), 135 (75%), 77 (100%); 13CNMR (300MHz,CDCl3) 8201.05, 8163.41,
5148.03, 5138.09, 5133.46, 5131.65, 5129.00, 5129.25, 5128.25, 5119.92,
8118.43, 8116.86, 821.95; IHNMR (300MHz,CDCl3) 82.34 (singlet,3H,CH3),
56.67 (doublet,IH,J=8.1Hz,Ar), 56.88 (singlet,1H,Ar), 57.46 (doublet,1H,
J=10.le,Ar), 57.51 (triplet,2H,J-9.9Hz,Ar), 57.57 (triplet,18,J-7.SHz,
Ar), 57.65 (doublet,ZH,J=7.5Hz,Ar), 512.13 (singlet,lfl,-Ofl).
c. 4-NaO-22MeBzP sodium salt of 4-hydroxy-2-methylbenzophenone
Prepared from 4-OH—2-MeBzP in the same manner as 4-NaO-2-MeAP

(product was a bright yellow-green powder).

163

The diketone was prepared from one equivalent of y-IBP ketal (4.09)
and one equivalent of 4-NaO-2-MeBzP (3.09) in the same manner as 1-(3-
Me—4-AcPhO)BP. The crude product was passed through a silica gel column
(9" x 1" diam.) with hexane/ethyl acetate (85/15). The isolated product
was decolorized with norit in hexane and recrystallized three times from
ethyl acetate/hexane to give 29 (43% yield) of white crystals, mp=53.0-
54.0°C. EI-MS m/e 212 (0.7%), 211 (3.2%), 147 (100%), 105 (68%), 77
(7.5%); IR (cc14) 2941 curl, 1692 curl (C=O,benzoyl), 1661 curl (c=o,4-
benzoylphenoxy), 1601 cmfl, 1581 cm'l, 1568 cm’l, 1449 cmfl, 1318 cm‘l,
1273 cm'l, 1241 cm’l, 1206 cm’l, 1175 cm‘l, 1111 cm'l, 1049 cm’l; 13CNMR
(300MHz,CDCl3) 5199.20 (C=O,benzoyl), 5197.44 (C=O,4-benzoylphenoxy),
5160.50, 5140.45, 5138.70, 5136.75, 5132.97, 5132.34, 5131.95, 5130.55,
8129.84, 5128.48, 8128.13, 8127.87, 8117.20, 8110.51, 866.89, 834.34,
823.58, 820.63; IHNMR (300MHz,CDCl3) 82.24 (quintet,ZH, J=6.5H2,Ha),
82.38 (singlet,3H,Hb), 83.19 (triplet,2H,J=7.1Hz,Hc), 84.10 (triplet,ZH,
J=6.3Hz,Hd), 86.71 (doublet of doublet,lH,J=8.6&2.le,He), 86.80
(doublet,1H,J=2.1Hz,Hf), 87.29 (doublet,1H,J=8.4Hz,Hg), 87.40-7.46 (two
overlapping triplets in phase,4H,J=7.6Hz,Hh&Hh.), 57.49-7.57 (multiplet,

 

n- 7-(3-Me-4-BzPhO)BP

 

 

164

5. 5-(3-Me-4-AcPhO)VP 5-(3-methyl-4-acetylphenoxy)valerophenone
a. 5-ClVP 5-chlorovalerophenone

This was prepared from one equivalent of 5—chlorovaleryl chloride
(15.09, 0.097mol), one equivalent of AlCl3, and one equivalent of
benzene in the same manner as y-ClBP. All solvent was removed on the
rotavap to yield 16.39 (86% yield) of crude product. This was
recrystallized once from hexane to give a yellow-white solid, mp=44.0-
4s.o°c (lit. so°c57). EI-MS m/e 198 (1.3%), 196 (M+,3%), 161 (4%), 120
(21%), 105 (100%), 77 (42%); IHNMR (250MHz,CDCl3) 81.89 (multiplet,4H,
PhCOCHZCflZCHZCHZCl), 83.02 (triplet,ZH,J=7.0Hz,PhCOCflz), 83.59 (triplet,
2H,J=6.OHz,CHZCl), 57.46 (triplet,2H,J=7.382,m-Ar), 57.57 (triplet,1H,
J=7.0Hz,p-Ar), 87.95 (doublet,ZH,J=7.0Hz,o-Ar).

b. 5-IVP 5-iodovalerophenone

'Prepared from 10 equivalents of NaI (989, 0.65mol) and one
equivalent of 5-C1VP (139, 0.065mol) in the same manner as Y-IBP. All
solvent was removed on the rotavap to yield 139 (69% yield) of crude
product which was recrystallized twice from hexane to yield a yellow-
white solid, mp=69.5-70.0°C (lit. 71 EPCSB). EI-MS m/e 288 (M+,
(0.01%), 199 (0.36%), 161 (32%), 133 (2.5%), 121 (1.1%), 105 (100%), 84
(15%), 77 (46%); IHNMR (250MHz,CDCl3) 81.93 (multiplet,4H,PhCOCH2Cflz-
CHZCHZI), 53.01 (triplet,2H,J=7.0Hz,PhCOCflQ), 53.23 (triplet,2H,
J=7.oaz,ca21), 87.46 (triplet,2H,J=6.9Hz,m-Ar), 87.57 (triplet,lH,
J=7.3Hz,p-Ar), 87.96 (doublet,2H,J=6.7Hz,o-Ar).

The diketone was prepared as follows. Under a N2 atmosphere, one
equivalent of 4-NaO-2-MeAP (9.59, 0.055mol) was dissolved in 100mL of
dry DMF. One equivalent of 5-IVP (13g), dissolved in SOmL of dry DMF,

was added slowly. This mixture was heated to 60°C and allowed to react

165

overnight in the dark. The resulting mixture was cooled to room
temperature and diluted with 200mL of water and extracted with ether (3
x 200mL). The ether solution was washed with distilled water (2 x
200mL), 1M NaOH solution (2 x 200mL), distilled water (3 x 200mL),
saturated NaCl solution (1 x 200mL), and dried over anhydrous M9304.
All solvent was removed to yield 9.59 (68% yield) of a yellow-white
solid which was recrystallized 4 times from hexane to give white
cotton-like crystals, mp=79.0—79.59C. EI-MS m/e 310 (M+,0.52%), 161
(74%), 135 (13%), 121 (1.7%), 105 (100%), 91 (2.8%), 77 (33%); IR
(cc14) 2958 cnfl, 1690 curl (sh,C=O), 1680 curl (C=O), 1600 cmfl, 1567
cm-1, 1500 curl; 13CNMR (300MHz,CDCl3) 8199.68, 8199.29, 8161.28,
5142.05, 5136.85, 5132.92, 5132.44, 5129.75, 5128.50, 5127.91, 5117.93,
8110.88, 867.58, 837.88, 528.95, 828.56, 822.48, 820.70; IHNMR (300MHz,
CDC13) 51.91 (multiplet,4H,Ha), 52.53 (singlet,3H,Hb), 52.55 (singlet,
3H,Hc), 53.06 (triplet,2H,J=6.9Hz,Hd), 84.05 (triplet,2H,J=6.0Hz,He),
56.71 (singlet,1H,Hf), 56.73 (doublet of doublet,1H,J=8.3&2.7H2,Hf.),
87.45 (triplet,ZH,J=7.5Hz,Hg), 87.56 (triplet,1H,J=7.2Hz,Hh), 87.73
(doublet, 18,J=8.3Hz,Hi), 57.96 (doublet,2H,J=6.9Hz,Hj); see pg 197

concerning the resolution of Hf and Hf..

f.

 

9 5(35MhtJWThCDVP

166

6. 8—(3-ua-4-Vaiphowp 5-(3-methyl-4-valerylphenoxy)-

valerophenone
5-m-cresy1VP 5-m-cresylvalerophenone

Prepared from 5-IVP and the sodium salt of m-cresol in the same
manner as y—(3-Me-4-AcPhO)BP. The crude product was passed through a
silica gel column (9" x 1" diam.) with hexane and recrystallized from
hexane to give white crystals which melted just above room temperature
(ZS-30°C). 1HNMR(3001~mz,c0c13) 81.89 (multiplet,4H,PhCOCHZCfl2Cfl2CH2-m-
cresyl), 52.31 (singlet,3H,CH3), 53.05 (triplet,2H,J=7.0Hz,PhCOCflZ),
53.99 (triplet,2H,J=6.0Hz,Cfiz-m-cresyl), 56.68-6.77 (multiplet,3H,Ar),
57.15 (triplet,1H,Ar), 57.45 (triplet,ZH,Ar), 57.55 (triplet,1H,Ar),

87 96 (doublet,2H,Ar).

The diketone was prepared as follows. One equivalent of 5-m-
cresylVP (189, 0.067mol), two equivalents of valeric acid (149), and
3009 of polyphosphoric acid were heated to 50°C and stirred for 4 hours.
In an ice bath, the mixture was neutralized with solid K2C03 and
extracted with ether (3 x 200mL). The combined ether extracts were
washed with saturated NaHCO3 solution (3 x 200mL), distilled water (2 x
200mL), saturated NaCl solution (1 x 300mL), and dried over anhydrous
M9804. All solvent was removed on the rotavap to yield 209 (83% yield)
of a yellow oil which was passed through a silica gel column (9" x 1"
diam.) with hexane/ethyl acetate (85/15), decolorized with norit in
ethanol, and recrystallized twice from hexane to give white cotton-like
crystals, mp=37.0-38.0%2. EI-MS m/e 352 (M+,<0.01%), 295 (1.3%), 191
(1.7%), 161 (100%), 135 (35%), 105 (90%), 77 (47%): IR (CC14) 2961

‘

cm'*, 1696 curl (C=O), 1684 curl (C=O), 1601 cmrl, 1558 cmfl, 1541 cm‘l,

 

167

1522 cm'l, 1506 cm'l, 1456 cm-1, 1248 cmfil; 13CNMR (300MHz,CDCl3) 8202.45
(C=O,4-acylphenoxy), 5199.74 (C=O,benzoyl), 5160.99, 5141.66, 5136.89,
5132.95, 5131.35, 5130.20, 5128.53, 5127.94, 5117.90, 5110.89, 567.58,
840.53, 837.92, 828.62, 826.86, 822.45, 822.22, 820.76, 813.90; IHNMR
(250MHz,CDCl3) 80.914 (triplet,3H,J=7.3Hz,Ha), 81.36 (sextet,2H,
J=7.0Hz,Hb), 81.65 (quintet,2H,J=7.4Hz,Hc), 81.90 (multiplet,4H,Hd),
52.50 (singlet,3H,He), 52.84 (triplet,2H,J=7.BHz,Hf), 53.05 (triplet,
2H,J=6.9H2,Hg), 84.03 (triplet,2H,J=5.8Hz,Hh), 86.71 (singlet,1H,Hi),
56.72 (doublet of doublet,IH,J=8:3&2.7Hz,Hi.), 57.44 (triplet,2H,
J=7.ZHz,Hj), 87.55 (triplet,lH,J=7.3Hz,Hk), 87.67 (doublet,1H,J=9.5Hz,
H1), 57.95 (doublet,2H,J=7.0Hz,Hm); see pg 197 concerning the

resolution of Hi and “1'-

LJ.

 

3 5-(3-Me-4-ValPhO)VP

7 . 5-(3-143-4- (y-MeVal)PhO)VP 5- (3-methyl-4- (y-methyl valeryl) -

phenoxy)valerophenone
a . 4-OH-2-Me-y-MOVP 4-hydroxy-2-methyl -7—methyl valerophenone

Two equivalents of anhydrous AlCl3 (24g, 0.18mol) was dissolved in
SOmL of nitrobenzene and stirred at 0%: as one equivalent of mrcresol
(109, 0.09mol) was added slowly. One equivalent of 4-methylvaleryl
chloride (12.49, Aldrich Chemicals) was dissolved in 25mL of nitro-
benzene and added over a five minute period. The reaction was allowed

to run for 48 hours at 0%:. The reaction mixture was poured into a

168

beaker containing 2009 of ice/30mL conc HCl and extracted with ether (3
x 200mL). The combined ether extracts were washed with distilled water
(1 x 200mL) and extracted with 2M NaOH solution (3 x 150mL). The
combined NaOH extracts were washed with ether (1 x 200mL), neutralized
with cone HCl, and extracted with ether (3 x 200mL). The combined ether
extracts were washed with saturated NaHCO3 solution (2 x 200mL),
distilled water (2 x 200mL), saturated NaCl solution (1 x 300mL), and
dried over anhydrous M9504. All solvent was removed on the rotavap to
yield 109 (53% yield) of a yellow oil which was passed through a silica
gel column (12" x 2" diam.) with hexane/ethyl acetate (85/15). The
isolated product was recrystallized from ethyl acetate/hexane to give
white crystals, mp=75.0-76.0°C. EI—MS m/e 207 (M+1,0.13%), 206
(M+,0.45%), 163 (1.9%), 150 (20%), 135 (100%), 107 (13%), 77 (18%);
IHNMR (250MHz,CDCl3) 80.904 (doublet,6H,J=6.4Hz,CH(Cfl3)2), 81.57
(multiplet,3H,ArC0CHZC82Cfi), 82.45 (singlet,3H,o-CH3), 82.85 (triplet,
2H,J=7.5Hz,ArCOCfi2), 56.68-6.72 (multiplet,2H,Ar), 87.65 (doublet,lH,
J=9.2Hz,Ar).
b. 4-NaO-2-Me-y-MeVP sodium salt of 4-hydroxy-2-methyl-y-

methylvalerophenone

Prepared from 4-OH—2-Me-7HMeVP in the same manner as 4-NaO-2-MeAP.

The diketone was prepared from.5-IVP (1 equivalent, 2.89, 0.01mol)
and 4—NaO-2—Me-y-MeVP (1 equivalent, 2.29) in the same manner as 1-(3-
Me-4-AcPhO)BP. The crude product (a yellow oil) was recrystallized
twice from hexane to give 2.59 (71% yield) of white, cotton-like
crystals, mp=45.0-46.0°C. EI-MS m/e 366 (M+,1.7%), 310 (3.4%), 161

(100%), 135 (33%), 105 (90%), 91 (22%), 77 (48%); IR (cc14) 2959 cm-1,

169

1690 cm-1 (C=O,sh), 1684 curl (C=O), 1601 cm-1, 1559 cm'l, 1506 cm-1,
1456 cm-1, 1314 cm”, 1248 cm-1, 1119 cm-1; 13mm (300MH2,CDC13) 8202.58
(C=O,4-acylphenoxy), 5199.71 (C=O,benzoyl), 5160.98, 5141.64, 5136.88,
8132.93, 8131.29, 8130.18, 8128.52, 8127.93, 8117.89, 8110.89, 867.57,
538.82, 537.90, 533.60, 528.60, 527.80, 522.35, 522.20, 520.75; 1HNMR
(300Mflz,CDCl3) 50.925 (doublet,68,J=6.4Hz,Ha), 51.60 (complex,3H,
absnb.), 81.93 (complex,4H,HC), 82.52 (singlet,3H,Hd), 82.86 (triplet,2H,
J=7.5Hz,He), 53.06 (triplet,2H,J=6.8Hz,Hf), 54.04 (triplet,ZH,J=5.9Hz,
Hg), 56.71 (singlet,IH,Hh), 56.73 (doublet of doublet,1H,J-8.3&2.7Hz,flh.)
57.45 (triplet,2H,J=7.5Hz,Hi), 57.56 (triplet,1H,J=7.5Hz,Hj), 57.69
(doublet, 1H,J=9.0Hz,HK), 57.96 (doublet,2H,J=9.0Hz,Hl); see pg 197

concerning the resolution of Rh and Hh..

 

i 5-(3-Me-4-(y—McVaDPhOWP

8. 5-(4-BzPhO)VP 5-(4-benzoylphenoxy)valerophenone

The diketone was prepared from 5-IVP (1 equivalent, 59, 0.017mol)
and 4-NaOBzP (1 equivalent, 49) in the same manner as y-(3-Me-4-AcPhO)BP
(ethyl acetate had to be added to the ether solution during the work-up
to keep product from falling out of solution). The crude product
(yellow solid, 4.59, 73% yield) was decolorized with norit in ethyl
acetate/ether and recrystallized from ether to give white, cotton-like
crystals, mp=93.5-94.0%2. EI-MS m/e 211 (0.15%), 198 (1.8%), 161 (59%),

121 (10%), 105 (100%), 77 (18%); IR (cc14) 2947 cm'l, 1693 cmfl (c=0,

170

benzoyl), 1658 cm“1 (C=O,4-benzoylphenoxy), 1603 cm’l, 1559 cm'l, 1508
cm-1, 1449 cm-1, 1420 cm'l, 1317 cm‘l, 1306 cm'l, 1280 cm“, 1254 cm’l,
1173 cm-1, 1150 cm-1; 13cm (300MHz,CDCl3) 8199.61 (C=O,benzoyl),
5195.29 (£80,4-benzoylphenoxy), 5162.53, 5138.18, 5136.79, 5132.88,
8132.39, 8131.69, 8129.86, 8129.54, 8128.46, 8128.03, 8127.86, 8113.88,
567.78, 537.83, 528.51, 520.65; 1HNMR (300MHz,CDC13) 51.80-2.00
(complex,4H,Ha), 53.04, (triplet,2H,J=6.8Hz,Hb), 54.05 (triplet,2H,
J=5.7Hz,Hc), 56.89 (doublet,2H,J=8.7Hz,Hd), 57.42 (two overlapping
triplets,4H,J=7.4Hz,He), 57.52 (two overlapping triplets,2H,J=7.4Hz,
Hfauf.), 87.72 (doublet,2H,J=8.1Hz,Hg), 87.78 (doublet,2H,J=8.7Hz,Hh),

57.94 (doublet,2H,8.4Hz,Hi).

 

e 5—(4-BzPhO)VP

9. 5-(3-Me-4-BzPhO)VP 5e(3-methyl-4-benzoylphenoxy)-
valerophenone

The diketone was prepared from 5-IVP (1 equivalent, 1.6g, 0.0056mol)
and 4-NaO-2-MeBzP (1 equivalent, 1.39) in the same manner as 7-(3-Me-4-
AcPhO)BP. The crude product, a yellow oil, was passed through a silica
gel column (12" x 1" diam.) and eluted with hexane/ethyl acetate (85/15).
A clear, colorless oil (1.59, 71% yield) believed to be the desired
product by TLC comparison with y—(3-Me-4-BzPhO)BP was isolated and
recrystallized twice from i-PrOH/water (a primary crystallization was

induced by freezing the solution in dry ice and then allowing it to warm

171

in the refrigerator overnight) to give white crystals, mp=44.0-45.0%3.
EI-MS m/e 373 (0.3%), 372 (M+,0.2%), 316 (0.2%), 211 (11%), 161 (77%),
105 (100%), 77 (74%); IR (cc14) 2945 curl, 1692 cmfl (C=O,benzoyl), 1661
cnfl (C=O,4-benzoy1phenoxy), 1601 cm‘l, 1566 cmfl, 1449 cmfl, 1318 cmfl,
1288 cmfl, 1273 cmfl, 1240 cm-1, 1177 cm'l, 1111 curl; 13CNMR (300MHz,
CDCl3) 5199.83 (C=O,benzoyl), 5197.66 (C=O,4-benzoylphenoxy), 5160.72,
8140.59, 8138.86, 8136.97, 8132.99, 8132.43, 8132.08, 8130.59, 8129.98,
8128.58, 8128.24, 5128.01, 8117.30, 8110.58, 867.66, 838.00, 828.71,
820.85, 820.76; IRNMR (300MHz,COC13) 51.84—2.00 (complex,4H,Ha&Ha.),
82.38 (Singlet,3H,Hb), 83.06 (triplet,2H,J=6.9Hz,Hc), 84.05 (triplet,2H,
J=5.9Hz,Hd), 56.69 (doublet of doublet,1H,J=8.4&2.7H2,He), 56.77 (doublet,
1H,J=2.7H2,Hf), 57.29 (doublet,1H,J=8.7Hz,Hg), 57.40-7.47 (triplet,4H,
J=7.8Hz,Hh), 87.51-7 56 (complex,2H,Hi&Hi.), 87.74 (doublet,2H,J=6.9Hz,

Hj), 87.95 (doublet,2H,J=8.4Hz,Hk).

 

5—(3-Me-4-BzPhO)VP

10. 5-(2'-Me-4-BzPhO)VP 5-(2'emethyl-4-benzoylphenoxy7-»
valerophenone
5-PhOVP 5thenoxyvalerophenone
Prepared from one equivalent of 5-IVP (209, 0.094mol) and two
equivalents of sodium phenoxide (229) in the same manner as y—(B-Me-4-
AcPhO)BP. The crude product was recrystallized from hexane to give 209

(83% yield) of a yellow—white powder, mp=67.0-67.5%2 (lit. 68.75-

172

69.0°c59). lHNMR (3OOMH2,CDC13) 81.90 (multiplet,4H,PhCOCH2CH2Cflz-
cnzopn'), 83.05 (triplet,2H,J-7.1Hz,PhCOCflZ), 84.00 (triplet,2H,J=6.0Hz,
CHQOPh), 56.85-6.93 (overlapping triplet and doublet,3H,o&p-Ph'), 57.25
(triplet,2H,J=6.9Hz,m-Ph'), 57.45 (triplet,2H,J=7.SHz,m-Ph), 57.55
(triplet,1H,J=7.5Hz,p-Ph), 57.95 (doublet,2H,J=7.5Hz,o-Ph).

The diketone was prepared from the Friedel-Crafts acylation of 5—
PhOVP (1 equivalent, 3.59, 0.012mol), AlC13, and o-toluyl chloride (1
equivalent, 1.89) in the same manner as y-ClBP. The crude product was
passed through a silica gel column (12" x 1" diam.) with hexane/ethyl
acetate (85/15). The isolated product was recrystallized twice from
hexane to give 29 (45% yield) of white crystals, mp=71.0-72.0°C. EI-MS
m/e 372 (M+,0.2%), 267 (0.2%), 251 (0.7%), 212 (4%), 211 (19%), 161
(68%), 105 (100%), 91 (16%), 77 (42%); IR (cc14) 2950 cm‘l, 1692 cm‘1
(C=O,benzoyl), 1663 cm”1 (C=O,4-benzoylphenoxy), 1601 cm'l, 1576 cm'l,
1509 cm’l, 1449 cmfl, 1254 cm'l, 1177 cm’l, 1152 cmfl, 1047 cm‘l, 926
curl; 13CNMR (300MHz,CDCl3) 8199.63 (C=O,benzoyl), 8197.18 (c=o,4-
benzoylphenoxy), 8163.06, 8139.18, 8136.84, 8136.00, 8132.93, 8132.37,
8130.70, 8130.33, 8129.64, 5128.50, 8127.89, 8127.80, 8125.06, 8114.06,
867.86, 837.86, 828.54, 820.68, 819.67; IHNMR (300MHz,CDCl3) 51.80—2.00
(complex,4H,Ha&Ha.), 52.29 (singlet,3H,Hb), 53.06 (triplet,ZH,J-6.5Hz,
Hc), 54.06 (triplet,2H,J=5.6Hz,Hd), 56.89 (doublet,ZH,J=8.lflz,He), 57.20-
7.28 (complex,3n,nf,uf.,afu), 87.35 (triplet,lH,J-7.2H2,Hg), 87.44
(triplet,2H,7.7Hz,Hh), 57.55 (triplet,lfl,J-7.1H2,Hi), 57.76 (doublet,2H,

J=8.1Hz,Hj), 87 95 (doublet,2H,J=8.le,Hk).

173

 

5—(2'-M84-BzPhO)VP

11” 5-(4-CNPhO)VP 5-(4-cyanophenoxy)valerophenone

4-NaOBzCN sodium salt of 4-hydroxybenzonitrile

Prepared from 4-hydroxybenzonitri1e (Aldrich Chemicals) in the same
manner as 4-NaO—2-MeAP.

The ketone was prepared from 5-IVP (1 equivalent, 19, 0.0035mol)
and 4-NaOBzCN (1.5 equivalents, 0.749) in the same manner as y-(3-Me-4-
AcPhO)BP. The crude product (yellow solid) was recrystallized twice
from ethyl acetate/hexane to give 0.89 (82% yield) of white, cotton-like
crystals, mp=96.0-96.5°C (lit. 96.25-96.50°c6°). sI—Ms m/e 279 (m,
0.12%), 200 (0.12%), 161 (62%), 105 (100%), 91 (4%), 77 (44%); IR
(cc14) 2950 cmrl, 2229 cmfil (CN), 1693 curl (C=O), 1609 cmfil, 1511 cmfil,
1450 cm-1, 1301 cm'l, 1257 cm’l, 1172 cm-1; lHNMR (250MH2,CDC13) 81.91
(multiplet,4H,Ha), 83.05 (triplet,2H,J=6.7Hz,Hb), 84.04 (triplet,2H,
J=5.6Hz,Hc), 86.90 (doublet,2H,J=8.8Hz,Hd), 87.45 (triplet,ZH,J=7.5Hz,
He), 87.54 (triplet,1H,J=7.8Hz,Hf), 87.55 (doublet,2H,J=9.0Hz,Hg), 87.93

(doublet,2H,J=7.0Hz,Hh).

 

e 8-(4-CNPhO)VP

i
6

 

174

12. €-(2'-Me-4-BzPhO)HxP 6-(2'-methyl-4-benzoylphenoxy)-

hexanophenone
I. e-BerP e-bromohexanophenone

Under a nitrogen atmosphere, one equivalent of 6—bromohexanoic acid
(7.09, 0.036mol, Aldrich Chemicals) and one half equivalent of PC13
(2.59) were heated to 60°C for 1.5 hrs. The reaction mixture was cooled
to 0°C, diluted with 50mL of CHZClz, and 1.1 equivalents of AlCl3 (5.39)
was added. After stirring for 10 minutes, one equivalent of benzene
(2.89) was added slowly and the reaction was allowed to run for two
hours. The usual work-up (see y-ClBP) gave 9.09 of a white solid. The
crude bromide was not purified because a large amount of product could
have been the chloride (from a halogen exchange side reaction) and since
a NaI displacement reaction would convert both bromide and chloride to
the desired iodide.

b. e-IHxP E-iodohexanophenone

Prepared from e-BerP (1 equivalent, 5.59, 0.022mol) and NaI (10
equivalents, 329) in the same manner as Y-IBP. The crude product was
recrystallized from hexane to give 4.09 (60% yield) of light brown
crystals, mp=40.5-41.SWZ. EI-MS m/e 302 (M+,0.94%), 231 (0.10%), 193
(0.10%), 175 (14%), 149 (1.9%), 133 (2.9%), 120 (39%), 105 (100%), 91
(3.3%), 77 (45%). 1HNMR (300MHz,CDCl3) 51.49 (multiplet,2H,PhCOCH2CHZ-
CEZCHZCHZI), 81.77 (quintet,2H,J-7.6Hz,PhCOCH2Cfl2), 81.88 (quintet,ZH,
J=7.3Hz,CH2CHZI), 52.99 (triplet,ZH,J=7.4Hz,PhCOCflz), 53.20 (triplet,2H,
J=7.1Hz,CflzI), 87.47 (triplet,2H,J=7.8Hz,m-Ar), 87.55 (triplet,1H,

J=7.4Hz,p-Ar), 57.94 (doublet,2H,J=9.0Hz,o-Ar).

 

175

c. e-IHxP ketal ethylene glycol ketal of £—iodohexanophenone
Prepared from one equivalent of e-IHxP (7.09,0.023mol) and 6.6
equivalents of ethylene glycol (9.59) in the same manner as Y-IBP ketal.

The crude product (7.09, yellow oil) was not purified. 1HNMR (CDC13)
51.10-1.80 (multiplet,8H,4xCHz), 83.01 (triplet,2H,J=7.2Hz,Cfl21), 83.64
(multiplet,2H,CH2,ketal), 53.86 (multiplet,ZH,CHZ,ketal), 57.00-7.40
(multiplet,SH,Ar).
d. E-PhOHxP E-phenoxyhexanophenone

Prepared from one equivalent of e-IHxP ketal (6.59, 0.02mol) and
1.1 equivalents of sodium phenoxide (2.4g) in the same manner as y-(3-
Me-4-AcPhO)BP. (NOTE: The ketal had to be used because the ketone gave
only the result of an enolate attack on the e-methylene. This was
confirmed by the fact that the only isolable product was phenyl-
cyclopentyl ketone which was identified by lHNMR) The crude product was
passed through a silica gel column (12" x 2" diam.) with hexane/ethyl
acetate (85/15) and 3.59 (70% yield) of product was isolated.
Recrystallization from hexane gave white crystals, mp=46.0-47.5°C. EI-
MS m/e 268 (M+,0.33%), 242 (0.66%), 199 (0.10%), 175 (15%), 133 (13%),
105 (100%), 91 (6.5%), 77 (60%). inNMR (c0c13) 81.60 (multiplet,28,
phcocuzcazcnzcazcazoph'), 81.82 (sextet,4H,J=6.5Hz,PhCOCH2Cfl2CH2Cfl2-
CHZOPh'), 53.00 (triplet,ZH,J=7.SHz,PhCOCHZ), 53.97 (triplet,2H,J=6.0Hz,
CHQOPh'), 56.87-6.95 (overlapping triplet and doublet,3H,o&p-Ph'), 57.26
(triplet,2H,J=7.5Hz,m-Ph'), 87.44 (triplet,2H,J=7.2Hz,m-Ph), 87.53
(triplet,1H,J=7.2Hz,p-Ph), 57.94 (doublet,2H,J-7.2Hz,o-Ph).

The diketone was prepared from from the Friedel-Crafts acylation of

E-PhOHxP (one equivalent, 3.59, 0.013mol), o—toluoyl chloride (1.1

 

176

equivalents, 2.29), and of AlCl3 (2.2 equivalents) in the same manner as
YbClBP. The crude product was passed through a silica gel column (12“ x
2" diam., 85% hexane/15% ethyl acetate). The isolated product was
decolorized with norit in isopropanol/water and recrystallized twice
from isopropanol/water to give 3.09 (59% yield) of white crystals,
mp=41.0—42.0°C. EI-MS m/e 386 (0.72%), 368 (1.1%), 212 (8.1%), 211
(4.8%), 195 (11.5%), 175 (12%), 121 (10%), 105 (100%), 91 (18%), 77
(38%). IR (CC14) 2946 cm‘l, 1692 cm”1 (C=O,benzoyl), 1663 cnfl (C=O,4-
benzoylphenoxy), 1601 cmfil, 1576 cmfl, 1508 cm'l, 1449 cmfl, 1254 cmfl,
1177 cmfl, 1152 cmfl, 926 curl; 13CNMR (300MHz,CDC13) 8199.95 (cs0,
benzoyl), 8197.19 (C=O,4-benzoylphenoxy), 8163.16, 8139.20, 8136.92,
8136.01, 8132.87, 8132.38, 8130 70, 8130.28, 8129 64, 8128.49, 8127.91,
8127 80, 8125.07, 8114.08, 867.92, 838.25, 828.90, 825.68, 823.82,
819.67; lHNMR (300MHz,CDCl3) 81.58 (multiplet,2H,Ha), 81.83 (multiplet,
4H,Hb&Hb.), 82.28 (singlet,3H,Hc), 83.00 (triplet,2H,J=7.4Hz,Hd), 84.03
(triplet,2H,J=6.3Hz,He), 56.90 (doublet,ZH,J=8.4Hz,Hf), 87.20-7.28
(complex,3H,Hg,Hg.,ng), 57.35 (triplet,1H,J=7.4Hz,Hh), 57.44 (triplet,
2H,J=7.7H2,Hi), 87.55 (triplet,1H,J=7.2Hz,Hj), 87.77 (doublet,2H,

J=8.7Hz,Hk), 87.95 (doublet,2H,J=8.1Hz,Hl).

    

1 £-(2'-Mc~4-BZPhO)HxP

177

13. €-(4-CNPhO)HxP £-(4-cyanophenoxy)hexanophenone

Prepared from one equivalent of e-IHxP ketal (5.7g, 0.017mol) and
1.1 equivalents of 4-NaOBzCN (2.6g) in the same manner as Y-(3-Me-4-
AcPhO)BP. The crude product was decolorized with norit in hexane and
recrystallized three times from hexane to give white crystals, mp=83.0-
83.5%2. EI-MS m/e 293 (M+,0.14%), 175 (15%), 149 (1.6%), 133 (5.5%),
120 (18%), 105 (100%), 91 (5.8%), 77 (43%); IR (cc14) 2948 cm‘l, 2229
cm’1 (CN), 1692 cm”1 (C=O), 1609 cm‘l, 1576 cm'l, 1510 cm‘l, 1450 cmfl,
1300 cm-1, 1258 cm'l, 1172 cm'l, 1002 curl; 13CNMR (300MH2,CDC13)
8199.65, 8162.06, 8136.67, 8133.58, 8132.67, 8128.29, 8127.68, 8118.96,
8114.92, 8103.31 (cN), 867.84, 837.98, 828.57, 825.38, 823.54; 1HNMR
(c0c13) 81.55 (multiplet,2H,Ha), 51.83 (multiplet,4H,Hb), 83.00 (triplet,
2H,J=7.SHz,HC), 54.00 (triplet,2H,J=6.3Hz,Hd), 56.90 (doublet,2H,
J=9.3Hz,He), 87.44 (triplet,2H,J=7.2Hz,Hf), 87.54 (triplet,lH,
J=7.8Hz,Hg), 57.55 (doublet,3H,J=9.0Hz,Hn), 57.94 (doublet,2H,

J=8.1HZ, H1) .

 

f e44tnunmnnxp

14. C-(2'-Me-4-82PhO)HpP C-(Z'—methyl-4-benzoylphenoxy)-
heptanophenone
a. C-BerP {-bromoheptanophenone
Prepared by the Grignard reaction of one equivalent of 7-bromo-

heptanonitrile (4.09, 0.02mol, Aldrich Chemicals) and one equivalent of

 

178

phenyl magnesium bromide in the same manner as Y-ClBP. The reaction
mixture had to be extracted with ethyl acetate because the product would
not dissolve in ether. Following the usual workup, the crude product
was recrystallized from ether to give 59 (89% yield) of brown crystals,
mp=94.0-97.0%3. EI-MS m/e 259 (10%), 221 (0.5%), 175 (8.3%), 149 (18%),
133 (9.1%), 129 (11%), 120 (43%), 105 (100%), 91 (8.4%), 77 (41%); 1HNMR
(c0c13) 81.30 (multiplet,8H,PhCOCHZCHZCHZCflz-C112CHZBr), 81.71 (multiplet,
2H,CflzBr), 52.94 (triplet,ZH,J-7.5Hz,PhCOCH2), 57.43 (triplet,2H,m-Ar),
57.55 (triplet,1H,p-Ar), 57.98 (doublet,2H,o-Ar).
b. C-BerP ethylene glycol ketal of C-bromoheptanophenone
Prepared from one equivalent of C-BerP (7.09, 0.026mol) and
ethylene glycol in the same manner as Y—IBP ketal. The crude product
(~89) was a yellow oil which did not solidify in the freezer and was not
purified further.
c. C-IRpP ketal ethylene glycol ketal of {-iodoheptanophenone
Prepared from one equivalent of C-BerP ketal (8.09, 0.026mol) and
10 equivalents of NaI (399) in the same manner as y-IBP. The crude
product (~99, yellow oil) was not purified further.
d. C-PhOHpP C-phenoxyheptanophenone
Prepared from one equivalent of C-IHpP ketal (9.09, 0.025mol) and
1.1 equivalents of sodium phenoxide (3.29) in the same manner as Y-(3-
Me-4-AcPhO)BP. (NOTE: The ketal had to be used because the ketone gave
only the result of an enolate attack on the C-methylene. This was
confirmed by the fact that the only isolable product was phenyl-
cyclohexyl ketone which was identified by 1HNMR.) The resulting yellow
oil was passed through a silica gel column (8" x 2" diam., hexane/ethyl

acetate, 85/15) and the isolated product was recrystallized from ethyl

179

acetate/hexane to give 2.09 (29% yield) of white crystals, mp=64.0-
65.0°C. inNMR (coc13) 81.20-1.80 (multiplet,8H,PhCOCH2CBZCHQCfl2Cfi2-
CHZOPh'), 82.97 (triplet,ZH,J=7.ZHz,PhCOCfi2), 83.94 (triplet,2H,J=6.3Hz,
CHZOPh'), 56.80-6.95 (overlapping triplet and doublet,3H,o&p-Ph'), 57.25
(triplet,2H,J=7.5Hz,m-Ph'), 87.45 (triplet,ZH,J=7.2Hz,m-Ph), 87.55
(triplet,lH,J=7.2Hz,p-Ph), 87.98 (doublet,2H,J=7.2Hz,o-Ph).

The diketone was prepared by the Friedel-Crafts acylation of one
equivalent C-PhOHpP (2.59, 0.009mol), 1.1 equivalents of o-toluoyl
chloride (1.59), and 2.2 equivalents of AlCl3 (2.69) in the same manner
as Y—ClBP. The resulting oil was passed through a silica gel column
(12" x 2" diam.) with hexane/ethyl acetate (85/15) and the isolated
product was decolorized with norit in isopropanol/water. The resulting
white solid was recrystallized twice from isopropanol/water to give 1.09
(28% yield) of white crystals, mp=77.0-78.0°C. EI-MS m/e 400 (M+,2.7%),
382 (24%), 212 (22%), 211(100%), 195 (23%), 105 (81%), 91 (5.0%), 85
(25%), 71 (7.0%); IR (CClq) 2944 curl, 1692 cm’1 (C=O,benzoyl), 1662
cm‘1 (C=O,4-benzoylphenoxy), 1600 cm'l, 1575 cm‘l, 1509 cm'l, 1450 cmfl,
1254 cm-1, 1176 cm-1, 1152 cm-1, 927 curl; 13CNMR (300MH2,CDC13) 8200.8
(C=O,benzoyl), 5197.12 (C=O,4-benzoylphenoxy), 5163.18, 5139.17,
5136.91, 5135.96, 5132.79, 5132.34, 5130.66, 5130.19, 5129.60, 5128.44,
8127.88, 8127.77, 8125.03, 8114.05, 868.02, 538.25, 828.88, 828.81,
825.76, 824 03, 819.65; IHNMR (300MHz,CDCl3) 81.50 (complex,4H,Ha&Ha.),
51.80 (septet,4H,J-6.9Hz,Hb&Hb.), 52.29 (singlet,3H,Hc), 52.98 (triplet,
2H,J=7.ZHz,Hd), 84.02 (triplet,2H,J=6.5Hz,He), 56.90 (doublet,ZH,
J=8.7H2,Hf), 87.19-7.29 (complex,3a,Hg,Hg.,Hg.), 87.35 (triplet,lH,

J=7.7Hz,Hh), 87.44 (triplet,ZH,J=7.SHz,Hi), 87.54 (triplet,1H,J=7.ZHz,

 

180

Hj), 87.77 (doublet,2H,J=9.0Hz,Hk), 87.95 (doublet,2H,J=7.5Hz,Hl).

 

i C-(2'-Me-4-BzPhO)HpP

15. C-(Q-CNPhO)RpP {-(4-cyanophenoxy)heptanophenone

Prepared from one equivalent of C-IHpP ketal (6.09) and 1.1
equivalents of 4-NaOBzCN (2.69) in the same manner as y-(3-Me-4-AcPhO)BP.
The crude product was decolorized three times with norit in ethyl
acetate/hexane and recrystallized three times from ethyl acetate/hexane
to give 4.09 (77% yield) of white crystals, mp=78.5-79.5%2. EI-MS m/e
307 (M+,0.1%), 189 (6.4%), 149 (2.5%), 133 (4.9%), 129 (2.2%), 120 (34%),
105 (100%), 91 (5.7%), 77 (44%); IR (cc14) 2942 cm-1, 2230 curl (CN),
1692 curl (C=O), 1609 curl, 1576 cmfl, 1510 cmfl, 1449 cmrl, 1356 cm-1,
1300 cm-1, 1258 cm-1, 1219 cm'l, 1171 cm‘l, 1111 cmfl, 1003 cm'l, 976 cm'l;
13CNMR (300MHz,CDCl3) 8199.93, 8162.16, 8136.76, 8133.64, 8132.69, 8128.32,
8127.74, 8119.03, 8114.96, 8103.33, 868.01, 838.09, 828.70, 828.55, 825.57,
523.85; 1HNMR (CDC13) 51.47 (complex,4H,Ha&Ha.), 51.78 (overlapping
quintets,4H,J=7.0Hz,Hb&Hb.), 82.97 (triplet,2H,J=7.5Hz,Hc), 83.97
(triplet,2H,J=6.GHz,Hd), 56.90 (doublet,2H,J=9.0Hz,He), 57.44 (triplet,
2H,J=7.5H2,Hf), 87.54 (triplet,1H,J-7.8H2,Hg), 87.55 (doublet,3H,J=9.0Hz,

ah), 87.93 (doublet,2H,J=6.9Hz,Hi).

 

181

 

‘ C-(4-CNPhO)HpP

16. n-(2'-Me-4-BzPhO)OtP n-(2'-methyl-4-benzoylphenoxy)-
octanophenone
a. n-BrOtP n-bromooctanophenone
Prepared from one equivalent of 8-bromooctanoic acid (109,
0.045mol, Aldrich Chemicals), 0.5 equivalents of PC13 (3.1g), one
equivalent of benzene (2.89), and 1.1 equivalents of A1C13 in the same
manner as e-BerP. The crude product (~129) was a yellow oil and not
purified further.
b. n-IOtP n-iodooctanophenone
Prepared from one equivalent of n-BrOtP (12.79, 0.045mol) and 10
equivalents of NaI (689) in the same manner as y-IBP. The crude product
was recrystallized from hexane to give 139 (87% yield) of brown
crystals, mp=37.0-38.0°C. EI-MS m/e 330 (M+,0.77%), 203 (2.6%), 173
(0.42%), 155 (1.2%), 135 (6.6%), 120 (62%), 105 (100%), 91 (7.2%), 85
(30%), 77 (45%); lHNMR (300MHz,CDCl3) 51.36 (multiplet,GH,PhCOCHZCI-12Cfl2-
CHQCHQCHZCHZI), 51.63-1.88 (two overlapping septets,4H,PhCOCH2CEQCH2CH2-
CHZCHZCHZI), 82.95 (triplet,2H,J=7.4Hz,PhCOCH2), 83.17 (triplet,2H,
J=6.9Hz,CflZI), 87.44 (triplet,2H,J=6.9Hz,m-Ar), 87.54 (triplet,lH,

J=7.2Hz,p-Ar), 57.93 (doublet,2H,J=6.9Hz,o-Ar).

182

c. n-IOtP ketal ethylene glycol ketal of n-iodooctanophenone
Prepared from one equivalent of n-IOtP (159, 0.045mol) and 6.6
equivalents of ethylene glycol (199) in the same manner as y—IBP ketal.

The crude product (yellow oi1,~17g) was not purified further.
d. n-PhOOtP n-phenoxyoctanophenone

Prepared from one equivalent of n-IOtP ketal (99, 0.024mol) and 1.1
equivalents of sodium phenoxide (3.19) in the same manner as y—(3-Me-4-
AcPhO)BP. (NOTE: The ketal was used instead of the ketone to avoid an
intramolecular enolate attack on the n—methylene which would yield
phenyl-cycloheptyl ketone.) The crude product was recrystallized from
hexane to give 6.59 (92% yield) of white crystals, mp=43.0-43.5W3. BI—
MS m/e 296 (M+,1.9%), 203 (5.3%), 176 (3.5%), 159 (0.41%), 145 (1.8%),
133 (6.1%), 120 (9.1%), 105 (100%), 94 (51%), 91 (6.1%), 77 (60%);
lRNMR (300MHz,CDCl3) 81.35-1.52 (multiplet,6H,Phcocazcnzca2ca2ca2-
CHZCHZOPh'), 51.69-1.82 (multiplet,4H,PhCOCHZCHQCHZ-CH2CH2Cfl2CHZOPh'),
52.96 (triplet,2H,J=7.5Hz,PhCOCHZ), 53.93 (triplet,2H,J=6.GHz,CflZOPh'),
56.78-6.93 (overlapping triplet and doublet,3H,o&p-Ph'), 57.25 (triplet,
2H,J=7.5Hz,m-Ph'), 87.45 (triplet,2H,J=7.5Hz,m-Ph), 87.54 (triplet,lH,
J=7.5Hz,p-Ph), 87.94 (doublet,2H,J=6.9Hz,o-Ph).

The diketone was prepared from one equivalent of n-PhOOtP (5.09),
2.2 equivalents of A1C13, and 1.1 equivalents of o-toluoyl chloride
(2.9g) in the same manner as erlBP. The crude product (59, 71% yield)
was passed through a silica gel column (12" x 2" diam.) with
hexane/ethyl acetate (85/15). The isolated product was decolorized
three times with norit in isopropanol/water and recrystallized three

times from isopropanol/water to give 59 (71% yield) of white crystals,

183

mp=52.0-53.0%:. EI-MS m/e 414 (M+,0.5%), 396 (4.9%), 211 (29%), 195
(10%), 165 (3.4%), 149 (2.6%), 133 (4.6%), 121 (14%), 105 (100%), 91
(21%), 77 (50%); IR 2944 cm'l, 1692 curl (C=O,benzoyl), 1663 cm'1
(C=O,4-benzoylphenoxy), 1601 cm’l, 1576 cmfl, 1508 cm'l, 1449 cm'l, 1420
cm'l, 1312 cm'l, 1254 cm‘l, 1177 cm'l, 1152 cm‘l, 1113 cm"1, 1024 cm'l,
926 cm'%; l3CNMR (300MHz,CDCl3) 8200.26 (C=O,benzoyl), 8197.21 (2:0,4-
benzoylphenoxy), 5163.24, 5139.21, 5136.98, 5136.02, 5132.81, 5132.39,
8130.70, 8130.22, 8129.63, 8128.47, 8127.93, 8127.80, 8125.07, 8114.08,
868.13, 838.40, 829.14, 829.09, 828.94, 825.75, 824.12, 819.69; luNMR
(300MHz,CDCl3) 51.36-1.53 (complex,6H,Ha,Ha.,Han), 51.78 (overlapping
quintets,4H,J=7.0Hz,Hb&Hb.), 52.30 (singlet,3H,Hc), 52.97 (triplet,2H,
J=7.2Hz,Hd), 84.01 (triplet,2H,J=6.5Hz,He), 86.90 (doublet,2H,J=8.7Hz,
Hf), 87.19-7.30 (Complex,3H,Hg,Hg.,ng), 87.35 (triplet,lH,J=7.BHz,Hh),

87.44 (triplet,2H,J=7.ZHz,Hi), 87.54 (triplet,lH,J=7.2Hz,Hj), 87 77

(doublet,2H,J=9.0Hz,Hk), 87.95 (doublet,2H,J=7.7Hz,Hl).

 

1 n-(2'-Mc-4-BzPhO)OtP

17. n-(d-CNPhO)OtP n-(4-cyanophenoxy)octanophenone

Prepared from one equivalent of n-IOtP ketal (5.69, 0.015mol) and
1.1 equivalents of 4-NaOBzCN (2.3g) in the same manner as 7-(3-Me-4-
AcPhO)BP. The crude product was decolorized with norit in ethyl
acetate/hexane and recrystallized twice from ethyl acetate/hexane to

give 3.59 (73% yield) of white crystals, mp=74.5-75.0°C. EI-MS m/e 321

 

184

(M+,0.6%), 296 (0.05%), 203 (2.6%), 175 (0.43%), 159 (0.17%), 145
(1.1%), 133 (6.9%), 120 (48%), 105 (100%), 91 (5.2%), 77 (45%); IR
(cc14) 2940 cm’l, 2228 curl (CN), 1692 cm’1 (C=O), 1609 cm‘l, 1576 cm'l,
1510 cm-1, 1447 cm-1, 1358 cm‘l, 1300 cm'l, 1258 cm'l, 1217 cm'l, 1171
cm-1, 1113 cmfl, 1020 curl; 13CNMR (300MHz,CDCl3) 8200.07, 8162.22,
8136.85, 8133.68, 5132.69, 8128.35, 8127.79, 8119.06, 8115.00, 8103.39,
868.13, 838.24, 828.97, 828.93, 828.69, 825.55, 823.96; laNMR (300MHz,
CDCl3) 51.27-1.57 (multiplet,6H,Ha), 51.76 (overlapping quintets,4H,
J=6.6Hz,Hb&Hb.), 82.96 (triplet,2H,J=7.5Hz,Hc), 83.97 (triplet,2H,
J=6.6Hz,Hd), 86.89 (doublet,2H,J=9.0Hz,He), 87.44 (triplet,2H,J=7.2Hz,

(doublet,ZH,J=7.ZHz,Hi).

 

f n-(4-CNPhO)OtP

18. 1-82-4-(2-Me-4-An)8t 1-benzoyl-4-(2-methyl-4-anisoyl)butane
a. 4-MeO-2-He-5-C1VP 4-methoxy-2-methyl-5-chlorovalerophenone

Prepared by the Friedel-Crafts acylation of one equivalent of 4-
chlorovaleryl chloride (139,0.082mol) and one equivalent of m-methyl-
anisole (109) in the same manner as 19C1BP. The crude product was
recrystallized from hexane to give 199 (95% yield) of white crystals,
mp=50.5-51.5%:. EI-MS m/e 242 (M+1,0.86%), 241 (M+,0.27%), 240 (3%),
205 (2%), 149 (100%), 135 (5%), 121 (8%), 91 (7%), 77 (5%); 13CNMR

(300MH2,CDC13) 8201.24, 8161.70, 8141.83, 8131.38, 8129.76, 8117.41,

185

8110.49, 855.15, 844.64, 839.54, 832.00, 822.27, 821.83; lRNMR (300MHz,
coc13) 81.84 (multiplet,4H,Arcocazcazcn2cxzc1), 82.54 (singlet,3H,ArCfi3),
82.91 (multiplet,2H,ArCOCflz), 83.56 (multiplet,2H,CH2Cl), 83.83
(singlet,3H,ArOCfi3) 56.73-6.77 (overlapping singlet and doublet,28),
57.71 (doublet,1H,J=9.6Hz).
b. G-MeO-2-Me-5-C1VP ketal ethylene glycol ketal of 4-

methoxy-Z-methyl-5-chlorovalerophenone

Prepared from 4-MeO-2-Me-5-C1VP (89) in the same manner as y-IBP
ketal. The crude product was a yellow oil (99, 95% yield) which was not
purified any further.

c. 4-MeO-2-Me-5-CNVP ketal ethylene glycol ketal of 4-

 

methoxy-Z-methyl-5-cyanovalerophenone

1".

The ketal nitrile was prepared as follows:61 1.1 equivalents of
NaCN (1.69, 0.033mol) was dissolved in 100mL of DMSO under a N2
atmosphere at 80°C. One equivalent of 4-MeO-2-Me-5-C1VP ketal (89,
0.030mol) was dissolved in DMSO and added slowly. The temperature rose
to 1103: upon addition of the chloride and the reaction was allowed to
cool to room temperature over a one hour period. The reaction mixture
was diluted with distilled water (100mL) and extracted with ether (3 x
200mL). (NOTE: the separated aqueous layer was treated with 500mL of
bleach and allowed to stand overnight to render any remaining NaCN
harmless.) The combined ether extracts were washed with saturated NaCl
solution (2 x 200mL) and dried over M9304. All solvent was removed to
yield 7.59 (94% yield) of a yellow oil which was not purified any
further.

The diketone was prepared from the Grignard reaction of 4-MeO-2-Me-

5-CNVP ketal (1 equivalent, 7.09) and 1.1 equivalents of phenyl-

186

magnesium bromide in the same manner as Y—ClBP. The ketal and
ketimine-HCl were hydrolyzed simultaneously by dissolving the crude
product in 20mL of acetone, 10 mL of water, 29 of H2504, and heating on
the steam bath for 10 minutes). The crude product was decolorized with
norit in hexane and recrystallized twice from hexane to give 59 (63%
yield) of white crystals, mp=82.5-83.5°C. EI-MS m/e 310 (1.3%), 224
(2.3%), 190 (10%), 164 (10%), 149 (100%), 121 (7.5%), 105 (10%), 91
(9%), 77 (13%); IR (cc14) 2938 cm-1, 1690 cmfl (sh,C=O), 1684 cm-1
(C=O), 1603 cm‘l, 1570 cm'l, 1559 cm'l, 1541 cm’l, 1507 cm’l, 1449 cm’l,
1362 cmfl, 1316 cm'l, 1250 cm‘l, 1217 cm'l, 1123 curl; 13CNMR (300MHz,
c0c13) 8201.31, 8199.55, 8161.42, 8141.43, 8136.68, 8132.58, 8131.19,
8129.79, 8128.23, 8127 68, 8117.21, 8110.26, 854.91, 840.22, 838.08,
824.03, 823.64, 822.01; IRNMR (300MHz,CDC13) 81.83 (quintet,4H,J=3.3Hz,
Ha), 82.57 (singlet,3H,Hb), 82 95 (triplet,2H,J=6.9Hz,Hc), 83.03
(triplet,2H,J=6.9Hz,Hd), 53.83 (singlet,3H,He), 56.76 (singlet,lH,Hf),
56.77 (doublet of doublet,lH,J=9.6&2.1Hz,Hf.), 57.46 (triplet,ZH,
J=7.7Hz,Hg), 87.56 (triplet,1H,J=7.4Hz,Hh), 87.74 (doublet,2H,J=9.6Hz,
Hi), 57.98 (doublet,2H,J=7.8Hz,Hj); see pg 197 concerning the

resolution of H, and Hf..

    

1 -Bz-4-(2-Me-4-An)Bt

 

187

19. 1-8:-4-(o-T1)Bt l-benzoyl-4-(o-toluoyl)butane
a. 5-C1VP ketal ethylene glycol ketal of 5-chlorovalerophenone

Prepared from 5-C1VP (1 equivalent, 8.59, 0.043mol) in the same
manner as y-IBP ketal. The crude product was a yellow oil which was not
purified any further.

b. 5-CNVP ketal ethylene glycol ketal of 5-cyanovalerophenone

Prepared from 5-C1VP ketal (11.59, 0.049mol) in the same manner as
4-MeO-2-Me-5-CNVP ketal. The crude product (99, 90% yield) was
recrystallized from hexane to give white crystals, mp=33.5—34.0°C. EI-
MS m/e 206 (0.2%), 191 (0.2%), 172 (0.2%), 165 (0.4%), 154 (6%), 149
(100%), 105 (22%); 13CNMR (3OOMHz,CDC13) 8142.24, 8135.25, 8128.08,
5127.88, 5125.56, 5119.59, 5109.92, 564.45, 539.47, 525.41, 522.82,
817.04; inNMR (3OOMHz,CDCl3) 81.45-1.56 (multiplet,2H,CH2CEZCH2CH2CN),
' 51.59-1.70 (multiplet,2H,CH2CH2Cfl2CH2CN), 51.91 (triplet,2H,J=7.5Hz,
cazcazcnzcnzcm, 82.29 (triplet,2H,J=6.9Hz,CflZCN), 83.74 (multiplet,2H,
CH2,ketal), 53.99-4.03 (multiplet,2H,CH2,ketal), 57.26-7.37 (multiplet,
3H,Ar), 57.43 (doublet,2H,J=6.6Hz,Ar).

The diketone was prepared from 5-CNVP ketal (1 equivalent, 7g,
0.030mol) and 1.1 equivalents of phenylmagnesium bromide in the same
manner as 1-Bz-4-(2-Me-4-An)Bt. The crude product was passed through a
silica gel column (12" x 2" diam.) with hexane/ethyl acetate (85/15),
decolorized twice with norit in hexane, and recrystallized twice from
hexane to give 49 (47% yield) of white crystals, mp-39.0-40.0°C. EI-MS
m/e 280 (M+,2%), 262 (3%), 244 (0.5%), 206 (3%), 160 (22%), 145 (12%),
134 (6%), 119 (100%), 105 (34%), 91 (39%), 77 (26%); IR (cc14) 2934 cm-1,
1690cm‘1 (C=O), 1685cm’1 (sh,C==O), 1559 cm-1, 1541 cm‘l, 1507 cm-1, 1456

cm‘l, 1362 cmfl, 1219 cnfl; 13CNMR (300MHz,CDCl3) 8203.94 (c=o,toluoy1),

188

5199.67 (C=O,benzoyl), 5137.95, 5137.63, 5136.79, 5132.75, 5131.71,
5130.92, 5128.38, 5128.13, 5127.82, 5125.48, 541.18, 538.18, 523.85,
823.69, 821.03; 18NMR (c0c13) 81.81 (quintet,4H,J=3.6Hz,Ha), 82.48
(singlet,3H,Hb), 82.94 (triplet,2H, J=7.0Hz,HC), 83.02 (triplet,2H,
J=6.9H2,Hd), 57.23 (overlapping triplet & doublet,2H,J=7.8Hz,He), 57.35
(triplet,1H,J=7.5Hz,Hf), 87.43 (triplet,2H,J=7.4Hz,Hg), 87.54 (triplet,lH,
J=7.4Hz,Hh), 57.62 (doublet,lH,J=7.8Hz,Hi), 57.94 (doublet of doublet,2H,

J=6.9&l.5HZ,Hj) .

 

l-Bz-4-(o-Tl)Bt

20. 4-MeO-2-M3AP 4-methoxy-Z-methylacetophenone

Prepared from 4-NaO-2-MeAP (1 equivalent, 109, 0.058mol) and methyl
iodide (1 equivalent, 8.39) in the same manner as y—(3-Me-4-AcPhO)BP.
The crude product was fractionally distilled (78-80%: at 0.5 torr) to
yield 6.3g (66% yield) of a clear, colorless liquid. 13CNMR (300MHz,
c0c13) 821.63, 827.87, 854.20, 8109.60, 8116.76, 8128.94, 8131.78,
8141.06, 8161.13, 8197.86; 1HNMR (250MHz,CDCl3) 82.49 (singlet,3H,Ha),
52.52 (singlet,3H,Hb), 53.78 (singlet,3H,H¢), 56.72 (singlet,1H,Hd),
56.73 (doublet of doublet,1H,J=9.5&2.7Hz,Hd.), 57.73 (doublet,lfl,

J=9.5Hz,He); see pg 197 concerning the resolution of Rd and Ho'-

 

 

c1130

(Lhk£}ZJWeAP

21. 4-MnO-2-ltAP 4-methoxy-2-ethylacetophenone
a. m-ethylphonyl acetate
Prepared from m-ethylphenol (1 equivalent, 59, 0.041mol) and acetic
anhydride (1.2 equivalents, 59) in the same manner as m-cresyl benzoate.
The crude product was a clear, colorless liquid (69, 90% yield) which
was not purified any further.
b. 4-03-2-ltAP 4-hydroxy-2-ethylacetophenone
Prepared from m-ethylphenyl acetate (1 equivalent, 4g, 0.024mol) in
the same manner as 4—OH-2-MeBzP. The crude product was washed with a
small amount of cold hexane (to remove any nitrobenzene, ester, or
phenol) and recrystallized twice from hexane to give 1.59 (38% yield) of
white needles, mp=107.0-107.5W3. EI-MS m/e 167 (4%), 149 (22%), 123
(2%), 97 (7%), 83 (13%), 71 (27%), 57 (67%), 43 (100%); luNMR (250MHz,
c0c13) 81.19 (triplet,3H,J=7.0H2,CHZCH3), 82.57 (singlet,3H,ArCOCHg),
52.93 (quartet,2H,J=7.OHz,CH2), 56.74-6.80 (multiplet,ZH,Ar), 57.71
(doublet,28,J=8.GHz,Ar).
c. 4-NaO-2-EtAP sodium salt of 4-0He2-EtAP
Prepared from one equivalent of 4-OH-2-EtAP (29, 0.012mol) in the
same manner as 4-NaO-2-MeAP.
The ketone was prepared from one equivalent of 4-NaO-2-EtAP (2.39)

and 1.5 equivalents of methyl iodide (2.69) in the same manner as y—(3-

190

Me-4-AcPhO)BP. The crude product was distilled (simple, 87°C at 0.6
torr) and passed through a silica gel column (9" x 1" diam.) with
hexane. The isolated product was a clear, colorless liquid (29, 92%
yield). 13CNMR (300MHz,CDC13) 8199.11, 8161.76, 8147.71, 8132.20,
8129.35, 8115.77, 8109.94, 854.81, 828.87, 827.48, 815.29; IRNMR
(300MHz,CDC13) 81.11 (triplet,2H,J=7.4Hz,Ha), 82.42 (singlet,3H,Hb),
52.84 (quartet,2H,J=7.4Hz,Hc), 53.71 (singlet,3H,Hd), 56.60-6.67
(overlapping doublet and doublet of doublet,2H,He&He.), 57.60 (doublet,

1H,J=8.1Hz,Hf); see pg 197 concerning the resolution of He and He..

 

22. 4-MeO-2-MQVP 4-methoxy-2-methylvalerophenone

Prepared from m-methylanisole (1 equivalent, 209) and valeric acid
(2 equivalents, 349) in the same manner as 5-(3-Me-4-ValPhO)VP. The
crude product was recrystallized four times from hexane to give 219 (62%
yield) of white, sugar-like crystals, mp=54.5-55.5%:. EI-MS m/e 206
(M+,5%), 177 (1.7%), 164 (10%), 149 (100%), 121 (8%), 91 (8%), 77 (7%);
13CNMR (300MHz,CDCl3) 8202.01, 8161.41, 8141.43, 8131.17, 8130.05,
8117.21, 8110.24, 854.91, 840.29, 826.66, 822 27, 822.01, 813.72; 1HNMR
(250MHz, c0c13) 80.910 (triplet,3H,J=7.3Hz,Ha), 81.35 (sextet,2H,
J=7.4Hz,ab), 51.65 (quintet,2H,J=7.5Hz,Hc), 82.50 (singlet,3H,Hd), 82.84
(triplet,2H,J=7.5Hz,He), 53.81 (singlet,3H,Hf), 56.70-6.80 (overlapping

doublet and doublet of doublet,3H,Hg&Hg.), 57.68 (doublet,1H,J=9.2Hz,

 

191

Hh); see pg 197 concerning the resolution of Hg and Hg..

CH3O

 

(48MX}24M8VP

23. 4-MbOBzP 4-methoxybenzophenone

Prepared from anisole (1 equivalent, 109, 0.093mol) and benzoyl
chloride (1 equivalent, 139) in the same manner as 5—ClVP. The crude
product was decolorized twice with norit in MeOH and recrystallized
twice from hexane to give 169 (80% yield) of white crystals, mp=58.5-
59.o°c. EI-MS m/e 212 (43%), 135 (100%), 105 (14%), 77 (39%); 13CNMR
(300MHz,CDCl3) 855.36, 8113.46, 8128.07, 8129.58, 8130.05, 8131.75,
8132.41, 8138.20, 8163.13, 8195.33; lHNMR (300MHz,CDCl3) 83.88 (singlet,
3H,Ha), 56.96 (doublet,2H,J=9.0Hz,Hb), 57.47 (triplet,2H,J=7.4Hz,HC),
87.56 (triplet,1H,J=7.4Hz,Hd), 87.76 (doublet,ZH,J=6.9Hz,He), 87.83

(doublet,2H,J=8.7Hz,Hf).

 

24. 4-MbO-2-NszP 4-methoxy-2-methylbenzophenone
Prepared from one equivalent of m-methylanisole (5.09, 0.041mol),

one equivalent of benzoyl chloride (6.09), and two equivalents of AlC13

 

192

(119) in the same manner as y—ClBP. The crude product (69, 67% yield)

was decolorized with norit in hexane, passed through a silica gel column
(12" x 2" diam.) with hexane/ethyl acetate (90/10), and distilled
(simple, 0.8 torr, bp=161—162°C) to give a clear, colorless liquid.
13CNMR (300MHz,CDCl3) 820.59, 855.06, 8109.97, 8116.64, 8128.09, 8129.79,
5130.49, 5131.88, 5132.30, 5138.66, 5140.37, 5161.16, 5197.37; 1HNMR
(300MHz,CDCl3) 52.40 (singlet,3H,Ha), 53.76 (singlet,3H,Hb), 56.69
(doublet of doublet,1H,J=8.4&2.4H2,Hc), 56.80 (doublet,1H,J-2.4Hz,fld),

57.29 (doublet,1H,J=8.7Hz,He), 57.38 (triplet,2H,J=7.4Hz,Hf), 57.49

(triplet,1H,J=6.6Hz,Hg), 87.40 (doublet,2H,J=6.9Hz,Hh).

 

4-MeO—2—MeBzP

25. 4-MeO-2'-MeBzP 4-methoxy-2'-methylbenzophenone

Prepared from one equivalent of anisole (5.09, 0.046mol), one

(equivalent of o-toluoyl chloride (7.29), and 1.1 equivalents of A1C13

(6.89) in the same manner as y-ClBP. The crude product (109, 96% yield)

(was distilled (simple, 0.75torr, bp=166.5W:) to give a clear, colorless

Jaiqpid. EI-MS m/e 227 (4.0%), 226 (24%), 225 (60%), 209 (10%), 195

(98%), 165 (13%), 135 (100%), 119 (33%), 107 (18%), 91 (85%), 77 (83%);
13c:.1~n~1R (300MHz,CDCl3) 819.48, 855.17, 8113.48, 8124.91, 8127.63, 8129.52,
51:30.25, 8130.56, 8132.16, 8135.82, 8138.99, 8163.47, 8196.89; laNMR

(300MHz,CDCl3) 52.28 (singlet,3H,Ha), 53.78 (singlet,31-1,Hb), 56.88

(d‘DLIblet,2H,J=6.OHz,HC), 57.16-7.27 (complex,3H,Hd&Hd.), 57.32 (triplet,

 

193

1H,J=7_4H2,He), 87.76 (doublet,2H,J=8.7Hz,Hf).
a

f O
c d'
b f d e
c1130 c d.
(LBMX}22MRBZP

26. BP butyrophenone

Prepared by the Friedel-Crafts acylation of one equivalent of

butyryl chloride (109, 0.093mol), 1.1 equivalents of benzene (8.09), and

1.1 equivalents of AlCl3 (1.4g) in the same manner as y-ClBP. The crude

IIroduct was distilled (fractional, 0.5 torr, bp=67-68°C) to give 109

073% yield) of a clear, colorless liquid. EI-MS m/e 148 (M+,7.4%), 130

(0.95%), 120 (8%), 105 (100%), 91 (2.4%), 77 (75%); 18mm (300MHz,
CDc13) 80.962 (triplet,3H,J=7.5Hz,Ha), 81.73 (sextet,2H,J=7.2Hz,Hb),
512.89 (triplet,ZH,J=7.SHz,Hc), 87.40 (triplet,2H,J=6.0Hz,Hd), 87.49

(t:rip1et,1H,J=6.6Hz,He), 87.91 (doublet,ZH,J=8.4Hz,Hf).

 

27. VP valerophenone

Prepared from the acylation of benzene with valeryl chloride by

Re epyung Nahm .

28. 2'MOVP 2-methylvalerophenone

Prepared from the Grignard reaction of valeronitrile (1 equivalent;

194

12g, 0.15mol) and o-toluylmagnesium bromide (1 equivalent) in the same
manner as y-ClBP. The crude product, a yellow oil (159, 58% yield), was
passed through a silica gel column (12" x 1” diam.) with hexane/ethyl
acetate (85/15) and fractionally distilled (100%: at 1.5 torr) to give a
clear, colorless oil. EI-MS m/e 176 (0.7%), 161 (6%), 147 (2%), 134
(12%), 119 (100%), 91 (48%), 77 (2%); 13CNMR (300MHz,CDC13) 8204.56,
8138.22, 8137.54, 8131.65, 8130.77, 8128.06, 8125.42, 841.18, 526.37,
822.28, 820.96, 813.75; laNMR (300MHz,CDCl3) 80.930 (triplet,3H,
J=7.2Hz,Ha), 51.38 (sextet,ZH,J=7.1Hz,Hb), 51.67 (quintet,ZH,J=7.5Hz,
ac), 82.47 (singlet,3H,Hd), 82.86 (triplet,ZH,J=7.2Hz,He), 87.21
(triplet,2H,J=7.ZHz,Hf), 87.32 (triplet,1H,J=7.5Hz,Hg), 87.59 (doublet,

1H, J=7 . 8H2, Hh) .

 

29. 2-MBAP 2-methylacetophenone

Prepared from the Grignard reaction of acetonitrile (1 equivalent,
69, 0.15mol) and o-toluylmagnesium bromide (1 equivalent) in the same
manner as ybClBP. The crude product (129, 60% yield) was fractionally
distilled (668C at 1.5 torr) to give a clear, colorless liquid. EI-MS
nVe 134 (M+,28%), 119 (99%), 91 (100%), 65 (30%); 13CNMR (300MHz,CDCl3)
8200.64, 8137.71, 8137.03,8131.44,8130.91, 8128.86, 8125.17, 828.74,
820.96; lHNMR (300MHz,CDC13) 82.53 (singlet,BH,Ha), 82.57 (singlet,3H,

Hb), 87.25 (triplet,2H,J=8.7Hz,Hc), 87.36 (triplet,lfl,J=7.5Hz,Hd), 87.68

 

 

195

(doublet,1H,J=7.BHz,He).

 

30. AP acetophenone

Purified by preceding group members. 13CNMR (CDC13) 5197.04,
8136.45, 8132.34, 8127.87, 8124.58, 825.72; 1HNMR (300MH2,CDC13) 82.54
(singlet,BH,CH3), 87.41 (triplet,2H,J=7.7Hz), 87.51 (triplet,1H,

J=7.4Hz), 87.92 (doublet,2H,J=7.8Hz).

II. Column Chromatography

All columns were run flash style with 200-425 mesh silica gel. The
best results were obtained with the following procedure. First the
column diameter was selected according to the amount of material to be
loaded: for up to one gram the diameter was 0.5", for one to three
grams the diameter was 1", and for three to ten grams the diameter was
2". Next the column was dry packed using glass wool at the stopcock and
a layer of sand upon which the silica gel was poured to fill about 60%
of the total column length (performed in the hood to avoid breathing any
silica gel), thus allowing ample room for solvent above the column. The
solvent (or solvent system) was poured onto the column carefully so as
not to disturb the silica gel and about one volume was allowed to elute
3by gravity. Once this gravity elution was complete and the column was

cool to the touch, another volume of solvent was added and this was

 

196

pushed through the column by air with a flash valve at a rate where fast
drops turned into a steady stream. It was important to maintain a
constant pressure during this solvent flushing since a sudden loss of
pressure could result in packing separation. This flash solvent elution
could be repeated if necessary to remove the last traces of air from the
column. Next a layer of sand was placed on the top of the column to
insure that the silica gel would not be disturbed during loading. The
material was loaded carefully by pipet (solids were dissolved in a
ndnimum of solvent) to the virtually dry sand layer with solvent

covering only the silica gel. Small amounts of solvent were added

 

behind the loaded material as it eluted into the silica gel. Once the

material was completely eluted onto the silica gel, a full volume of

 

W

solvent was added and an eluting pressure of about two drops/second was
maintained; this elution could be interupted at any time without

adversely effecting the separation.

III. Instrumentation

IR: Perkin-Elmer 599 Infrared Spectrophotometer

13 5 13C NMR: Bruker WM-ZSOMHz Fourier Transform Nuclear Magnetic
Resonance Spectrometer, Varian VXR-300MHz, and Varian T-60.

UV: Shimadzu UV-160 Recording UV-VIS 8 Cary 17 Spectrophotometer

lI-MS: Finnigan 4021 Mass Spectrometer

Melting Points: Thomas Hoover Capillary Melting Point Apparatus

GC: Varian 1200, 1400, and 3400 Gas Chromatographs with Hewlett
Packard HP3392A and HP3393A Integrators.

Phosphorescence: Perkin-Elmer MPF-44A Fluorescence

Spectrophotometer with HP3393A Integrator.

197

IV. 1HNMR Spectral Characteristics

The aromatic region for the various diketones was similar for
systems with basically the same chromophores. Most assignments could be
made easily when the spectra were compared to those of model ketones.
It should be noted that the two aromatic protons ortho to the alkoxy
linkage appear as a well resolved doublet for the isolated proton and
doublet of doublet for the other in the 3-methyl-4-benzoylphenoxy
chromophores, but overlap when the chromophore is 3-methy1-4-a1kanoyl-
phenoxy. These protons in the 3—methyl-4-alkanoylphenoxy chromophores
are reported as a singlet and a doublet of a doublet (J=8.3 & 2.7 Hz).
Based on the 3-methyl-4-benzoylphenoxy spectra, it is reasonable to
assume that in the 3-methyl-4—alkanoylphenoxy chromOphores, the isolated
aromatic proton is actually a doublet (with an expected coupling of
J~2.7 flz obscured by overlap) and the other is a doublet of a doublet
(with a measurable coupling of J=2.7 Hz and an expected coupling of

J~8.3 Hz obscured by overlap).

v. 'Uv Spectroscopy
All UV spectra were taken with a 1cm quartz cuvet. The baseline
correction was made by subtracting the spectrum of a solvent blank from

each run; error was kept to a minimum by using only one cuvet.

VI. Phosphorescence Spectroscopy
The energies of lowest lying triplet states were derived from their
phosphorescence spectra in 5mm pyrex NMR tubes at 77°K in either ZéMeTHF

or MeOH/BtOH (5:1). The slit width was 6nm for both emission and

 

 

198

excitation. To assure that the emission observed was solely
phosphorescence, a chopper was used at motor speeds of 2-50 rpm. The
spectra were recorded by retention times. The maximum of each band,
reported as a retention time, was converted to the corresponding
wavelength by multiplying the band retention time by the drive speed of
120nm/min and adding this to the initial wavelength setting of 360nm.
The energy of the triplet in kcal/mol was calculated with the following

conversion: Etrmnet = 28,600/lm“.

VII. Photokinetic Data
A” Glassware
All glassware used was class A volumtric except for the 5mL
syringes used to fill irradiation tubes which were pyrex with chrome
plated brass needles. All glassware was cleaned in the following
fashion: 1) rinsed with acetone, 2) soaked in a bath of distilled
water/alconox at a boil for several hours, 3) rinsed five times with
distilled water, 4) soaked in a bath of distilled water at a boil for
several hours, 5) rinsed five times with distilled water, and finally 6)
all glassware was left in a drying oven at 150°C overnight to dry
thoroughly.
3. Neighings
A11 weighings were done on either a Sartorius 2403 analytical
balance or Mettler A5163 top loading digital analytical balance, both of
which were accurate to within 0.000019.
c. Irradiation Tubes

Irradiation tubes were cleaned according to the glassware procedure

 

 

199

and stretched just below the teflon label to make sealing in vacuo
possible. The tubes used for long lived triplet studies were joined at
the mouth with 10/30 ground glass joints and kept in a drying oven
overnight to drive out any moisture that resulted from blowing.

Two brands of tubes were used, Kimax and Pyrex. Since the Kimax
glass is more transparent to UV light than Pyrex, it was important to
make sure that all of the tubes in a given run (including actinometers)
were the same brand.

D. Degassing Procedure

Irradiation tubes were filled with 2.8mL of sample, measured in a

5mL syringe, and fitted onto a 12-port degassing cow with #00 one hole
rubber stoppers (or 10/30 ground glass joints with high vacuum stopcocks
for the handblown tubes). Tubes were degassed by four freeze-pump-thaw
cycles using liquid nitrogen on a vacuum line with a mechanical and
diffusion pump (5 x 10‘4 torr) followed by sealing in vacuo.

E. Irradiation Chambers

Two irradiation chambers were used in this work. Both were set up
with a Hanovia 450W medium pressure mercury lamp cooled in a quartz
immersion well and placed inside a merry-go-round having 7.0mm slits.
The whole apparatus was placed inside a 10 gallon crock filled with
distilled water. The 313nm chamber used a 1 cm aqueous filter solution
consisting of 0.002M KZCrO4 and 1% KQCO3. The 366nm chamber used a
uranium sleeve in conjunction with Corning #7891-42 filters.

r. Sample Analysis
The photocleavage products observed, either acetophenones or

diketones, were analyzed using gas Chromatographs equipped with flame

 

 

200

ionization detectors. Retention times of observed photoproducts and
internal standards were compared with authentic samples of each to
confirm their presence and positions in the chromatogram. Response
factors for the various photoproducts and their corresponding internal

standards are listed below.

 

observed product/internal standard Rfcakyd RFemel
AP/C15 2.29 2.25
2-MeAP/C16 2.00 2.03
4-MeO-2-MeAP/C20 2.50 2.39
Y—(3-Me-4-AcPhO)BP/C19-Ph 1.56 1.36
5-(3-Me-4-AcPhO)VP/C:9-Ph 1.47 1.83

RFexmwl is the value obtained experimentally. RE‘calC.d was calculated

based on the following equation:

(# of carbons bonded to other carbons
+ 1/2 # of carbons single bonded to oxygen”nt std.

M5)

 

chalc'd =
(# of carbons bonded to other carbons

+ 1/2 8 of carbons single bonded to oxygen)phowmduct

Since the RE‘expt.l values for ‘y-(3-Me-4-AcPhO)BP/C19-Ph and 5-(3-Me-
4-AcPhO)VP/C19-Ph vary more than 5% from.RFcahyd, the RFcahvd values
were used for measuring quantum yields in experiments where 7-(3-Me-4-
AcPhO)BP and 5-(3-Me-4-AcPhO)VP were the photoproducts observed. All

product concentrations were calculated with the following equation:

[product] = (area of product)/(area of int.std.) x RF x (int.std.] (46)

 

 

201

The conditions for analyzing the various photoproducts are listed

below.

CC Condition Sets

 

 

#1 30 meter DBWAX Megabore Colwmn {3 15 meter D8210+ Megabore Column
varian Aerograph 1400 varian 3400
He - 30mL/min He = 25mL/min
column -= 110°C column 8 80°C—9220°C at 30°C/min
injector = 150%? injector - 180%?
detector 8 230°C , detector - 230°C
#2 30 meter DBWAX Megabore Column #4 15.meter 081+ Megabore Column
varian Aerograph 1400 varian 1400
He = 30mL/min He = 25mL/min
column = 170°C column =- 150°C
injector = 170%? injector = 150%?
detector = 230%? detector - 230%?
55"

 

1. Quantum. Yields

Quantum yields were measured using actinometers irradiated in
parallel of either valerophenone (VP) for irraditions up to 8 hours in
duration or 2-methylva1erophenone (Z-MeVP) for irradiations of over 8
hours long. The quantum yields of type II cleavage (051) for VP and 2-
MeVP at 0.10M in benzene are 0.3333 and 0.016,23 respectively. Quantum

yields were calculated by using the following equations:

dfiI = [product]/Io (47)

where,

I = [productlactflfiact (48)

O

2. Stilbene Sensitization Experiments

These were run in benzene with the ketone 4-MeO-2-MeAP at 0.102M

 

202

with varying amounts of trans-stilbene. The actinometer was
acetophenone (AP) at 0.0681M with 0.0500M trans-stilbene. At these
concentrations of 4-MeO-2-MeAP and AP, the amount of light absorbed by
samples in the quenching run was the same as that absorbed by
actinometer tubes; therefore, no light absorption correction was
necessary. The corrected amount of cis-stilbene produced ([cislcorr)

could be determined by using the following equations which adjusted for

 

back reaction:62
[Cis]corr = B'Itrans]o (49)
where,
B'= 0.596 ln[0.596/(o.596-B)l (50)
and
B = R/(R+1) (51) "
R = (area cis)/(area trans) (52)
From the actinometer,
IO = [cis]act/0.596 (53)

The quantum yield for conversion of trans-ecis for the ketone is then,

(pt—9c = [Cis]corr/Io (54)

The photostationary state of trans-stilbene with AP as sensitizer
in benezene is 0.59663 with a dkf,c of 0.41. When there is only one
triplet, a plot of 0.596/Qt",c versus 1/[trans]o will give a straight
line whose intercept is equal to the reciprocal of the intersystem

Crossing quantum yield (l/dfisc) and whose kqt can be obtained by

 

 

203

dividing the intercept by the slope.

3. Type II Quantum Yields (Cbn)

For all experiments, type II product observed was either
acetophenone, 2-methy1acetophenone, 4-methoxy—2-methylacetophenone, or a
diketone smaller than the starting material. Adjustments were made for
their different molar responses in the flame ionization detectors of the
gas chromatographs by using the response factors. Analysis of the
photoproducts made it necessary to use three internal standards, n-

hexadecane, n-eicosane, and 1-phenylnonadecane. These standards were

 

chosen according to their ability to satisfy generally accepted criteria
for the selection of internal standards; each was relatively non-

volatile, inert to the photochemistry, non-influential to the chemical

 

environment (ie. nonpolar), nicely soluble, and had retention times
near, but not overlapping with those of photoproducts observed. For
irradiations at 366nm, due to the low extinction coefficients of the
actinometers (either VP or 2-MeVP), not all of the light was absorbed by
the samples and corrections were made to compensate for light absorption
differences. These corrections were made with the following equation:

Icorr 3 I0 x (1'10-A) ketone/(l-lo-A) actinometer (55)

RAW DATA

 

 

 

 

 

204
Table 14: Stern-Volmer and 4) Data of y-(B-Me-G-AcPhO)BP at
313nm. in Benzene

Run 1
area_A£
area C16 [AP],M 4’ [Q],M ¢°/¢
1.06* 0.000494 0.0608 0.0 1.00
0.594 0.000277 0.0341 0.0106 1.78
0.468 0.000218 0.0268 0.0213 2.27
0.346 0.000161 0.0198 0.0319 3.07
0.248 0.000120 0.0148 0.0532 4.11
0.223 0.000104 0.0128 0.0745 4.75
0.182 0.0000846 0.0104 0.0958 5.85
Actinometry (average of 2 tubes):
0.377 0.00268 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.0317M, and Io=0.008128/hr
SV Run: [diK]=0.0100M and [C16]=0.000207M
(Irrad'd for 30 min, GC condition set 1)

Run 2
alfifiLmBE
area C16 [AP],M (D [Q],M d>°/<b
1.26" 0.000587 0.0617 0.0 1.00
0.777 0.000362 0.0380 0.0106 1.62
0.631 0.000294 0.0309 0.0213 2.00
0.525 0.000245 0.0257 0.0319 2.40
0.383 0.000178 0.0187 0.0532 3.30
0.340 0.000158 0.0166 0.0745 3.72
0.263 0.000123 0.0129 0.0958 4.78
Actinometry (average of 2 tubes):
0.139 0.00314 0.33 - -
Actinometers: [VP]-0.101M, [C161-0.0100M, and Io=0.009528/hr
SV Run: [diK]=0.0100M and [C16]=0.000207M

(Irrad'd for 30 min,

x

*

average of 2 tubes

GC condition set 1)

 

) 1'} «13". I.

T

205

Table 15: 4’14“ Data of y-(3-Me-4-AcPhO)BP at 313nm in Benzene

 

 

 

Run 1
aLeA_AE
area C16 [AP],M d> [Dioxane],M
0.734* 0.000818 0.0732 0.0
0.929 0.00104 0.0909 1.01
0.907 0.00101 0.0887 2.01
0.763 0.000851 0.0746 3.01
0.679 0.000757 0.0573 4.01
0.696 0.000776 0.0681 5.01
0.696 0.000776 0.0681 6.01
0.661 0.000737 0.0647 7.02
Actinometry (average of 3 tubes):
0.167 0.00378 0.33 -
Actinometers: [VP]=0.100M, [C16]=0.0100M, and Io=0.0114E/hr
dfimx Run: [diK]=0.0100M and [C16]=0.000496M
(Irrad'd for 1 hr, oc condition set 1) ‘
Run 2
§u3ia_lfli
area C16 [AP],M ¢> [Dioxane],M
o.591* 0.000654 0.0697 0.0
0.683 0.000755 0.0805 0.358
0.780 0.000862 0.0919 0.656
0.903 0.000998 0.106 0.974
0.844 0.000933 0.0995 1.30
0.897 0.000991 0.106 1.63
0.924 0.00102 0.109 1.95
0.979 0.00108 0.115 2.29
Actinometry (average of 3 tubes):
0.140 0.00938 0.33 -

Actinometers: [VP]-0.104M, [C16]-0.00984M, and Io=0.009388/hr
45,,“ Run: [diK]-=0.0100M and [C16]=0.000491M
(Irrad'd for 1.2 hrs, GC condition set 1)

 

 

*
average of 2 tubes

206

 

 

 

 

Table 16: Stern-Velma: and <0 Data of y-(3-Me-4-AcPhO)BP at
313nm in Methanol

Run 1
AIeA_A£
area C16 [AP],M d) [Q];M <b°/¢b
0.209* 0.000504 0 139 0.0 1.00
0.0301 0.0000725 0.0199 0.00826 6.98
0.0187 0.0000451 0.0124 0.0165 11.2
0.0161 0.0000388 0.0107 0.0248 13.0
0.0130 0.0000313 0.00860 0.0330 16.2
0.00998 0.0000240 0.00660 0.0495 21.1
0.00861 0.0000207 0.00569 0.0660 24.4
Actinometry (average of 3 tubes):
0.162 0.00120 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.00328M, and IO=0.00364E/hr
SV Run: [diK]=0.0101M and [C16]=0.000107M I
(Irrad'd for 14 min, GC condition set 1) L

Run.22
Ema—AB
area C16 [AP],M (D [Q],M d>°/<b
0.348* 0 000755 0.153 0.0 1.00
0.191 0.000414 0.0842 0.000840 1.82
0.139 0.000302 0.0614 0.00168 2.49
0.107 0.000232 0.0472 0.00252 3.24
0.0948 0.000206 0.0419 0.00336 3.65
0.0742 0.000161 0.0327 0.00504 4.68
0.0600 0.000130 0.0264 0.00672 5.80
Actinometry (average of 2 tubes):
0.220 0.00162 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.00328M, and Io=0.0049ZE/hr
SV Run: [diK]-0.0100M and [C16]=0.000965M

(Irrad'd for 20 min,

 

 

average of 4 tubes

GC condition set 1)

207

Table 16 (cont'd)

 

Run 3
3:23.32
area C16 [AP],M (D [Q],M ¢°l¢
0.281* 0.000582 0.145 0.0 1.00
0.130 0.000269 0.0669 0.000775 2.17
0.0938 0.000194 0.0483 0.00155 3.00
0.0785 0.000163 0.0405 0.00232 3.58
0.0502 0.000104 0.0259 0.00465 5.60
0.0437 0.0000905 0.0225 0.00617 6.44
Actinometry (average of 2 tubes):
0.422 0.00133 0.33 - -

Actinometers: [VP]=0.101M, [C16]=0.00139M, and Io=0.00402E/hr
SV Run: [diK]=0.00999M and [C16]=0.000920M
(Irrad'd for 30 min, GC condition set 1)

x
*
average of 3 tubes

 

208

Table 17: Stern-Velma: and (b Data of y-(3-Me-4-(y-
lleVal)PhO)BP at 313nm in Benzene

 

 

‘1]

 

Run 1

EUEHlHBE

area C16 [AP],M (b [Q],M ¢°I<b

0.319* 0.000857 0.0675 0.0 1.00

0.215 0.000578 0.0455 0.0100 1.48

0.173 0.000465 0.0366 0.0201 1.84

0.135 0.000363 0.0286 0.0401 2.36

0.111 0.000298 0.0235 0.0602 2.86

0.0884 0.000238 0.0187 0.0803 3.61

Actinometry (average of 2 tubes):

0.758 0.00420 0.33 - -

Actinometers: [VP]=0.101M, [C16]=0.00246M, and Io=0.0127E/hr

SV Run: [diK]=0.0100M and [C16]=0.00120M

(Irrad'd for 4.25 hrs, GC condition set 1)

i'K ',
area C19-Ph [diKobsv'd] ,M (D [Q] ,M ¢°I¢

0.176* 0.000129 0.0102 0.0 1.00
0.113 0.0000830 0.00654 0.0100 1.56
0.0927 0.0000681 0.00536 0.0201 1.90
0.0623 0.0000458 0.00360 0.0401 2.83
0.0471 0.0000346 0.00272 0.0602 3.74
0.0335 0.0000246 0.00194 0.0803 5.25

diKobsv'd = Y-(3-Me-4-ACPhO)BP
SV Run: [diK]=0.0100M and [Clg-Ph]=0.00047lM
(GC condition set 3)

‘h
*
average of 2 tubes

209

Table 17 (cont'd)

 

 

Id

 

Run 2

new

area C16 [AP],M ¢ [Q],M ¢°l0

0.358* 0.000806 0.0701 0.0 1.00

0.192 0.000432 0.0376 0.0211 1.87

0.141 0.000317 0.0276 0.0422 2.54

0.108 0.000243 0.0211 0.0633 3.32

0.0920 0.000207 0.0180 0.0844 3.89

Actinometry (average of 2 tubes):

0.788 0.00378 . 0.33 - -

Actinometers: [VP]=0.100M, [C16]=0.00213M, and Io=0.01153/hr

SV Run: [diK]=0.0100M and [C16]=0.00100M

(Irrad'd for 4 hrs, GC condition set 1)

W

area C19“Ph [diKobsv'd] ,M (D [Q] ,M ¢°/¢

0.157* 0.000137 0.0119 0.0 1.00
0.0693 0.0000603 0.00525 0.0211 2.27
0.0418 0.0000364 0.00316 0.0422 3.76
0.0340 0.0000296 0.00257 0.0633 4.62
0.0251 0.0000218 0.00190 0.0844 6.25

diKobsv 'd = 7- (3-Me-4-AcPhO) BP
SV Run: [diK]=0.0100M and [Clg-Ph]=0.000558M
(GC condition set 3)

 

*
average of 2 tubes

210

Table 18: (Dun Data of 7-(3-Me-4-(y-ueVal)PhO)BP at 313nm in

 

Benzene
area_AB
area C16 [AP],M d) [Dioxane],M
0.236* 0.000611 0.0694 0.0
0.365 0.000944 0.107 1.17
0.389 0.00101 0.115 2.38
0.407 0.00105 0.119 3.52
0.424 0.00110 0.125 4.61
0.417 0.00108 0.123 5.71
0.454 0.00117 0.133 6.83
0.436 0.00113 0.128 8.10
Actinometry (average of 2 tubes):
0.606 0.00291 0.33 -

Actinometers: [VP]=0.100M, [C16]=0.00213M, and Io=0.00881E/hr
(bMax Run: [diK]=0.0100M and [C16]=0.00115M
(Irrad'd for 3.75 hrs, GC condition set 1)

 

VI, .rnfl‘flils -rv- .—
‘ e
‘

 

W

area C1 9-Ph [diKobsv'd] ,M (D [Dioxane] ,M
0.123* 0.000102 0.0115 0.0
0.150 0.000124 0.0141 1.17
0.209 0.000173 0.0196 2.38
0.242 0.000200 0.0227 4.61
0.241 0.000199 0.0226 5.71
0.289 0.000239 0.0271 6.83
0.278 0.000230 0.0261 8.10

diKobsv'd = 1- (3-Me-4-AcPhO)BP
[diK]=0.0100M and [Clg-Ph]=0.000530M (GC condition set 3)

 

*
average of 2 tubes

 

 

211
Table 19: Stern-Volmer and d> Data of y-(B-He-d-(y-
MeVal)PhO)BP at 313nm in Methanol
area_AR
area €16 [AP],M (b [01.14 ¢°/¢
0.475* 0.00112 0.105 0.0 1.00
0.144 0.000338 0.0316 0.00580 3.31
0.107 0.000251 0.0235 0.0116 4.46
0.0649 0.000152 0.0142 0.0232 7.35
0.0533 0.000125 0.0117 0.0348 8.96
0.450 0.000106 0.00991 0.0464 10.6
Actinometry (average of 2 tubes):
0.770 0.00353 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.00204M, and o=0.0107E/hr
SV Run: [diK]=0.0101M and [C16]=0.00104M
(Irrad'd for 4 hrs, GC condition set 1)
W513:
area Clg-Ph [diKobsv'd],M (D [Q1704 ¢°l¢
0.377* 0 000277 0.0259 0.0 1.00
0.101 0.0000742 0.00694 0.00580 3.73
0.0472 0.0000347 0.00324 0.0116 7.99
0.0234 0.0000172 0.00161 0.0232 16.1
diKobsv 'd = y—(3-Me-(y—MeVa1)PhO)BP
SV Run: [diK]=0.0101M and [Clg-Ph]=0.000471M

(GC condition set 3)

 

'k

 

average of 2 tubes

 

L-

 

212

Table 20: Stern-Velma: and (b Data of y-(4-BzPhO)BP at 313nm

in Benzene

 

 

 

Run 1
31331.52.
area C16 [AP],M <D [Q],M ¢°I¢
0.274* 0.000746 0.0391 0.0 1.00
0.0479 0.000131 0.00686 0.00423 5.72
0.0386 0.000105 0.00550 0.00846 7.10
0.0316 0.0000862 0.00451 0.0169 8.67
0.0298 0.0000813 0.00426 0.0254 9.19
0.0264 0.0000720 . 0.00377 0.0338 10.4
Actinometry (average of 2 tubes):
1.14 0.000629 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.00246M, and Io=0.019lE/hr
SV Run: [diK]=0.0101M and [C16]=0.00121M
(Irrad'd for 9 hrs, GC condition set 1)

Rim) 2
az2a_AE
area C16 [1491,14 4) [01,04 <b°ld>
0.354* 0.000662 0.0430 0.0 1.00
0.236 0.000442 0.0307 0.000216 1.50
0.159 0.000298 0.0207 0.000433 2.23
0.0823 0.000154 0.0107 0.00107 4.30
Actinometry (average of 2 tubes):
0.0916 0.000507 0.33 - -

Actinometers: [VP]=0.101M, [C16]=0.00246M, and Io=0.0154E/hr
SV Run: [diK]=0.0100M and [C16]=0.000832M
(Irrad'd for 8 hrs, GC condition set 1)

 

*
average of 2 tubes

(1‘

 

213

 

Table 21: Stern-Volmer and (b Data of y- (4-BzPhO) BP at 313nm
in Methanol

alfihi_£u3
area C16 [AP],M d> [Q],M d>°l¢
0.219* 0.000423 0.0540 0.0 1.00
0.0631 0.000122 0.0156 0.000389 3.47
0.0397 0.0000767 0.00978 0.000778 5.52
0.0218 0.0000421 0.00537 0.00156 10.0
0.0173 0.0000334 0.00426 0.00234 12.7
0.0130 0.0000251 _ 0.00320 0.00311 16.8
Actinometry (average of 2 tubes):
0.539 0.00259 0.33 - -
Actinometers: [VP]=0.100M, [C16]=0.00213M, and IO=0.00784E/hr
SV Run: [diK]=0.0101M and [C16]=0.000858M

(Irrad'd for 3.5 hrs,

 

*
average of 3 tubes

GC condition set 1)

 

214

Table 22: Stern-Volmer and <1) Data of y-(4-BzPhO)BP at 366nm
in Benzene

 

EJIELDBE

area C16 [AP],M tbcorr [Q] ,M ¢°l¢
0.414* 0.000973 0.0425 0.0 1.00
0.106 0.000249 0.0109 0.000735 3.91
0.0611 0.000144 0.00630 0.00147 6.76
0.0482 0.000113 0.00494 0.00220 8.59
0.0361 0.0000849 0.00371 0.00294 11.5
Actinometry (average of 2 tubes):

1.04 0.00470 0.33 - —

Act: [VP]=0.101M, [C16]=0.00202M, Io=0.014ZE/hr, & Icorp=0.0229E/hr
SV Run: [diK]=0.0100M and [C16]=0.00104M
(Irrad'd for 6 hrs, GC condition set 1)

Quantum yield correction:

 

Icorr — I

x (1-10‘*‘*)3\./(1-10‘A)act

O

 

* .
average of 2 tubes

 

.-
up

I.

215

 

Table 23: Stern-Velma: and (b Data of 7-(4-BzPhO)BP at 366nm
in Methanol

area_AE
area C16 [AP],M tbcorr [Q],M ¢°l¢
0.302* 0.000698 0.0398 0.0 1.00
0.147 0.000340 0.0194 0.000193 2.05
0.0981 0.000227 0.0129 0.000385 3.08
0.0547 0.000126 0.00718 0.000771 5.52
0.0395 0.0000913 0.00521 0.00116 7.65
0.0315 0.0000728 0.00415 0.00154 9.59
Actinometry (average of 2 tubes):
0.847 0.00384 0.33 -
Act: [VP]=0.101M, [C16]=0.00202M, Io=0.0117E/hr, & Icorg=0.017SB/hr
SV Run: [diK]=0.0101M and [C16]=0.00103M

(Irrad'd for 5 hrs,

Quantum yield correction:

 

 

*
average of 2 tubes

COII‘

= I

O

GC condition set 1)

x (1-10'A)K/(1-10'A)

act

' "‘YL‘I'.‘IM'?.D;
.‘II

 

216

Table 24: 4),“), Data of y-(4-BzPhO)BP at 366nm in Benzene
w/added Dioxane

 

area_A£

area C16 [AP],M ¢gorr [Dioxane],M
0.176* 0.000355 0.0984 0.0
0.0659 0.000133 0.0369 2.33
0.521 0.000105 0.0291 4.03
0.0422 0.0000849 0.0235 5.48
0.0360 0.0000724 0.0201 6.17
0.0416 0.0000837 . 0.0232 7.03
Actinometry (average of 2 tubes):

0.159 0.000739 0.33 -

Act: [VP]=0.101M, [C16]=0.00207M, Io=0.00224E/hr, & I =0.00224E/hr
dnmx Run: [diK]=0.0100M and [C16]=0.000894M

(Irrad'd for 1 hr, GC condition set 1)

COII

 

Quantum yield correction:

 

= Io x (1-10‘A)K/<1-10'A>act

COI!

 

*
average of 3 tubes

 

 

 

217
Table 25: Stern-Volmer and 0 Data of y-(3-Me-4-BzPhO)BP at
313nm. in Benzene
Run 1
.alihi_1UZ
area C16 [AP],M 4? [01,14 ¢°l¢
0.385* 0.000682 0.00498 0.0 1.00
0.182 0.000333 0.00243 0.0610 2.11
0.129 0.000229 0.00167 0.122 2.98
0.0874 0.000155 0.00113 0.244 4.40
0.0585 0.000104 0.000759 0.366 6.58
0.0436 0.0000773 0.000564 0.488 8.83
Actinometry (average of 2 tubes):
W
area C16 [2-MeAP],M
0.00219 (<1) =0.016)

Actinometers:
SV Run:

 

*
average of 3 tubes

act

[2-MeVP]=0.102M,
[diK]=0.0100M and [C16]=0.000788M
(Irrad'd for 47 hrs,

[C16]=0.00195M, and Io=0.l37E/hr

GC condition set 1)

 

Lg.“ “

 

218

Table 25 (cont'd)

 

 

Run 2

M

area C16 [AP],M <D [Q],M <b°l<b

0.131* 0.000329 0.00534 0.0 1.00

0.120 0.000300 0.00487 0.000967 1.10

0.111 0.000279 0.00454 0.00194 1.18

0.108 0.000270 0.00439 0.00387 1.22

0.102 0.000255 0.00414 0.00581 1.29 -

0.0950 0.000238 0.00387 0.00774 1.38 3,

Actinometry (average of 2 tubes): E

MAP. 1
area C16 [2-MeAP],M 5. .

0.214 0.000985 (¢act=0.016) l‘_,J

 

Actinometers: [2-MeVP]=0.101M, [C16]=0.00227M, and Io=0.0616E/hr
SV Run: [diK]=0.0100M and [C16]=0.00112M
(Irrad'd for 46 hrs, GC condition set 1)

 

*
average of 3 tubes

 

219

Table 26: On”: Data of y-(3-ue-4-BzPhO)BP at 313nm in Benzene

 

 

 

 

areLAR
area C16 [AP],M ¢ [Dioxane],M
0.158* 0.000361 0.00544 0.0
0.221 0.000506 0.00763 0.690
0.252 0.000577 0.00870 1.35
0.265 0.000607 0.00916 2.08
0.271 0.000621 0.00937 2.99
0.284 0.000651 0.00982 3.86
0.285 0.000653 0.00985 5.47
0.310 0.000710 0.0107 7.96
Actinometry (average of 2 tubes):
W
area C16 [Z-MeAP],M l:
a
0.231 0.00106 (¢act=0.016) '5'

Actinometers: [2-MeVP]=0.101M, [C16]=0.00227M, and Io=0.06638/hr
¢Max Run: [diK]=0.0100M and [C16]=0.00102M
(Irrad'd for 44 hrs, GC condition set 1)

 

*
average of 3 tubes

 

220

Table 27: Stern-Volmer and <0 Data of 'y-(3-Me-4-BzPhO)BP at
313nm in Methanol

 

 

Run 1

area_AE
area C16 [AP] ,M 0 [O] ,M ¢°l¢
0.177* 0.000450 0.00520 0.0 1.00
0.0545 0.000139 0.00161 0.0151 3.24
0.0413 0.000105 0.00121 0.0301 4.29
0.0306 0.0000780 0.000902 0.0602 5.78
0.0244 0.0000622 0.000719 0.0904 7.23
0.0205 0.0000523 0.000605 0.121 8.61
Actinometry (average of 2 tubes):
W

area C16 [2—MeAP],M

0.301 0.00139 (¢act=0.016)

Actinometers: [2-MeVP]=0.101M, [C16]=0.00227M, and Io=0.08658/hr

(Irrad'd for 86 hrs, GC condition set 1)

\
*

average of 3 tubes

.-____._i__.i___._;r

Table 27 (cont'd)

221

 

Run 2

area_AE

area c16 [AP] ,M 4) [01,14 «we
0.682* 0.000951 0.00621 0.0 1.00
0.431 0.000600 0.00392 0 00120 1.58
0.347 0.000484 0.00316 0.00241 1.96
0.275 0.000383 0.00250 0.00482 2.48
0.245 0.000341 0.00223 0.00722 2.79
0.225 0.000314 0.00205 0.00963 3.03

Actinometry (average of 2 tubes):

 

0.00245 (dgct=0.016)

mm
area C16 [2-MeAP],M
0.533

Actinometers: [2-MeVP]=0.101M,

[C16]=0.00227M, and IC=0.1533/hr

SV Run: [diK]=0.0100M and [C16]=0.000620M

(Irrad'd for 46 hrs,

 

*
average of 3 tubes

GC condition set 1)

 

.¥—l
4
‘

L

 

222

 

 

Table 28: Stern-Volmer and <0 Data of y-(4-CNPhO)BP at 313nm
in Methanol

Run 1
area_AE
area C16 [AP],M <1) [Q],M O°Id>
0.214* 0.000495 0.525 0.0 1.00
0.158 0.000365 0.387 0.00188 1.36
0.125 0.000289 0.306 0.00375 1.72
0.0991 0.000229 0.243 0.00563 2.16
0.0900 0.000208 0.220 0.00750 2.39
0.0689 0.000159 0.168 0.0113 3.13
0.0545 0.000126 0.134 0.0150 3.92
Actinometry (average of 2 tubes):
0.0422 0.000312 0.33 -
Actinometers: [VP]=0.101M, [C16]=0.00328M, and Io=0.000944B/hr
SV Run: [K]=0.0100M and [C16]=0.00103M
(Irrad'd for 11 min, GC condition set 1)

Run 2
3123.32
area C16 [AP],M (D [Q],M ¢°Id>
0.352* 0.000687 0.528 0.0 1.00
0.245 0.000478 0.368 0.00246 1.43
0.185 0.000361 0.278 0.00491 1.90
0.156 0.000304 0.234 0.00737 2.26
0.133 0.000260 0.200 0.00982 2.64
0.0957 0.000187 0.144 0.0147 3.67
Actinometry (average of 2 tubes):
0.0579 0.000428 0.33 -
Actinometers: [VP]=0.101M, [C16]=0.00328M, and Io=0.001308/hr
SV Run: [K]=0.0101M and [C16]=0.000867M

(Irrad'd for 23 min, GC condition set 1)

 

*
average of 3 tubes

 

223

 

 

Table 29: Stern-Velma: and d> Data of 5-(3-Me-4-AcPhO)VP at
313nm in Benzene

Run 1
area_AE
area C16 [AP],M (b [Q],M ¢°l¢
0.547* 0.00103 0.0326 0.0 1.00
0.267 0.000489 0.0155 0.00696 2.11
0.207 0.000387 0.0122 0.0140 2.66
0.155 0.000290 0.00917 0.0209 3.55
0.130 0.000243 0.00769 0.0279 4.24
0.0966 0.000181 0.00572 0.0418 5.69
Actinometry (average of 2 tubes):
0.146 0.0104 0.33 - —
Actinometers: [VP]=0.101M, [C16]=0.0317M, and Io=0.0316E/hr
SV Run: [diK]=0.0100M and [C16]=0.000832M
(Irrad'd for 4 hrs, GC condition set 1)

Run 2
.alifli_lfli
area c16 [1491,14 d) [Q],M <b°l¢
0.323* 0.000759 0.0299 0.0 1.00
0.168 0.000388 0.0153 0.00698 1.95
0.132 0.000305 0.0120 0.0140 2.49
0.104 0.000240 0.00945 0.0209 3.16
0.0896 0.000207 0.00815 0.0279 3.67
0.0639 0.000148 0.00583 0.0419 5.13
0.0533 0.000123 0.00484 0.0558 6.18
Actinometry (average of 2 tubes):
0.371 0.00839 0.33 - -
Actinometers: [VP]=0.101M, [C161-0.0100M, and Io=0.0254E/hr
SV Run: [diK]=0.0100M and [C16]=0.00102M

(Irrad'd for 1.5 hrs,

 

*
average of 3 tubes

GC condition set 1)

 

224

Table 30: (Dun Data of 5-(3-Me-4—AcPhO)VP at 313nm in Benzene

 

Run 1
area_AB
area C16 [AP] ,M (b [Dioxane] ,M
0.341* 0.000469 0.0297 0.0
0.416 0.000455 0.0362 1.14
0.434 0.000588 0.0378 2.28
0.432 0.000585 0.0376 3.42
0.456 0.000617 0.0397 4.55
0.407 0.000551 0.0354 5.71
0.310 0.000420 0.0270 6.82
0.327 0.000443 0.0285 7.96
Actinometry (average of 2 tubes):
0.227 0.00513 0.33 -

Actinometers: [VP]=0.101M, [C16]=0.01004M, and Io=0.0156EI/hr
ohm Run; [diK]=0.0100M and [C16]=0.000602M
(Irrad'd for 3.75 hrs, GC condition set 1)

 

Run 2
area_AE
area C16 [AP],M (D [Dioxane],M
0.604* 0.000817 0.0311 0.0
0.669 0.000906 0.0343 1.14
0.679 0.000919 0.0347 2.28
0.692 0.000937 0.0354 3.42
0.669 0.000906 0.0343 4.55
0.702 0.000951 0.0360 5.72
0.699 0.000946 0.0358 6.82
0.745 0.00101 0.0381 7.96
Actinometry (average of 3 tubes):
0.386 0.00873 0.33 -

Actinometers: [VP]=0.101M, [C161-0.01004M, and Io=0.0265E/hr
4),,“ Run: [diK]-=0.0100M and [C15]=0.000602M
(Irrad'd for 1.75 hrs, GC condition set 1)

 

*
average of 2 tubes

225

 

Table 31: Stern-Volmer and 4) Data of 5-(3—Me-4-AcPhO)VP at
313nm in Methanol
Run 1
B13fi1_£fli
area C16 [AP],M <b [Q],M <D°I¢
0.463* 0.00117 0 0425 0.0 1.00
0.0705 0.000178 0.00647 0.00720 6.55
0.0450 0.000114 0.00415 0.0144 10.2
0.0354 0.0000872 0.00317 0.0216 13.4
0.0302 0.0000764 0.00278 0.0288 15.2
0.0227 0.0000574 0.00209 0.0432 20.3 In}
0.0187 0.0000473 0.00172 0.0576 24.6 '
Actinometry (average of 3 tubes):
0.410 0.00909 0.33 - -

Actinometers: [VP]=0.104M, [C16]=0.00984M, and Io=0.027SE/hr
SV Run: [diK]=0.0100M and [C16]=0.00112M
(Irrad'd for 1.7 hrs, GC condition set 1)

 

mm.
1

I.

 

Run 2
aI£a_AE
area C16 [AP],M (D [Q],M ¢°l¢
0.228* 0.000594 0.0419 0.0 1.00
0.102 0.000266 0.0187 0.000833 2.24
0.0720 0.000188 0.0132 0.00167 3.17
0.0558 0.000146 0.0130 0.00250 4.07
0.0473 0.000123 0.00866 0.00333 4.84
0.0383 0.0000999 0.00704 0.00500 5.95
0.0324 0.0000845 0.00595 0.00666 7.04
Actinometry (average of 3 tubes):
0.212 0.00468 0.33 - -

Actinometers: [VP]=0.104M, [C16]=0.00984M, and I°=0.014ZE/hr
SV Run: [diK]=0.0101M and [C16]=0.00116M
(Irrad'd for 50 min, GC condition set 1)

 

.average of 3 tubes

226

Table 31 (cont'd)

 

Run 3
area_A2
area C16 [AP],M <0 [Q],M ¢°I¢
0.284* 0.000633 0.0386 0.0 1.00
0.213 0.000475 0.0289 0.000180 1.34
0.173 0.000386 0.0235 0.000360 1.64
0 146 0.000326 0.0199 0.000540 1.94
0.143 0.000319 0.0195 0.000720 1.98
0.115 0.000256 0.0156 0.00108 2.47
0.0952 0.000212 0.0129 0.00144 2.99
Actinometry (average of 2 tubes):
2.59 0.00541 0.33 - -

Actinometers: [VP]=0.102M, [C16]=0.000929M, and Io=0.0164E/hr
SV Run: [diK]=0.0100M and [C16]=0.000991M
(Irrad'd for 2 hrs, GC condition set 1)

 

*-
average of 2 tubes

 

227

Table 32: Stern-Valuer and (b Data of 5-(3-Me-4-ValPhO)VP at
313nm in Benzene

 

area_AR
area 016 [1121,14 «I» [Q] ,M 0°14)
0.382* 0.000966 0.0273 0.0 1.00
0.184 0.000465 0.0131 0.0168 2.08
0 120 0.000303 0.00856 0 0335 3.19
0.0870 0.000220 0.00621 0.0503 4.39
0.0685 0 000173 0.00489 0.0670 5.58
Actinometry (average of 2 tubes):

5.58 0 0117 0.33 - -

 

Actinometers: [VP]=0.102M, [C16]=0.000929M, and Io=0.0354E/hr
SV Run: [diK]=0.0101M and [C16]=0.00112M
(Irrad'd for 7.75 hrs, GC condition set 1)

 

Tau-440ml“

 

a.“ U,
area C24 [diKobsv'd],M (1) [Q1114
0.0739* 0.0000589 0.00166 0.0

diKobsv'd= 8- (3-Me-4-AcPhO) VP
(0 Run: [diK]=0.0101M and [C24]=0.000438M
(GC condition set 3)

 

4
average of 2 tubes

228

Table 33: Stern-Volmer and (b Data of 5-(3-Me-4-(y-
MeVa1)PhO)VP at 313nm in Benzene

 

 

 

Run 1

AI£B_A2

area €16 [1491,14 d) [Q],M ¢°Id>

0.323* 0.000682 0.0303 0.0 1.00

0.187 0.000395 0.0176 0.00850 1.73

0.138 0.000291 0.0129 0.0170 2.34

0.109 0.000230 0.0102 0.0255 2.96

0.0918 0.000194 0.00862 0.0340 3.52

Actinometry (average of 2 tubes):

3.54 0.00740 0.33 - —

Actinometers: [VP]=0.102M, [C16]=0.000929M, and Io=0.02255/hr

SV Run: [diK]=0.0102M and [C16]=0.000581M

(Irrad'd for 7.75 hrs, GC condition set 1)

azea_difinhsxzi

area Clg-Ph [diKobsv'd] ,M ¢ [Q] ,M ¢°/¢
0.298* 0.000255 0.0113 0.0 1.00
0.122 0.000104 0.00463 0.00850 2.44
0.0665 0.0000568 0.00252 0.0170 4.48
0.0411 0.0000351 0.00156 0.0340 7.25

diKobsv'd== 8— (3-Me-4-AcPhO) VP
SV Run: [diK]=0.0102M and [Clg-Ph]=0.000581M
(GC condition set 3)

 

*
average of 2 tubes

 

229

Table 33 (cont'd)

Run 2
new
area C16 [APJIM ¢ [QJIM ¢°l¢
0.259* 0.000505 0.0269 0.0 1.00
0.201 0.000392 0.0209 0.00310 1.29
0.173 0.000338 0.0180 0.00620 1.49
0.149 0.000291 0.0155 0.00929 1.74
0.136 0.000265 0.0141 0.0124 1.91
Actinometry (average of 2 tubes):
0.799 0.00619 , 0.33 - -

Actinometers: [VP]=0.101M, [C16]=0.00343M, and Io=0.0188E/hr
SV Run: [diK]=0.0101M and [C16]=0.000867M
(Irrad'd for 12 hrs, GC condition set 1)

 

A w].

 

area Clg-Ph [diKobsv'd] ,M (D [O] ,M ¢°l¢
0.247* 0.000171 0.00910 0.0 1.00
0.139 0.0000962 0.00512 0 00310 1.77
0.114 0.0000789 0.00420 0.00620 2.16
0.0919 0.0000636 0.00338 0.00929 2.68
0.0720 0.0000499 0.00265 0 0124 3.42

diKobmfld= 5-(3-Me-4-AcPhO)VP
SV Run: [diK]=0.0101M and [Clg-Ph]=0.000471M
(GC condition set 3)

 

 

*
average of 2 tubes

230

Table 34: (bun, Data of 5-(3-Me-4-(y-MeVal)PhO)VP at 313nm in

 

 

 

Benzene
area_A2
area C16 [AP],M (D [Dioxane],M
0.204* 0.000507 0.0277 0.0
0.251 0.000625 0.0342 1.16
0.265 0.000659 0.0360 2.26
0.279 0.000694 0.0379 3.40
0.301 0.000749 0.0409 4.44 “a
0.308 0.000766 0.0419 5.67 . 1
0.301 0.000749 0.0409 6.83 J
0.317 0.000789 0.0431 8.01 ;
Actinometry (average of 2 tubes): 0
0.782 0.00604 0.33‘ - .
i

Actinometers: [VP]=0.101M, [C16]=0.00343M, and Io=0.0183E/hr
oMax Run: [diK]=0.0100M and [C16]=0.00111M “—
(Irrad'd for 5.5 hrs, GC condition set 1)
area diKQDS'C'd
area Clg'Ph [diKoomwd],M d) [Dioxane],M

0.306* 0.000175 0.00958 0.0

0.512 0.000293 0.0160 1.16

0.663 0.000380 0.0207 2.26

0.785 0.000450 0.0246 3.40

0.822 0.000471 0.0257 4.44

0.959 0.000549 0.0300 5.67

0.949 0.000544 0.0297 6.83

0.954 0.000546 0.0299 8.01

dixoosv 'd= 8- (3-Me-4-AcPhO) VP
<1)Max Run: [diK]=0.0100M and [Clg-Ph]=0.000390M
(GC condition set 3)

 

*
average of 3 tubes

231

 

 

 

Table 35: Stern-Valuer and (D Data of 5-(3-Me-4-(y-
MeVal)PhO)VP at 313nm in Methanol
Run 1

azzui.AE.

area C16 [AP],M (D [Q],M ¢°l¢

0.164* 0.000399 0.0300 0.0 1.00

0.0489 0.000119 0.00895 0.00394 3.35

0.0336 0.0000816 0.00614 0.00788 4.89

0.0269 0.0000654 0.00492 0.0118 6.10

0.0228 0.0000554 0.00417 0.0158 7.19

Actinometry (average of 2 tubes):

0.565 0.00436 0.33 — -

Actinometers: [VP]=0.101M, [C16]=0.00343M, and Io=0.0133E/hr

SV Run: [diK]=0.0101M and [C16]=0.00108M

(Irrad'd for 7.75 hrs, GC condition set 1)

W3

area Clg-Ph [diKobsv'd],M d) [Q],M ¢°l¢
0.933* 0.000575 0.0432 0.0 1.00
0.137 0.0000844 0.00634 0.00394 6.81
0.0525 0.0000323 0.00243 0.00788 17.8
0.0213 .0'0000131 0.000986 0.0118 43.7

diKobsv'd= 8- (3-Me-4-AcPhO) VP

SV Run: [diK]=0.0101M and [C19‘Ph]=0.000419M

(GC condition set 3)

 

*
average of 2 tubes

 

 

 

 

232
Table 35 (cont'd)
Run 2
area_A£
area C16 [AP],M (b [Q],M <b°l¢
0.231* 0.000538 0.0309 0.0 1.00
0.156 0.000363 0.0209 0.000611 1.48
0.122 0.000284 0.0163 0.00122 1.89
0.104 0.000242 0.0139 0.00183 2.22
0.0898 0.000209 0.0120 _ 0.00244 2.57
Actinometry (average of 2 tubes):
0.743 0.00573 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.00343M, and IO=0.0174E/hr
SV Run: [diK]=0.0101M and [C16]=0.00104M
(Irrad'd for 3.5 hrs, GC condition set 1)
52mm
area Clg-Ph [diKobsv'd]v,M (D [Q] 7M (Do/(b
1.08* 0.000748 0.0430 0.0 1.00
0.729 0.000505 0.0290 0.000611 1.48
0.470 0.000325 0.0187 0.00122 2.30
0.381 0.000264 0.0152 0.00183 2.84
0.270 0.000187 0.0107 0.00244 4.00

diKobsv'd= 8- (3-Me-4-AcPhO)VP

SV Run:

[diK]=0.0101M and [C19'Ph]=0.000471M
(GC condition set 3)

 

at
average of 2 tubes

 

233

Table 36: Stern-Volmer and (D Data of 5-(4-BzPhO)VP at 313nm

in Benzene

 

 

Run 1

mm
area C16 [AP]IM d, [QJIM ¢°I°
0.244* 0.000569 0.00572 0.0 1.00
0.0758 0.000177 0.00178 0.00239 3.21
0.0663 0.000154 0.00155 0.00479 3.69
0.0672 0.000156 0.00157 0.00718 3.65
0.0582 0.000136 0.00137 0.00957 4.18
Actinometry (average of 2 tubes):
areLL-lieAP.

area C16 [2-MeAP],M

0.340 0.00160 (¢> =0.016)

Actinometers: [2—MeVP]=0.104M,

sv Run: [diK]=0.00997M and [C16]=0.00104M

(Irrad'd for 18 hrs, GC conditio

act

[C16]=0.00232M, and Io=0.00994E/hr

n set 1)

 

 

Run 2
3131fl_1u3
area C16 [AP],M (D [Q],M ¢°I¢
0.186* 0.000447 0.00575 0.0 1.00
0.0939 0.000226 0.00291 0.000400 1.98
0.0739 0.000178 0.00229 0.000800 2.51
0.0664 0.000160 0.00206 0.00160 2.79
Actinometry (average of 2 tubes):
MAP.
area C16 [2-MeAP],M
0.264 0.00124 (¢act=0.016)

Actinometers: [2-MeVP]=0.104M,

(Irrad'd for 16 hrs, GC conditio

 

*
average of 2 tubes

[C16]=0.00232M, and Io=0.00777E/hr
SV Run: [diK]=0.0100M and [C16]=0.00107M

n set 1)

234

Table 37: Stern-Volmer and (b Data of 5-(4-BzPhO)VP at 313nm
in Methanol

 

 

Run 1

area_AE
area C16 [AP],M (b [Q],M ¢°I¢
0.560* 0.00118 0.0268 0.0 1.00
0.146 0.000307 0.00698 0.000182 3.84
0.0798 0.000168 0.00382 0.000364 7.02
0.0587 0.000123 0.00280 0.000546 9.59
0.0357 0.0000751 0.00171 0.000909 15.7
0.0317 0.0000667 0.00152 0.00109 17.7
Actinometry (average of 2 tubes):
area_2:MeAE

area C16 [2—MeAP],M

0.178 0.000704 (dgct=0.016)

Actinometers: [2-MeVP]=0.102M, [C16]=0.00195M, and IO=0.044OE/hr
SV Run: [diK]=0.0100M and [C16]=0'000935M
(Irrad'd for 9 hrs, GC condition set 1)

 

7:
average of 2 tubes

 

 

 

235

Table 37 (cont'd)

 

 

Run 2

w
area C16 [AP],M 0 [Q],M <b°l¢
0.261* 0.000602 0.0300 0.0 1.00
0.0357 0.0000825 0.00410 0.000322 7.30
0.0210 0.0000485 0.00241 0.000643 12.4
0.0135 0.0000312 0.00155 0.000964 19.3
0.0114 0.0000263 0.00131 0.00129 22.9
Actinometry (average of 2 tubes):
W

area C16 [2’M6AP],M

0.0815 0.000322 (d) =0.016)

3C1

Actinometers: [2-MeVP]=0.102M, [C16]=0.00195M, and Io=0.0201E/hr

SV Run: [diK]=0.0100M and [C16]=0.00103M
(Irrad'd for 5.5 hrs, GC condition set 1)

E

at
average of 2 tubes

4..

£5.11.

 

 

T‘ble 38: Stern-Volmer and

in Benzene

 

236

4) Data of 5-(4-BzPhO)VP at 366nm

 

area_AE

area c16 (1191,14 “’66:: [Q],M o°/o
0.2oo* 0.000454 0.0189 0.0 1.00
0.0724 0.000164 0.00683 0.000196 2.77
0.0434 0.0000986 0.00411 0.000393 4.60
0.0286 0.0000649 0.00270 0.000786 6.99
0.0233 0.0000529 0.00220 0.00112 8.58
0.01.98 0.0000450 0.00188 0.00157 10.1
Actinometry (average of 2 tubes):

1.05 0.00487 0.33 - -
Act: [VP]=0.101M, [C16]=0.00207M, Io=0.01488/nr, 4 Imxm=0.024OE/hr
SV Run: [diK]=0.0101M and [C16]=0.00101M

(Irrad'd for 6.75 hrs, GC condition set 1)

Quant Um yield correction:

\

\
*

aVerage of 2 tubes

I =

COfI

x (1-10"‘)K/(1-10"‘)act

 

237

 

Table 39: Stern-Volmer and (b Data of 5-(4-BzPhO)VP at 366nm
in Methanol

m
area C16 [AP],M (been. [Q],M ¢°I¢
0.229* 0.000547 0.0160 0.0 1.00
0.134 0.000320 0.00936 0.0000771 1.71
0.0943 0.000225 0.00658 0.000154 2.43
0.0571 0.000136 0.00398 0.000308 4.01
0.0439 0.000105 0.00307 0.000463 5.22
0.0334 0.0000798 0.00234 0.000617 6.86
Actinometry (average of 2 tubes):
1.57 0.00753 0.33 - -
Act: [VP]=0.100M, [C16]=0.00213M, Io=0.02283/hr, & Icorg=0.034ZE/hr
SV Run: [diK]=0.0100M and [C16]=0.00106M

(Irrad'd for 12 hrs,

Quantum yield correction:

 

 

*
average of 3 tubes

Icorr = Io x (1-10‘A)K/(1-10“A)

GC condition set 1)

act

 

238

Table 40: Stern-Volmer and <b Data of 5-(3-Me-4-BzPhO)VP at

313nm. in Benzene

 

 

mm
area C16 [AP],M (b [Q],M ¢°l¢
0.205* 0.000391 0.00234 0.0 1.00
0.0693 0.000133 0.000796 0.0355 2.94
0.0455 0.0000870 0.000521 0.0710 4.50
0.0274 0.0000524 0.000314 0.142 7.46
0.0203 0.0000388 0.000232 0.213 10.1
Actinometry (average of 2 tubes):
area.2:MeAP.

area C16 [2-MeAP],M

0.653 0.00268 =0.016)
Actinometers: [2-MeVP]=0.100M, [C16]=0.00202M, and IO=0.167E/hr

SV Run: [diK]=0.0100M and [C16]=0.000850M
(Irrad'd for 56 hrs,

 

1k
average of 2 tubes

GC condition set 1)

239

 

Table 41: 4),,“ Data of 5-(3-Me-4-BzPhO)VP at 313nm in Benzene
area_AE
area C16 [AP],M d) [Dioxane],M
0.0479* 0.000118 0.00242 0.0
0.0808 0.000199 0.00408 2.27
0.0929 0.00229 0.00469 3.86
0.0963 0.00238 0.00488 5.46
0.0984 0.00243 0.00498 6.14
0.102 0.00252 0.00516 6.82
0.115 0.00283 0.00580 7.75
0.116 0.00286 0.00586 8.18

Actinometry (average of 2 tubes):

 

W
area C16 [2~MeAP],M
0.191 0.000781 (dgct=0.016)
Actinometers: [2-MeVP]=0.100M, [C16]=0.00202M, and IO=0.0488E/hr
d5MX Run: [diK]=0.0100M and [C16]=0.00110M

(Irrad'd for 17.5 hrs, GC condition set 1)

 

1*
average of 3 tubes

 

240

 

 

Table 42: Stern-Volmer and 4) Data of 5-(3-Me-4-BzPhO)VP at
313nm in Methanol

31:51.103
area C16 [AP],M (D [Q],M ¢°I¢
0.133* 0.000278 0.00166 0.0 1.00
0.0445 0.0000930 0.000557 0.00962 2.99
0.0357 0.0000746 0.000447 0.0192 3.73
0.0268 0.0000560 0.000335 0.0385 4.96
0.0206 0.0000437 0.000258 0.0577 6.46
Actinometry (average of 2 tubes):
“MAE

area C16 [2"M€AP],M

0.652 0.00267 (oaC,=0.016)

Actinometers: [2-MeVP]=0.100M, [C16]=0.00202M, and Io=0.167E/hr

SV Run: [diK]=0.0100M and [C16]=0.000929M
(Irrad'd for 208 hrs, GC condition set 1)

 

*
average of 2 tubes

 

241

Table 43: Stern-Volmer and 4? Data of 5-(2'-Me-4-BzPhO)VP at
313nm in Benzene

 

 

 

 

 

Run 1

.allfil_£li
area C16 [AP],M <b [Q],M <b°l<b
0.159* 0.000329 0.00435 0.0 1.00
0.0736 0.000152 0.00201 0.0304 2.16
0.0485 0.000100 0.00132 0.0609 3.28
0.0325 0.0000673 0.000890 0.122 4.89
0.0215 0.0000445 0.000589 0.183 7.39
0.0167 0.0000346 0.000458 0.244 9.51
Actinometry (average of 2 tubes):
W

area C16 [2-MeAP],M

0.265 0.00121 (dgct=0.016)
Actinometers: [2-MeVP]=0.102M, [C16]=0.00225M, and Io=0.07568/hr
SV Run: [diK]=0.0100M and [C16]=0.000920M
(Irrad'd for 49 hrs, GC condition set 1)

Run 2

area_AE
area C16 [AP],M <b [Q],M ¢°/d>
0.163* 0.000348 0.00483 0.0 1.00
0.128 0.000273 0.00379 0.00527 1.27
0.110 0.000234 0.00325 0.0105 1.49
0.0868 0.000185 0.00257 0.0211 1.88
0.0703 0.000150 0.00208 0.0316 2.32
0.0608 0.000130 0.00180 0.0422 2.68
Actinometry (average of 2 tubes):
W

area C16 [2-MeAP],M

0.522 0.00115 (dgct=0.016)

Actinometers: [2-MeVP]=0.101M, [C16]=0.00109M, and Io=0.0721E/hr
SV Run: [diK]=0.0101M and [C16]=0.000947M
(Irrad'd for 20.5 hrs, GC condition set 1)

 

*
average of 3 tubes

242

Table 44: din‘x Data of 5-(2'-Me-4-BzPhO)VP at 313nm in Benzene

 

area_AE

area C16 [AP] ,M d> [Dioxane] ,M
0.0154* 0.0000350 0.00445 0.0
0.0238 0.0000540 0.00686 1.71
0.0283 0.0000642 0.00816 3.34
0.0385 0.0000874 0.0111 6.65
0.0322 0.0000731 0.00929 7.06
0.0297 0.0000674 0.00856 7.50
0.0269 0.0000611. 0.00776 7.97

Actinometry (average of 2 tubes):

 

areLZdieAP.
area C16 [2’M€AP],M
0.0570 0.000126 (¢> =0.016)

act

 

Actinometers: [2-MeVP]=0.101M, [C16]=0.00109M, and Io=0.00787E/hr
¢Max Run: [diK]=0.0100M and [C16]=0.00101M
(Irrad'd for 15 hrs, GC condition set 1)

 

*
average of 3 tubes

243

 

 

Table 45: Stern-Volmer and d) Data of 5- (4-CNPhO)V'P at 313nm
in Methanol

Run 1
31331.52.
area C16 [AP],M (D [Q],M ¢°l0
0.395* 0.000944 0.552 0.0 1.00
0.174 0.000416 0.243 0.00159 2.27
0.141 0.000337 0.197 0.00238 2.80
0.121 0.000289 0.169 0.00317 3.27
0.0861 0.000206 0.120 0.00476 4.60
0.0712 0.000170 0.0994 0.00634 5.55
Actinometry (average of 2 tubes):
0.0763 0.000564 0.33 - -
Actinometers: [VP]=0.101M, [C16]=0.00328M, and Io=0.0017lE/hr
SV Run: [K]=0.0100M and [C16]=0.00106M
(Irrad'd for 15 min, GC condition set 1)

Run 2
alfiia_lU3
area C16 [AP],M [Q],M ¢°l¢
0.393* 0.000837 0.0 1.00
0.229 0.000488 0.000756 1.71
0.124 0.000264 0.00303 3.17
0.0915 0.000195 0.00454 4.27
0.0691 0.000147 0.00605 5.69
SV Run: [K]=0.00996M and [C16]=0.000947M

(Irrad'd for 19 min,

 

*
average of 2 tubes

GC condition set 1)

 

‘37,. r _

244

 

 

Table 46: Stern-Volmer and 0 Data of £-(2'-Me-4-BzPhO)MxP at
313nm in Benzene
Run 1
mm
area C16 [AP],M <1) [Q],M <b°/<D
0.367* 0.000862 0.00920 0.0 1.00
0.270 0.000634 0.00677 0.0153 1.36
0.211 0.000496 0.00529 0.0307 1.74
0.152 0.000357 0.00381 0.0613 2.41
0.129 0.000303 0.00323 0.0920 2.84
0.0938 0.000220 . 0.00235 0.123 3.91
Actinometry (average of 2 tubes):
areLZflIeAP.
area C16 [2-MeAP],M
0.326 0.00150 (¢gct=0.016)
Actinometers: [2-MeVP]=0.101M, [C16]=0.00227M, and Io=0.0937E/hr
SV Run: [diK]=0.0101M and [C16]=0.00104M

(Irrad'd for 37.5 hrs,

 

*

 

average of 3 tubes

GC condition set 1)

 

 

 

245

lele 46 (cont'd)

 

 

RUn 2
m
area C16 [AP],M <0 [Q],M <b°l¢
0.200" 0.000442 0.00961 0.0 1.00
0.128 0.000283 0.00615 0.0187 1.56
0.0992 0.000219 0.00476 0.0375 2.02
0.0698 0.000154 0.00335 0.0750 2.87
0.0539 0.000119 0.00259 0.112 3.71
0.0415 0.0000917 0.00199 0.150 4.82
Actinometry (average of 2 tubes):
area—2:11am
area C16 [2-MeAP],M
O . 333 0.000735 (<Dact=0.016)

Actinometers: [2-MeVP]=O.101M, [C16]=0.00109M, and Io=0.046OE/hr
SV Run: [diK]=0.0100M and [C16]=0.000982M
(Irrad'd for 13 hrs, GC condition set 1)

*\

av
erage of 3 tubes

 

246

 

Table 47: (Dan Data of e-(2'-Me-4-BzPhO)HxP at 313nm in Benzene
areLAP
area C16 [AP],M d) [Dioxane],M
0.0489* 0.000108 0.00947 0.0
0.0909 0.000201 0.0176 1.59
0.104 0.000230 0.0202 3.21
0.118 0.000261 0.0229 4.78
0.121 0.000267 0.0234 6.64
0.124 0.000274 0.0240 7.28
0.126 0.000278 0.0244 7.49

Actinometry (average of 2 tubes):

 

MAP.
area C16 [2-MeAP],M
0.0394 0.000182 (dgct=0.016)

Actinometers: [2-MeVP]=0.101M, [C16]=0.00227M, and Io=0.0114E/hr
dHMx Run: [diK]=0.0101M and [C16]=0.000982M
(Irrad'd for 7 hrs, GC condition set 1)

 

*
average of 3 tubes

 

 

 

247

Table 48: Stern-Volmer and d> Data of €-(4-CNPhO)BzP at 313nm
in Benzene

 

at

.
Ijfi _,. -
t

 

 

Run 1
area_AE
area C16 [AP],M <1) [Q],M <b°/d>
0.288* 0.000674 0.242 0.0 1.00
0.149 0.000349 0.126 0.0123 1.93
0.0998 0.000234 0.0842 0.0247 2.88
0.0754 0.000176 0.0633 0.0370 3.83
0.0621 0.000145 0.0522 0.0493 4.65
Actinometry (average of 2 tubes):
0.0189 0.000918 0.33 - -
Actinometers: [VP]=0.102M, [C16]=0.00216M, and Io=0.002783/hr
SV Run: [K]=0.0100M and [C16]=0.00104M
(Irrad'd for 1.25 hrs, GC condition set 1)

Run 2
£123.32
area C16 [AP],M d) [Q],M ¢°l¢
0.293* 0.000666 0-257 0.0 1.00
0.135 0.000307 0.119 0.0143 2.17
0.0908 0.000206 0.0795 0.0286 3.23
0.0662 0.000150 0.0579 0.0429 4.43
0.0530 0.000120 0.0463 0.0571 5.53
Actinometry (average of 2 tubes):
0.176 0.000855 0.33 - -

Actinometers: [VP]=0.102M, [C16]=0.00216M, and Io=0.00259E/hr
SV Run: [K]‘0.0100M and [C16]-0°00101M
(Irrad'd for 1.5 hrs, GC condition set 1)

 

*
average of 2 tubes

248

Table 49: 45‘“ Data of e-(4-CNPhO)HzP at 313nm in Benzene

 

areLAP.

area C16 [AP],M ¢) [Dioxane],M
0.0483* 0 000120 0 201 0.0
0.0707 0.000175 0.294 0.770
0.0781 0.000193 0.324 1.41
0.0858 0.000212 0.356 2.08
0.0877 0.000217 0.364 2.76
0.0863 0.000214 0.359 3.41
0.0860 0.000213 0.357 4.10
0.0804 0.000199 0.334 5.56
Actinometry (average of 2 tubes)

0.0405 0.000197 0.33. -

Actinometers: [VP]=0.102M, [C16]=0.00216M, and Io=0.000596E/hr
char Run: [diK]=0.0100M and [C16]=0.00110M
(Irrad'd for 10 min, GC condition set 1)

 

*
average of 2 tubes

 

249

Table 50: Stern-Volmer and (D Data of C-(2'-Me-4-BzPhO)MpP at
313nm. in Benzene

 

 

mm
area C16 [AP],M <0 [Q],M ¢°I¢
0.227* 0.000552 0.0105 0.0 1.00
0.169 0.000411 0.00782 0.0199 1.34
0.135 0.000328 0.00624 0.0398 1.68
0.0943 0.000229 0.00435 0.0795 2.41
0.0753 0.000183 0.00348 0.119 3.01
0.0566 0.000138 .0.00262 0.159 4.01
Actinometry (average of 2 tubes):
MAP.

area C16 [Z‘MEAP] ,M

0.183 0.000841 (d>act=0.016)

Actinometers: [2-MeVP]=0.101M, [C16]=0.00227M, and Io=0.0526E/hr
SV Run: [diK]=0.0100M and [C16]=0.00108M
(Irrad'd for 37 hrs, GC condition set 1)

 

*
average of 2 tubes

 

 

250

Table 51: (0,,“ Data of fi-(2'-Me-4-BzPhO)HpP at 313nm in Benzene

 

area_A2

area C16 [AP],M d) [Dioxane],M
0.0168* 0.000120 0.0237 0.0
0.0422 0.000303 0.0598 4.71
0.0437 0.000313 0.0618 6.24
0.0444 0.000318 0.0628 7.00

Actinometry (average of 2 tubes):

 

 

 

 

area Z'MEBE j
area C16 [2-MeAP],M i
0.0367 0.0000811 (45C,=0.016) Z
Actinometers: [2-MeVP]=0.101M, [C16]=0.00109M, and IO=0.00507E/hr 3x“;
(1),,ax Run; [diK]=0.0100M and [C16]=0.00319M L.

(Irrad'd for 6 hrs, GC condition set 1)

 

at
average of 2 tubes

 

251

Table 52: Stern-Volmer and (D Data of C-(4-CNPhOHIpP at 313nm
in Benzene

 

 

 

 

Run 1
area_AR
area C16 [AP],M [Q],M <b°/<D
0.686* 0.000758 0.0 1.00
0.458 0.000506 0.0108 1.50
0.300 0.000331 0.0270 2.29
0.253 0.000280 0.0378 2.71
0.212 0.000234 0.0486 3.24
SV Run: [K]=0.0100M and [C16]=0.000491M
(Irrad'd for 1.25 hrs, GC condition set 1)

Run 2
ar£a_AR
area Cl6 [AP],M [Q],M ¢°l¢
0.694* 0.000767 0.0 1.00
0.444 0.000491 0.0108 1.56
0.294 0.000325 0.0270 2.35
0.248 0.000274 0.0378 2.80
0.212 0.000234 0.0486 3.27

SV Run: [K]=0.0100M and [C16]=0.000491M
(Irrad'd for 1.25 hrs, GC condition set 1)

 

*
average of 2 tubes

 

252

Table 53: than Data of C-(4-CNPhO)HpP at 313nm in Benzene

 

area_A£

area C16 [AP],M d> [Dioxane],M
0.0266* 0.0000599 0.108 0.0
0.0482 0.000108 0.195 0.705
0.0531 0.000119 0.215 1.38
0.0575 0.000129 0.233 2.05
0.0583 0.000131 0.237 3.52
0.0611 0.000137 0.248 4.10
Actinometry (average of 2 tubes)

0.0351 0.000192 0.33 -

Actinometers: [VP]=0.100M, [C16]=0.00231M, and IO=0.000553E/hr
4),,“ Run: [diK]=0.0100M and [C16]=0.00100M
(Irrad'd for 10 min, GC condition set 1)

 

*
average of 2 tubes

 

 

 

 

253

Table 54: Stern-Volmer and 11> Data of n-(2'-Me-4-BzPhO)OtP

at 313nm in Benzene

 

 

Run 1

m
area C16 [AP],M (D [Q],M ¢°Id>
0.323* 0.000720 0.00895 0.0 1.00
0.204 0.000455 0.00565 0.0512 1.58
0.141 0.000314 0.00391 0.102 2.29
0.0895 0.000200 0.00248 0.205 3.61
0.0605 0.000135 0.00168 0.307 5.34
0.0447 0.0000997 0.00124 0.409 7.23
Actinometry (average of 2 tubes):
W

area C16 [2-MeAP],M

0.583 0.00129 (dgct=0.016)

Actinometers: [2-MeVP]=0.101M, [C16]=0.00109M, and Io=0.0805E/hr

SV Run: [diK]=0.0100M and [C16]=0.000991M
(Irrad'd for 42 hrs, GC condition set 1)

r1 .‘ ...

 

Run 2

area_82

area C16 [AP],M [Q],M ¢°ld>
0.187* 0.000442 0.0 1.00
0.122 0.000288 0.0362 1.53
0.0911 0.000215 0.0723 2.05
0.0590 0.000139 0.145 3.17
0.0464 0.000110 0.217 4.03
0.0344 0.0000813 0.289 5.44

SV Run: [diK]=0.0100M and [C16]=0.00105M
(Irrad'd for 34 hrs, GC condition set 1)

 

*
average of 2 tubes

 

' i.'I-J:

 

 

 

254

 

Table 55: 45,“, Data of n-(2'-Me-4-BzPhO)OtP at 313nm in Benzene
mm
area C16 [AP],M ¢> [Dioxane],M
0.0292* 0.0000736 0 0122 0.0
0.0647 0.000163 0.0269 1.62
0.0763 0.000192 0.0317 3.23
0.0771 0.000194 0.0321 4.74
0.0849 0.000214 0.0354 6.84
0.0811 0.000204 0.0337 7.31
0.0930 0.000234 0.0387 7.51
0.0979 0.000247 0.0408 7.78

Actinometry (average of 2 tubes):

 

MAE
area C16 [2-MeAP],M
0.0438
Actinometers: [2—MeVP]=0.101M,
¢Max Run:

(Irrad'd for 2.5 hrs,

0.0000967 (¢g£:=0.016)

[C16]=0.00109M, and IO=0.006058/hr

[diK]=0.0100M and [C16]=0.00112M

 

* .
average of 2 tubes

GC condition set 1)

 

255

Table 56: Stern-Volmer and (b Data of n-(4-CNPhO)OtP at

313nm in Benzene

 

 

Run 1
area_AE
area C16 [AP],M d> [Q],M d>°ld>
0.252* 0.000573 0.190 0.0 1.00
0.149 0.000339 0.112 0.0184 1.69
0.107 0.000243 0.0805 0.0369 2.36
0.0781 0.000177 0.0587 0.0553 3.23
0.0667 0.000152 0.0504 0.0737 3.78
Actinometry (average of 2 tubes):
0.205 0.000996 0.33 - -
Actinometers: [VP]=0.102M, [C16]=0.00216M, and Io=0.003OZE/hr
SV Run: [K]=0.0100M and [C16]=0.00101M
(Irrad'd for 1.75 hrs, GC condition set 1)

Rrul 2
area_AE
area C16 [AP],M <b [Q],M <b°l<b
0.229* 0.000554 0.193 0.0 1.00
0.124 0.000299 0.104 0.0217 1.85
0.0890 0.000214 0.0746 0.0435 2.58
0.0682 0.000164 0.0571 0.0652 3.37
0.0541 0.000130 0.0453 0.0870 4.25
Actinometry (average of 2 tubes):
0.182 0.000946 0.33 - -
Actinometers: [VP]=0.100M, [C16]=0.00231M, and I°=0.00287E/hr
SV Run: [K]=0.0100M and [C16]=0.00107M

(Irrad'd for 1.75 hrs, GC condition set 1)

 

*
average of 3 tubes

‘1 ("IF " L I":

 

256

Table 57: (Dan Data of n-(4-CNPhO)OtP at 313nm in Benzene

 

area_A£

area C16 [AP],M ¢> [Dioxane],M
0.0583* 0.000136 0.130 0.0
0.128 0.000300 0.286 1.83
0.131 0.000307 0.293 2.26
0.132 0.000309 0.295 2.59
0.137 0.000321 0.306 2.94
0.141 0.000330 0.315 3.29
0.141 0.000330 0.315 4.11
Actinometry (average of 2 tubes)

0.0665 0.000346 0.33 -

Actinometers: [VP]=0.100M, [C16]=0.00231M, and Io=0.001058/hr
¢Max Run: [diK]=0.0100M and [C16]=0.00104M
(Irrad'd for 20 min, GC condition set 1)

 

a .
average of 2 tubes

|—.v~_-

 

257

Table 58: Stern-Volmer' Data of BP Quenched. w/42MeO-2-MeBzP
at 313nm in Benzene

 

 

 

 

Run 1
exam -
area C16 [APJIM [CHIN ¢ol¢uncorr (Do/(boon:
0.487* 0.00232 0.0 1.00 1.00
0.197 0.000940 0.00214 2.48 1.56
0.115 0.000549 0.00428 4.23 1.95
0.0696 0.000332 0.00641 7.00 2.54
0.0485 0.000231 0.00855 10.0 3.00
sv Run: [BP]=0.101M and (gal-0.0021214
quxur=233 (Irrad'd for 2 hrs, GC condition set 1)

Run 2
a13fi1_£fli
area C16 [AP],M [Q],M <1>°l<l>uncorr (IV/(beerr
1.03* 0.00234 0.0 1.00 1.00
0.411 0.000934 0.00238 2.51 1.52
0.233 0.000529 0.00476 4.42 1.92
0.142 0.000323 0.00715 7.26 2.46
0.107 0.000243 0.00953 9.63 2.67
kqtcorr=201 (Irrad'd for 2 hrs, GC condition set 1)

Correction Factor (for partial absorption of light by Q):

8313 for Q = 1314 cm-1M-1 £313 for BP 3 47.6 cm-lM‘l

4>°/<b = ovouncm x eBPIBPl/ (eBPIBPJ+eQ(01)

COI'I'

 

*
average of 2 tubes

258

Table 59: Stern-Volmer Data of BP Quenched w/4-MeO-2'-MeBzP

at 313nm in Benzene

 

 

Run 1
arruLsAE.
area C16 [AP],M [Q] ,M ¢°l¢uncorr (IV/(Deon
0.186* 0.00246 0.0 1.00 1.00
0.130 0.00172 0.00108 1.43 1.33
0.0954 0.00126 0.00217 1.95 1.69
0.0608 0.000806 0.00433 3.06 2.33
0.0424 0.000562 0.00650 4.39 2.99
0.0324 0.000429 0.00866 5.74 3.56
sv Run: [BP]=0.100M and [C16]=0.00589M
quxxr = 297 (Irrad'd for 5 hrs, GC condition set 1)

Rtul 2
area_AB
area C16 [AP],M [Q],M ¢°l¢uncorr <1>°l<15corr
1.19* 0.00562 0.0 1.00 1.00
0.691 0.00326 0.00187 1.72 1.52
0.458 0.00216 0.00374 2.60 2.05
0.328 0.00155 0.00561 3.63 2.59
0.244 0 00115 0.00748 4.89 3.19

SV Run: [BP]=0.100M and [C16]=0.00210M

kthuT = 291 (Irrad'd for 4.5 hrs,

GC condition set 1)

Correction Factor (for partial absorption of light by Q):

 

£313 for Q = 339 cm'lM'l

£313 fOr BP

47.6 canM-l

ovocorr = ovouncorr x captspl/cgpmpmotol)

 

*
average of 2 tubes

 

259

Table 60: Stern-Volmer Data of 4-MeO-2-MeVP at 313nm in Benzene

 

 

Run 1
area C20 [Q],M d>°l¢
0.758* 0.0 1.00
0.190 0.0500 3.99
0.126 0.100 6.02
0.0992 0.150 7.64
0.0870 0.200 8.71
0.0750 0.300 10.1
SV Run: [K]=0.0101M and [C20]=0.000362M
(Irrad'd for 184 hrs, GC condition set 2)
Run 2
area C20 [Q] ,M <D°ld>
0.352* 0.0 1.00
0.161 0.0142 2.19
0.129 0.0283 2.73
0.0908 0.0425 3.88
0.0762 0.0567 4.62

SV Run: [K]=0.0101M and [C20]=0.000461M
(GC condition set 2)

x
*

aVerage of 2 tubes

 

 

 

 

 

260

Table 61: 4),," Data of 4-MeO-2-MeVP at 313nm in Benzene

 

Run 1
area C20 [4-MeO-2-MeAP],M [Dioxane],M <0
0.313* 0.000393 0.0 0.00109
0.537 0.000674 1.58 0.00186
0.439 0.000551 3.18 0.00152
0.185 0.000232 4.81 0.000641
0.130 0.000163 6.34 0.000450

Actinometry (average of 2 tubes):

 

MAE
area C16 [2-MeAP],M
1.23 0.00580 (0! =0.016)

act

Actinometers: [2-MeVP]=0.104M, [C16]=0.00232M, and IO=0.3628/hr
dNMx Run: [K]=0.0101M and [C20]=0.000525M

(Irrad'd for 120 hrs, GC condition set 2 for dmax Run and set 1
for Actinometers)

 

*
average of 2 tubes

 

 

261

Table 61 (cont'd)

 

 

Run 2

area C20 [4-MeO-2-MeAP],M [Dioxane],M d)
0.245* 0.000378 0.0 0.000915
0.610 0.000941 0.456 0.00228
0.536 0.000827 0.900 0.00200
0.531 0.000819 1.35 0.00198
0.463 0.000714 1.82 0.00173
0.471 0.000727 2.32 0.00176

Actinometry (average of 2 tubes):

 

MAB
area C16 [2-MeAP],M
1.40 0.00659

Actinometers: [2—MeVP]=0.104M, [C16]=0.00232M, and Io=0.413E/hr
¢Max Run: [K]=0.0101M and [C20]=0.000645M
(Irrad'd for 115 hrs, GC condition set 2 for ¢an Run and set 1

for Actinometers)

 

*
average of 2 tubes

 

 

 

262

 

 

Table 62: Stern-Volmer and (b Data of 4-MeO-2-MeVP at 313nm
in Methanol
Run 1
area C20 [4-MeO-2-MeAP],M ¢ [0]!“ ¢OI¢
0.617* 0.000732 0.00737 0.0 1.00
0.0485 0.0000575 0.000579 0.0152 12.7
0.0243 0.0000288 0.000290 0.0303 25.4
0.0181 0.0000215 0.000217 0.0455 34.0
0.0147 0.0000174 0.000175 0.0606 42.1
Actinometry (average of 2 tubes):
W
area C16 [2-MeAP],M
0.375 0.00164 (dkct=0-015)
Actinometers: [2-MeVP]=0.103M, [C16]=0.00209M, and Io=0.0993E/hr.
SV Run: [K]=0.0103M and [C20]=0.000496M

(Irrad'd for 15 hrs, GC condition set 2)

 

Run 2
area C20 [4-MeO-2-MeAP] , M (D [O] ,M ¢°l<b
0.386* 0.000478 0.00625 0.0 . 1.00
0 105 0.000130 0.00170 0 00270 3.68
0.0636 0.0000787 0.00103 0.00540 6.07
0.0448 0.0000554 0.000724 0.00809 8.63
0 0362 0.0000448 0.000586 0.0104 10.7

Actinometry (average of 2 tubes):

 

0.00122 (oac,=0.016)

area_2:_MeAP.
area C16 [2-MeAP],M
0.288
Actinometers: [2-MeVP]=0.103M,
SV Run:

(Irrad'd for 15 hrs,

[K1‘0 . 0103" and [C20] I'0 . OOOSIBM

 

*
average of 3 tubes

GC condition set 2)

[C16]=0.00209M, and Io=0.07653/hr.

 

 

263

 

Table 62 (cont'd)

Run 3
area C20 [4-MeO-2-MeAP] ,M ¢ [Q] ,M ¢°/<b
0.440* 0.000579 0.00597 0.0 1.00
0.313 0.000412 0.00425 0.000384 1.41
0.247 0.000325 0 00335 0.000767 1.78
0.210 0.000276 0.00285 0.00115 2.10
0 207 0.000272 0.00281 0.00153 2.13
0.166 0.000218 0.00225 0.00192 2.65
0.147 0.000193 0 00199 0.00230 2.99
0.130 0.000171 0.00176 0.00269 3.38

Actinometry (average of 2 tubes):

 

=0.016)

[C16]=0.00209M, and Io=0.097OE/hr.

MP.
area C16 [2-MeAP],M
0.366 0.00155 ((Dact
Actinometers: [2—MeVP]=0.103M,
SV Run: [K]=0.0101M and [C20]=0.000550M

(Irrad'd for 10 hrs,

 

*
average of 3 tubes

GC condition set 2)

 

 

 

264

 

 

Table 63: Stern-Volmer and (0 Data of l-Bz-4-(2-Me-4-An)Bt
at 313nm in Benzene

areLAE
area C16 [AP],M d) [Q],M ¢°I¢
0.354* 0.000811 0.0718 0.0 1.00
0.219 0.000502 0.0444 0.0109 1.62
0.154 0.000353 0.0312 0.0218 2.30
0.110 0.000252 0.0223 0.0435 3.22
0.0842 0.000193 0.0171 0.0653 4.21
0.0667 0.000153 , 0.0135 0.0870 5.31
Actinometry (average of 2 tubes):
0.859 0.00371 0.33 -
Actinometers: [VP]=0.101M, [C16]=0.00204M, and IO=0.0113E/hr
SV Run: [diK]=0.0100M and [C16]=0.00102M
(Irrad'd for 4.5 hrs, GC condition set 1)

area c2O [4-MeO-2-MeAP],M (b [01.14

0.0113* 0.0000203 0.00179 0.0
sv Run; [diK]=0.0100M and [C20]=0.000752M

(GC condition set 2)

 

3:
average of 2 tubes

 

 

 

265

Table 64: ¢Max Data of 1-Bz-4-(2-Me-4-An)Bt at 313nm in Benzene

 

 

 

3:23.52
area C16 [AP],M [Dioxane],M d)
0.227* 0.000511 0.0 0.0693
0.249 0.000560 1.16 0.0760
0.278 0.000627 3.40 0.0849
0.277 0.000623 4.57 0.0845
0.297 0.000668 5.68 0.0906
0.301 0.000676 6.83 0.0917
0.299 0.000672 7.96 0.0912
Actinometry (average of 2 tubes):
0.532 0.00244 - 0.33
Actinometers: [VP]=0.101M, [C16]=0.00204M, and IO=0.00737E/hr
dQMX Run: [diK]=0.0100M and [C16]=0.00100M
(Irrad'd for 2.75 hrs, GC condition set 1)
area C20 [4-MeO-2-MeAP],M [Dioxane],M <9
0.00605* 0.0000124 0.0 0.00168
0.00820 0.0000168 1.16 0.00228
0.00847 0.0000174 4.57 0.00236
0.00985 0.0000202 7.96 0.00274

(1),,“ Run: [diK]=0.0100M and [C20]=0.000858M
(GC condition set 2)

 

1:
average of 3 tubes

 

 

 

 

 

266

 

 

Table 65: Stern-Volmer and <0 Data of l-Bz-4-(2-Me-4-An) Bt
at 313nm in Methanol

3:23.32
area C16 [AP],M <0 [Q],M <b°l<b
0.343* 0.000757 0.0758 0.0 1.00
0.0966 0.000214 0.0214 0.0109 3.55
0.0663 0.000147 0.0147 0.0218 5.17
0.0472 0.000104 0.0104 0.0435 7.26
0.0385 0.0000851 0.00852 0.0653 8.90
0.0302 0.0000668 0.00669 0.0870 11.3
Actinometry (average of 2 tubes):
0.720 0.00330 0.33 -
Actinometers: [VP]=0.101M, [C16]=0.00204M, and Io=0.00999E/hr
Sv Run: [diK]=0.0100M and [C16]=0.000982M
(Irrad'd for 3.75 hrs, GC condition set 1)

area c20 [4-MeO-2-MeAP],M <0 [01.14

0.0204* 0.0000294 0.00294 0.0
<0 Run: [diK]=0.0100M and [C20]=0.000603M

(GC condition set 2)

 

*
average of 2 tubes

 

 

 

267

 

 

 

 

Table 66: Stern-Volmer and <b Data of 1-Bz-4-(o-Tl)Bt at
313nm in Benzene

area_AB

area C16 [AP],M <13 [Q],M <b°l<b

0.322* 0.000730 0.0490 0.0 1.00

0.223 0.000506 0.0340 0.0159 1.44

0.169 0.000384 0.0258 0.0318 1.90

0.118 0.000268 0.0180 0.0636 2.73

0.0904 0.000205 0.0138 0.0954 3.56

0.0708 0.000161 . 0.0108 0.127 4.54

Actinometry (average of 2 tubes):

1.09 0.00492 0.33 - -

Actinometers: [VP]=0.101M, [C16]=0.00202M, and Io=0.0149E/hr

SV Run: [diK]=0.0100M and [C16]=0.00101M

(Irrad'd for 5 hrs, GC condition set 1)

W
area C16 [2-MeAP],M (b [Q],M <b°ld>
0.0430* 0.0000881 0.00591 0.0 1.00
0.0223 0.0000457 0.00307 0.0159 ‘1.93
0.0143 0.0000293 0.00197 0.0318 3.01
0.00959 0.0000196 0.00132 0.0636 4.49
0.00706 0.0000145 0.000973 0.0954 6.08
0.00693 0.0000142 0.000953 0.127 6.21

(GC condition set 1)

 

*
average of 2 tubes

 

 

 

 

1"average of 3 tubes

Table 67: <03“, Data of 1-Bz-4-(o-Tl)Bt at 313nm in Benzene

3:33.32

area C16 [AP],M [Dioxane],M <0

0.108* 0.000244 0.0 0.0516

0.139 0.000316 1.46 0.0668

0.151 0.000343 2.76 0.0725

0.157 0.000356 4.09 0.0753

0.171 0.000388 5.46 0.0820

0.166 0.000377 6.40 0.0797

0.169 0.000384 7.06 0.0812

0.181 0.000411 8.23 0.0869

Actinometry (average of 2 tubes):

0.335 0.00156 - 0.33

Actinometers: [VP]=0.101M, [C16]=0.00207M, and Io=0.00473E/hr

¢Max Run: [diK]=0.0100M and [C16]=0.00101M

(Irrad'd for 1.5 hrs, GC condition set 1)

MAP.
area C16 [2-MeAP],M [Dioxane],M <D
0.0144* 0.0000295 0.0 0.00624
0.0181 0.0000371 1.46 0.00784
0.0193 0.0000395 2.76 0.00835
0.0206 0.0000418 4.09 0.00884
0.0224 0.0000459 5.46 0.00970
0.0222 0.0000455 6.40 0.00962
0.0230 0.0000471 7.06 0.00996
0.0248 0.0000508 8.23 0.0107

(GC condition set 1)

 

269

Table 68: Stern-Velma: and 4? Data of 1-Bz-4-(o-Tl)Bt
at 313nm in Methanol

 

3:33.32

area C16 [AP],M <b [Q],M <b°l<b
0.308* 0.000650 0.0674 0.0 1.00
0.206 0.000435 0.0451 0.00882 1.50
0.152 0.000321 0.0333 0.0176 2.03
0.102 0.000215 0.0223 0.0353 3.02
0.0784 0.000165 0.0171 0.0529 3.93
0.0572 0.000121 0.0125 0.0705 5.38
Actinometry (average of 2 tubes):

0.684 0.00319 0.33 - -

Actinometers: [VP]=0.101M, [C16]=0.00207M, and Io=0.00965E/hr
SV Run: [diK]=0.0100M and [C16]=0.000938M
(Irrad'd for 4 hrs, GC condition set 1)

 

 

MP.
area C16 [2-MeAP],M <1) [Q],M <D°l¢
0.0275* 0.0000524 0.00543 0.0 1.00
0.0153 0.0000291 0.00302 0.00882 1.80
0.0110 0.0000209 0.00217 0.0176 2.50
0.00725 0.0000138 0.00143 0.0353 3.79
0.00618 0.0000118 0.00122 0.0529 4.45

(GC condition set 1)

 

«k
average of 2 tubes

 

 

270

 

 

Table 69: Stilbene Sensitization1 of 4-MeO-2-MeAP at 366nm
in Benzene

Run 1
3221.9
area (1 [Ci51corr (pt—9c l/[Q],M—1 0:596/¢t—)c
0.0586 0.00280 0.348 19.7 1.72
0.0489 0.00296 0.368 15.4 1.62
0.0440 0.00279 0.347 14.6 1.72
0.0421 0.00289 0.359 13.5 1.66
0.0392 0.00291 0.361 12.4 1.65
0.0362 0.00288 0.358 11.5 1.66
0.0341 0.00294 0.365 10.6 1.63
0.0336 0.00305 0.379 10.0 1.57

Actinometry (average of 2 tubes):
0.0696 0.00330 0.41 — -

Actinometers: [AP]=0.681M, [t-stil]0=0.0500M, and Io=0.008058/hr
(Irrad'd for 2.5 hrs, GC condition set 4)

 

Sensitization Run: [K]=0.102M

 

Run 2
31.9.3.3
area t [cis]corr ¢t_,c l/[Q],M'1 0.596/¢t_,c
0.128 0.00128 0.259 96.2 2.30
0.105 0.00136 0.275 73.7 2.17
0.0860 0.00134 0.271 61.2 2.20
0.0815 0.00139 0.281 55.9 2.12
0.0773 0.00144 0.291 51.1 2.05
0.0720 0.00144 0.291 47.4 2.05
0.0695 0.00155 0.314 42.7 1.90
0.0638 0.00157 0.318 38.5 1.87
Actinometry (average of 2 tubes):
0.0436 0.00203 0.41 - -

Actinometers: [AP]=0.681M,

Sensitization Run:

[K]=0.102M

[t-stilbene]°=0.0500M, and Io=0.00494E/hr
(Irrad'd for 1.5 hrs,

GC condition set 4)

 

271

Table 69 (cont'd)

 

Run 3

EIEEL.Q

area t [cis]corr 0H,: 1/(01,M-1 0.596/<1)He
0.117 0.000704 0.225 145 2.65
0.103 0.000739 0.236 120 2.53
0.0928 0.000735 0.235 107 2.54
0.0815 0.000767 0.245 88.3 2.43
0.0759 0.000823 0.263 75.6 2.27
0.0667 0.000792 0.253 67.2 2.36
0.0663 0.000839 0.268 62.9 2.22
0.0608 0.000851 0.272 55.9 2.19

Actinometry (average of 2 tubes):
0.0297 0.00128 0.41 - -

Actinometers: [AP]=0.681M, [t-stilbene]o=0.0500M, and I°=0.00313E/hr
Sensitization Run: [K]=0.102M (Irrad'd for 1.5 hrs, GC condition set 4)

 

 

*
average of 2 tubes

10.

11.

12.

13.

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MICHIGAN STATE UNIV. L IBRRRIES
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31293008824116

   

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