1.1,???) " " '{uflg “iv-r1115. "x-i‘. “9W \ " A ‘11 11: ' J? . ' . ‘W; m ' \‘ I I V , . -"u'\‘. ‘yflfl ' 11 . . - ‘ ,; 31; x 1 .-E1”-_.. £1 kl. “ ' "1'.“ . 'I -1 ' K. ‘ 1 2' 3.11% .'_‘ “uni. Hg‘f: It: 1 1 .. 1 '1 . ‘1 . ' , ., 111.: 11-. s ’3'?” "-"11.;-',;1 1 .- . - , 1.1.1, E! ., ,. 3 .1 "..b. 1. Uri-“C | .. ‘12:“:k. .111 ,m31.‘!r3q :fi‘: v1 ‘1 'A. I“ ‘t! 1:15“ 1'1\;I 1 3r” l.-w-v v r‘.;~ \\{1 1111-1113.: .1?1"-*- 1:111 1111.1. ' r1111"? l_.' :'1' \""'A' ‘1 1“ ‘1‘." .|.. r \':l \(‘1i\i“.. "111:; ‘ 1‘1'1'1'1'1”! H:Xm ,‘v- '. v 'I'Ebr: (' 11‘“. ”.1 "1113'! 1‘ 1'. “durih'aféh‘t‘i "1 R1 ’3 1. 1', 1.11 ‘I ' [ll-l’ ”1‘1.‘ ' 1,.“ 1 1 11.. . o‘Lcigh-fi" LIB RA R Y Michigan Sui: University 3111551 W! This is to certify that the thesis entitled INTRAMOLECULAR INTERACTIONS OF TRIPLET STATE DI- [PHENYL ALKYL KETONES] presented by Harlan William Frerking, Jr. has been accepted towards fulfillment of the requirements for Ph . D . degree in Chemistry (131171.11, ' r professor Date (lea. asfl??? a / 0-7 639 1 l l 1 mm n3 2 31925 111 17 1111111111111111 1, INTRAMOLECULAR INTERACTIONS OF TRIPLET STATE DI-[PHENYL ALKYL KETONES] BY Harlan William Frerking, Jr. A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1978 ABSTRACT INTRAMOLECULAR INTERACTIONS OF TRIPLET STATE DI-[PHENYL ALKYL KETONES] BY Harlan William Frerking, Jr. The intramolecular interactions of the triplet excited state of one aroyl chromophore with the ground state of a second aroyl chromophore are reported for a number of symmetric and unsymmetric diketones. Two phenomena involving both chromOphores were commonly observed: reversible energy transfer between the two chromophores, and self-quenching of the excited chromophOre by the ground state chromophore. It is shown how rates for both the endothermic and exothermic energy transfer steps may be obtained for unsymmetric diketones where the rate of decay of one of the isolated chromophores is fast enough to compete with the slower energy transfer process. If the rates of decay for the chromophores are slow compared to energy transfer then equilibrium between the triplet states of the two chromophores is observed and the minimum rates of energy transfer necessary to attain this equilibrium are determined. The rates observed range from greater than 1.0 x 108 and 4.6 x 107 sec.1 for Harlan William Frerking, Jr. l-phenyl-S-(4'-valerylphenyl)~pentan-l-one (the triplet 8 states for this ketone equilibrate) to 1.0 x 10 and 7sec"1 1.0 x lo for l-phenyl-S-(4'-valerylphenoxy)- pentan-l-one. The ratio of the rates of energy transfer is determined by Boltzmann's Law. The symmetric diketones studied show self-quenching at rates of approximately 1.0 x 107 to 3.4 x 106 sec-1 for diketones where the carbonyl oxygens can approach each other without too much steric hindrance. The absence of measurable self-quenching for 1,5-diphenyl- pentan—l,5-dione allows one to establish some of the geometric constraints on the self-quenching phenomenon observed. Ab-initio calculations including a reasonably large CI study on systems containing two formaldehyde molecules indicate the presence of a weak singlet excimer for head-to-head in-plane orientations of the formaldehydes. This is in qualitative agreement with the observed kinetics for the symmetric diketones studied. ACKNOWLEDGMENTS I wish to thank Dr. Peter J. Wagner for his advice and support of the research and preparation of this dissertation, and for his help in meeting the many other degree requirements. I also wish to thank my fellow graduate students and post-doctoral students for many helpful discussions which served as testing grounds for many of the ideas presented in this dissertation, along with many more which were flawed and whose flaws1 were discovered through these discussions.. I also wish to thank the Department of Chemistry for its financial support through teaching and research assistantships and the National Science Foundation for its financial support through research assistantships paid out of Dr. Wagner's research grants. A special thanks is due to my wife, Mary, who, in addition to typing and retyping this manuscript, has offered me considerable moral support during the many crises, both large and small, which mark my graduate career at Michigan State University. ii TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . LIST OF ABBREVIATIONS . . . . . . . . INTRODUCTION . . . . . . . . . . . . I. II. III. IV. V. Reasons for Studying Triplet Energy Transfer . Previous Work Involving Intramolecular Triplet Energy Transfer . . . . . . . . The Approach Used in this Dissertation . Phenyl Alkyl Ketone Photochemistry . Photokinetics of Phenyl Alkyl Ketones . RESULTS 0 O O O O O O O O O O O O O O I. II. General Techniques . . . . . . . A. Irradiations .1. . . . . . . B. Product Quantum Yields . . . C. Disappearance Quantum Yields D. Maximum Quantum Yields . . . E. Intersystem Crossing Yields . F. Triplet Lifetimes . . . . . G. Spectroscopy . . . . . . . . Energy Transfer Studies . . . . A. Photokinetic Results . . . . iii xiv xvii ll 14 20 26 26 26 27 27 27 28 28 29 30 31 III. Iv. B. A. B. iv Spectroscopic Results . . . . . . . . . . . Self-Quenching Studies . . . . . . . . . . . . Photokinetic Results . . . . . . . . . . . . Spectroscopic Results . . . . . . . . . . . Quantum Mechanical Calculations . . . . . . . . DISCUSSION . . . . . . . . . . . . . . . . . . . . I. II. III. IV. Derivation of Rate Constants . . . . . . . . . A. Triplet Lifetimes . . . . . . . . . . . . . B. Maximum Quantum Yields of Disappearance and Cyclobutanol Formation . . . . . . . . . . . C. The Rate of y-Hydrogen Abstraction . . . . D. The Rate of Non-Productive Triplet Decay . E. Rates of Energy Transfer . . . . . . . . . F. The Fraction of Excitation at a Chromophore Energy Transfer Systems . . . . . . . . . . . A. The 6ValPhVP and 6AcPhVP Systems . . . . . . B. The le4pEthBt System . . . . . . . . . . C. The YvalPhOBP and YAcPhOBP Systems . . . . D. The 6ValPhOVP and 6AcPhOVP Systems . . . . . E. The le4AnBt System . . . . . . . . . . . . F. Energy Transfer Conclusions . . . . . . . . Self-Quenching Studies . . . . . . . . . . . Quantum Mechanical Calculations . . . . . . . . EXPERIMENTAL . . . . . . . . . . . . . . . . . . . I. Chemicals 0 O O O O O O O O O O O O O O O O O O A. Ketones O O O O O O O O O O O O O O O O O O 1. General Comments . . . . . . . . . . . 40 42 42 52 56 62 62 62 62 63 64 66 69 69 71 75 78 82 85 86 88 95 100 100 100 100 V 2,2-Dimethyl-1,3-dipheny1propane-l,3-dione (DiBzdiMeMt) . . . . . . . . . . . . . . . 101 1,4-Diphenylbutane—1,4-dione (DiBzEt) . . 101 1,5-Diphenylpentane-l,5-dione (DiBzPr) . . 102 1,6-Diphenylhexane-1,6-dione (DiBzEt) . . . 102 1,7-Dipheny1heptane-l,7-dione (DiBth) . . 102 1,6-Bis-(4-ethy1pheny1)-hexane-l,6-dione (DipEthBt) . . . . . . . . . . . . . . . . 103 l- (4'-Ethy1pheny1) —6-phenylhexane- -l, 6—dione (le4pEthBt) . . . . . . . . . . . . . . 104 a. Methyl S-Benzoylvalerate . . . . . . . 104 b. S-Benzoylvaleric acid . . . . . . . . . 105 c. S-Benzoylvaleroyl chloride . . . . . . 105 d. 1- (4'-Ethy1phenyl) -6-pheny1hexan—l, 6- dione (le4pEthBt) . . . . . . . 105 1,5-Diphenylpentan-l-one (6PhVP) . . . . . 106 a. Method A . . . . . . . . . . . . . . . 106 1) Acetophenone cyclohexylimine . . . 106 2) 1,5-Diphenylpentan-l-one . . . . . 107 b. Method B . . . . . . . . . . . . . . . 108 c. Purification . . . . . . . . . . . . . 109 l-Phenyl- -5- (4'-acetylphenyl)-pentan- -1-one (SACPhVP) . . . . . . . . . . . . . . 109 l-Phenyl- -5- (4'-valery1phenyl)-pentan— —l-one (6ValPhVP) . . . . . . . . . . . . . . 110 12. 13. 14. 15. l-(4'-Ethy1pheny1)-pentan-l-one (pEtVP) 111 4-Phenoxy-l-phenylbutan-l-one (yPhOBP) 112 4- (4'-Acetylphenoxy) -1-phenylbutan- -1-one (yAcPhOBP) . . . . . . . . . . 113 4- (4'-Valerylphenoxy) -l-pheny1butan— —1-one (yValPhOBP) . . . . . . 114 vi 16. 4-(4'—Cyanophenoxy)-l-phenylbutan-l-one (yCNPhOBP) . . . . . . . . . . . . . . . 115 a. 4-Chloro-1-pheny1butan—l-one . . . . 115 b. 4-Iodo-1-phenylbutan-l-one . . . . . 115 c. Ethylene Glycol Ketal of 4-Iodo-l- phenyl-butan-l-one . . . . . . . . . 116 d. 4- (4'-Cyanophenoxy)- -1- -phenylbutan—l- one (YCNPhOBP) o o o o o o 0 Q 116 17. 5-Phenoxy-1-pheny1pentan-l-one (6PhOVP). 117 a. Method A . . . . . . . . . . . . . . 117 1) l-Phenylcyclopentanol . . . . . . 117 2) 5-Chloro-l-pheny1pentan-l-one . . 118 3) 5-Iodo-l-phenylpentan-l-one . . . 119 4) 5-Phenoxy-1-pheny1pentan-1-one . 119 b. Method B . . . . . . . . .,. . . . . 120 l) 5-Phenoxy—l-pheny1pentan-1-one . 120 c. Purification . . . . . . . . . . . . 121 18. 5- (4'-Acetylphenoxy) -1-phenylpentan— —l—one (GACPhOVP) o o o o o o o o o o o o o 121 19. S-(4'-Valery1phenoxy)-1-phenylpentan-l- one (6ValPhOVP) . . . . . . . . . . . . 122 20. 5-(4'-Cyan0phenoxy)-l-phenylpentan-l-one (GCNPhOVP) o o o o o o o o o o o o o o c 122 21. 4-Ethylacetophenone (pEtAc) . . . . . . 123 22. Acetophenone (Ac) . . . . . . . . . . . 123 23. l-Phenylpentan—l-one (VP) . . . . . . . 123 24. Benzophenone . . . . . . . . . . . . . . 124 25. 4-Methoxyacetophenone (pMeOAc) . . . . . 124 26. l- (4-Methoxyphenyl) -pentan- -l-one (pMeOVP) .‘. . . . . . . . . . . . . 124 B. Internal Standards . . . . . . . . . . . . . 124 1. Tetradecane . . . . . .. . . . . . . . . 124 2. Hexadecane . . . . . .. . . . . . . . . 124 3. Octadecane . . . . . . . . . . . . . . . 125 4. Di-n-ethyl Phthalate . . . . . . . . . . 125 5. Di-n-propyl Phthalate . . . . . . . . . 125 6. Di-n-butyl Phthalate . . . . . . . . . . 125 C. Quenchers . . . . . . . . . . . . . . . . . 125 l. 2,5-Dimethylhexa-2,4-diene . . . . . . . 125 2. cis-1,3-Pentadiene . . . . . . . . . . . 125 3. trans-Stilbene . . . . . . . . . . . . . 125 D. Solvents . . . . . . . . . . . . . . . . . . 126 1. Benzene . . . . . . . . . . . . . . . . 126 2. Pyridine . . . . . . . . . . . . . . . . 126 3. Dioxane . . . . . . . . . . . . . . . . 127 4. Ethanol . . . . . . . . . . . . . . . . 127 5. Methylcyclohexane . . . . . . . . . . . 128 6. Cyclohexane . . . . . . . . . . . . . . 128 7. 2-Methyltetrahydrofuran . . . . . . . . 128 8. 2-Methylbutane . . . . . . . . . . . . . 129 II. Preparative Scale Photolysis of 5-(4-Acetyle phenyl)fl-phenylpentan-l-one (5AcPhVP) . . . . 129 III. Electronic Absorption Spectra . . . . . . . . 132 IV. Emission Spectra . . . . . . . . . . . . . . . 132 V. Photokinetic Data . . . . . . . . . . . . . . . 132 A. General COmments . . . . . . . . . . . . . . 132 l. Glassware . . . . . . . . . . . . . . . 132 viii 2. Weights . . . . . . . . . . . . . . . . . 133 3. Irradiation tubes . . . . . . . . . . . . 133 4. Degassing procedure . . . . . . . . . . 133 5. Irradiation lamps . . . . . . . . . . . 133 6. Sample Analysis . . . . . . . . . . . . . 134 Stern-Volmer Plots . . . . . . . . . . . . . 136 Lewis Base Studies, Maximum Quantum Yields . 137 Product Quantum Yields, Actinometry . . . . . 137 Sensitization Plots, Quantum Yields of Intersystem Crossing . . . . . . . . . . .-. 138 Disappearance Yields . . . . . . . . . . . . 139 Data . . . . . . . . . . . . . . . . . . . . 140 l. DiBzdiMeMt . . . . . . . . . . . . . . . 140 2. DiBzEt . . . . . . . . . . . . . . . . . 142 3. DiBzPr . . . . . . . . . . . . . . . . . 142 4. DiBth . . . . . . . . . . . . . . . . . 142 5. DiBth . . . . . . . . . . . . . . . . . 152 6. DipEtBt . . . . . . . . . . . . . . . . . 152 7. le4pEthBt . . . . . . . . . . . . . . . 152 8. 6PhVP . . . . . . . . . . . . . . . . . . 163 9. pEtVP . . . . . . . . . . . . . . . . . . 163 10. 6AcPhVP . . . . . . . . . . . . . . . . 163 ll. 6ValPhVP . . . . . . . . . . . . . . . . 174 12. yPhOBP . . . . . . . . . . . . . . . . . 174 13. yCNPhOBP . . . . . . . . . . . . . . . . 174 14. yACPhOBP . . . . . . . . . . . . . . . . 174 15. YvalPhOBP . . . . . . . . . . . . . . . 183 16. 5PhOVP l7. GCNPhOVP 18. GACPhOVP 19. 6Va1PhOVP . LIST OF REFERENCES 183 183 189 189 193 Table Table Table Table Table Table Table Table Table Table Table Table Table Table 10: 11: 12: 13: 14: LIST OF TABLES Quantum Yields and qu° values for Unsymmetric Diketones and Model Monoketones . . . . . . . . . . . . . . . . Spectroscopic Data for Unsymmetric Diketones and Monoketone Models . . . . . . Quantum Yields and qu values for Symmetric Diketones . . . . . . . . . . . . Spectrosc0pic Data For Symmetric Diketones Di-Formaldehyde Energies vs Distance Head-to-Tail Orientation . . . . . . . . . Di-Formaldehyde Energies vs Distance Head-to-Head Orientation . . . . . . . . . SCF Energies for the Head-to-Head Orientation of the Di-Formaldehyde system O O O O O O O O O O I O O O O O O O Orbital Interactions for the Di-Formaldehyde System . . . . . . . . . . Energy Differences Relative to the Ground State for the Di-Formaldehyde System . . . Derived Kinetic Parameters for Unsymmetric Diketones . . . . . . . . . . Kinetic Parameters for Model Ketones . . . Derived Kinetic Parameters for Symmetric Diketones . . . . . . . . . . . . . . . Gas Chromatography Conditions . . . . . . Stilbene Sensitization Data for DiBzdiMeMt . . . . Page 32 41 48 .55 59 59 60 60 61 68 70 89 135 141 Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table l6: 17: 18: 19: 20: 21: 22: 23: 24: 25: 26: 27: 28: 29: 30: 31: 33: 34: 35: 36: xi 1,3-Pentadiene Sensitization Data for DiBZEt O O O O O O I O O O O O O O O O O 143 Stern-Volmer Data for DiBzPr . . . . . . 144 Conversion Dependence of 4 for DiBzPr . 145 II Effects of Varying Concentration of Dioxane on ¢II for DiBzPr . . . . . . . . . . . . 146 Conversion Dependence of QII in 4.5 M Dioxane for DiBzPr . . . . . . . . . . . 147 Intersystem Crossing Yield for DiBzPr . . 147 ¢Dis for DiBzPr . . . . . . . . . . . . . 148 Max . 4013 for DiBzPr . . .. . . . . . . . . . 148 Stern-Volmer Data for DiBth . . . . . . 149 Effects of Varying Concentrations of Dioxane on QII for DiBth . . . . . . . . 150 Intersystem Crossing Yield for DiBth . . 151 QDis for DleBt . . . . . . . . . . . . . 151 ¢M3x for DiBth . . . . . . . . . . . . . 153 Dis Stern-Volmer Data for DiBth . . . . . . 154 Effects of Varying Concentrations of Dioxane on ¢II for DiBth . . . . . . . . 155 Effects of Varying Concentrations of Pyridine on ¢II for DiBth . . . . . . . 156 Stern-Volmer Data for DipEthBt . . . . . 157 Effects of Varying Concentrations of Dioxane on ¢II for DipEthBt . . . . . . 159 Intersystem Crossing Yield for DipEthBt 160 ¢Dis for DipEthBt . . . . . . . . . . . 160 Stern-Volmer Data for le4pEthBt . . . . 161' Effects of Varying Concentrations of Dioxane on 4 for le4pEthBt . . . . 162 II Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table 37: 38: 39: 40: 41: 42: 43: 44: 45: 46: 47: 48: 49: 50: 51: 52: 53: 54: 55: 56: 57: 58: xii Effects of.Varying Concentrations of Pyridine on 4 for le4pEthBt . . . . II ¢Dis for 1Bz4pEthBt . . . . . . . . . Stern-Volmer Data for 6PhVP . . . . . . Effects of Varying Concentrations of Dioxane on ¢II for 6PhVP . . . . . . . . Stern-Volmer Data for pEtVP . . . . . . Intersystem Crossing Yield for pEtVP . . Effects of Varying Concentrations of Dioxane on ¢II and ¢CB for pEtVP . . . . Stern-Volmer Data for 5AcPhVP . . . . . Effects of Varying Concentrations of Dioxane on 411 for 6AcPhVP . . . . . . . Effects of Varying Concentrations of Pyridine on QII for 6AcPhVP . . . . . . Intersystem Crossing Yield for 6AcPhVP . 4 . for 6AcPhVP . . . . . . . . . . . . D13 4 . for 6AcPhVP in 4.5 M Dioxane . DIS Stern-Volmer Data for 6Va1PhVP . . . . . Effects of Varying Concentrations of Dioxane on 411 for 6ValPhVP . . . . . . Intersystem Crossing Yield for 6ValPhVP 4015 for 6Va1PhVP in 4.5 M Dioxane . . . Effects of Varying Concentrations of Pyridine on ¢II for yPhOBP . . . . . . . Stern-Volmer Data for YcNPhOBP . . . . . Effects of Varying Concentrations of Pyridine on 411 for VCNPhOBP . . . . . . Stern-Volmer Data for yAcPhOBP . . . . . Effects of Varying Concentrations of Pyridine on 411 for yAcPhOBP . . . . . . 162 164 165 166 167 168 169 170 171 172 173 173 173 175 176 177 177 178 179 180 181 182 Table Table Table Table Table Table Table Table Table Table Table 59: 60: 61: 62: 63: 64: 65: 66: 67: 68: 69: xiii Stern-Volmer Data for YvalPhOBP . . Effects of Varying Concentrations of Pyridine on ®II for YvalPhOBP Stern-Volmer Data for 6PhOVP . . . . Effects of Varying Concentrations of Dioxane on QII for 6PhOVP . . . . . Effects of Varying Concentrations of Pyridine on QII for 6PhOVP . . . . . Stern-Volmer Data for GCNPhOVP Effects of Varying Concentrations of Pyridine on ¢II for 6CNPhOVP . . . . Stern-Volmer Data for 6AcPhOVP . . . Effects of Varying Concentrations of Pyridine on ¢II for 6AcPhOVP . . . Stern-Volmer Data for 6Va1PhOVP . Effects of Varying Concentrations of Pyridine on ¢II for 6Va1PhOVP . . . 184 184 185 186 187 188 190 191 191 192 192 LIST OF FIGURES Figure l: Intramolecular Energy Transfer Systems .Page Figure 2: Rigid Energy Transfer Systems . . . . . 6 Figure 3: Keller and Dolby's Systems . . . . . . . 9 Figure 4: Equilibrating Chromophores in the l-Benzoy1-4-p-anisoylbutane System . . . 10 Figure 5: The Norrish type II Reaction . . ... . 18 Figure 6: Stern-Volmer Kinetics for the 6ValPhVP System ( OSPhVP; I AC, 5Va1PhVP; D Pr, (SValPhVP; A 6AcPhVP; O pEtVP) . 34 Figure 7: Stern-Volmer Plots for the le4pEthBt System ( O diBth; O dipEthBt; D le4pEthBt, Ac; A 1Bz4pEthBt, pEtAc) . . . . . . . . . . . . . . . . . 35 Figure 8: Stern-Volmer Plots for yValPhOBP System (---yPhOBP; --pMeOVP; O YCNPhOBP; OyAcPhOBP; E] yValPhOBP, Ac; [37ValPhOBP, Pr) . . . . . . . . . . . 36 Stern-Volmer Plots for the 6ValPhOVP System ( D 5ValPhOVP, Pr; I. 6ValPhOVP, Ac; 0 (SAcPhOVP; A GCNPhOVP; o 6PhOVP; --~n-pMeOVP) . . . . . . . .', . . . . . 37 .0 Figure 9 Figure 10: Phosphorescence Spectra for the 5ValPhVP System . . . . . . .'. . . . . 43 Figure 11: Phosphorescence Spectra for the 6AcPhVP System . . . . . . . . .. . . . 44 Figure 12: Phosphorescence Spectra for the le4pEthBt System . . . . . . . . . . 45 Figure 13: Phosphorescence Spectra for the YvalPhOBP System . . . . . . . . . . . 46 xiv xv Figure 14: Sensitization Plot for diBzdiMeMt . . . . 49 Figure 15: Sensitization Plot for diBzEt . . . . . . 50 Figure 16: Variation of ¢II with Conversion for diBzPr ( 0 no additive, A 4.5 M Dioxane) . 51 Figure 17: Determination of $21 for diBzPr ( 0 no additive, 13 4.5 M Dioxane) . . . 53 Figure 18: Stern-Volmer Plots for diBzPr and diBth ( Q diBzPr, 7.85% conv.; diBzPr, 4.89% conv: O diBth) . . . . . . . . . . . . 54 Figure 19: Phosphorescence Spectra of diBzdiMeMt and diBzEt . . . . . . . . . . . . . . . 57 Figure 20: Predicted Stern-Volmer Plots for the 6ValPhVP System ( 0 observed for aceto- phenone; 0 observed for propene; -——-1.0 x loasec-l, 4.6 x 107sec-l; ----1.o x 109sec‘l, 4.6 x 1083ec-l; 8 -1 7 -l -.- 1.2 x 10 sec , 3.7 x 10 sec : 7 l 7 -l --- 8.0 x 10 sec' , 5.5 x 10 sec ) . . . 73 Figure 21: Predicted Stern-Volmer Plots for the 1Bz4pEthBt System ( 0 observed for acetophenone; 0 observed for pEtAc; -——-8 x 107sec-l, 6.4 x 107sec-l; ----1.6 x 1ogsec’l, 1.23 x 108sec-l: 7 -.- 4 x 10 sec-l, 3.2 x 107sec‘l; l 7 -.-1.o x 108sec‘ , 5.1 x 10 sec-1 )...77 Figure 22: Predicted Stern-Volmer Plots for the yValPhOBP System ( 0 observed for Ac; 0 observed for propene; -—-1.2 x loasec_l, 3.0 x 107sec ---6.0 x 10 sec-l, 1.5 x 107sec -— 2.4 x 10 sec-l, 6.0 x 10 sec -H_.1.3 x 10 sec- , 2.7 x 10 sec 1 1 .-.-1.1 x 10 sec” , 3.3 x 10 sec ) . . . 81 o I I I 00‘) \l o I (D \l I -1 -1 -1 -1 '1 no \I xvi Figure 23: Predicted Stern-Volmer Plots for the GValPhOVP System C 0 Ac, 5ValPhOVP; O Pr, 6Va1PhOVP; -—-l.0 x loasec-l, 1.0 X 107seC-l; 7 -1 7 -1 --u.9,1 x 10 sec , 1.1 x 10 sec ; --— 1.1 x lossec’l, 8.9 x 106sec'1; 8 -1 7 -1 -~-2.o x 10 sec , 2.0 x 10 sec 7 --~ 5.0 x lossec-l, 5.0 x lOGSec-l) . . . 84 Figure 24: Excited State Interactions . . . .. . . . 96 Pr An AC T1 VP pMeOAc pMeOVP pEtAc pEth 6PhVP 6AcPhVP 6ValPhVP yPhOBP yCNPhOBP yAcPhOBP YvalPhOBP 6PhOVP GCNPhOVP GACPhOVP 6ValPhOVP LIST OF ABBREVIATIONS Propene Anisoyl Acetophenone Toluoyl 1—Pheny1pentan-1-one (Valerophenone) 4-Methoxyacetophenone 1-(4'Methoxypheny1)~pentna-l-one ijethoxyValerophenone) 4-Ethylacetophenone 1-(4-Ethy1pheny1)-pentan-1-one (p Ethylvalerophenone) 1,5-Diphenylpentan-l-one (6 Phenylvalerophenone) 5-(4'-Acetylpheny1)-1-pheny1pentan-l-one 5-(4'-Va1ery1pheny1)-1-pheny1pentan-1-one 4-Phenoxy-1-phenylbutan-1-one (y Phenoxybutyrophenone) 4-(4'-Cyanophenoxy)-1-pheny1butan-1-one 4-(4'-Acety1phenoxy)-1-phenylbutan-1-one 4-(4'-Valery1phenoxy)-1-pheny1butan-l-one S-Phenoxy-l-phenylpentan-l-one (6 Phenoxyvalerophenone) 5-(4'-Cyanophenoxy)-1-phenylpentan-l-one 5-(4'-Acetylphenoxy)-1-pheny1pentan-l-one 5-(4'-Va1ery1phenoxy)-l-pheny1pentan—1—one xvii DiBzdiMeMt DiBzEt DiBzPr DiBth DiBth DipEthBt DiAnBt 1Bz4EthBt 1324AnBt 7CarbOMEBP 6CarbOMEVP PhBten xviii 2,2-Dimethy1-1,3~dipheny1propan-l,3-dione 1,4-Diphenylbutan-1,4-dione (1,2-dibenzoy1ethane) 1,5-Diphenylpentan-1,S-dione (1,3-dibenzoy1propane) 1,6-Dipheny1hexan-1,6-dione (1,4-dibenzoy1butane) 1,7-Dipheny1heptan-l,7-dione (1,5-dibenzoy1pentane) 1,6-Bis-(4'-ethy1pheny1)-hexane-1,6-dione 1,6-Bis-(4'-methoxypheny1)-hexane-1,6-dione 1-(4'-Ethy1pheny1)-6-pehnylhexane-1,6-dione 1-(4'-Methoxypheny1)-6-phenylhexane—1,6-dione Methyl 5-phenyl-4-oxocaproate Methyl 4-pheny1-3-oxovalerate 1-pheny1but-3-en-1—one INTRODUCTION The main area of study covered in this dissertation is triplet energy transfer. Intramolecular systems, such as those shown in Figure 1, were used because they offered more control over the distances and orientations involved in energy transfer than intermolecular systems. During the course of these studies a second phenomenon was frequently observed which, at the beginning of this pro- ject, was not defined in the chemical literature. This process involves the interaction of the triplet state of one chromophore with the ground state of a second similar or identical chromophore resulting in thermal dissipation of energy to give two ground state chromophores. This process is called self-quenching. I. Reasons for Studying Triplet Energy Transfer Triplet energy transfer is a common means of elec- tronically exciting a molecule when direct irradiation is impossible, inconvenient, or does not give an excited state of the desired multiplicity.l My initial interest in triplet energy transfer arose from research I carried out on the sensitization of photopolymer etching resists. In such systems direct irradiation would require high l-(4'-Ethy1phenyl)-6- phenylhexan-1,6-dione (le4EthBt) l-Phenyl-S-(4'-va1ery1- pheny1)-pentan-1-one (5Va1PhVP) 1-Phenyl-4-(4'-valeryl- phenoxy)-butan-l-one (yValPhOBP) M O 5-(4'-Acety1pheny1)-1- phenylpentan-l-one (6AcPhVP) gown, 4-(4'-Acety1phenoxy)-l- phenylbutan-l-one (yAcPhOBP) dot/WK)“K 5-(4'-Acety1phenoxy)-1- phenylpentan-l-one (6AcPhOVP) Ofiww’w 1-Pheny1-5-(4'-valeryl- phenoxy)-pentan-1-one (6ValPhOVP) Figure 1: Intramolecular Energy Transfer Systems 3 energy light sources and quartz optics. By the correct choice of sensitizer it is possible to use near ultraviolet light and pyrex optics, or, in some cases, even visible light and flint glass optics.2 Many compounds of interest to organic photochemists have low intersystem crossing yields or substantial reac- tivity from the singlet state. The use of a triplet sensitizer is often convenient and sometimes essential in the study of the photochemistry of the triplet states of such compounds.3 Triplet energy transfer from a mole— cule under study to a triplet quencher is often used to make a qualitative judgment about the multiplicity of the reactive state of the molecule.4 In a more quantitative sense quenching studies involving diffusion controlled triplet energy transfer have been one of the main tools of photokineticists for several decades.5 II. Previous Work Involving Intramolecular Triplet Energy Transfer At the onset of my research very little was actually known about the mechanism of triplet energy transfer. It was generally understood that the difference in triplet energies between the donor and acceptor chromophores has to be at least 3 kcal/mole if energy transfer is to be efficient.6 This is simply recognition that the processes involved in energy transfer are reversible,7”ll and that, if the rates of energy transfer are fast compared to the other decay paths of the chromophores, the populations 4 of the triplet states involved would follow a Boltzmann 8.11 At room temperature under these distribution. conditions a triplet energy separation of 3 kcal/mole between the chromophores would result in 99.3% of the excitation residing in the chromophore with the lowest triplet energy. It had also been observed that the collision radii needed for triplet energy transfer are generally small, usually on the order of only a few angstroms.12 The dipole-dipole mechanism for singlet energy transfer 13 was correctly described by Forster and very convincingly 14 with molecules where proved by Latt, Cheung, and Blout the two chromophores were separated by a rigid steroid bridge. Dexterls has considered several possible mech- anisms for triplet energy transfer including dipole-dipole, dipole-quadrupole, and exchange mechanisms. Only the exchange mechanism comes close to predicting the inter- chromophore distance relationships observed for triplet energy transfer and as a result it is favored by most researchers. Several researchers have studied triplet energy transfer using intramolecular systems. These studies can be divided into three classes: those in which triplet energy transfer is totally efficient in one direction, those in which triplet energy transfer is not complete but no attempt was made to estimate the rate of energy transfer, and those for which estimates of the rates 5 of energy transfer were obtained. Among the earliest of the first type of these studies was a study of the phosphorescence of 4-(1-naphthyl-methyl)-benzophenone undertaken by Hammond.16 In this system singlet energy transfer from the naphthalene chromophore to the benzo- phenone chromophore occurs with about 90% efficiency and triplet energy transfer from the benzophenone chromophore to the naphthalene chromophore is 100% efficient. Breen and Keller17 also studied several systems in the first class in which naphthalene and either phthalimide or carbazole chromophores were separated by one to three methylene groups. The phosphorescence spectra and life- times of these systems indicate that triplet energy transfer to the chromophore of lowest energy is complete in all systems. Since these studies were carried out in a rigid glass matrix it is safe to assume that triplet energy transfer between these chromophores is fast over the average separation of the systems (2 5 A for three methylene groups). Both Dexter's15 and Forster'sl3 descriptions of energy transfer mechanisms contain orientation terms which would imply that chromophores held perpendicular to each other should not undergo energy transfer. A number of researchers have attempted to verify these 18-21 predictions with rigid systems. No one has succeeded, primarily because it takes only a small amount 6 of distortion in the molecule to make energy transfer allowed; but the attempts have led to a number of well defined systems in which energy transfer does occur. Keller18 studied the emission spectra of Spiro-[9,10- dihydro-9-oxoanthracene-10,2‘-(3'H)-phenalene] and spiro-[9.l0-dihydro-9-oxoanthracene-10,2'-5',6‘-benzidan] and observed complete energy transfer to the chromophore with the lower energy in both the singlet and triplet manifolds. The structures of these molecules are shown 19 in Figure 2. When Filipescu and DeMember studied the Spiro-[9,10-dihydro-9-oxo- Spiro-[9,10-dihydro-9-oxo- anthracene-lO,2'-5',6— anthracene-lO,2'-(3'H)- benzidan] phenalene] l,4-Dimethoxy-5,8-methano- l,4-Methano-2,3-exo-[fluor- 6,7-exo-[f1uorene-9'-spiro-l"- ene-9'-spiro-1"-cyclopro- cyclopropane]-naphtha1ene pane]-9,lO-diketoanthracene Figure 2: Rigid Energy Transfer Systems spectroscopy of 1,4-dimethoxy-5,8—methano—6,7-exo-[fluorene- 9'-spiro-1"-cyclopropane]-naphthalene (structure in Figure 2) they were unable to detect either singlet or triplet 7 energy-transfer, but Lamola20 was able to observe efficient singlet energy transfer in this system. Filipescu, De- Member, and Minn21 studied 1,4-methano-2,3-exo-[f1uorene- 9'-spiro-l"-cyclopropane]-9,10-diketoanthracene (structure in Figure 2) and observed efficient triplet energy transfer but were unable to detect any singlet energy transfer. There are numerous examples in the literature where triplet energy transfer from a suitable sensitizer to an olefin has been used to study the triplet state photo- chemistry of the olefin.22 Several intramolecular systems 23 have been studied. Morrison and Peiffer and later 24 studied l-phenyl-Z-butene and found Nakagawa and Sigel triplet energy transfer from the phenyl chromophore to the olefin to be essentially complete and about 360 times as efficient as in the comparable intermolecular case. Cowan and Baum25 studied a series of compounds in which styryl and benzoyl chromophores are separated by one to four methylene groups and observed that irradiation of the benzoyl chromophore results in efficient isomerization of the styryl chromophore. One potential pitfall of studying energy transfer through photochemical products has been illustrated by Morrison's26 observation that trans-4-hexen-2-one and trans-S-hepten-Z-one are efficiently isomerized by light absorbed by the carbonyl group, presumably as a result of energy transfer. Later studies of the 1-pheny1hexen- 1-one and l-phenyl-Z-ethyl-4-penten-l-one systems by 8 Morrison, Tisdale, Wagner, and Liu27 indicate that the observed isomerization occurs by a chemical (Schenk) mechanism involving the formation of a charge transfer complex and the products of its collapse. Zimmerman and McKelvey28 studied the emission spectroscopy of 1-benzoy1-4-(a-naphthyl)—bicyclo[2.2.2]— octane and observed that irradiation of the naphthalene chromophore results in approximately 99% efficient singlet energy transfer to the benzoyl chromophore while irradiation of the benzoyl group results in complete triplet energy transfer to the naphthalene. Since the bridge between the chromophores is rigid the interchromophore spacing is known to be about 3 A with very little possible variation. Keller and Dolby29 investigated energy transfer using two systems in which the chromophores are held apart by rigid steroid bridges, 3-naphthy1-Sa—androstan— 178-(p-benzoy1benzoate) and 3-naphthy1-5a-androstan-l7B- (9-carbazoleacetate). The structures of these systems are shown in Figure 3. The interchromophore separations for these compounds, determined using Forster's equation,13 are 14 A and 15 A respectively. The phosphorescence emission intensity for the first system indicates that triplet energy transfer is 35-39% efficient while the phosphorescence lifetimes indicate a 12% efficiency with a rate of 25 sec-l. The phosphorescence spectral intensity for the second system indicates 30% efficient triplet 3-Naphthyl-5a—androstan— 3-Naphthyl-5a-androstan- l7B-(p-benzoylbenzoate) l78-(9-carbazoeacetate) Figure 3: Keller and Dolby's Systems energy transfer while the triplet lifetimes indicate 21% efficient triplet energy transfer with a rate of 0.04 sec-l. Reverse energy transfer was not considered for either system but may be important in the second. 8 studied 2-hydroxymethyltriphenylene Lamola 4-benzoylbenzoate and found that at room temperature in a cured poly (methylmethacrylate) film the phosphorescence observed is the sum of the phosphorescence of the two chromophores in a 2:3 ratio. At liquid nitrogen temper- ature only phosphorescence from the benzophenone chromo- phore is observed. It appears that triplet excitation equilibrates between the two chromophores and that the position of the equilibrium can be predicted by a Boltzmann distribution. By observing the Norrish type II reactions30 of 10 6-(4'-methoxypheny1)-l«pheny1hexan—1,6—dione Wagner and Nakahiralo were able to determine that the triplet lifetimes of the two chromophores are almost identical. This indicates that the triplet states of the two chromophores must be almost equilibrated since the life- times of these chromophores when in separate molecules are quite different. The product ratios obtained are close to what one would predict from a Boltzmann diStribution of triplet excitation. A scheme depicting this situation is shown in Figure 4. n+fl* \ anisoyl products 3n+n* / \ 3...”. benzoyl products Figure 4: Equilibrating Chromophores in the l-Benzoyl-4-p-anisoylbutane System 11 III. The Approach Used in this Dissertation When one looked at the data available at the start of this research, it was obvious that most triplet energy transfer could be explained, at least qualitatively, by the exchange mechanism proposed by Dexter.15 There do seem to be two general factors that control the rate of triplet energy transfer. The first is the physical separation between the two chromophores. It is obvious that the rate of triplet energy transfer drops off very rapidly with increasing distance. Thus the rates of energy transfer observed by Keller and Dolby29 at 15 A are seven to eight orders of magnitude slower than those estimated by Wagner and Nakahiralo at an average distance of about 7 A. The second is that the rate of triplet energy transfer is dependent upon the energy differences between the triplet states of the chromophores involved. In most of the studies done to date the triplet energy separation between the chromo- phores is greater than about 3 kcal/mole and only the exothermic process is observed. With the exception of Keller and Dolby's systems29 energy transfer is always complete in the exothermic direction. There are three systems reported in the literature in which the triplet energy separation is less than 3 kcal/mole. In the earliest, Keller and Dolby's naphthalene-carbazole system,29 it is not known whether triplet energy transfer takes place in the endothermic direction. In Lamola's8 12 and in Wagner and Nakahira's,lo it obviously does. In most of the systems which have been studied, no estimation of the rates of energy transfer is possible. The data which would be most useful in establishing the mechanism(s) of triplet energy transfer are the rates of triplet energy transfer in systems where the distances between chromophores can be estimated and the energy separation between the triplet states is known. The first of these requires an intramolecular system while the second requires some knowledge of the energy levels in the individual chromophores, usually obtainable from their phosphorescence spectra. In order to obtain rate constants it is necessary to have some process of known rate that can compete successfully with triplet energy transfer. While most of the systems discussed meet the first two of these requirements, it is impossible to do more than put lower limits on the rate constants for triplet energy transfer since none of the decay processes of the donor chromophore can compete successfully with triplet energy transfer to the acceptor chromophore. In 29 the large distance between Keller and Dolby's systems the chromophores results in rates of triplet energy transfer that are slow enough to allow the natural decay processes of the donor chromophores to compete with energy transfer. In Wagner and Nakahira'slo system the same result was obtained by choosing a triplet energy separation such that endothermic energy transfer is slow 13 enough to allow the natural decay rates of the lower energy chromophore to perturb the equilibrium between the triplet states in the system. This allows one to estimate the rate constants for energy transfer in both directions, as will be shown later in this dissertation. I chose to follow Wagner and Nakahira's approach for this research because I could use the Norrish type II reaction of phenyl alkyl ketones to monitor energy transfer. The mechanistic aspects of the Norrish type II reaction are well understood,31 and it is relatively fast which makes it an ideal monitor for triplet energy transfer. Intersystem crossing yields for most phenyl 35 so that complications arising alkyl ketones are unity from the singlet states are eliminated. Other reasons for using this approach include the relative ease of synthesis for compounds which are held apart by simple methylene chains and a greater interest in rate constants of energy transfer which are closer to those involved in intermolecular sensitization and quenching studies where diffusion is often the rate limiting factor. In addition to Wagner and Nakahira's communication,10 three other research groups have published papers in which the photochemistry of molecules containing two or more phenyl ketone chromophores was reported. David, Demarteau, and Geuskens32 reported the quantum yields of Norrish type II cleavage for poly (phenyl vinyl ketone) and the l4 copolymer of styrene and acrylophenone. Guillet and his coworkers33 studied the photochemistry of these polymers in considerable detail. The main interest of both of these research groups involved the facile photodegradation observed for these polymers. There is no way to observe energy transfer in these systems since the chromophores are identical. Salvin and his coworkers34 studied the photochemistry of the symmetric and unsymmetric dimers and trimers of acrylophenone. While it is theoretically possible to establish the position of equilibrium between the triplet states of the chromophores in the unsymmetric molecules the difference in triplet energies is so small that such an exercise is fruitless. Some very interesting stereochemical effects on the Norrish type II reactions of these systems were observed but these effects have no bearing on the work presented in this dissertation. IV. Phenyl Alkyl Ketone Photochemistry Since almost all of the results presented in this dissertation depend on the Norrish type II reaction of phenyl alkyl ketones some discussion of the mechanism of this reaction and the processes known to compete with it is in order. A comprehensive review of this reaction has been published by Wagner.31 Only the aspects of phenyl alkyl ketone photochemistry which are pertinent to the results presented in this dissertation will be 15 discussed here. In simple phenyl alkyl ketones the intersystem crossing yields are almost always unity35 indicating that intersystem crossing is faster than the normal decay processes of the singlet states of phenyl alkyl ketones. The rate of intersystem crossing has been estimated to be approximately 1011 sec"1 for phenyl 36,37 alkyl ketones. Therefore almost all photochemistry observed from phenyl alkyl ketones arises from their triplet states. In the triplet manifold of a phenyl alkyl ketone there are two triplet states which lie reasonably close to each other in energy, an n+n* state and a n+n* state.38 In simple valence bond terms the n+n* triplet closely 39 resembles an alkoxy radical, and its chemical behavior 31,40 supports this resemblance. The w+n* triplet has most of its excitation localized on the aromatic ring41 and spectroscopically resembles the lowest triplet state 8 These two triplet states are generally of benzene (3L3).3 close enough to each other in energy to equilibrate, their relative populations being determined by a Boltzmann 42 with the position of the equilibrium distribution, determined by the substituents on the phenyl ring. There are several routes by which the triplet states can decay. They can phosphoresce, undergo intersystem crossing to an upper vibrational state of the ground state singlet which then undergoes internal conversion to the ground 16 state, transfer their excitation to some quencher, and react. Since they equilibrate it is usually convenient to treat them kinetically as a single state with some mixture of the characters of both states. At room temperature phosphorescence can be observed from phenyl alkyl ketones only if they possess no Y hydrogens. At liquid nitrogen temperature most simple phenyl alkyl ketones phosphoresce because the small (3-4 kcal/mole) activation energy for hydrogen abstraction is insurmountable.43 Random intermolecular quenching of the triplet is a decay process which can be eliminated by scrupulous purification of the solvents and ketones used. It can be intentionally introduced and its effects measured quantitatively to provide one of the most powerful tools available to the photochemist.5 Intramolecular quenching of the triplet falls into two classes, those processes which form another excited state at a different location within the molecule, and those processes which result in decay to a ground state without the formation of a second excited state. The first of these intra- molecular quenching processes is triplet energy transfer and the main subject of this dissertation. The second involves several possible chemical inter- actions. The best understood mechanism is the formation of an intramolecular charge transfer complex which can decay to the starting ketone.44 Such processes have 17 been thoroughly studied with a variety of ketones.45 In most of the non—conjugated diketones discussed in this dissertation which contain two phenyl ketone chromophores internal quenching occurs by yet another process, self-quenching, which involves quenching, without energy transfer, of an excited chromophore by an identical or almost identical ground state chromo- phore. When the research for this dissertation was initiated the literature contained several reports of intermolecular self-quenching by ketones containing other functionalities conducive to charge transfer quenching, such as 4,4'-bis-(dimethylamino)-benzo- 46-51 phenone, but only two brief communications existed concerning self-quenching of phenyl ketones without 52’53 During the course of my research, such substituents. Singer and his coworkers54 reported the bimolecular rate constants for self-quenching of various benzophenones substituted in both para positions. They found that the rate constant of self-quenching was enhanced by both electron withdrawing and electron donating substituents and proposed the formation of exciplexes having some charge transfer character in both cases. For benzophenones with electron-donating substituents they proposed an n-type exciplex in which the carbonyl triplet acts as an acceptor and the phenyl ring of another benzophenone as a donor. In the case of electron withdrawing substituents the w system of the triplet was proposed to act as a donor and 18 the phenyl ring of an adjacent benZOphenone as an acceptor. They called this a w-type exciplex. The self-quenching processes observed during the course of this research allow important clarifications of this model. In most phenyl alkyl ketones containing y-hydrogens the main decay process of the triplet state is the Norrish 31 type II reaction. The mechanism of this reaction is shown in Figure 5. The reaction proceeds by abstraction H H .H 0 3*0 ' 1) hv g) y4fidnxfm #4’ 2) Inter- Numzactux1 system crossing 1H. E::g/§§ ZZBS Figure 5: The Norrish Type II Reaction of the y-hydrogen by the triplet n+n* state of the ketone 55'56 The rate of y-hydrogen to form a 1,4 biradical. abstraction is controlled by the ease with which the y—hydrogen bond can be cleaved, which is determined by the inductive and resonance effects of the substituents 19 on or near the y-carbon,57 and by the reactivity of the triplet carbonyl towards hydrogen abstraction, determined by the substituents on the phenyl ring.58 Once the 1,4-biradical has been formed it can react by three different pathways: 8 cleavage, cyclobutanol formation, and abstraction of the hydroxy hydrogen by the y radical site. The various parameters affecting these processes have been considered in depth by wagner and coworkers.59 The most important parameter affecting the reactions of 1,4-biradicals is the effect of Lewis bases on the revertibility of the biradical to starting ketone. For simple phenyl alkyl ketones addition of enough Lewis base raises the sum of quantum yields of cleavage and cyclization to unity, at which point rever- sion back to the ground state of the starting ketone has been eliminated.60 Presumably this suppression of reverse H-transfer occurs because the hydroxyl group of the 1,4- biradical forms a strong hydrogen bond with the Lewis base. The second major observation concerning the behavior of 1,4-biradicals is that the yield of cyclobutanols is about 10 to 20% of the yields of cleavage products and that similar biradicals give similar ratios of cleavage to cyclization.59 Addition of Lewis bases usually decreases the proportion of cyclization, generally reducing the yield of trans-cyclobutanol by about half while not 59 affecting the cis-cyclobutanol yield. This constancy 20 of behavior allows one to estimate the yield of cyclo- butanols with a reasonable amount of certainty in situations where neither the disappearance of the ketone not the formation of cyclobutanols can be readily measured. In systems which have a é-hydrogen the carbonyl can abstract this hydrogen in competition with the y—hydrogen.61 This reaction is generally mostly revertible. The apparent rates of 5-hydrogen abstraction have been reported,61 and are generally about 5% of the rates of y-hydrogen abstraction for similar hydrogens. V. Photokinetics of Phenyl Alkyl Ketones The photokinetics of simple phenyl alkyl ketones are relatively straightforward. The only things that can be measured directly are the formation of cleavage products, the formation of cyclization products, and the disappearance of the starting ketone. The mass balance is usually good. The effects of added quencher or Lewis base on the quantum yields of these products completes the picture of type II kinetics. The quantum yield for the cleavage product from the Norrish type II reaction may be expressed as follows: = o ¢II ¢isc ky T P11 (1) where ¢isc = quantum yield of intersystem crossing kY = the rate of hydrogen abstraction 21 1° = the lifetime of the triplet state in the absence of quencher PII = the probability that the 1,4-biradical will cleave to enol plus olefin By definition l/T = the sum of all decay processes of the triplet state and P g the rate of cleavage II sum of the rates of all biradical decay processes If one adds a known amount of quencher the equation for the quantum yield becomes: - 1‘7 PH (2) ¢II ‘ 1/16 + kqu] It is possible to extract the lifetime, 1°, from these equations using the Stern-Volmer relationship (equation 3)35’62 if one knows kq for the solvent and quencher used. ¢°/¢ = l + qu°IQJ (3) Measurement of P the quantum yield and the lifetime II' allow determination of the rate of y-hydrogen abstraction. Since, in a large number of cases, the sum of the quantum yields of the Norrish type II products is unity in the presence of a sufficient amount of Lewis base,60 it is usually safe to assume that PII + PCy = 1 at the maximum quantum yield rises no further upon addition of more Lewis base. In phenyl ketone systems where no photochemical reaction occurs it is possible to measure the triplet 22 lifetime by allowing the ketone to sensitize the cis- trans isomerization of either piperylene or stilbene and measuring the quantum yield of this isomerization.63 The equation describing this procedure kinetically is: = -1 O a/c+t ¢isc (1 + 1/(qu 101)) (4) where a is the photostationary cis/trans ratio of the olefin quencher and 9C is the measured quantum yield +1: for isomerization of the olefin. When two chromophores are placed in the same molecule the situation becomes considerably more complicated. All of the processes mentioned above can occur at both chromophores giving two complete sets of products to analyze. In addition two new processes involving the interaction of the two chromophores can occur. These processes are the subject of this dissertation. The first is energy transfer from the triplet state of one chromophore to the other chromophore. The second process is self-quenching of the excited chromophore by the ground state chromophore which returns both chromophores to their ground states. The kinetics of two chromophore systems have been 11 64 and are derived by Wagner and Nakahira and Shetlar expressed by Equations 5 and 6. An equation equivalent to 5 describes the quantum yield for products from chromophore B. .. . 7 EA + er 'kt"i; k A €A+€B €A+€B l/TB.+ quQJ ¢A - l/TA I R [Q] 1 ’ 1/1 f-; To] 1/f .EtkToI PA (5) q A q E q $0 55'- (1+quAIQ])(l+quB[Ql) - k_t TA kt TB (6) A (l-k_t kt TATB) 1 + kq[Q]TB 1 + is kt TB 8A where 9A = the quantum yield for product formation from chromophore A = o l/rA l/IA + k_t + ksq (7) 6A = the extinction coefficient of chromophore A k_t = the rate of energy transfer from chromophore A to chromophore B s the rate of self-quenching of chromophore A g by chromophore B All the terms of this equation except the rates of energy transfer can be determined from the appropriate model systems. While these equations are too complex to computer curve fit, it is possible to generate a family of curves and compare the experimental data to these curves to obtain the approximate rates of energy transfer. The exact forms of equations 5 and 6 used to do this will be discussed later. One special case of the Stern-Volmer equation for bichromophoric systems deserves special consideration. 24 If the decay rates of the individual chromophores are slow compared to the rates of energy transfer away from that chromophore then the triplets will equilibrate and the position of this equilibrium will be determined by a Boltzmann distribution.lo Under these conditions the equations for the quantum yield and Stern-Volmer rela- tionship simplify as follows: A ¢II = XA kY T PA (8) __ A A A B B B l/rA - XA(ky + kd + ksq[B]) + XB(kY + kd + ksq[A]) (9) “’11“ I .35.— .. 1 + (XA + X13) qu[Q] (10) II assuming B B B (kY + kd + ksqIAl) << k-t[B] and B B B (kY + kd + ksq[A]) << kt[A] When these conditions are met the lifetimes of both chromophores are equal and determined by the equilibrium distribution of triplet excitation between the chromophores. The quantum yields of products from the individual chromophores are also determined by this distribution. Under these conditions all one can do is set lower limits on the rates of energy transfer. It is possible to calculate the position of equilibrium from either the equation for the lifetime and the fact _ . = A obs A that XA + XB - l or from the equation XA (ky) /kY 25 since k3, kg, and kngB] can be determined from model systems. RESULTS I. General Techniques Several general techniques were used to obtain the kinetic parameters which form the basis for this disser- tation. Most of these were discussed briefly in the introduction and the experimental details will be presented in the experimental section. This section discusses only those aspects of these techniques necessary to understand and critically evaluate the data presented. A. Irradiations Unless otherwise specified irradiations used to determine kinetic data were carried out at 0.01 M ketone concentration in degassed, highly purified benzene at wavelengths where the n+n* singlets were populated almost exclusively. A merry-go-round immersed in a constant temperature bath was used to insure equal amounts of incident light for all samples in a given run and to maintain a constant temperature, usually 30.0°, throughout a series of experiments. 26 27 B. Product Quantum Yields Quantum yields of product formation were determined relative to l-phenylpentan-l—one (VP) secondary actinometers. Acetophenone (Ac), 4-ethy1acetophenone (p-EtAc), and propene were the products most generally determined because the experimental conditions required for their determination were well developed. All results presented are corrected for differences in the amount of light absorbed by the sample and actinometer and for their different gas chromatograph detector responses. C. Disappearance Quantum Yields Quantum yields of disappearance were determined relative to the cleavage products of the same ketone. The errors in these determinations are fairly large, but they are accurate enough to determine if any significant photoreactions other than the Norrish type II reaction and the normal 10 to 20% cyclobutanol59 formation occur. D. Maximum Quantum Yields Quantum yields of the cleavage products in the presence of various amounts of added Lewis bases were determined using the same techniques discussed above. For most of the ketones discussed in this dissertation it is not possible to obtain a quantum yield of unity for total product formation no matter how much or which Lewis base is used, but they do reach a point at which further increases in the concentration of Lewis base 28 leave ¢II unchanged or cauSe it to decrease. The results reported here are the maximum quantum yields observable. E. Intersystem Crossing Yields Intersystem crossing yields were determined by comparing the relative abilities of the ketone in question and of acetophenone at sensitizing the cis— trans isomerization of 1,3-pentadiene at concentrations of both ketone and acetOphenone where essentially all the incident light was absorbed and at 1,3-pentadiene concentrations where the triplet states of both the ketone and acetophenone are essentially completely quenched. The quantum yield for acetophenone is known to be unity.65 With the exception of 2,2-dimethyl-1,3-diphenylpropan- 1,3-dione (diBzdiMeMt) all of the ketones whose inter— system crossing yields were measured have intersystem crossing yields of unity. Since this is what is generally observed for phenyl ketones35 and since there are no structural differences which would be expected to affect the intersystem crossing yield in any of the ketones whose intersystem crossing yields were not measured, it can safely be assumed that their intersystem crossing yields are also unity. F. Triplet Lifetimes The triplet lifetimes of all ketones which undergo the Norrish type II reaction were determined by Stern— 35,62 Volmer kinetics with 2,5-dimethylhexa-2,4—diene as a quencher. Equations 3, 6, and 10 in the introduction 29 describe this type of kinetics for the three types of systems discussed in this dissertation. In all cases a plot of ¢°/¢ versus quencher concentration gives a straight line at low quencher concentration with the slope equal to qu° where 1° is the triplet lifetime in the absence of quencher. The lifetimes can be determined from qu° since the value of kq for 2,5-dimethy1hexa-2,4-diene is known to be 5 x 109 M-lsec-l in benzene.66 In cases where no photochemical reaction was observed, values for qu° were obtained from the efficiency with which the ketone sensitizes the cis-trans isomerization of either 1,3-pentadiene67 or stilbene. Equation 4 in 63 the introduction describes sensitization kinetics. When a/9. I . . ' f lsomerization lS plotted versus the inverse o the quencher concentration, where a is 0.55 for 1,3- pentadiene68 and 0.59 for stilbene,68 a straight line is obtained with intercept of 1/9iSC and slope qu°/¢isc' G. Spectroscopy Ultraviolet spectra were taken in benzene in order to determine the extinction coefficient at the wavelength used to irradiate the ketone. These data are necessary in order to correct for differences in the amount of light absorbed by the actinometer and diketone solutions used. Spectra were also taken in alkane solvents in order to check for ground state interactions between 30 chromophores. Occasionally spectra were also taken in ethanol. Phosphorescence spectra were taken in methyltetra- hydrofuran glass at 77° K in order to determine the energy of the lowest triplet state in the system and also to check for interchromophore complexation. In almost all 69 This of the spectra dual phosphorescence is observed. phenomenon is believed to arise from several causes in- cluding slow relaxation of the Franck-Condon triplet to the conformationally relaxed triplet. Both values are reported for ketones where they were observable. Attempts to take spectra in hydrocarbon solvents resulted in broad, structureless, red shifted spectra for most of the diketones discussed in this dissertation. This is probably due to microcrystallization upon cooling caused by the low solubilities of the ketones in hydrocarbon solvents. II. Energy Transfer Studies The results obtained from several unsymmetric di- ketones and the ketones containing the appropriate model chromophores are presented in this section. It is possible to determine approximate rates for the energy transfer between the chromophores of these diketones using the methods presented in the discussion section of this dissertation. The diketones studied and their abbrevia- tions are presented in Figure l. The ketones used to pro- vide models for the independent chromophores are as 31 follows: 1,5-diphenylpentan-l-one (6PhVP), l-(4'-ethyl- phenyl)-pentan-l-one (pEtVP), 4-ethy1acetophenone (pEtAc), l,6-bis-(4'-ethylphenyl)-hexan-l,6-dione (dipEthBt), l,6-diphenylhexan-l,6-dione (diBth),7O 4-(4'-cyano- phenoxy)-l-pheny1butan-l-one (yCNPhOBP), 4-phenoxy-l- phenylbutan-l-one (yPhOBP),57 l-(4'—methoxyphenyl)-pentan- l-one (pMeOVP),59'60 4-methoxyacetophenone (4MeOAc), 5-(4'-cyanophenoxy)-l-phenylpentan-l-one (6CNPhOVP), and 5-phenoxy-l-phenylpentan-1-one (GPhOVP). The syntheses or sources of these ketones are presented in the experimental section of this dissertation. A. Photokinetic Results The basic types of studies used to determine the photokinetic results were presented in the introduction and section I of the results portion of this dissertation. The detailed descriptions of the techniques used and the experimental data are presented in the experimental section. The quantum yields and qu values are presented in Table l. The Stern-Volmer plots (slope = qu) are presented in Figures 6-9. In all cases the qu values obtained for the chromophores of an unsymmetric diketone lie between those obtained for model ketones containing the individual chromophores. In the 6ValPhVP system the data for the benzoyl chromophore (Bz) were obtained by measuring the amount of acetophenone produced under the appropriate conditions. The data for the toluoyl chromophore (T1) was obtained 32 NNHmmN No.H H .H¢m. QAHm.vHo.Hbm. m>umm n n o hm mum «v cmo Hem nAmm vac “om m>sm© «How one. Ho.Avm. m>onmmo<.e aema use. moo.ameo. ca «mad can. Ho.HH~. um m>onmmm>.q mahmmm cmm. Hc.Am~. mmonm>o<.v mme ammo. soo.fimmo. :4 mem new. Ho.Amm. um mmonm»m>.q Named 6.0Ho.fiaa. Ho.A~eo. «name we. mnmea s.omo.fimm. mo.amm. um umumummquma nxaeaceea nmo.H ems. mm. c.0mo.fiflm. namm.vao.wom. m>smoo¢.v .o.mmva.~m mo.Hm~. Aqa.vao.nma. as n neo.a 0mm. 0 n nmeoavm.mm , oao.hvm. nA-.vao.HH~. um m>nmcm>.q w one we m muonm op x .e xmme Ace xwme HHe nosouso museums mucoumxocoz Home: can mmcoumxwo ownumeshmca new mosam> opvx can moamw» Enucmoo “a canoe 33 mm mfimma mwvov .mmu Eouu mosam> swoon mcfloflumm totem mosmuu mcoumxfip 2 mo.o Hoomm mmm ©.HHm.om OHHHhm MHHMH m Hmm v.NHH.om 0P 6 x o.H oo.a No.H mm. owe me e .0 Xflz mm .MGH EOHH mQ5HM> .2 mm .HQH EOHM mmsHm> .M AQCOHTXflG z Hocv m0 .MTH EOHH mm3Hw> .p swoon wcmeeU .n omumym mmwzumnuo mmmacs mcmwcmn Ge 2 Ho.o pom vo «me cao.amm. mo.wmm. nmm sea com. mmm. omo.wmm. mo.Hov. m5. Hm. Ho.Hom. oHo.«m~. mo.fie~. Mme mo “mm Ho.flmq. oao.flvm. ~o.g~v. mac HH HH muonm . mee e sosouno A.o.u:ooc a manna .M .m .m .0 .m m>onme m>onm©zo.e m>omza among» mmozm>zo.v mm>omzonumoe umumumdnc mumnmflo umnmes MOCOuOM 34 13 ' 12 ' 11 ' . 0 . L . . . 1 L . 1 0 .01 .02 .03 .04 .05 'quencher concentration Figure 6: Stern-Volmer Kinetics for the 6ValPhVP System ( O 6PhVP; I Ac, 6ValPhVP; D Pr, 6ValPhVP; A 6AcPhVP; IprtVP) 14- 13 - 12 - 11 - 10 - Figure 7: ( O diBzEt; pEtAc) .‘ I} I b L— J .01 .02 35 L A .03 .04 quencher concentration, M .05 Stern-Volmer Plots for the 1Bz4pEthBt System 0 dipEthBt; D le4pEthBt, Ac; A le4pEthBt , i ! O I 13 i i 12 : . i ! 11 I i 10 t ! 9 ! ! ! l 9138 i l i I 7 i ! 6. g ‘ ! O 5 ! I ! l j p 4 ! ! O I A 3 : . n . . . ! .. ”.---.- 2 ! t .0 ””,,,2 . . ’II” ' I../ . .””""”’ 1 I ’4- .025 0 01 015 n .0420 0 .005 quencher ncentratio , lPhOBP System 8 Stern—-Volmer Plots fo he «(Va F igure : CPhOBP' pMeOVP: 0 ~{CNPhOBP , “(A -~{PhOBP. -—- A - A 1ValPhOBP, Pr) l3 . II I 12 . [I 11 - / 1o . ,’ N D D D JA 1 0 . . . 0 .002 .004 .006 .008 .010 quencher concentration, M Figure 9: Stern-Volmer Plots for the 6ValPhOVP System ( Cl 6Va1PhOVP, Pr; I 6ValPhOVP, Ac; 0 (SACPhOVP: A GCNPhOVP; o 6PhOVP; ----- pMeOVP) 38 from propene measurements. The results for the 0AcPhVP system and the model ketones used for these systems, 6PhVP and pEtVP, were obtained from the appropriate acetophenone determinations. The values obtained at 0.05 M and 0.01 M show only the slight enhancement in ‘ the Norrish type II quantum yields normally observed for phenyl alkyl ketones when the ketone concentration is increased.60 Within experimental error the qu values observed for the two chromophores in the GValPhVP system are the same. The ¢Cy for GAcPhVP, determined from product ratios observed in preparative scale photolysis, is 0.060. The 0Cy and 033* 0.058:0.001 and 0.085i0.003. The values obtained for Max Dis for pEtVP are 9 for 6Va1PhVP and 6AcPhVP are slightly less than those observed for the sum of the product quantum yields under these conditions due to the large error involved in the determination of dissappearance quantum yields. The le4pEthBt system contains the same chromophores at approximately the same spacing as the 6ValPhVP system but the toluoyl chromophore is turned around. The Stern- Volmer data for the toluoyl chromophore in le4pEthBt was obtained from measurements of the amount of l-phenyl- but-3-en-1-one under the appropriate conditions while quantum yields for this chromophore were obtained from measurements of the amount of pEtAc produced. All the data for the toluoyl chromophore of le4pEthBt as well 39 as for the model ketones, diBth and dipEthBt, were obtained by measurement of the appropriate acetophenone. The quantum yields and qu value Kemppainen7o reported for diBth are lower than those I obtained for this ketone indicating that the ketone he used may have contained a quenching impurity. The maximum quantum yields observed for diBth, dipEthBt, and 1Bz4pEthBt are much lower than in model ketones, including methyl 5-phenyl-4-oxocaproate (6-CarbOMeVP).57 The 9%:: for diBth is in good agreement with the 10% cyclobutanol formation expected for this ketone.59 As in the case of 6ValPhVP the qu values for the two chromophores of le4pEthBt are the same within experimental error. The yValPhOBP system contains the same chromophores as the l-(4'—methoxyphenyl)—6-phenylhexan-1,6-dione (le4AnBt) system studied by Wagner and Nakahira,lo and if the ether oxygen is not considered part of the anisoyl chromophore, approximately the same interchromophore spacing. The data for the anisoyl chromophore was determined by measuring the propene produced under the appropriate conditions. For the benzoyl chromophore of YValPhOBP and yAcPhOBP and their 57 59 the model ketones, yCNPhOBP, yPhOBP, and pMeOVP, data was obtained from the appropriate acetophenone determination. In order to estimate the effects of the substituents on the phenoxy group on the rate of y-hydrogen abstraction by the benzoyl group, it is 40 necessary to consider both YcNPhOBP and yPhOBP. As was observed for le4AnBt10 the difference in the qu values for the two chromophores of the yValPhOBP system is just barely greater than the experimental error in their determination, with the lifetimes of the chromophores displaced from their average towards the lifetimes observed for these chromophores in the appropriate model ketones. The 6ValPhOVP system also contains the same chromo- phores as the le4AnBt system studied by Wagner and Nakahira,10 but in this system the same interchromophore distance would be observed with the anisoyl chromophore turned around if the ether oxygen is considered part of the anisoyl chromophore. The data was obtained by measuring the same products as were measured for the 7ValPhOBP and yAcPhOBP systems. The observed qu values for both chromophores of 5ValPhOVP, 6AcPhOVP, and for SCNPhOVP and 6PhOVP are considerably higher than those observed for yValPhOBP and its model systems. There is a much greater difference in the qu values obtained for the 0ValPhOVP system than was observed with the 7ValPhOBP system. B. Spectroscopic Results The spectroscopic results for the ketones used in these energy transfer studies are tabulated in Table 2. The ultraviolet spectra of the unsymmetric diketones are essentially the sum of the spectra observed for the individual chromophores from model systems. As can be 41 Table 2: Spectroscopic Data for Unsymmetric Diketones and Monoketone Models Ketone n+n* absoré'ptiona phosphorescenceb AMax 313 relaxed Franck-Condon nm [M]-lcm-1 nm(kcal/mole) nm(kcal/mole) 6ValPhVP 320 127.7 400(71.5) 392(72.9) 6AcPhVP . 317 128.4 401(7l.3) 392(72.9) le4pEthBt 317 144.6 401(7l.3) 392(72.7) yValPhOBP 316 211.2 409(69.9) 401(7l.3) yAcPhOBP 316 226.7 411(69.6) 401(7l.3) 6ValPhOVP 317 224.6 408(70.l) 400(71.5) 6AcPhOVP 317 190.7 411(69.6) 402(71.l) 6PhVP 319 49.0 390(73.3) 384(74.5) pEtVP 309 75.7 401(7l.3) 392(72.9) pEtAc 309 77.7 401(7l.3) 392(72.9) diBth 319 109.7 392(72.9) 385(74.3) dipEthBt 318 157.0 402(7l.l) 393(72.7) YcNPhOBP 316 59.8 392(72.9) 384(74.5) yPhOBP 316 53.7 392(72.9) 384(74.5) pMeOVP 313 147.1 397(72.0) pMeOAc 132.1 408(70.l) 399(7l.7) 6CNPhOVP 318 57.3 39l(73.l) 384(74.5) 6PhOVP 318 52.2 392(72.9) 384(74.5) VP 320 47.3 393(72.7) 385(74.3) a. in benzene b. in 2-methyltetrahydrofuran at 77° 42 seen from the representative phosphorescence spectra shown in Figures 10-13, the phosphorescence spectra of the unsymmetric diketones are identical to those of the model ketones containing their lowest energy chromo- phores. The phosphorescence spectra for the yAcPhOBP, 6Va1PhOVP, and 5AcPhOVP systems are identical to those of the yValPhOBP system. III. Self-Quenching Studies The results obtained from several symmetric diketones in which self-quenching appears to occur are presented in this section. A detailed discussion of the self- quenching phenomena will be given in the discussion section of this dissertation. The ketones studied and their abbreviations are as follows: 2,2-dimethyl-l,3-diphenyl- propan-l,3-dione (diBzdiMeMt), l,4-diphenylbutan-l,4-dione (diBzEt), l,S-diphenylpentan-l,5-dione (diBzPr),34 1,6- diphenylhexan-1,6-dione (diBth),7O 1,7-diphenylheptan- 1,7-dione (diBth), and l,6-bis-(4'—ethylphenyl)-hexan- 1,6-dione (dipEthBt). The synthesis and sources of these ketones may be found in the experimental section of this dissertation. A. Photokinetic Results The basic types of studies used to determine the photokinetic results were presented in the introduction and section I of the results portion of this dissertation. The detailed descriptions of the techniques used and the experimental data are presented in the experimental section. 43 5ValPhVP 300nm ’ r L 600nm —— .n 60666 scams .6 6m .mmu Eonm mosam> .p .>coo mcoumx we 0» omumHommuuxm mmsH6> .n msama o.H as. omv o.H coca oafiasm so.H Ho.scm. q.Hsa.mv msmm «.msa.om No.H 0mm. Ho.sm¢. oma hasvma No.H o.nmc.fio.a nao.ss~. 6mscom 6o.H o saws mos. o 3:: .svx owes ”Mme meme U monouoxfla Denumfisam Hem mosam> p x can moamew Educmso mm .mmu Eouu mosam> cocoa mswpenhm mm .wwu Bonn ©0606 mcmons muoHQ coeumueuemcmm Scum .A .6 .3 .0 .M as. Hm>0zonsmom om. Ammmzonnmor 666. so. numsae6 oac.smm. mo.fle~. umumumme6 6.0mo.smm. mo.sem. umsme6 mmv. mo.smm. mumsmfl6 oao.svm. mo.s~¢. umume6 . .HNH cm 6 m 6.6 o.nes. nmm. H.3636 umume6 uzmze6ume6 HHe HHs msouws x62 "m OHQME 49 L 0 200 Figure 14: 400 600 800 [stilbene]-l Sensitization Plot for diBzdiMeMt 50 0 100 200 300 [l,3-—pentadiene]"l Figure 15: Sensitization Plot for diBzEt 51 Amcmxown 2 m6 4 636666 o: o . Hmumep How cOanm>coo :ue3 HHe mo coflumeum> “6H musmem ma. :oflumuucmocoo mcoumxflo x :0wmum>coo OH. I 4 mo. d 1 d N.o m.o m.o m.o h.o HH 52 ...1._=_%_ + kqxfm (11) $11 $11 ¢iscPIIkY where X is the fraction of the final quenching product concentration which gives the effective quencher concentration over the full length of the experiment and C is the percent conversion of diketone. The intercept of a plot of 1/9II versus C[K] is l/¢II‘ These plots for diBzPr in the presence and absence of added Lewis base are shown in Figure 17. Stern-Volmer plots for diBzPr are presented in Figure 18. The k T q values obtained from these plots may be corrected for product quenching using equation 12.60 o = o (qu) %_ (qu)obs (12) obs The Stern-Volmer plot of diBth is also presented in Figure 18. The Stern-Volmer plots for diBth and dipEthBt were presented in Figure 6. The values of 10 56 k T, 9 and 9Max for diAnBt, yCarbOMeBP and q 11’ II 6CarbOMeVP,56 obtained from the literature, are included in Table 3. B. Spectroscopic Results The spectroscopic results for symmetric diketones and the appropriate monoketone models are tabulated in Table 4. The extinction coefficients for diBzdiMeMt and diBzEt are considerably higher than those of the other dibenzoyl alkanes. The other dibenzoylalkanes 53 Amcmxofia z m.6 6V .9>Huwp©6 o: O V umumeo MOM Hme no c0eumcefiumumo "ha Gunmen odoumxeo coHumuusmocou x cowmum>cou mace. QHoo. mooc. o u q d H. . N 4 m . v 0 O O . m o 0 Au HH '9' 54 $0 9- I 2.0 b AS O AD 0 I [J A O I (O /;u I ‘, 1.0 0 ‘ 1 0 .01 .02 Quencher Concentration, M Figure 18: Stern-Volmer Plots for diBzPr and diBth ( DdiBzPr, 7.85% conv.; A diBzPr, 4.89% conv.; OdiBth) 55 Table 4: Spectrosc0pic Data for Symmetric Diketones Ketone n+n* absorptiona phosphorescenceb AMax e313 relaxed Franck-Condon nm -1 -l nm(kcal/mole) nm(kcal/mole) [M] cm diBzdiMeMt 320 214.8 394(72.6) C diBzEt 313 128.8 392(72.9) 384(74.5) diBzPr 317 100.0 393(72.7) 386(74.l) diBth 319 109.7 392(72.9) 385(74.3) diBth 318 109.8 39l(73.1) 384(74.5) dipEthBt 318 157.0 402(71.l) 393(72.7) VP 320 47.3 393(72.7) 385(74.3) pEtVP 309 75.7 401(7l.3) 392(72.9) a. in benzene b. at 77° in methyltetrahydrofuran glass c. only one set of peaks observed for this ketone 56 appear to be only the sum of two valerophenone chromo- phores. The phosphorescence spectra of diBzdiMeMt and diBzEt are shown in Figure 19. The phosphorescence spectra of diBth and dipEthBt were presented in Figure 12. The phosphorescence spectra of diBzPr and diBth are identical with that of diBth. The spectrum of diBzdiMeMt is interesting in that it does not show the dual phosphorescence normally observed with phenyl alkyl ketones in 2-methyltetrahydrofuran. IV. Quantum Mechanical Calculations The self-quenching data presented in the previous section prompted a more theoretical study of possible carbonyl excimer formation. The ground state and lowest excited singlet and triplet states of a pair of formaldehyde molecules at various separations for two different relative orientations were studied by ab- initio SCF and CI theory. The first was a head-to-tail orientation in which the two molecules are placed in parallel planes of varying separations with the oxygen of one formaldehyde occupying the same coordinates in its plane as the carbon atom of the second molecule does in its plane. This orientation should leave both the n and n orbitals unavailable for possible interactions. The second orientation studied was one in which the two molecules are placed in the same plane with the oxygens aligned with the carbons. This orientation should give rise to almost the maximum amount of n orbital interaction. 57 diBzdiMeMt 300nm 600nm diBzEt m2; 1 L l I I 300nm 600nm Figure 19: Phosphorescence Spectra of diBzdiMeMt and diBzEt 58 A third orientation in which the formaldehydes are placed head-to-head in parallel planes would also be of interest. This orientation, which should lead to maximum w orbital interaction, would amount to a broken dioxatane at small separations and possible exciplexes arising from it have 71 been designated as "crypto" excimers by Turro. This orientation had already been studied by Dewar and Kirschner.72 The calculations were carried out using standard integral and SCF programs, IBMOL and POLYATOM,73 and a CI program, CIDAW, developed at Michigan State University by Dr. J. F. Harrison. The computer used used was a Control Data Corporation model 6500. A STO-ZG basis set“ was used for reasons of economy. The geometry of the formaldehyde molecules used was the standard one proposed by Gordon and Pople74 and was held constant throughout the calculations. The results of these calculations are presented in Tables 5 and 6. To check the reliability of the STO-ZG basis set the SCF calculations for the head-to-head approach were repeated using a STO-BG basis set and the results are presented in Table 7 and show the same relative changes with geometry. The one electron-energies for the n and w orbitals in the head-to-head and head-to-tail orientations are given in Table 8. The head-to-head orientation produces the predicted n orbital interactions. The energy differences relative to the ground state for the two 59 Di-Formaldehyde Energiesa vs Head-to-Tail Orientation 4 A —218.02074 -218.0547l -217.9018l -217.87ll3 Di-Formaldehyde Energiesa 3 A -218.01976 -218.05576 -217.90168 -217.87143 Head—to-Head Orientation 4 A -218.0l968 -218.05348 -217.9008l Table 5: 0 State R= 5 A lAg(SCF) -218.02076 lAng) -218.05366 389 -217.90165 lag -217.87087 a. Energies in Hartrees Table 6: 0 State R= 5 A 1A1(SCF) -218.02056 lAl(CI) -218.05340 3A2 -217.90136 1B1 -217.87054 -217.87018 a. Energies in Hartrees 3 A -217.99944 -218.03301 —217.89690 -217.87072 VS Distance 2 A ' -217.93266 -217.96625 -217.86264 -217.84812 Distance 2.5 A -217.92529 -217.96016 -217.83587 -217.81048 60 Table 7: SCF Energiesa for the Head-to-Head Orientation of the Di-Formaldehyde System Carbonyl o STO-3G STO-2G Difference .separation,A 5 «224.41866 ~218.02056 -6.39810 4 -224.4l790 -218.01968 -6.39822 3 -224.40295 -217.99944 -6.40351 2.5 ~224.33968 -217.92529 -6.4l438 a. Energies in Hartrees Table 8: Orbital Interactions for the Di-Formaldehyde System Head-to-Head Orientation Orbital one electron energya separationa |n+> -0.3122290 0.0145182 |n_> -0.2977718 |n+> -0.4300376 0.0000967 In > -0.4301343 Head-to-Tail Orientation |n+> -0.3077229 .0002296 |n_> -0.3079525 |n+> -0.4327992 .0011729 In > -0.4339721 a. Energies in Hartrees 61 orientations studied are presented in Table 9. Table 9: Energya Differences Relative to the Ground State for the Di-formaldehyde System Symmetry Separationb between Carbonyls, A 2.0 2.5 3.0 -4.0 5.0 1B1 --- 0.14968 0.16229 0.18330 0.18294 3B2 --- 0.12429 0.13611 0.15267 0.15212 Head-to-Tail Orientation B 0.11813 --- 0.18433 0.18358 0.18279 A 0.07852 --- 0.16637 0.16474 0.16353 a. Energies in Hartrees b. Distance in Angstroms DISCUSSION I. Derivation of Rate Constants Several rate constants can be obtained from the results presented in this dissertation. Most of these are derived in the same manner for all the ketones discussed. It is the derivations of these rate constants which are presented in this section. A. Triplet Lifetimes Triplet lifetimes, T, for the various chromophores considered in this dissertation were obtained from the kqt values for the chromophores. The value of kq has 9 1 l in benzene for been determined to be 5 x 10 sec- M- all the quenchers used in this dissertation.66 Since all the conclusions of this dissertation are based on relative lifetimes, a systematic error in the value of kq would not affect them. Because l/T is equal to the sum of all the rates of decay of the state whose quenching is being observed, it is more useful to report l/r values rather than T values. B. Maximum Quantum Yields of Disappearance and Cyclobutanol Formation For some of the ketones discussed in this dissertation the maximum quantum yields of disappearance were measured 62 63 directly and a reasonable value for this quantity obtained. For most of the ketones discussed satisfactory conditions for the analysis of the ketones were not available or the conditions used were not sufficiently accurate to be useful except to eliminate substantial reaction pathways other than the Norrish type II reaction and concurrent cyclobutanol formation. In no instance was any other product expected or observed: so, in Max general, the assumption was made that 9Dis equaled the Max Max II and 9Cy the cyclobutanols were no easier to determine than the sum of 9 . For most of the ketones involved parent ketones; but, fortunately for this dissertation, the fate of the biradicals involved can be reasonably well predicted from the fate of similar biradicals where the starting ketone or cyclobutanols are more readily 59 determined. The validity of these predictions may be estimated by considering the observed predictability of the reaction patterns of a large number of biradicals formed as intermediates in the Norrish type II reactions of phenyl alkyl ketones.59 C. The Rate of y-Hydrogen Abstraction The rate of y-hydrogen abstraction, ky, was obtained by multiplying 9%:: by 1/1.57 The most important assump- Max tion involved in this calculation is that 9Dis represents the quantum yield of y-hydrogen abstraction, or, in other words, that solvation by the Lewis base used in the Max determination of 9Dis completely eliminates all 64 revertibility of the biradical. This is what is observed for most phenyl alkyl ketones,60 and there is no reason to believe it is not the case for the ketones discussed in this dissertation. D. The Rate of Non-Productive Triplet Decay The rate of non-productive triplet decay, kd' is the sum of the rates of all processes occurring from the triplet state which do not produce measurable products. Since the Norrish type II reaction products and cyclobutanols are the only products observed from the ketones discussed in this dissertation and since these products come from a common biradical intermediate which is the result of y-hydrogen abstraction by the triplet states of the chromophore,31 kd is the difference between l/T and ky. Traditionally kd is divided into radiative processes. For the ketones discussed in this dissertation one would not expect to be able to observe phosphorescence at room temperature since the rates of phosphorescence from phenyl alkyl ketones which do phosphoresce at room temperature68 are 105 times slower than the values of l/T obtained for the chromophores discussed in this dissertation. The non-radiative decay observed for the chromophores discussed in this dissertation can be expected to include at least three specific processes, 6-hydrogen abstraction,61 intramolecular charge transfer quenching,45 and intra- molecular self-quenching. In order to determine the 65 rates of energy transfer for the unsymmetric diketones included in this thesis it is only necessary to estimate the total kd for each chromophore involved in the system. This is done by first determining the fraction of excitation residing at the chromophore in question and then multiplying this fraction by the kd obtained from the best model system for this chromophore. There are several ways in which the fraction of excitation residing at one chromophore can be determined; these will be discussed in a later section. For the self- quenching studies it is necessary to separate the rate of self-quenching, k , from the rest of kd. The sq methods used to estimate ksq are discussed below. Methods of estimating the rate of—6-hydrogen abstraction were discussed briefly in the introduction and have been discussed in more detail by Wagner, Kelso, 61 Kemppainen, and Zepp. Methods of estimating the rates of intramolecular charge transfer have been described 75 by Weller. Charge transfer quenching of phenyl alkyl 45’76 27’77 and aromatic ketones by amines, olefins, compounds78 has been observed. Since neither of these processes are being studied in this dissertation, no attempt was made to separate them from the other decay routes of an individual chromophore. In order to obtain the rate of self-quenching, k it is necessary to sq' estimate what the rate of non-radiative decay for the chromophore would be in the absence of the second 66 chromophore involved in the self-quenching. This estimated kd for the chromophore is obtained by multiplying kd from an appropriate model system by the fraction of excitation residing at the chromophore in question. For symmetric ketones and for ketones with equilibrating chromophores ksq is estimated by subtracting the sum of the estimated kd values for the two chromophores from l/T. For unsymmetric ketones it is necessary to determine the quantum yield expected for non-radiative decay from each chromophore in the system and then subtract all the quantum yields, known and estimated, for that chromophore from the fraction of excitation residing at the chromophore to obtain a quantum yield of self-quenching for the chromophore. The rate of self-quenching for the chromophore is then obtained by multiplying the quantum yield of self- quenching for the chromophore by the l/T value for the chromophore. E. Rates of Energy Transfer In systems in which the chromophores do not equili- brate the rates of energy transfer, ket’ can be estimated by comparing the Stern-Volmer plots of the chromophores with those predicted for the system with various values of ket using equation 13, which is a rearranged version of equation 6. When the rates of energy transfer become fast compared to l/T for the chromophores the triplet states of the chromophores almost reach equilibrium before 67 43 g (l/TA + kAB + kq[Q])(l/Té_+ kBA + kqu]) - kABkBA] 4A (l/TA + kAB)(kBA + 1/13) - kABkBA J -1 x 1 + kg[Q] (13) T 1/1B + (1 + sB/EA)kBA . l A A where l/TA — kY + kd , (l4) , _ B B and l/TB - kY + kd (15) reaction or decay takes place. Under these conditions all that can be obtained is a lower limit on the rates of energy transfer. This is done by finding what rates of energy transfer are required to give a deviation from equilibrium equal to the experimental error in the Stern-Volmer plots for the chromophores involved. It is also possible to determine the rates of energy transfer by solving the equations for quantum yields of product formation from the individual chromo- phores (equation 16, which is a rearranged version of equation 5) simultaneously for the rates of energy . EA e:13 -———— (l/T'+k +k [Q])+k ————— ¢ =kA 8BISA B BA q BA €A+EB 1 (16) A Y 3 l - L(1/TA+kAB+kq[Q])(1/TB+kBA+kq[Q]) kABkBA J transfer. The main problem with this approach is that Max Dis a number of approximations. In Table 10 the rates of it is based on 9 for the chromophore which includes energy transfer obtained by both methods are reported under the donor chromophore. 68 ca .umu co Ummmn mwsam> .a poesmmm maocmusnoHowo wad .m HH x62 pxfixnox .0 H9608 m.o u o.a m.H o.oau m. mo.o o.m u o.H o.o o.mHu o.oa o.o M; 9m o.o o.ma o.~a o.m v.6 v.a o.oa o.m m.o o.m m.v A 6.o o.oH o.oaA um um gm Gem um Usfl v— 0 X mmcoumxwo UHHDGEEhmcD Hem mumumamuom oeumcwx om>wumo maocmusnoHo>o wma e co comma mmsam> r a > H9UOE x.xn x Hm. mHo.c ¢.H mm. Nv.o H.N NH. NH.o mm.o ha. Hmc.o mm.o who. md.o v¢.o ma. ow.o Hm.c 6N. «mo.o H.H hm. mm.c «.H mm. om.o o.m mm. v.H v.m h. h.H m.N h. m.a N.m h. m.H m.v 0.66 n.6>x 6e\H .0 .6 use on as as mm 666 who was NH u now mm mmm man man x62 0 .: ooesmmm maocmusnoHo>o mom .m p\H co canon monam> .o 096 ca x .6 HI 5 :6 am umcavuma um m>osmo¢6 :6 mm m>onmam>6 um mmonm0<> s< um mmonmam>> umumm um umumDMQvumH 6m m>nmo<6 as am m>an6>6 muozm nosounu occumx nod manme 69 F. The Fraction of Excitation at a Chromophore There are three ways which may be used to determine the fraction of excitation at a given chromophore. Probably the most accurate method for systems in which the triplet states are equilibrated or almost equilibrated is based on the lifetime of the equilibrated system, l/T, and the lifetimes of the separated chromophores, l/T' using equation 17 for chromophores A and B. l/T - l/TB' 1/TA' - 1/TB' (17) XA If the triplet states do not equilibrate equation 17 can not be used. For such systems the fraction of excitation at chromophore A is determined by dividing kYA by the k obtained from the appropriate model system. This method contains the errors from both the lifetime Max Dis was used to obtain the values for the more reactive determination and the 9 determination. This method chromophore of a system. The fraction of excitation for the less reactive chromophore was obtained by subtracting the fraction of excitation of the most reactive chromophore from one. II. Energy Transfer Systems The derived kinetic parameters for the energy transfer systems and their model compounds are presented in Table 10 and 11. The kY values reported in the table Max were obtained from 9Dis and 1/T and hence are equivalent to xi le where le is the kY which would be observed 70 Table 11: Ketone ¢gig _1/1 -1 -§Y x10 sec x10 sec 6PhVP .71a 11.8 8.4 pEtVP .63 2.0 1.3 diBth .59 6.2 3.7 dipEthBt .31a 1.3 0.40 YcNPhOBP .70b 6.2 4.3 yPhOBP .83b 21.7 18.0 pMeOVP .26c 0.23d 0.060 6CNPhOVP .62e 1.2 0.74 6PhOVP .82e _ 2.6 2.1 diAnBtf .066a 0.50 0.033 a. 10% cyclobutanols assumed b. 20% cyclobutanols assumed c. values based on reference 59 d. values based on reference 58 e. 15% cyclobutanols assumed values based on reference 10 Kinetic Parameters for Model Ketones k -1 --7d - x10 sec 1 3.4 1.0 2.5 0.90 1.9 3.7 0.17 0.46 0.5 .47 71 if xi was one. A. The 6ValPhVP and 6AcPhVP Systems The lack of significant concentration effects for these ketones indicates that the interactions observed are intramolecular in nature. If they were inter- molecular one would expect to see 1) a decrease in the quantum yields with increasing diketone concentration due to an increase in the rates of decay, and 2) a significant shift in the ratio of the quantum yields of products due to increased rates of energy transfer. All that was observed was a slight increase in the quantum yields with no shift in their relative values. This increase is expected and probably caused by solvation of the biradical intermediates by ground state ketone.6O The l/T values obtained for the benzoyl and toluoyl chromophores of 6ValPhVP are within experimental error of being the same indicating that the triplet states of the system have essentially equilibrated. Since the decay rate of the toluoyl chromophore of 6AcPhVP is certainly smaller than the sum of the decay rate and rate of y-hydrogen abstraction for the toluoyl chromophore in 6ValPhVP, the triplet states of 0AcPhVP should also be equilibrated. The sum of the cyclobutanol yield obtained from the preparative scale photolysis of 6AcPhVP and the maximum quantum yield of acetophenone formation is in 72 Max Dis hence no estimates are needed in order to obtain 9 good agreement with the 9 measured for 0AcPhVP and Max Dis Max obtained for 5ValPhVP is less for this ketone. The 9Dis Max II ketone. For this reason it is necessary to make some than the sum of the 9 for the two chromophores of this sort of estimate of the quantum yields of cyclobutanol' formation from these chromophores. The percentage of cyclobutanol formation out of the total quantum yield. in the presence of Lewis base is about 10% for VP, pEtVP, 0AcPhVP, and several other ketones which form similar 59 and for this reason it was assumed to be biradicals 10% for both chromophores of the 6ValPhVP system. The ratio of the rates of energy transfer should be predictable by use of the Boltzmann equation, on the assumption that energy transfer is microscopically reversible. The main problems with the ratios thus obtained arise from the difficulties involved in obtaining accurate room temperature energies for the triplet states involved. For 6ValPhVP the observed difference in triplet energy at liquid nitrogen temperature is 1.6 kcal, which predicts a Boltzmann ratio of 0.07 for this system and x values of 0.065 and 0.935. This is very different from what is observed. If one matches the Stern-Volmer plots obtained for this ketone to those predicted for this system (Figure 20) one determines that the ratio of rates of energy transfer must be 0.46 and the actual rates at least 73 I / z s I 1 I ‘I I’ o I /' I Q I I a” x. 6 L. [I I; ’I x/ . .- I I I” I til 0" ’ I .I I, , I I" 3’. I”, ’1’ I I I. e/ 1’ I, I' I l I, I In /.' ’I I, I . 1’ I I I / I I I . a I 5 L I " / I, I" I ./ ” I, I ’. ' I I 1’ ../ I; , I ’ I z I. 3’ ’l’ ’I I. 1" . / I I ’.l I: . / ’I I " I .' /’ ” ’ I I ’ ’l " O ’l I, I" l . 4 b I I I "l”’o ’0’ o ’ / I”p ’ 2 I " I’II’ .0 ’a " I ¢ / I "I I’I” '°;" I I I’ll" "5' I ’ ’l’l ’2’. I I I ’ I "5:” I I I /’ 1’: I I .I' I" 3 . I I. ’I’ f I ’.':,/’ O" I . I : I .l'xfl .I‘ O ’ I'd’ I. " ..é‘ ‘0 I .45 4’ I. [’1' .-’ /' '.-’ ’.I' x’..-/ 2 h '1' I. I. I’. ' I ’. Q’. 1 0 .1 L 1 IA 4 0 0.01 0.02’ 0.03 0.04 0.05 Quencher Concentration Figure 20: Predicted Stern-Volmer Plots for the 6ValPhVP System ( 0 Observed for acetophenone; O observed for propene; l -l.0 x 108 sec-l, 4.6 x 107 sec-l;-~"-l.0 x 109 sec- , 7 -1 4.6 x 108 sec‘l; --- 1.2 x 108 sec-1, 3.7 x 10 sec ...1) -u- 8.0 x 107 sec‘l, 5.5 x 107 sec 74 1.0 x 108 sec_1 and 4.6 x 107 sec—l. Similarly the observed quantum yields require a ratio of .3 and rates of at least 1.0 x 108 sec"1 and 3.0 x 107 sec-l. These determinations require a large number of rate constants each of which contains some error but even so the energy difference in the two chromophores must be between 0.42 and 0.72 kcal to account for the observed data. One must conclude that the changes in energy levels on warming are not the same for each chromophore. Wagner, Thomas, and Harris79 have made similar conclusions for various phenyl alkyl ketones. Because no photochemistry occurs at the toluoyl chromophore of dAcPhVP no direct measurement of l/T for this chromophore can be made. If it is assumed that the triplet states of the two chromophores of 5AcPhVP equilibrate and that kd for the toluoyl chromophore is the same as observed for pEtVP then the rates of energy transfer must be greater than 1.0 x 109 sec"1 and 2.4 x 108 sec.1 based on the observed l/T value. This is in good agreement with the observed x of 0.20 for the toluoyl chromophore of GAcPhVP. These rates predict an energy difference of 0.69 kcal which is quite different from the 1.6 kcal observed for the phosphores- cence of these chromophores at liquid nitrogen temperatures. Inspection of the observed rates of reaction and decay for the chromophores of 5ValPhVP and 6AcPhVP 75 indicate that the maximum rates of self-quenching for these systems are 4 x 106 sec"1 and 3 x 106 sec-l, both of which are less than the experimental error in the l/T values for these diketones. B. The le4pEthBt System The l/T values obtained from the benzoyl and p-ethylbenzoyl chromophores of le4pEthBt are separated from each other by just about the experimental error in their determination. This means that the energy transfer processes are no slower than the minimum rates which would allow measurable perturbation by the rates of reaction and decay of the individual chromophores. The only ¢gi§ determined for ketones related to this system was for diBth. It is in good agreement with the expected 10% cyclobutanol formation. It was assumed that the ratio of cyclobutanol formation to Norrish type II products for dipEthBt and the individual chromophores of le4pEthBt are the same, and this assumption was used to calculate the @EEE values reported for these compounds in Table 10. The kd values reported for le4pEthBt and its model compounds, diBth and dipEthBt, are much larger than one would predict from VP or pEtVP. While some of this increase in kd may be due to 6-hydrogen abstraction and charge transfer quenching, neither of these routes of decay can adequately explain the large kd values observed, indicating rates of self-quenching 76 of 1.4 x 107 sec"1 for le4pEthBt, 2.5 x 107 sec”1 for DiBth and 4.5 x 106 sec-1 for dipEthBt. The explanation must therefore involve selfequenching. This phenomenon will be discussed in more detail later. From an energy transfer point of view all that is necessary is that the model systems used contain the same ratio of decay to reaction as the equivalent chromophore in the unsymmetric diketone and for this reason the symmetric diketones were chosen as models. The phosphorescence spectra for these ketones indicate that the energy difference between the two chromophores of le4pEthBt should be about 1.6 kcal. If the triplet states involved equilibrate then the ratio of x values should be .07. The observed ratio of x values for le4pEthBt is 0.61. If the system were equilibrated the energy difference required to obtain this ratio would be .30 kcal. It is worth remembering that this system may not be equilibrated and lack of equilibrium would cause the x values to shift towards the ratio of the chromophores' extinction coefficients. The rates of energy transfer between the chromophores of le4pEthBt were estimated to be 8.0 x 107 sec.1 and 6.4 x 107 sec”1 from the lAT values (Figure 21). .The ratio of these rates of 0.8 and would require an energy difference of 0.13 kcal. When the rates of energy transfer are estimated using the product quantum yields: 77 12 ' O 640 l 0 0.01 0.02 0.03 0.04 Quencher Concentration Figure 21: Predicted Stern-Volmer Plots for the 1Bz4pEthBt System ( 0 observed for acetophenone; 0 observed for pEtAc; ——8 x 107 sec—l, 6.4 x 107 sec-l;--—-l.6 x 108 sec-l, 1.28 x 108 sec-l; —-— 4 x 107 sec-l, 3.2 x 107 sec-1; 8 -l 7 -1 -~— 1.0 x 10 sec , 5.1 x 10 sec ) 78 rates of 1.0 x 108 and 5 x 107 are obtained. The ratio of these rates is 0.50 requiring an energy difference between chromophores of 0.42 kcal. It is obvious that there is a large amount of error in these rates of energy transfer but the difference in energy between the states responsible for phosphorescence at liquid nitrogen temperatures and the difference in energy between the states involved in energy transfer at room temperature are quite different. C. The YvalPhOBP and yAcPhOBP Systems The difference in the values of l/T for the two chromophores of yValPhOBP is greater than the experimental error in their determination. The lifetimes observed for the individual chromophores are displaced from their average towards the lifetimes of model systems containing only the single chromophore being considered. This indicates that the Norrish type II reactions and decay paths of the chromophores are causing considerable disruption of the equilibrium between the triplet states of the two chromophores. 7CNPhOBP is a better model for the rate of y-hydrogen abstraction by the benzoyl chromophore of these systems than yPhOBP because the resonance and inductive effects of the cyano group should be similar to those of a ketone carbonyl group. If it is used as a model one would predict a kd of 3.8 x 106 sec-1 for this chromophore. A more exact prediction can be made by using the kY values-of 79 7CNPhOBP and yPhOBP to produce a Hammett plot. The op value for a cyano group is .66.80 This predicts a p value of -.95 for this system. Since an aliphatic acyl group has a GP value of .5080 one would predict that kY for an ideal model system should be 6.1 x 107 sec"1 d should be 2.7 x 106 sec-1 for the benzoyl and that k chromophore in 7ValPhOBP. The various rates applicable to the yAcPhOBP system may be estimated in a similar manner. The maximum disappearance quantum yield for the anisoyl chromophore was estimated using the percent cyclobutanol observed in the Norrish type II reaction of pMeOVP.59 Similar data for yPhOBP57 was used to estimate the maximum disappearance quantum yields of the benzoyl chromophores. The rates of self-quenching for yValPhOBP can be estimated by adding the expected quantum yields of decay for the benzoyl and toluoyl chromophores, 0.19 and 0.22 Max II Since 110 percent of the light is accounted for in this to the observed ¢ values for these chromophores. manner it is unlikely that any self-quenching occurs in this system. A similar analysis of the yAcPhOBP system also accounts for all the light absorbed in the system. The phosphorescence spectra of yValPhOBP and yAcPhOBP and their model ketones indicate triplet energy differences between chromophores of 2.5 and 2.8 kcal respectively. 80 These systems are clearly not equilibrated. The energy differences do, however, predict ratios of energy transfer rate constants of 0.016 and 0.0096 for these systems. Since reversible energy transfer obviously occurs in both systems the spectroscopic energy differences obtained at liquid nitrogen temperature must be much larger than the energy differences between the states involved in energy transfer at room temperature. When one uses the l/T values to estimate the rates of energy transfer for the yValPhOBP system (Figure 22) rates of 1.2 x 108 sec"1 and 3.0 x 107 sec“1 are obtained. The ratio of these rate constants predicts an energy difference of 0.66 kcal for the two chromophores in this system. If one uses the quantum yields of product formation to estimate these rates values of 1.5 x 108 sec-1 and 1.3 x 107 sec"1 are obtained indicating an energy difference of 0.87 kcal between the two chromophores in this system. If one assumes the ket rate ratio of 0.10 predicted by Wagner and Nakahiralo for benzoyl and anisoyl chromo- phores and that l/T' for the anisoyl chromophore of yAcPhOBP is equal to kd for pMeOVP then the rates of energy transfer calculated from the observed l/T value for yAcPhOBP are 2.0 x 108 and 2.0 x 107 M-lsec-l. These predict an energy difference of 1.4 kcal. 81 / / 9 I / I, I'. 6 F ,/ , l I 1’ .l'. , . I, ff '9’ l ’1' l I” 1",. I I..-’-" 5 - [III/u". [Iii/.I.’-:" I I. ’.i' ./°,” l” ..’ ’5. a,” I". ’I” /-" .’.I/’ ”I”’..l’. 4 ’,/’:,.’ O -/”../’”":”’ :- .° .%.’ , ’1 a (pa ’1’:,/"’ III/z" . ”1' , ’ ¢ ’/’..I ’.::’/,- ”"’.’.- ’2’ ,.”'".,' .1" ,2/ x75,'./ I’./. ,1'3".”v",-" 3 » ’ " ’6’") fr" II}/ I”..’ .’/ ,. I .flfi’./ 2 . l 0 4 J LL 1 L 0 0.002 0.004 0.006 0.008 0.01 Quencher Concentration Figure 22: Predicted Stern-Volmer Plots for the yValPhOBP System ( 0 observed for Ac; 0 observed for propene; —- 1.2 x 108 sec-1, 3.0 x 107 sec-l; ---6.0 x 107 sec-l, 1.5 x 107 sec-l; —-- 2.4 x 108 sec-1, 6.0 x 107 sec-l; ---- 1.3 x 108 sec-1, 7 -l 8 -1 7 -l 2.7 x 10 sec --~ 1.1 x 10 sec , 3.3 x 10 sec ) ‘0 82 D. The 6ValPhOVP and dAcPhOVP Systems The relative difference in the values of l/T for the two chromophores of 6ValPhOVP is greater than it was for yValPhOBP. This indicates that there is an even greater disruption of the equilibrium between the triplet states of the two chromophores. The maximum dissappearance quantum yield for the anisoyl chromophore was again estimated from the reported 59 Similar data for S-methoxy-l- behavior of pMeOVP. phenylpentan-l-one57 was used to estimate the maximum dissappearance quantum yields of the benzoyl chromophores in both 5ValPhOVP and 6AcPhOVP. The same types of arguments that were used to predict the inductive and resonance effects of the carbonyl group on kY for the yValPhOBP system can be used for these systems. The Hammett equation gives a p of -.69 for this system which allows one to predict a model kY of 9.5 x 106 sec'l. The rates of self-quenching for 6ValPhOVP and 6AcPhOVP are predicted to be 0.0 and 2 x 10.5 by the same methods used for yValPhOBP. In both cases this is insignificant when compared to the l/T values for these diketones. The phosphorescence spectra of 6Va1PhOVP and 6AcPhOVP and their appropriate model ketones indicate triplet energy differences between chromophores of 2.5 and 2.8 kcal respectively. These energy differences predict ratios of rates of energy transfer of .016 and .0096. As in 83 the yValPhOBP and yAcPhOBP systems reversible energy transfer obviously occurs in both systems so the spectroscopic energy differences obtained at liquid nitrogen temperature must be much larger than the energy differences between the states involved in energy transfer at room temperature. Since l/T for pMeOAc is not known it is impossible to estimate energy transfer rate constants for 6AcPhOVP. If one assumes the ket rate ratio is 0.10 for benzoyl and anisoyl chromophores as predicted by Wagner and 10 Nakahira and that 1/1' for the anisoyl chromophore is equal to k for pMeOVP one finds that it is mathemati- d cally impossible to obtain rates for energy transfer equations 13 and 16. Either l/T' for the anisoyl chromo- phore is smaller than kd for pMeOVP or the ratio of rates of energy transfer is smaller. It is, however, possible to estimate rates of energy transfer for the 5Va1PhOVP system. When one uses the l/T values to estimate the rates of energy transfer for the 6ValPhOVP system 8 and 1.0 x 107 are (Figure 22) rates of 1.0 x 10 obtained. The ratio of these rate constants predicts an energy difference of 1.4 kcal for the two chromo- phores in this system. If one uses the quantum yields of product formation to estimate these rates, values of 1.5 x 108 sec-1 and 3 x 107 sec"1 are obtained indicating an energy difference of 0.97 kcal between the two chromophores. 84 'I A {I .l.’ I I, o .0 ’ .{I / , I, .' I 12 ” ’/ n 'I 0 ['4 .ol” 1;" .I’I’ .’.-’ .”I 1]. r .{I I z I, .' I I'- ’ ’ ' . .’ I (I ’1’ L- /"” 9’1." -' - ' I I I/ I I o' i- .. ,’ _.’ AI, [’1 I 9 P '(I 0", I "’ I.” .I’ I: 3’! 'l ’ n!’ I.:’ I. . ’; " ¢ 0 2” ’I .I 0 ’0:0’ - 8 ' I -”' I' , ’x’ ¢ ; I", I, o’.’” .6 ’I’ I .CI’ II I, -’v , I}. ’0’ I .5” . ’ . 1. ' I I ’0'] I 7 " .l’. ’ .6” ’ I, ’l l 1” / I I .‘I/ / .’ / O, I, [I I I ‘7. I.’ I ’I’ I I /’ I," 6 - #77 ’ 4’ ’ ('1' i.” I I)" ’ I .‘I .' ’I .ll’ .’ ” ’ 1,5” ”I I, ’ ' I ‘ II / I 5 " / . , II . / I 15” .a' ’ .l 4;, ’0 l.”l’ /./ "I;’/ .l’o” ’I’ 4 . .s’.’ ..l’ .. ,”,,/,/ - .’I’.' 1’ / I 3” I o. {.1 I ,- l .l I”.. 3 5 I.) ,’/' i,’ I ,. ' a I _/ C l’.’ V a ’ 'I 2 b '. .l /’ I’. 0 .002 .004 .006 .008 Quencher Concentration Figure 23: Predicted Stern-Volmer Plots for the GValPhOVP System ( OAc, 6ValPhOVP; O Pr, 6ValPhOVP; — 1.0 x 108 sec-l, 1.0 x 107 sec-1;-u--9.l x 107 sec-1, 1.1 x 107 sec-l; -- 1.1 x 108 sec-1, 8.9 x 106 sec-l;'~--2.0 x 108 sec-1, 2.0 x 107 sec'1,~-~ 5.0 x 108 sec-l, 5.0 x 106 sec-l) 85 E. The le4AnBt System The basic results for this system were reported by Wagner and Nakahira.lo In this dissertation I have analyzed their results using the same approaches I have used with my compounds. When Wagner and Nakahiralo originally reported their results for this diketone they assumed that the l/T values for the two chromophores in the system were the same within experimental error and that the triplet states of le4AnBt equilibrate. The l/T values reported deviate from their average by 20% which is at least twice the normal error in a l/T value determined by Stern-Volmer kinetics. For this reason I have decided to consider this system as a non- equilibrating system. The phosphorescence spectra of the appropriate model systems for the le4AnBt system indicate that the energy difference between chromophores at liquid nitrogen temperature is 2.5 kcal. This energy difference would predict a ratio of rates of energy transfer of 0.016. Since reversible energy transfer obviously occurs in this system, the energy difference between chromophores at room temperature must be considerably less than that observed at liquid nitrogen temperature. If one uses the reported l/T values to determine the rates of energy transfer for this system one obtains values of 0.9 x 107 and 1.0 x 107 sec"1 which would indicate practically no energy difference between the two chromophores. If one 86 uses the quantum yields of product formation to determine the rates of energy transfer for the le4AnBt system values of 1.0 x 108 and 5 x 106 sec-1 are obtained. These rates predict an energy difference of about 1.09 kcal for the two chromophores in this system. This second value is not very different from the 1.4 kcal value Wagner and Nakahiralo predict for this diketone. F. Energy Transfer Conclusions The most obvious observation which can be made from the mixed chromophore systems discussed above is that the energy difference observed for the chromophores at liquid nitrogen temperature is much greater than the energy differences implied by their room temperature photochemistry. This observation, in addition to the fact that decreasing the temperature decreases the Boltzman population of higher energy states for a given energy separation, explains why phosphorescence is only observed from the lowest energy chromophore for the mixed chromophore systems discussed in this dissertation. Comparison of the relative rates of energy transfer between benzoyl and toluoyl chromophores and benzoyl and anisoyl chromophores show a definite increase in the rate of back energy transfer in the benzoyl/toluoyl systems over that observed in benzoyl/anisoyl systems. This is an indication that a decrease in the energy separation between chromophores increases the rate of 87 the endothermic energy transfer. If the rate of eXo- thermic energy transfer decreases as the energies of the two chromophores approach each other, this decrease is not observed for the system discussed in this dissertation. The experimental errors in the rates of energy transfer may be too large to detect any subtle changes. Comparison of the rates of energy transfer in the GValPhVP system to those obtained in the le4pEthBt system and the rates of energy transfer in the yValPhOBP or 6ValPhOVP systems to those obtained in the le4AnBt system indicate that the rate of endothermic energy transfer is slowed slightly when the anisoyl or toluoyl chromophore is positioned with its carbonyl closer to the benzoyl chromophore. This is probably a result of the anisoyl and toluoyl chromOphores having w+n* lowest triplets resulting in the center of excitation residing in the phenyl ring of these chromophores and hence being farther away from the benzoyl chromophore when the carbonyl group is turned in. Unfortunately the observed effect is not much greater than the experimental error in the determinations of the energy transfer rates. The only clear cut systems in which the effects of increased separation between chromophores might be observed are the yValPhOBP and GValPhOVP systems. While it looks like the rates of energy transfer may decrease slightly when the additional methylene group is placed 88 between them, the observed change is less than the errors in the rates of energy transfer determined for these systems and is no more than that observed by simply turning one of the chromophores around. This is somewhat different than half an order of magnitude change in rate of energy transfer observed for the styryl/benzoyl system at somewhat smaller separations25 but a combination of the relatively large experimental errors involved in both sets of energy transfer rates and the greater separation between the chromophores in my systems adequately explains these differences. The results reported in this dissertation indicate that is is possible to obtain actual rates for energy transfer in intramolecular systems where reversible energy transfer occurs. Future work in the area should involve systems in which the separation between chromophores is greater and perhaps in which the energy separation between the chromophores is smaller. It would also be interesting to do temperature studies on some of the mixed chromophore systems reported in this dissertation in order to determine activation parameters for the various processes involved and to check the applicability of Boltzmann's Law to these systems. III. Self-Quenching Studies The derived kinetic parameters for the self-quenching systems discussed in this dissertation and their model systems are presented in Table 12. As can be seen from 89 mm mocmuommu Eoum mosam> .6 mHocmusnoHo>o moa mofismmm .n o ha.o o h.o o o o o o o vm.o ma.o no.0 mv.o mv.o om.o m.m o m.m m.N o m.m o o o h.a h.a o.H o.H HIomwwloex anwomhloax HIothloax x x umo x mGGOHoxwo oflHumEE>m How muouoEmumm oauocfix ©o>flumo mm mocoumumu OH monouomou maosmusnoHoao wo.o mm.c m.H o.~ m.~H m.~a m.m m.m o.a o.H mao.o mmo.c om.o oq.c ov.o m.H v.5 «.5 o.HH m.m h.m m.m ~.m ~.m o o 5.H o o c.a Homhnoax alothchx comp x umm x pxa -cHx Scum monam> .0 Scum mosam> .o wma mmasmmm .m m~.o mm>0¢2d mm.o m>umd o.a mm> o.H cm>w=onumoc o.H cmmmzonumo> mo.o oumcmflc nam.o pmumumdflu 8mm.o umumflo mm.o umnmwo o.H umumflc o unnmao o uZmzfloumflp mHQ meG mcouox "NH manna 90 the kSq values reported in Table 10 the only unsymmetric diketones in which significant self-quenching occurs are le4pEthBt and le4AnBt. It is possible to estimate kY for these ketones from assorted model ketones and the closeness of these estimates to the observed kY values provides a check on the accuracy of the values of l/T and ¢g2§ obtained. Since diBzdiMeMt and diBzEt do not contain y-hydrogens, kY must be zero. The kY for diBzEt can be predicted using the Hammett plot for rates of y-hydrogen abstraction by phenyl alkyl ketones substituted in the 6 position developed by Wagner and Kemppainen.57 This plot has a slope of -l.85 and the GI value for a 81 carbonyl group is 0.28. These data_predict a value of 3.8 x 107 sec"1 for kY which is easily within experimental error of the value actually observed. One obtains an estimate of kY for diBth of 7.6 x 107 sec-1 using a p value of -0.76 for the inductive effects of e-substituents on y-hydrogen abstraction. The rate of y-hydrogen abstraction for diBzPr cannot be estimated in this manner because the rates of y-hydrogen abstraction for compounds substituted in the y-hydrogen position do not form a good Hammett plot. If one assumes that the reactivity of a triplet phenyl ketone should be affected the same way by ring substituents regardless of what substituents are attached to the 5 carbon then one can estimate kY for dipEthBt and diAnBt using valerophenones 91 with similar ring substituents. The values obtained in this manner are 4 x 106 sec"1 and 1.8 x 105 sec"1 respectively. The close match of the kY values to the kYeSt values for these ketones is evidence that the low maximum quantum yields observed for these ketones are not the result of a failure to totally solvate the biradical intermediates, but indicate instead some type of quenching of the triplet state of the carbonyl. External quenching by impurities in the solvents and additives used can be ruled out since these same solvents and additives do not quench other systems with longer triplet lifetimes. It would take about 50% quenching impurity in diBth and about 80% quenching impurity in diBth to account for the quenching observed. For these reasons it must be assumed that the quenching observed is a true self-quenching phenomenon. The ultraviolet spectra of diBzdiMeMt and diBzEt show considerably greater extinction coefficients at 313 nm than would be predicted for two benzoyl chromo- phores acting independently. Some of the enhancement observed in the case of diBzdiMeMt may be due to the a methyl groups but much of it is probably due to ground state interactions of the carbonyl groups in these di- ketones. It is also interesting that the phosphorescence spectrum of diBzdiMeMt shows only a single set of lines, presumably from the conformationally relaxed triplet 92 while the dual phosphorescence spectra of diBzEt shows much more emission from the relaxed triplet state than is observed for the other symmetric diketones studied. This probably arises from increased restrictions on bond rotations in the relatively hard 2-methyltetrahydro- furan glass as the chain length between chromophores increases. Several more general statements may be made about the self~quenching observed for these diketones. Since no self-quenching is observed for 7CarbOMeBP and 5CarbOMeVP the self-quenching phenomenon must arise from some property of the second carbonyl group which is greatly diminished in esters. The absence of self- quenching in diBzPr indicates that the self-quenching requires a geometry which is not available to this ketone. It is possible that one such conformation is one in which both carbonyl groups are in the same plane with their oxygens approaching each other. Such a conformation requires that the a carbons attached to the carbonyl carbon also lie in the same plane resulting in considerable eclipsing of the various hydrogens in the system. The addition of methylene groups between the two chromophores which can account for the increase in the rate of self-quenching observed in diBzEt and diBth. In diBzEt this conformation is somewhat eclipsed but no more unstable than the conformation of a 1,5-hexa- diene necessary for a Cope rearrangement. The increase 93 in extinction coefficient observed for this diketone is in fact an indication of a ground state interaction of the carbonyls. The resulting preassociation of the chromophores might aid in attaining the proposed conformation for self-quenching. DiBzdiMeMt is interesting because, in addition to a fairly rapid triplet decay rate, its intersystem crossing yield is less than one. Apparently a decay route is available to the singlet which is faster than the rate of intersystem crossing. The ab initio calculations which will be discussed in the next section predict a weak singlet excimer for conformations of formaldehyde pairs which are similar to the orientation of this molecule in which.the carbonyls are adjacent. Such an excimer would be enhanced by the addition of phenyl groups to the carbonyls and may therefore account for the intersystem crossing yield observed in this ketone. The rapid decay of the triplet state of this ketone is probably self-quenching, the geometry proposed for self-quenching being readily obtainable. It should be noted however, that no adequate model system is available to estimate the natural decay of these chromophores. Such a system would have to account for the inductive and resonance effects of the benzoyl group on the excited carbonyl as well as the effects of a,a-dimethyl substitution. 94 The effects of ring substituents on the rates of self-quenching indicate that it is a phenomenon of n+n* triplets and not of w+w* triplets. This observation is exactly the opposite of the observation made by Singer and coworkers53 for the intermolecular self- quenching of substituted benzophenones. They speculate that the self-quenching they observed was a charge‘ transfer phenomenon involving the excited carbonyl and the ground state phenyl ring of an adjacent benzophenone. Such intramolecular charge transfer quenching was observed in the GValPhOBP and YvalPhOBP systems and perhaps even in the 6ValPhVP system discussed in the energy transfer section of this discussion, but is clearly not a function of the second carbonyl group in these systems since it can be adequately predicted by model systems which do not contain a second carbonyl group. The larger rates of self-quenching observed for n+n* triplets in my systems are probably due to the greater electrophilicity of an n+w* triplet when compared to a n+n* triplet. If this is the case self-quenching in my systems may simply be charge transfer quenching of the triplet state of the excited chromophore by the non-bonding electron pairs on the carbonyl oxygen of the second chromophore. Future work in the area of self-quenching of phenyl ketones should include investigations of systems where the chromophores are separated by more methylenes, at 95 least to the point where the rate of self—quenching begins to drop off significantly, and also studies involving a larger number of ring substituents. It would also be interesting to study aliphatic diketones to see if a similar self-quenching phenomenon occurs. IV. Quantum Mechanical Calculations The self-quenching discussed above prompted a more theoretical study of possible carbonyl excimer formation. The results of this study were reported in the results section of this dissertation and are discussed in this section. They are not directly applicable to the photo- chemical results presented in this dissertation due to the necessity of using greatly simplified systems to carry out the type of calculations required. They do, however, offer some insight into the types of phenomena which may be occurring, particularly in the diBzdiMeMt and diBzEt systems. Experimental results indicate that excimers formed by encounters between excited and ground state aliphatic ketones do not exist at detectable levels.71 Physically this corresponds to the absence of any substantial minimum in the potential surfaces described by the excited states of the encounter pairs (Figure 24). A minimum may exist in an excited state surface but must be too shallow with respect to the thermal energy in solution to allow the existence of a well defined, long lived excimer. 96 L 18 °S A. No Excimer Formation R __ 1s _1 __1T °S B. Excimer Formation R Figure 24: Excited State Interactions 97 The theoretical predictions for formaldehyde excimers appear to bear this out. In the case of the head—to-tail orientation a stabilization of .1004 kcal/mole is observed for the 3Bg state at 4 A and .3515 kcal/mole for the 1B9 state at 3 A. In addition a stabilization of 1.32 kcal/mole is observed in the ground state complex. Ground state aggregates of acetone have been observed.82 The stabilization energies in the excited states represent reductions in the ground state stabilization energy and at room temperature do not have sufficient binding energy to exist for any length of time. The following scheme depicts the kinetics of such systems: k Aggregate formation A + A —a—+ (A°--A)° (A---A) -22——+ (AH-A)l Aggregate excitation A ——EX—» Al Monomer excitation 1 kdif 1 . . . (A---A) -————» A + A Aggregate dissoc1ation k A1 -——£—+ A° + hv Fluorescence k. A1 -—$§2+ A3 Intersystem crossing k A34———E—+ A° + hv Phosphorescence (A---A)l —————» (A---A) + hv or A Aggregate decay k (A---A)1 << k (A---A)1 d dif For the head-to-head orientation the 3A2 state shows no stabilization while the singlet state has a shallow 0 dip of .1129 kcal/mole at 3 A and a ground state 0 stabilization of .05021 kcal/mole at 4 A. Since the 98 ground state stabilization is small with respect to thermal energy at room temperature no ground state aggregate should exist. Under these circumstances, a true excimer can exist as depicted by the following scheme: A + A -————+ (A°--A) + A hv A1 1 kex l A +A+—]?—-+ (A'°°A) -ex k Al—£—+A°+hv k. Al isc A3 In the case of formaldehyde and, by intuitive extension, acetone, k-ex would be expected to be approximately equal to kex so that the complex would be little more than an encounter complex and observable properties such as fluorescence would not be affected noticeably.83 Addition of a phenyl group to the system would be expected to stabilize such an exciplex but the rate of intersystem crossing in phenyl ketones is relatively fast, probably fast enough so that exciplex formation could not successfully compete with it. It should be noted, however, that the separation between the excited 'states and ground state decreases with proximity in all cases (Table 9). While this means very little in bimolecular systems since the probability of two molecules approaching each other this closely is low due to obvious energetic disadvantages, in intramolecular systems the 99 energy in the ground state should show less of an increase as the carbonyls are brought together increasing the chance of excimer formation or at least an easy route back to the ground state for a reasonably long lived excited state. EXPERIMENTAL 1. Chemicals A. Ketones 1. General Comments While the syntheses of the ketones were varied, all ketones were identified by their spectroscopic characteristics. The instruments used were as follows: infrared spectra, Perkin-Elmer 237B Grating Infrared Spectrometer; proton spectra, Varian T-60 NMR Spectrometer; carbon-13 spectra, Varian CFT-20 NMR Spectrometer; mass spectra, Hitachi EMU-6 Mass Spectrometer. All chemical shifts are reported in ppm downfield from tetramethylsilane. The purity of solid ketones was estimated from their physical appearance and melting point range obtained on a Thomas-Hoover Unimelt Capillary Melting Point Apparatus. The reported melting points are uncorrected. Ketones which were sufficiently volatile were checked for purity by phase chromatography. Futher proof of purity is available in the constancy of their photochemical properties. 100 101 2. 2,2-Dimethyl-l,3-diphenylpropan-l,3-dione (DiBzdiMeMt) This diketone was prepared by Smedley's procedure84 in 25% yield from 25g of dimethyl malonic acid (Aldrich Chemical Company) by treatment with excess thionyl chloride followed by Friedel-Crafts acylation with excess benzene and aluminum chloride. It was then purified by several recrystallizations from ethanol to yield white crystals. mp 97.0 - 97.25°, dec. (lit. 99°84 1 )3 ir (CHC13) 1670cm- ; pmr (CDC13) 1.6ppm (s,6H,CH3), 7.2 (m,6H,Ph), 7.7 (m,4H,Ph); cmr (00013) 25.14ppm, 59.32, 128.36, 128.95, 132.69, 135.50, 200.01; ms, m/e 252 (2.2%), 147 (.5%), n+w* 105 (100%), 77 (41.5%), UV, AMax,¢H 320nm. 3. 1,4-Dipheny1butane-l,4-dione (DiBzEt) This diketone was prepared by the photolysis of 450 ml of acetophenone catalyzed by phenol on silica 85 gel in 5% yield by Becker's procedure and purified by three recrystallizations from ethanol to yield white crystals. mp 144.9 - 145.1° (lit. 144 - 145085 l ): ir (CHClB) l690cm- ; pmr (cuc13) 3.39ppm (s,4H,CH2), 7.35 (m,6H,Ph), 7.90 (m,4H,Ph); cmr (00013) 32.43ppm, 127.9, 128.38, 132.91, 136.66, 198.4; ms, m/e 239 (1.8%), 238 (8.7%), 221 (1.1%), 220 (6.0%), 134 (1.1%), 133 (10.1%), 115 (2.7%). 106 (8.1%), 105 (100%), 99 (2.1%), 91 (1.0%), 86 (1.8%), n+n* 78 (3.9%), 77 (40.6%); UV AMax,¢H 313nm. 102 4. 1,5-Diphenylpentane-l,5-dione (DiBzPr) This diketone was prepared by Donna Nezich by the Friedel-Crafts acylation of benzene86 with 17.09 of glutaryl chloride (Aldrich Chemical Company) and 44g of aluminum chloride in 85% yield and purified by six recrystallizations from ethanol/water to yield white crystals, mp 64.0 - 64.25° (lit. 66 - 67°87); ir (CHC13) 1690cm‘1; pmr (c0013) 2.15ppm (t,2H,j=3Hz,CH2), 3.00 (t,4H,j=3Hz,CH2), 7.35 (m,6H,Ph), 7.80 (m,4H,Ph); cmr (CDC13) 18.45ppm, 37.24, 127.69, 128.23, 132.69, 136.61, 199.36; ms, m/e 253 (3%), 252 (14%), 147 (5%), 133 (11%). +nt n 120 (19%). 106 (100%): 77 (41%), UV AMax.¢H 5. l,6-Diphenylhexane-1,6-dione (DiBth) 317nm. This diketone was prepared by the Friedel-Crafts acylation of benzene88 with 18.39 of adipoyl chloride (Aldrich Chemical Company) and 40g of aluminum chloride in 95% yield and purified by four recrystallizations from ethanol/water to yield white crystals, mp 105.9 - 106.0°C (lit. 106 - 108°89); ir (CHC13) 1.80ppm (m,4H,CH2), 2.95 (t,4H,j=3H2,CH2), 7.35 (m,6H,Ph), 7.80 (m,4H,Ph); cmr (CDC13) 23.52ppm, 37.97, 127.63, 128.18, 132.54, 136.63, 199.45; ms, m/e 266 (2%), 248 (16.3%), 247 (19.7%), 147 (21%), 146 (74.8%), 120 (55.8%), 106 (16.3%), 105 (57.8%), 77 (100%); UV 1§§lt¢fi 319nm. 6. 1,7-Diphenylheptane-1,7-dione (DiBth) This diketone was prepared by the Friedel-Crafts acylation of benzene86 with 33h of pimeloyl chloride 103 (prepared by the treatment of pimelic acid (Aldrich Chemical Company) with a 2.2 molar excess of thionyl chloride) and 62.49 of aluminum chloride in 90% yield and purified by five recrystallizations from ethanol to yield white crystals, mp 65.5 - 66.0° (lit. 67 - 68°89); ir (CHC13) 1690cm'l ; pmr (CDC13) l.7ppm (m,10H,CH2), 2.95 (t,4H,j=3Hz,CH2), 7.35 (m,6H,Ph), 7.80 (m,4H,Ph); cmr 23.54ppm, 28.39, 37.71, 127.45, 128.00, 132.31, 136.38, 199.44; ms, m/e 280 (2.2%), 175 (6.8%), 162 (6.8%), 161 (56.9%), 160 (11.1%), 146 (10.3%), 144 (5.3%), 133 (14.4%), 130 (7.4%), 121 (10.2%), 120 (100%), 106 (27.9%), 105 (69.2%); 0v 13§§f¢fi 318nm. 7. 1,6-Bis-(4-ethylphenyl)-hexane-1,6-dione (DipEthBt) 40.09 of aluminum chloride and 250ml of ethylbenzene were cooled to ice water temperature and 18.39 of adipoyl chloride (Aldrich Chemical Company) was added dropwise with stirring. The mixture was stirred for three hours and then poured onto about 5009 of ice. The layers were separated and the water layer extracted with three 100ml portions of ether. The combined organic layers were washed with three 100ml portions of water, three 100ml portions of saturated NaHCO solution, three 100ml 3 portions of water, and one 100ml portion of saturated NaCl solution and then dried over magnesium sulfate. The solvents were removed to yield 52.39 of solid which was shown by pmr to be mostly ethylbenzene. One 104 recrystallization from ethanol/water yielded 8.09 of crude product, mp 92 - 93°, 25% yield. Two additional recrystallizations from ethanol/water yielded pure white, crystalline product, mp 96.0 - 96.25°; ir (CHC13) 1685cm‘1; pmr (CDC13) 1.22ppm (t,6H,j=4Hz,CH3), 1.80 (m,4H,CH2), 2.70 (q,4H,j=4Hz,CH2), 2.99 (t,4H,j=3Hz,CH2), 7.18 (d,4H,j=4Hz,Ph), 7.82 (d,4H,j=4Hz,Ph); cmr 14.71ppm, 23.70, 28.48, 37.87, 127.61, 127.85, 134.42, 149.29, 199.06; ms, m/e 322 (1.3%), 175 (7.5%), 174 (25.0%), 161 (5.2%), 149 (6.0%), 148 (48.3%), 145 (13.0%), 134 (11.8%), 133 (100.0%), 105 (18.8%), 79 (15.7%), 77 (13.0%); n+n* Max,¢H 8. l-(4'-Ethylphenyl)-6-pheny1hexane-l,6-dione UV 1 318nm. (le4pEthBt) a. Methyl 5-Benzoylva1erate This ester was prepared by Friedel-Crafts acylation of excess benzene with the 41.89 of acid chloride of adipic acid monomethyl ester (prepared by treating adipic acid monomethyl ester (Aldrich Chemical Company) with excess thionyl chloride at room temperature) and 86.09 of aluminum chloride at room temperature in 94% yield by Kemppainen's procedure.70 The crude product was used for the next step of the synthesis. ir (neat 1750cm-1, 1 1690cm- , 16006m'1, 1450cm'1; pmr (0014) 1.6ppm (m,4H, CH2), 2.2 (t,ZH,j=3Hz,CH2), 2.75 (t,2H,j=3Hz,CH2), 3.40 (s,3H,CO CH3), 7.1 (m,3H,Ph), 7.75 (m,2H,Ph). 2 105 b. S-Benzoylvaleric acid The acid was prepared in 52% yield by refluxing Methyl 5-Benzoylvalerate with an excess of 6% aqueous sodium hydroxide for 2 hours and neutralizing the resulting salt with concentrated hydrochloric acid. Recrystallization from ethanol/water gave a solid of mp 70 - 73° (lit. 77 - 78°90 1 1 ); ir (CHC13) 3100cm‘ , 1690cm‘1; pmr (00013) 1.80ppm (broad), 1720cm- (m,4H,CH2), 2.2 (t,2H,j=3Hz,CH2), 2.95 (t,2H,j=3Hz,CH2), 7.4 (m,3H,Ph), 7.9 (m,3H,Ph), 7.9 (m,2H,Ph), 11 (s,1H,COOH). c. S-Benzoylvaleroyl chloride 9.29 of 5-benzoylvaleric acid and 5.859 of thionyl chloride were stirred together at room temperature for two hours and then the excess thionyl chloride was removed at aspirator pressure to give 9.09 (90%) of 1, 1690cm-l brown solid, ir (neat) l810cm- ; pmr (CC14) l.7ppm (m,4H,CH2), 2.95 (m,4H,CH2), 7.3 (m,3H,Ph), 7.8 (m,2H,Ph). d. 1-(4'-Ethylphenyl)-6-phenylhexan-l,6—dione (le4pEthBt) 16.59 of aluminum chloride and 20ml of methylene chloride were placed in a flask and cooled with an ice water bath. 9.09 of S-Benzoylvaleroyl chloride dissolved in 15ml of methylene chloride were added dropwise, then 5.09 of ethyl benzene dissolved in 15ml of methylene chloride was added dropwise. The mixture was stirred for 2.5 hours and then poured onto about 2009 of ice. 106 The resulting mixture was extracted with three 100ml portions of benzene. The combined benzene extracts were washed with three 100ml portions of distilled water, three 100ml portions of saturated sodium bicarbonate solution, three 100ml portions of water and one 100ml portion of saturated sodium chloride solution and then dried over potassium carbonate. The solvent was removed on a rotary evaporator to give 8.89 (75%) of brown solid. Six recrystallizations from ethanol/ water gave a white, crystalline solid, mp 77.5 - 78.0°; ir (cc14) 1690cm'l, 1605em‘1, 1450cm‘1, 1410cm'1, 1 1 1, 1180czm'l 1360cm7 , 1270cm' , 1220cm' ; pmr (0014) 1.2ppm (t,3H,j=4Hz,CH3), 1.75 (m,4H,CH2), 2.65 (q,2H,j=4Hz,CH2), 2.85 (m,4H,CH2), 6.9 - 7.9 (m,9H,Ph); ms, m/e 294 (1.48%), 276 (2.96%), 174 (15.5%), 148 (44.4%), 146 (17.0%), 134 (11.8%), 133 (100%), 105 (55.6%), UV Agglf¢fi 317nm. 9. 1,5-Dipheny1pentan-1-one (5PhVP) a . Method A 1) Acetophenone cyclohexylimine 1209 of acetophenone (Eastman Organic Chemicals), 1009 of cyclohexylamine (Aldrich Chemical Company), 112ml of benzene and 0.5m1 of concentrated H2804 were placed in a flask equipped with a Dean-Stark trap and refluxed until 21ml of H20 had been collected (21 hours). The benzene was removed on a rotary evaporator and then the resulting oil was distilled under reduced pressure. After removal of the unreacted starting materials, 68.39 107 (34%) of the desired product was collected at bp. 112 - l 1 , 2850cm‘ , , 1280cm'1, 765cm'l, 695cm'1; 115° (0.25 torr); ir (neat) 3050cm'1, 29zscm' l 1, 1450cm’l 1640cm' , 1580cm' pmr (CC14) 1.6ppm (m,11H,CH2), 2.1 (s,3H,CH3), 7.1 (m, 3H,Ph), 7.6 (m,2H,Ph). 2) 1,5-Dipheny1pentan-l-one (0PhVP) The procedure used is similar to one used by Stork and Dowd.91 4.689 of magnesium and 50ml of tetrahydro- furan (THF) (freshly distilled from lithium aluminum hydride) were placed in a flame dried flask under nitrogen. A small portion of 21.969 of bromoethane was added and Grignard formation initiated. 300ml of THF (freshly distilled from lithium aluminum hydride) was added, then the rest of the bromoethane was added at a rate which maintained a gently reflux. The mixture was refluxed for one hour. 32.379 of acetophenone cyclohexylimine was then added dropwise and the mixture refluxed for two hours. 35.359 of 1-bromo-3-pheny1propane (Aldrich Chemical Company) was then added dropwise and refluxed for 24 hours. 200ml of 6M hydrochloric acid solution was then added dropwise and the mixture allowed to stir overnight. The resulting mixture was extracted with three 200ml portions of benzene and the combined benzene extracts were washed with three 200ml portions of 6 M hydrochloric acid, three 200ml portions of distilled water, three 200ml portions of saturated aqueous sodium bicarbonate solution, two 200ml portions 108 of distilled water, and one 200ml portion of saturated aqueous sodium chloride solution and were then dried over sodium sulfate. The benzene was removed with a rotary evaporator to give 44.59 of oil. This oil was fractionally distilled at reduced pressure, 10.39 (23%) of the product being collected at bp 133 - 142° (.025 torr). b. Method B One pint of freshly opened dimethylsulfoxide was placed in a flame dried flask under nitrogen. 139 of 50% Nan/mineral oil dispersion was washed with benzene to remove the mineral oil and placed in the flask. 309 of acetophenone was added dropwise over about an hour and the resulting solution was stirred for an additional two hours. 509 of 1-bromo-3-pheny1propane was then added dropwise over about an hour and the mixture was stirred for 24 hours. 200ml of water was added and the mixture stirred overnight. The mixture was extracted with three 300ml portions of ether. The combined ether extracts were washed with three 300ml portions of distilled water, three 300ml portions of 3 M hydrochloric acid solution, three 300ml portions of distilled water, three 300ml portions of saturated aqueous sodium bicar— bonate, two 300ml portions of distilled water and one 300ml portion of saturated aqueous sodium chloride solution and then was dried over sodium sulfate. The ether was removed on a rotary evaporator to give 58.69 109 of oil. This oil was fractionally distilled distilled at reduced pressure, 10.79 of product being collected at bp 130 - 150° (.01 torr). c. Purification Crude GPhVP was recrystallized six times from ethanol/ water to give white crystals, mp 44.25 - 44.50° (lit. 92 1, 1450cm-1; pmr (CDC13) 47° ), ir (0014) 1695cm‘ 1.65ppm (m,4H,CH2), 2.60 (t,2H,j=3Hz,CHz), 3.05 (t,2H,j=3Hz,CH2), 7.1 (m,5H,Ph), 7.3 (m,3H,Ph), 7.8 (m,2H,Ph); cmr (CDC13) 23.70ppm, 30.75, 35.51, 38.03, 125.42, 127.69, 128.23, 132.54, 136.82, 141.93, 199.74; ms, m/e 238 (12.6%), 148 (12.9%), 133 (58.2%), 120 (97.9%), 118 (16.5%), 117 (15.5%), 105 (100%), 91 (62.2%), 77 (75.5%); UV A§§£f¢fi 319nm. 10. 1-Phenyl-5-(4'-acetylpheny1)-pentan-1-one (0AcPhVP) 15.29 of aluminum chloride and 25ml of methylene chloride were placed in a flask and cooled in an ice water bath. 3.69 of acetyl chloride dissolved in 10ml of methylene was added dropwise and stirred for 30 minutes. 9.09 of 1,5-dipheny1pentan-1-one dissolved in 10ml of methylene chloride was added dropwise and stirred for two hours at room temperature. The resulting mixture was poured onto about 1509 of ice. Enough additional water was added to dissolve the inorganic salts. The mixture was extracted with three 100ml portions of ether. The combined ether extracts were washed with 110 three 100ml portions of distilled water, three 100ml portions of saturated aqueous sodium bicarbonate solution, two 100ml portions of distilled water, and one 100ml portion of saturated aqueous sodium chloride solution and then dried over sodium sulfate. The ether was removed on a rotary evaporator to give 10.09 (94%) of solid. Four recrystallizations from methanol/water gave white crystals, mp 64.25 - 64.50°; ir (CHC13) 1 1 1 1 1 1695cm‘ , 1610cm’ , 1450cm‘ , 1420cm‘ , 1370cm‘ , 1275c:m"l ; pmr (CDC13) l.75ppm (m,4H,CH2), 2.50 (s,3H, CH3), 2.65 (t,2H,j=3Hz,CH2), 2.95 (t,2H,j=3Hz,CH2), 7.25 (m,5H,Ph), 7.80 (m,4H,Ph); cmr (CDC13) 23.55ppm, 26.13, 30.28, 35.44, 37.87, 127.64, 128.23, 132.63, 134.79, 136.69, 147.73, 199.53; ms, m/e 281 (8.42%), 280 (41.3%), 162 (25.6%), 160 (100%), 133 (13.8%), 120 (20.4%), 105 (88%), 77 (52%); UV Afi§lt¢fi 317nm. 11. l-Phenyl-S-(4'-valery1phenyl)-pentan-1-one (0ValPhVP) This compound was prepared in the same manner as the 0AcPhVP except valeryl chloride was used. 9.09 of 1,5-diphenylpentan-1-one gave 12.29 (100%) of crude product. Five recrystallizations from methanol gave white crystals, mp 60.0 - 60.25°; ir (CC14) 1695cm-1, 1, 1450cm'l 1610cm' ; pmr (cc14) 1.0ppm (t,3H,j=3Hz,CH3), 1.7 (m,8H,CH2), 2.9 (m,4H,CH2), 7.25 (m,5H,Ph), 7.8 (m,4H,Ph); cmr (CDC13) 13.68ppm, 22.23, 23.62, 26.36, 30.36, 35.52, 37.95, 127.76, 128.01, 128.31, 132.69, 111 134.81, 136.76, 147.49, 199.68, 199.84; ms, m/e 323 (8.12%), 322 (31.5%), 280 (3.94%), 266 (20.4%), 265 (100%), 203 (25.36%), 202 (93.88%), 167 (12.8%), 161 (15.3%), 160 (30.0%), 147 (10.1%), 133 (12.3%), 131 (11.1%), 120 (12.2%), 105 (71.1%), 91 (16.4%), 90 (13 9%) '77 (59 5%)- uv 1n*"* 320 " ' ' ' Max,¢H nm‘ 12. l-(4'Ethylphenyl)-pentan-l-one (pEtVP) This ketone was prepared in 86% yield by the Friedel- Crafts acylation86 of excess ethyl benzene with 14.59 of valeryl chloride and 26.69 of aluminum chloride, and then purified by repeated distillation at reduced pressure to give a colorless oil, bp 93.0 - 93.1° (.35 torr) (lit. bp 169 - 171° (32 torr)93). The purity of this ketone was checked by vpc on an 8' x 1/8" 4% QF-l, 1% Carbowax 20 M on Chromosorb G column with a carrier gas flow rate of 30m/min at 115° C. The ketone contains 99.15% of the para isomer, 0.84% of the ortho isomer and 0.01% of an unknown contaminate. The spectral data for this ketone are as follows: 1, 1605cm-l; pmr (CC14) 1.2ppm (m,10H, ir (neat) 1690cm- CH2,CH3), 2.65 (m,4H,CH2), 7.0 (d,2H,Ph), 7.65 (d,2H,Ph); cmr (CDC13) 13.60ppm, 14.85, 22.21, 26.35, 28.62, 37.88, 127.69, 238.00, 134.64, 149.36, 199.75; ms, m/e 190 (1.3%), 161 (13.8%), 148 (37.7%), 134 (10.4%), 133 (100%), n+w* 105 (15.1%); UV AMax,¢H 309nm. 112 13. 4-Phenoxy-1-pheny1butan-1-one (yPhOBP) The synthesis of this ketone is similar to a number of syntheses carried out by Kalir and Balderman.94 125ml of dimethylsulfoxide and 3.169 of dry sodium hydride were placed in a flask under a nitrogen atmosphere. 15.29 of O-(tetrahydropyran-Z-yl)-mandelonitri1e (prepared by Michael J. Thomas by Kalir and Balderman's procedure94) was added dropwise and the mixture stirred for 22 hours. .15.09 of 1-bromo-3-phenoxypropane (Aldrich Chemical Company) was added and the reaction stirred for 2 hours. The reaction mixture was then poured onto 250ml of 10% hydrochloric acid ice water and stirred for 5 hours. The resulting mixture was then extracted with three 100ml portions of ether and the combined ether extracts were washed with three 100ml portions of distilled water, three 100ml portions of saturated aqueous sodium bicarbonate solution, two 100ml portions of distilled water, and one 100ml portion of saturated aqueous sodium chloride solution. The ether was removed with a rotary evaporator and the resulting oil was refluxed for two hours in 15% aqueous hydrochloric acid. The mixture was cooled and extracted with three 100ml portions of ether. The combined ether extracts were washed with three 100ml portions of distilled water, three 100ml portions of saturated aqueous sodium bicarbonate, two 100ml portions of distilled water and one 100ml portion of saturated aqueous sodium chloride 113 solution and then was dried over NaZSO4. The ether was removed with a rotary evaporator and the resulting oil was stirred overnight with 200ml water, 109 sodium bicarbonate, 59 potassium carbonate, and 0.59 sodium hydroxide. The resulting mixture was extracted with three 100ml portions ether and the combined ether extracts washed with three 100ml portions of distilled water and one 100ml portion of saturated aqueous sodium chloride, then dried over sodium sulfate. The ether was removed with a rotary evaporator to give 16.59 (97%) of pale yellow crystals. Three recrystallizations from ethanol gave white crystals, mp 61.75 - 62.0° C (lit. 62.5 - 63.5°57); ir (cnc13) 169sem'1 l l 1 , 1603cm’ , 1500cm' , 1475cm' , 1450cm‘1, pmr (00013) 2.25ppm (q,2H,j=3Hz,CH2), 3.15 (t,2H,j=3Hz,CH2), 4.05 (t,2H,j=3Hz,CH2), 7.0 (m, 8H,Ph), 7.85 (m,2H,Ph); cmr (CDC13) 23.53ppm, 34.57, 66.50, 114.21, 120.36, 127.68, 128.23, 129.13, 132.66, 136.63, 158.59, 199.07; ms, m/e 240 (2.3%), 148 (9%), 147 (100%), 120 (10%), 106 (5.7%), 105 (58%); UV 43;;768 316nm. l4. 4-(4-Acety1phenoxy)-l-pheny1butan-1-one (yAcPhOBP) This diketone was prepared in 76% yield by the same procedure as 6AcPhVP using 8.09 of yPhOBP, 3.29 of acetyl chloride and 13.59 of aluminum chloride and then purified by three recrystallizations from ethanol to give white 1 1 crystals, mp 91.75 - 92.0°; ir (CHC13) 1690cm- , 1605cm- 114 1510cm"l , 1365cm‘1; pmr (cuc13) 2.20ppm (t,2H,j=3Hz,CH2), 2.40 (s,3H,CH3), 3.1 (t,2H,j=3Hz,CH2), 4.0 (t,2H,j=3Hz, CH2), 6.75 (d,2H,j=4Hz,Ph), 7.35 (m,3H,Ph), 7.75 (m,4H, Ph); cmr (CDC13) 23.47ppm, 26.12, 34.51, 67.06, 113.99, 127.83, 128.46, 130.21, 130.41, 132.96, 135.64, 162.71, 196.46, 199.04; ms, m/e 282 (2%), 163 (5%), 149 (2%), 148 (11%), 147 (100%), 121 (5%), 120 (5%), 106 (5%), 105 (66%); UV 1§;::¢H 316nm. 15. 4-(4'-Va1ery1phenoxy)-1-pheny1butan-1-one (yValPhOBP) This diketone was prepared in 87% yield by the . same procedure as 6AcPhVP using 7.79 of yPhOBP, 4.79 of valeryl chloride and 13.09 of aluminum chloride and then purified by two recrystallizations from ethanol to yield white crystals, mp 115.75 - 116.0°; ir (CHClB) 1690cm'1, 1 1, 1450cm“l 1603cm‘ , lslocm' ; pmr (c0c13) 1.0ppm (t,3H, j=3Hz,CH3), 1.6 (m,4H,CH2), 2.25 (q,2H,j=3Hz,CH2), 2.85 (t,2H,j=3Hz,CH2), 3.15 (t,2H,j=3Hz,CH2), 4.10 (t,2H,j=3Hz, CH2), 6.85 (d,2H, j=4Hz,Ph), 7.35 (m,3H,Ph), 7.85 (m,4H, Ph); cmr (c0c13) 13.71ppm, 22.30, 23.42, 26.54, 34.49, 37.76, 67.01, 113.94, 127.80, 128.41, 130.09, 132.93, 136.66, 162.43, 198.91, 199.05; ms, m/e 324 (0.1%), 282 (0.23%), 268 (0.28%), 206 (0.51%), 205 (3.6%), 191 (0.20%), 186 (0.36%), 178 (0.23%), 177 (1.42%), 149 (10.3%), 148 (100%), 121 (5.6%), 120 (2.3%), 106 (3.6%), 105 (39%); n+n* UV AMax,¢H 316nm. 115 16. 4-(4'-Cyanophenoxy)-l-phenylbutan-1-one (chPhOBP) a. 4-Chloro-1-pheny1butan-1-one This ketone was prepared in 95% yield by the Friedel- Crafts acylation86 of excess benzene with 35.39 of 4- chloro—butyryl chloride (Aldrich Chemical Company) and 36.09 of aluminum chloride at ice water bath temperature. Distillation of the crude material gave a 70% yield of pure product, bp 100 - 103° (0.55 torr) (lit. 126 - 129° 1 1, 1450cm-1, (5 torr)96), ir (neat) 1690cm‘ , 1600cm' 1225cm‘1; pmr (cc14) 2.15ppm (q,2H,j=3Hz,CH2), 3.0 (t, 2H,j=3Hz,CH2), 3.55 (t,2H,j=3Hz,CH2), 7.35 (m,3H,Ph), 7.80 (m,2H,Ph). b. 4-Iodo-1-pheny1butan-1-one 43.19 of 4—chloro-1-pheny1butan-1-one, 759 of sodium iodide and 500ml of butan-Z-one were placed in a flask and refluxed for two hours. The butan-Z-one was then removed on a rotary evaporator. The resulting sludge was dissolved in 500ml of ether and 500ml of distilled water. The layers were separated, and the ether layer was washed with three 300ml portions of distilled water and one 300ml portion of saturated aqueous sodium chloride solution and then dried over sodium sulfate. The ether was removed with a rotary evaporator to give 50.79 (78%) 1 1 l 1 of oil, ir (neat) 1690cm5 , 1450cm’ , 1230cm' , 745cm" , 1 695cm- ; pmr (00013) 2.2ppm (m,2H,CH2), 3.0 (t,2H,j=3Hz, CH2), 3.3 (t,2H,j=3Hz,CH2), 7.35 (m,3H,Ph), 7.85 (m,2H,Ph). 116 c. Ethylene Glycol Ketal of 4-Iodo-1-pheny1- butan-l-one 50.79 of 4-Iodo-1-pheny1butan-l-one, 50ml of ethylene glycol, 0.59 of toluenesulfonic acid and 500ml of benzene were placed in a flask equipped with a Dean-Stark trap and refluxed for 24 hours. The resulting mixture was washed with three 300ml portions of distilled water and one 300ml portion of saturated aqueous sodium chloride solution and then was dried over sodium sulfate. The benzene was removed with a rotary evaporator to give 54.59 (93%) of oil, pmr (CDC13) 1.9ppm (t,2H,j=2Hz,CH2), 3.0-4.0 (m,8H,CH2), 7.25 (m,5H,Ph). d. 4-(4'-Cyanophenoxy)-1-pheny1butan-1-one (VCNPhOBP) 300ml of dimethylsulfoxide and4.69 of sodium were placed in a flame dried flask under nitrogen. 23.89 of 4-cyanophenol (Aldrich Chemical Company) dissolved in 300ml of dimethylsulfoxide was added dropwise and then stirred until all the sodium had reacted. 54.49 of the ethylene glycol ketal of 4-iodo-l-phenylbutan-l-one dissolved in 300ml of dimethylsulfoxide was then added over about a 6 hour period and let stir for an additional 24 hours. the mixture was then heated to 60° for one hour. 500ml of distilled water was added and the resulting mixture was extracted with four 500ml portions of ether. The combined ether extracts were washed with three 500ml portions of distilled water, 117 three 500ml portions of 3 M aqueous hydrochloric acid, three 500ml portions of distilled water, three 500ml portions of 10% aqueous sodium hydroxide solution, two 500ml portions of distilled water, and one 500ml portion of saturated aqueous sodium chloride solution and then dried over sodium sulfate. The ether was removed on a rotary evaporator to give 33.39 (73%) of light brown solid. Two recrystallizations from ethanol gave a white crystalline solid, mp 117.0 - 1 1 1 117.25°; ir (CHC13) 2210cm‘ , 1690cmT , 1515cm‘ , 1, 1175cm'1 1260cm7 ; pmr (CDC13) 2.2ppm (q,2H,j=3Hz,CH2), 3.15 (t,2H,j=3Hz,CH2), 4.05 (t,2H,j=3Hz,CHz), 6.75 (d,2H,j=4Hz,Ph), 7.35 (m,5H,Ph), 7.8 (m,2H,Ph); cmr (CDC13) 23.16ppm, 34.25, 67.12, 103.57, 114.94, 118.91, 127.66, 128.33, 132.88, 133.63, 136.48, 161.88, 198.81; ms, m/e 265 (0.5%), 148 (10%), 147 (100%), 120 (12%), 106 (4%), 105 (44%), 77 (22%); UV 232::0H 316nm. l7. 5-Phenoxy-1-phenylpentan-l-one (5PhOVP) a. Method A 1) l-Phenylcyclopentanol This alcohol was prepared in 90% yield, by a method 90 similar to Fieser's, from 60.09 of cyclopentanone and phenyl Grignard prepared from 20.89 of magnesium and 118 135.09 of bromobenzene in ether. It was not purified before use in the next step of the reaction sequence; 1 1, 1450cm'1; ir (neat) 3400cm- (broad), 1500cm- pmr (CDC13) 1.95ppm (m,10H,CH2), 2.6 (m,1H,CH), 3.0 (s,1H,OH), 7.2 (m,5H,Ph). 2) 5-Chloro-1-phenylpentan-1-one This ketone was prepared by a method similar to that 96 1150m1 of commercial household of Wilt and Hill. bleach (5.25% sodium hypochlorite, 94.75% "inert ingredients"), 80ml of carbon tetrachloride and 92ml of glacial acetic acid were placed in a flask and cooled to 15°. 57.59 of 1-phenylcyclopentanol was added dropwise and stirred for three hours. The mixture was extracted with four 200ml portions of carbon tetrachloride and the combined carbon tetrachloride extracts washed with three 200ml portions of distilled water, three 200ml portions of saturated aqueous sodium bicarbonate solution, three 200ml portions of distilled water, and one 200ml portion of saturated sodium chloride solution and then dried over sodium sulfate. Nitrogen was bubbled through the resulting solution while it was irradiated for three hours with a 250 watt sunlamp. The carbon tetrachloride was then removed with a rotary evaporator to give 63.09 of brown solid which contained 65% of the desired product by pmr (59% yield). Repeated recrystallization from hexane gave 20.89 (30%) of light brown solid, mp 40 - 45° (lit. 49 - 50°97); ir (neat) l690cm‘l, 1600cm’l, 1450cm'1; 119 pmr (CDC13) 1.9ppm (m,4H,CH2), 3.0 (t,2H,j=3Hz,CH2), 3.55 (t,2H,j=3Hz,CH2), 7.45 (m,3H,Ph), 7.85 (m,2H,Ph). 3) 5-Iodo-l-pheny1pentan-l-one This ketone was prepared in 75% yield by the Finklestein Reaction from 50.09 of S-chloro-l-phenyl- pentan-l-one and 285.69 of sodium iodide in acetone following the procedures described by J. H. Sedon.98 1 1 1, 1210cm51; ir (0014) 1700cm' , 1601cm‘ , 1451cm' pmr (CDC13) 1.85ppm (m,4H,CH2), 3.0 (m,4H,CH2), 7.35 (m,3H,Ph), 7.80 (m,3H,Ph). 4) 5-Phenoxy-l-pheny1pentan-l-one 500ml of dimethylsulfoxide and 8.29 of sodium were placed in a flame dried flask under nitrogen. 41.89 of phenol dissolved in 250ml of dimethylsulfoxide was added dropwise and the mixture stirred until all of the sodium had reacted. 64.09 of S-Iodo-1-phenylpentan-1-one dissolved in 250ml of dimethylsulfoxide was added drop- wise. The reaction mixture was heated to 60° and kept there one hour then allowed to cool to room temperature and stirred overnight. 175ml of 3 M aqueous hydrochloric acid was added followed by 300ml of distilled water. The resulting mixture was extracted with four 300ml portions of ether. The combined ether layers were washed with three 200ml portions of distilled water, three 200ml portions of 1 M aqueous sodium hydroxide solution, three 300ml portions of distilled water, and one 300ml portion of saturated aqueous sodium chloride solution and then 120 dried over sodium sulfate. The ether was removed on a rotary evaporator to give 45.89 of dark brown oil whose pmr showed it to be a complex mixture of products. The mixture was refluxed for two hours with 600ml of xylene and 71.09 of pyrollidine. It was then washed with three 300ml portions of 6 M aqueous hydrochloric acid, three 300ml portions of distilled water, three 200ml portions of 1 M aqueous sodium hydroxide solution, two 300ml portions of distilled water, and one 300ml portion of saturated aqueous sodium chloride solution and then dried over sodium sulfate. The xylene was removed with a rotary evaporator to give 30.29 of brown oil. A pmr spectrum of this oil showed that the starting iodide had been removed but it was still a very complex mixture. It was chromatographed through 3 pounds of alumina using continuously varying solvent mixtures ranging from hexane to ethylacetate. 11.79 (21%) of the desired product was collected in the chloroform fraction; it solidified upon removal of the chloroform. b. Method B 1) 5-Phenoxy-l-phenylpentan-1-one The desired ketone was prepared in 39% yield from 24.79 of O-(tetrahydropyran-Z-yl)-mandelonitri1e and 259 of l-bromo-4-phenoxy-butane following the procedure used for yPhOBP. 121 c. Purification Three recrystallizations from ethanol gave white crystals, mp 68.75 - 69.0° c; ir (CHC13) 1690cm‘1, 1 1, 1450cm’l 1603cm‘ , 1500cm‘1, 1475cm' ; pmr (c0c13) 1.95ppm (m,4H,CH2), 3.0 (t,2H,j=3Hz,CH2), 3.95 (t,2H, j=3Hz,CH2), 6.85 (d,2H,j=4Hz,Ph), 7.20 (m,5H,Ph), 7.85 (m,2H,Ph); cmr (CDC13) 20.74ppm, 28.63, 37.87, 67.28, 114.31, 120.41, 127.84, 128.38, 129.18, 132.70, 136.84, 158.82, 199.59; ms, m/e 254 (2%), 162 (9.7%), 161 (74%), 131 (12.6%), 106 (8%), 105 (100%), 94 (12.6%), 91 (11.5%), 78 (6.9%), 77 (54%); UV lgglt¢fi 318nm. 18. 5-(4'-Acety1phenoxy)-l-phenylpentan-1-one (6AcPhOVP) This diketone was prepared in 98% yield from 5.09 of 6PhOVP, 1.59 of acetyl chloride and 8.09 of aluminum chloride by the same procedure used to prepare 5AcPhVP. It was recrystallized seven times from ethanol to give white crystals, mp 125.25 - 125.50°; ir (CHC13) 1685cm’1, 1 1, 1365cm"l 1603cm‘ , 1515cm' , 1175cm‘1; pmr (cuc13) 1.9ppm (m,4H,CH2), 2.5 (s,3a,ca3), 3.0 (m,2H,CH2), 4.0 (t,2H, j=3Hz,CH2), 6.75 (d,2H,j=5Hz,Ph), 7.35 (m,3H,Ph), 7.8 (m,4H,Ph); cmr (coc13) 20.56ppm, 26.05, 28.40, 37.72, 67.68, 113.93, 127.79, 128.40, 130.05, 130.36, 132.81, 136.73, 162.71, 196.47, 199.54; ms, m/e 296 (3%), 162 (12%), 161 (100%), 149 (6%), 120 (10%), 106 (9%), 105 n+w* (99%), 77 (35%); UV AMax,¢H 317nm. 122 19. 5-(4'-Va1erylphenoxy)-1-phenylpentan-1-one (5Va1PhOVP) This dione was prepared in 82% yield from 5.09 of 0PhOVP, 4.09 valeryl chloride, and 8.09 of aluminum chloride by the same procedure used to prepare 5AcPhVP. Six recrystallizations from ethanol gave a white crystalline material, mp 111.75 - 112.0°; ir (CHC13) l l 1, ll75cm-l; pmr (CDC13) 1690cm' , 1600cm‘ , 1515cm' 1.0ppm (t,3H,j=3Hz,CH3), 1.2 - 2.0 (m,8H,CH2), 3.0 (m,4H,CH2), 4.1 (t,2H,j=3Hz,CH2), 6.85 (d,2H,j=5Hz,Ph), 7.35 (m,3H,Ph), 7.85 (m,4H,Ph); cmr (CDC13) 13.77ppm, 20.61, 22.33, 26.59, 28.48, 37.80, 67.69, 113.84, 128.37, 129.94, 130.06, 132.79, 136.75, 162.53, 199.02, 199.63; ms, m/e 338 (3%), 296 (4%), 281 (3%), 177 (5%), 162 (13%), 161 (100%), 147 (6%), 121 (11%), 120 (4%), 106 (4%), 105 (43%), 77 (17%), UV 13;;t0H 317nm. 20. 5-(4'-Cyanophenoxy)-1-pheny1pentan-l-one (GCNPhOVP) This ketone was prepared in 70% yield from 11.09 of 5-iodo-l-phenylpentan-l-one and 9.089 of 4-cyanophenol by the procedure described for the preparation of 7CNPhOBP. Six recrystallizations from ethanol gave a white crystalline material, mp 96.25 - 96.50°; ir (CHC13) 1 1 l 1 1 2215cm' , 1690cm' , 1605cm' , 1515cm' , 1175cm' ; pmr (CDC13) 1.9ppm (m,4H,CH2), 3.05 (t,2H,j=3Hz,CH2), 4.0 (t,2H,j-3Hz,CH2), 6.85 (d,2H,j=5Hz,Ph), 7.40 (m,5H,Ph), 7.85 (m,2H,Ph); cmr (CDC13) 20.46ppm, 28.32, 37.67, 103.57, 123 114.99, 127.75, 128.06, 128.36, 132.81, 133.68, 136.72, 162.05, 199.41; ms m/e 279 (1.4%), 162 (39.6%), 161 (100%), 160 (4.8%), 143 (5.2%), 133 (12.3%), 132 (8.6%), 120 (7.9%), 119 (13.0%), 106 (38.2%), 105 (100%), 104 (7.4%), 103 (6.7%), 102 (20.1%); UV 132E7¢H 318nm. 21. 4-Ethylacetophenone (pEtAc) This ketone was prepared in 92% yield by the Friedel- Crafts acylation86 of excess ethyl benzene with 9.49 of acetyl chloride and 26.69 of aluminum chloride. Repeated distillation gave a material of bp 50.5 - 51.0° (0.1 torr) (lit. 125° (20 torr)99). Analysis by gas chromatography using the same column used to check the purity of pEtVP at 120° showed it to be 99.07% of para and .85% ortho. 1 1 1 1 1 , 1605cm‘ , 1420cm’ , 1360cm‘ , 1275cm’ , 1 ir (neat) 1690cm' 1 1, 830cm- 1180cm- , 955cm- ; pmr (CC14) 1.25ppm (t,3H, j=4Hz,CH3), 2.45 (s,3H,CH3), 2.65 (q,2H,j=4Hz,CH2), 7.10 (d,2H,j=4Hz,Ph), 7.70 (d,2H,j=4Hz,Ph); ms, m/e 148 (24.5%), 134 (10.1%), 133 (100%), 105 (29.4%), 103 (10.3%); 90 (5.5%), 89 (5.7%), 79 (18.1%), 78 (5.7%), 77 (20.6%); Uv 1E2§t¢fl 309nm. 22. Acetophenone (Ac) This ketone was obtained from Eastman Chemical Company and purified by A. E. Puchalski by repeated distillation through a spinning band column. 23. l-Phenylpentan-l-one (VP) This ketone was prepared by either E. J. Siebert or M. J. Thomas by the Friedel-Crafts acylation of benzene 124 with valeryl chloride and purified by repeated distillation at reduced pressure. 24. Benzophenone This ketone was obtained from Aldrich Chemical Company and purified by W. B. Mueller by repeated recrystallization from ethanol. 25. 4-Methoxyacetophenone (pMeOAc) This ketone was obtained from Aldrich Chemical Company and had been purified by H. N. Schott by repeated recrystallization from petroleum ether. 26. 1-(4-Methoxyphenyl)-pentan-l-one (pMeOVP) This ketone was prepared by Friedel-Crafts acylation of anisoyl with valeroylchloride and purified by repeated recrystallization from pentane/methanol by H. N. Schott. B. Internal Standards 1. Tetradecane Tetradecane was obtained from Columbia Organic Chemicals and purified by washing with sulfuric acid then distilling (bp 119 - 120° (10 torr)) by Dr. Peter J. Wagner. 2. Hexadecane Hexadecane was obtained from Aldrich Chemical Company and purified by washing with sulfuric acid then distilling (bp 146/10 torr) by Dr. Peter J. Wagner. 125 3. Octadecane Octadecane was obtained from Aldrich Chemical Company and purified by recrystallization from ethanol by Dr. Peter J. Wagner. 4. Di-n-ethyl Phthalate This ester was used as received from Aldrich Chemical Company. 5. Di-n-propyl Phthalate This ester was prepared by Fischer esterification of phthalic anhydride with 1-propanol and purified by distillation, bp 128°/1.2 torr. 6. Di-n-Butyl Phthalate This ester was used as received from Aldrich Chemical Company. C. Quenchers 1. 2,5-Dimethylhexa-2,4-diene 2,5-Dimethylhexa-2,4-diene was obtained from Chemical Samples Company and upon sitting in the refrigerator sublimed up aroung the sides of the bottle. This sublimed material was used.68 2. cis-l,3-Pentadiene This diene was used as received from Chemical Samples Company. 3. trans-Stilbene This olefin was used as received from J. T. Baker Company. 126 D. Solvents 1. Benzene The method used to purify benzene was similar to the method used by Kemppainen.69 One gallon of A. C. S. reagent grade benzene obtained either from Fisher Scientific Company, Mallinckrodt Chemical Company, or Drake Brothers Chemical Company, was stirred over several changes of concentrated sulfuric acid (200ml/gal benzene; minimum stirring time per change, one day) until the sulfuric acid no longer discolored. It was then washed with three 300ml portions of distilled water, three 300ml portions of saturated aqueous sodium bicarbonate solution, two 300ml portions of distilled water, and one 300ml portion of saturated aqueous sodium chloride solution and then dried over magnesium sulfate. It was then refluxed over phosphorous pentoxide overnight and distilled through a one meter column packed with stainless steel helices at a rate of about two liters a day. The first and last 750ml portions were discarded. The center cut was distilled a second time through this same column with the first and last 450ml portions being discarded. 2. Pyridine A. C. S. reagent grade pyridine obtained from Fisher Scientific Company, Mallinckrodt Chemical Company, or Drake Brothers Chemical was distilled from barium oxide through a half meter column packed with stainless steel 127 helices. All material boiling below 115° C was discarded along with about a 10% forerun. 3. Dioxane Dioxane was purified by Riddick's technique.loo 1500m1 of Fischer Scientific Company Scintanalyzed grade dioxane was allowed to stand over ferrous sulfate for several weeks. It was then refluxed under nitrogen with 150ml of distilled water and 42ml of concentrated hydrochloric acid overnight. Potassium hydroxide pellets were added at a temperature just below boiling until the pellets maintained their integrity. This mixture was allowed to sit overnight under nitrogen. The dioxane was then decanted from the saturated potassium hydroxide solution and distilled from sodium using a three foot column packed with glass helices. A forerun of about 300ml was discarded and 300ml were left in the distillation pot. The dioxane was then recrystallized from itself three times, discarding about 20% each time. It was then stored frozen. Towards the end of the work presented in this thesis it was determined that distillation through a half meter column packed with stainless steel helices immediately before use was as effective as the above procedure. 4. Ethanol Ethanol was purified by Riddich's Technique.100 One gallon of U. S. P. grade 190 proof ethanol was distilled from 100ml of concentrated sulfuric acid 128 through a one meter column packed with glass helices at a rate of one liter every 24 hours. The first and last 500ml portions were discarded. The middle fraction was then distilled from 609 of potassium hydroxide and 309 of silver nitrate through the same column at the same rate discarding the first and last 10%. 200ml of distilled water was then added tothe middle fraction and the mixture distilled through the same column at the same rate discarding the first and last 10%. 5. Methylcyclohexane Methylcyclohexane was purified by Forster's 101 500ml of Methylcyclohexane (Eastman technique. Chemical Company) was stirred over concentrated sulfuric acid until the acid was no longer discolored. It was then washed with three 100ml portions of distilled water, three 100ml portions of saturated aqueous sodium bicarbonate, three 100ml portions of distilled water, and then dried over magnesium sulfate. It was distilled through a half meter column packed with stainless steel helices. The first and last 20% was discarded. 6. Cyclohexane Cyclohexane (Matheson, Coleman, and Bell, spectrograde) was recrystallized from itself twice. 7. 2-Methyltetrahydrofuran Z-Methyltetrahydrofuran was purified by Gordon and Fords procedure.102 750ml of 2-methyltetrahydrofuran 129 (Aldrich Chemical Company) was distilled from cuprious chloride through a 40cm Vigreoux column, the first and last 20% being discarded, and then from lithium aluminum hydride, the first and last 10% being discarded. 8. Z-Methylbutane Gold label grade 2-methy1butane was used as received from Aldrich Chemical Company. II. Preparative Scale Photolysis of 5-(4-Acety1pheny1)- 1-phenylpental-l-one (6AcPhVP) 2.09 of 5AcPhVP and 450ml of benzene were placed in a flask equipped with a quartz well holding a 450 watt medium pressure mercury lamp. Nitrogen was bubbled through the solution. After six hours of irradiation the diketone was no longer detectable by high pressure liquid chromatography. Removal of the benzene with the aid of a rotary evaporator left 2.09 of oil. This oil was dissolved in a small amount of hexane; the solution was placed on 5.09 of silica gel (Mallinckrodt Silicar CC-7) and the hexane then removed with the aid of a rotary evaporator. This coated silica gel was placed on top of a 2.0cm o.d. column packed with 609 of silica gel (about 50cm in height) and was eluted with the following solvent mixtures: 130 Fraction Solvent total numbers mls 1-20 hexane 200 21-31 10:90 Methylene chloride/hexane 100 32-41 20:80 Methylene chloride/hexane 100 42—51 30:70 Methylene chloride/hexane 100 52-61 40:60 Methylene chloride/hexane 100 62-72 50:50 Methylene chloride/hexane 100 73-82 60:40 Methylene chloride/hexane 100 83-92 70:30 Methylene chloride/hexane 100 93-101 80:20 Methylene chloride/hexane 100 102-112 90:10 Methylene chloride/hexane 100 113-121 Methylene chloride .100 122-131 10:90 Ethylacetate/methylene chloride 100 132-141 20:80 Ethylacetate/methylene chloride 100 142-151 30:70 Ethylacetate/methylene chloride 100 152-160 40:60 Ethylacetate/methylene chloride 100 161-169 50:50 Ethylacetate/methylene chloride 100 170-179 60:40 Ethylacetate/methylene chloride 100 180-189 70:30 Ethylacetate/methylene chloride 100 190-199 80:20 Ethylacetate/methylene chloride 100 200-208 90:10 Ethylacetate/methylene chloride 100 208-214 Ethylacetate 100 The average flow rate was 1.46ml/minute. Analysis by gas chromatography indicated that fractions 55-80 were a mixture of acetophenone and 4-a11y1acetophenone, and that 81-100 were 4-a11ylacetophenone. Fractions 55-80 were combined and analysis indicated that the combined 131 fractions were 39% acetophenone. The solvent was removed from these fractions. Evaporation of fractions 81-100 gave .16759 of white crystals. Before spectra could be taken of this material it became partially insoluble. Fractions 109-138 were analyzed by high pressure liquid chromatography and found to contain a mixture of the starting diketone and cis-l-phenyl—2,4'— acetylphenylmethylcyclobutanol. The combined fractions were evaporated to give 0.04899 which was found to be 57% cyclobutanol. Fractions 139-143 were found to con- tain essentially pure cis-1-phenyl-2,4'-acetylphenyl- methylcyclobutanol. Evaporation of the solvents gave 1 1 1 , l690cm‘ , 1 , 3475cm‘ 1 .20629 of oil, ir (CHCL3) 3580cm‘ 1 1 1 1 1605cm‘ , 1450cm5 , l420cm‘ , 1365cm‘ , 1275cm‘ , 1185cm' ; pmr (CDC13) 1.5ppm (m,1H,CH2), 2.0 (m,2H,CH2), 2.2 (d, lH,j=2Hz,OH), 2.4 (s,3H,CH3), 2.95 (m,4H,CH2), 7.15 (m,3H,Ph), 7.65 (m,2H,Ph); ms, m/e 281 (.813%), 280 (3.66%), 252 (7.72%), 237 (3.66%), 162 (7.59%), 161 (53.7%), 145 (8.81%), 134 (16.5%), 122 (51.2%), 121 (100%), 120 (46.3%), 115 (6.91%), 107 (10.3%), 106 (12.7%), methylene chloride 254 (1.5 x 104). 105 (61.8%); UV AMax Fractions 144-149 were found to contain a 30:70 mixture of cis and trans-cyclobutanols. Evaporation of the solvent gave 0.20569 of oil. Fractions 150-154 were found to contain 0.07419 of oil that was 93% trans-cyclobutanol. 1 1 1 1 1 ir (CHC13) 3580cm‘ , 3450cm' , 1690cm‘ , 1605cm‘ , 1365cm‘ 1 1 1275cm' , 1185cm’ ; pmr (c0013) 1.2 - 3.0 (m,1lH), 132 6.8 - 7.75 (m,9H); ms, m/e 821 (1.21%), 280 (5.1%), 252 (7.7%), 237 (4.2%), 162 (9.7%), 161 (76.1%), 145 (10.6%), 134 (11.0%), 122 (2.7%), 121 (16.4%), 120 (100%), 115 (10.4%), 107 (2.3%), 106 (7.7%), 105 (82.6%); methylene chloride 254 (9 5 x 103) W )‘Max III. Electronic Absorption Spectra Ultraviolet spectra were taken using a Cary Model 17 Spectrophotometer and 1 cm quartz cells. IV. Emission Spectra Phosphorescence spectra were taken with either a Perkin-Elmer MPF-44A Fluorescence Spectrophotometer equipped with a Differential Corrected Spectra Unit and Hitachi Phosphorescence Accessory, or with an Aminco Bowman Spectrophotofluorometer. Spectra were taken at 77° K using a quartz dewar and 5mm quartz tubes. The choppers were used only to assure that the observed total emission was only phosphorescence. V. Photokinetic Data A. General Comments 1. Glassware All glassware used was class A volumetric ware except for syringes used to fill irradiation tubes which were pyrex with chrome plated brass needles. All glassware was cleaned by rinsing with acetone and then distilled water followed by soaking in a 90° distilled water solution of laboratory glassware detergent for 24 hours, repeating the detergent soak, then soaking in distilled 133 water at 90° for four days changing the water daily. 2. Weights A11 weighing was done on Sartorius Model 2403 analytical balance which was accurate to a tenth of a milligram. 3. Irradiation tubes Irradiation tubes were prepared by carefully sizing pyrex culture tubes to an outside diameter of 13.5mm i 0.1mm, cleaning these tubes by the procedure described for glassware and then drawing them out to a uniform length with a neck of 2 to 3 mm diameter. 4. Degassing procedure Irradiation tubes were filled with 3.0ml of the solution to be irradiated with a 5 m1 syringe. Great care was taken to make sure that all tubes for a given run contained exactly the same amount of solution. All samples were degassed by six freeze-pump-thaw cycles on a vacuum line at 5 x 10-4 torr and were then sealed in vacuo. 5. Irradiation lamps Three different irradiation apparati were used during the course of this research. In all cases the light source was a Hanovia 450 watt medium pressure mercury lamp cooled by a quartz immersion well. To assure equal irradiation of the samples and minimize temperature changes during photolysis, these wells were placed inside a merry-go-round apparatus100 with slit 134 widths of 7.0 mm, and the whole apparatus placed inside a large crock filled with distilled water. Two of these apparati contained 1 cm filters consisting of a 0.002 M potassium chromate, 1% potassium carbonate aqueous filter solution to isolate the 3130 A mercury line. One of the 3130 A setups was equipped with a thermostat system capable of maintaining at a temperature of 30.0 r 0.1° C. The other was operated at ambient temperature (17 - 28° C). The third apparatus was equipped with a set of Corning No. 7083 filter to isolate the 3660 A mercury line. This apparatus was operated at ambient temperature. 6. Sample Analysis Samples were generally analyzed for cleavage products or cis - trans isomerization of the quencher by vapor phase chromatography. Several different conditions and instruments were used during the course of this research. The most common conditions are listed in Table 13. All gas chromatographs used were equipped with flame ionization detectors. Internal standards were used for all analyses except cis - trans isomerizations. The response factors for the various internal standards with respect to the acetophenones analyzed are as follows: tetradecane/acetophenone 2.000 hexadecane/acetophenone 2.324 hexadecane/4-ethylacetophenone 1.8514 octadecane/4-ethy1acetophenone 1.9000 135 ocva moanom nmcucoumd smaum> coco ammo: :mcumouod scaum> ocva moauom nomucoumm coaum> cova moauom nmoumouod smaum> coma moanom smoumouo< scaum> coma moauom somuoouod coaum> coma moauom gamumouod coaum> coma moauom cmoumoum¢ smaum> coma moauom zmmuoouod cmaum> usoEsHumca :aE\aEco cas\asm~ oas\asoo cas\asoo sas\a5mm ca8\a5mm cas\asmm oasxasmm cas\asm~ out“ scam mCOauaocoo anomumoumsouao mow coma com com omva ocaa ocva 6mm ocma omca ousum (nomEou =m\a x .o Aomummwu moza .omanmz pause a nuomosohao :0 omumm mm =m\a x .mm m QHOmosouso co osmooum Ahxonumocm>01mc mauulm.m.a wmm o :a mo ofimm .=o\a x .va Aomuoouu mOzo .oonmmz oaomc 0 QuomOEouao so 2 cm xmzonumu «mm.a .anmo mm m :a mo 08mm m :a mm 039m .so\a x .va 3 anemoeowzo so 2 cm xmzonumo am .almo «ca a ca mm mama ..mxa x .oa .ooumowu muzo .oonmmz oaomv 0 nuomoeouno :0 2 cm xosonsmo ma .anmo we CEDHCU COflHflQCOU uma manna a now 136 The response factor for cyclohexane/propene was never determined because cyclohexane is almost always a contaminant in purified benzene. Relative peak areas were determined using either an Infotronics CRS 208 Automatic Digital Integrator or an Infotronics CRS 309 Computing Integrator for Chromatography. Analysis for the various diketones was carried out using a Waters Associates Analytical Liquid Chromatograph Model 202 with Differential U. V. Detector. The conditions used varied greatly and will be reported with the actual data. Di-n-ethyl, Di-n-propyl, and Di-n-Butyl phthalates were used as internal standards. B. Stern-Volmer Plots Solutions for irradiation were normally prepared by making stock ketone solution containing both ketone and internal standard in a 10 ml volumetric flask. 2.0 m1 of this stock solution was then pipetted into a 10 m1 volumetric flask and diluted to be used to make unquenched ketone samples. 1.0 ml of the ketone stock solution was pipetted into a number of 5 m1 volumetric flasks and the desired amount of a stock 2,5-dimethyl— 2,4-hexadiene solution added by use of a graduated pipette and the flasks brought to volume. Irradiation tubes were then filled, degassed, irradiated, and analyzed in the manner previously described. ¢°/¢ was obtained for each quenched solution by dividing the average ratio of the area under the product peak to the area under the 137 internal standard peak for the unquenched tubes by the equivalent ratio for the quenched tubes. ¢°/¢ is plotted versus the concentration of 2,S-dimethyl-Z,4-hexadiene. The error in the slope arises from a combination of the precision with which the unquenched tubes were filled and the accuracy of the dilution of the quencher. Normally a valerophenone (VP) solution was prepared at the same time with the same concentration of internal standard so that the quantum yields for product formation could be determined from the unquenched ketone solution. C. Lewis Base Studies, Maximum Quantum Yields Samples were prepared in the same manner as for Stern-Volmer kinetics except a stock Lewis base solution was used instead of a stock quencher solution. D. Product Quantum Yields, Actinometry Quantum yields were calculated using the following formula: (Prod/Std) _ (4 ) x (absorb. corr.) 4 — TProd/Std)Act. Act. (conc. Std.) (RF) x (conc. Std.) (RF1Act. Act. where RF is the gc detector response factor. The absorbence correction was calculated using the following equation based on Biers Law: 1 - Ta Absorb. Corr. = 1 _ ECt ketone where T = antilog (-elc) 138 It can be demonstrated by simple geometry that the average path length for the irradiation tubes used (1.10 cm inside diameter and slit width .70 cm) is 1.018 cm. Valerophenone (VP) was used as an actinometer for the product quantum yields. Its 4 of acetophenone or propene formation at 0.05 M is .315 and at 0.01 M is .300.60 E. Sensitization Plots, Quantum Yields of Intersystem Crossing For ketones with no photochemistry, lifetimes were obtained by observing their effectiveness as sensitizers for the cis - trans isomerization of either cis-1,3- pentadiene or trans-stilbene. Normally solutions for these studies were prepared by preparing a stock ketone solution 1.0 ml of which was pipetted into several 5 m1 volumetric flasks. A quencher stock solution was prepared and the appropriate amount of this solution pipetted into the flasks containing the ketone solution. Actinometers were prepared by making a solution of the appropriate ketone (acetOphenone for 3130 A, benzophenone for 3660 A) and adding enough quencher stock solution to quench more than 99% of the triplet state. Irradiation tubes were then filled with 3.0 m1 of the appropriate solution and then degassed, irradiated, and analyzed by the procedures described above. Results were analyzed by plotting 9/4. versus l/[quencher]. isomerization 139 (8")ketone [quenCherlketone a/¢isomerization = (B')act. [quencher] act. where a is the photostationary state for the quencher isomerization (a = 0.555 for cis-1,4-pentadiene, and 0.596_for trans-stilbenesa) and B" is the percentage of the newly formed isomer corrected for backreaction as follows:104 8" = B' - B unirradiated quencher 8' = a in (a/(a - % new isomer)) For ketones where products were formed by comparing the efficiency with which they sensitized the cis - trans isomerization of cis-1,3-pentadiene to the efficiency of acetophenone at causing the same isomerization. The solutions for these experiments were prepared by weighing ketone and acetophenone into two separate flasks and pipetting enough quencher stock solution into each to quench 99% of the ketone's reaction. F. Disappearance Yields Solutions for determining disappearance yields were prepared by weighing the amount of ketone required to make the desired concentration into three separate 5.0 ml volumetric flasks and adding 1.0 m1 of a stock solution of the internal standard used to measure one of the cleavage products. Irradiation tubes were filled, degassed, and irradiated as previously described. The irradiated samples were then analyzed by gas chromatography for the cleavage product and the percent conversion to the 140 cleavage product determined as follows: (area prod. peak) [std] (RF) (100%) (area std. peak) [ketone] % conv. C1. = the percent conversion of the ketone was then determined by pipetting 0.5 m1 of irradiated ketone solution and 0.5 m1 of a solution of the appropriate phthalate ester into a vial and analyzing by high pressure liquid chromatography. The same procedure was followed with the unirradiated ketone solution. 'ketone peak area1 - Std peak area . irr. ketone ketone peak area‘ std peak area ' ‘ unirr. ketone % conv ketone = 100% The dissappearance quantum yield is then calculated as follows: ¢ = % conv. ketone x ¢ Dis % conv. to product prod G. Data 1. DiBzdiMeMt Stilbene sensitization data for this diketone indicating a Qisc of 0.70 and-a qu value of 488 M-lsec-1 are presented in Table 14. The dissappearance yield for this ketone was determined to be 0.00 by irradiation of a 0.51 M solution of the diketone in benzene-d6 in a pyrex nmr tube at 313 nm for 184 hours. No change was detectable by either pmr or gc. 141 Table 14: Stilbene Sensitization Data for DiBzdiMeMt oisc = 0.70, qu = 488 M'1sec'1 [Stilbene] cisiiians .596/t+c x10 M 1.34 .336 3.61 1.79 .337 2.71 2.24 .284 2.77 3.58 .233 2.38 4.48 .210 2.08 8.96 .137 1.75 Benzophenone Actinometer (average of 3 tubes) 8.96 .217r.007 [diketone] = 0.0541 M, [benzophenone] = 0.0307 M, benzene solvent, 366 nm, ambient temperature, g.c. condition set 9. 142 2. DiBzEt 1,3-pentadiene sensitization data for this diketone indicating a ¢isc of 1.0 and a qu value of 30013 Mmlsec“l are presented in Table 15. The dissappearance yield for this ketone was determined to be 0.00 by irradiation of a 0.5 M solution of the diketone in benzene-d6 in a pyrex nmr tube at 313 nm for 72 hours. No change was detectable by either pmr or go. 3. DiBzPr All data presented here are not corrected for product quenching. The crude Stern-Volmer data are presented in Table 16. Data used to extrapolate $11 to zero conversion are shown in Table 17. The data used Max 11 are shown in Table 18. The data used to extrapolate to determine the crude 4 with dioxane as a Lewis base ¢¥ix to zero conversion are shown in Table 19. The data used to determine ¢isc are shown in Table 20. The Max data used to determine ¢Dis and ¢Dis are presented in Tables 21 and 22. 4. DiBth The Stern-Volmer data for this diketone are presented in Table 23. The observed kqt value is 80.1 r 2.4 M-lsec-l. The effects of various concentrations of dioxane on 011 Max II 0.54 i .01, and the average QII observed in the Stern- experiments was 0.42 i .02. The data are presented in Table 24. 0 was observed to be Max Volmer and 411 used to determine Qisc are shown in Table 25. The data 143 Table 15: 1,3-Pentadiene Sensitization Data for DiBzEt Run 1 @isc=1.0, qu=297M-lsec-l, lamp intensity=0.00179E/hr [1,3-Pentadiene] trans ‘555/¢c+t x103M ols+trans 3.86 .345 1.89 4.83 .304 1.86 5.80 .302 1.57 6.76 .284 1.47 7.73 .266 1.41 . 8.69 .252 1.35 Acetophenone Actinometer (average of three tubes) 242 .0163:.0002 [diketone] = .0249M, [acetophenone] = .0288M, Benzene solvent, 313nm, 30.0°, g.c. condition set 8. Run 2 ¢isc=l.0, kqt=303M-lsec-l, Lamp intensity=0.00185E/hr [1,3-Pentadiene] trans .555/¢c+t x103M Cls+trans 3.24 .320 2.01 4.32 .288 1.78 5.40 .264 1.61 7.56 .186 1.81 8.64 .216 1.31 Acetophenone Actinometer (average of three tubes) 270 .0114r.0007 [diketone]=.0249M, [acetophenone]=.0288M, benzene solvent, 313nm, 30.0°, g.c. condition set 8. 144 Table 16: Stern-Volmer Data for DiBzPr Run 1 @II=0.176, qu=122M-lsec-l, Lamp intensity=0.00651E/hr [Q] area Ac ¢O/¢ [Ac] x103M area C14 x104M 0.0 .831t.08a 7.81 (7.58% conv) .935 .643 1.29 6.04 1.87 .681 1.22 6.40 3.74 .514 1.62 4.83 5.61 .492 1.69 4.62 7.48 .467 1.77 4.39 9.35 .370 2.25 3.48 VP Actinometer (average from three tubes) 0.0 1.1211.03 10.54 [diketone]=0.0103M(0.0894%T), [VP]=0.0115M(0.279%), [c14]=4.70x10‘4M, benzene solvent; 313nm, 30.0°, g.c. condition set 5. Run 2 011:.192, qu=13lM-lsec-l, Lamp intensity=0.00317E/hr [Q] area Ac ¢°/¢ [Ac] x103M area C14 x104M 0.0 .59or.020a 10.62 (4.89% conv) 0.818 .562 1.05 10.12 1.64 .473 1.24 8.51 3.27 .359 1.65 6.46 4.91 .369 1.60 6.64 6.55 .327 1.80 5.89 8.18 .318 1.85 5.72 VP Actinometer (average from three tubes) 0.0 .860:.020 15.48 [diketone]=0.0217M(0.00618%T), [VP]=0.0239M(0.071%T), [C14]=9.00x10-4M, benzene solvent, 313nm, 30.0°, g.c. condition set 5. a. average from three tubes 145 Table 17: Conversion Dependence of ¢II for DiBzPr Run 1 Diketone VP Actinometer ¢II area Ac [Ac] % conv area Ac [Ac] area C14 x104M area Cl4 x104M .0634 1.72 .875 .119 3.24 .143 .142 3.86 1.96 .174 4.73 .219 .142 3.86 1.96 .174 4.73 .219 .192 5.22 2.65 .269 7.32 .191 .222 6.04 3.07 .309 8.40 .192 .280 7.62 3.87 .336 9.14 .224 [Diketone]=0.0197M(0.00988%T), [VP]=0.0195M(0.115%T), [C14]=0.00136M, benzene solvent, 313nm, 30.0°, g.c. condition set 5. Run 2 Diketone VP Actinometer 011 area Ac [Ac] % conv area Ac [Ac] area Cl4 x104M area C14 x104M .0958 2.30 1.09 .139 3.34 .191 .173 4.15 1.97 .214 5.14 .225 .299 7.18 3.40 .372 8.93 .223 .299 7.18 3.40 .397 9.53 .209 .385 9.24 4.38 .513 12.3 .208 .427 10.02 4.86 .609 14.6 .195 [Diketone]=0.0211M(0.00711%T), [VP]=0.0230M(0.0781%T), [C14]=0.00120M, benzene solvent, 313nm, 30.0°, g.c. condition set 5. 146 Table 18: Effects of Varying Concentrations of Dioxane on ¢II for DiBzPr Run 1 [Dioxane] area Ac [Ac] 411 M area C14 x103M 0.0 0.6151.01 0.659 .179 0.500 0.927 0.994 .270 0.999 1.13 1.21 .330 2.00 1.26 1.35 .367 3.00 1.52 1.63 .442 4.00 1.58 1.69 .460 5.00 1.65 1.77 .477 VP Actinometer (averave from three tubes) 0.0 0.97li.03 1.04 [diketone]=0.00985M(0.0994%T), [VP]=0.0170M(0.152%T), 4 [C14]=5.36x10- M, benzene solvent, 313nm, 30.0°, g.c. condition set 5, lamp intensity=.00136E/hr Run 2 [Dioxane] area Ac [Ac] ¢II M area Cl4 x103M 0.0 0.627i.01a 0.764 .187 1.50 1.16 1.41 .345 2.50 1.39 1.69 .413 3.50 1.58 1.92 .470 4.50 1.43 1.74 .425 6.00 1.45 1.77 .431 7.00 1.12 1.36 .333 VP Actinometer (average from three tubes) 0.0 0.949r.04 1.16 [diketone]=0.00988M(0.0987%T), [VP]=0.0170M(0.152%T), 4M, benzene solvent, 313nm, 30.0°, [C14]=6.09x10 g.c. condition set 5, lamp intensity = .00152E/hr a. average from three tubes 147 Table 19: Conversion Dependence of 4 in 4.5M Dioxane for DiBzPr II Diketone VP Actinometer(no Dioxane) 4II area Ac [Ac] % conv area Ac [Ac] area C14 x104M area C14 .x104M .361 4.40 4.53 .121 1.48 .667 .403 4.92 5.05 .138 1.68 .653 .595 7.26 7.46 .212 2.59 .627 .632 7.71 7.92 .287 3.50 .492 .923 11.26 11.6 .379 4.62 .544 1.16 14.15 14.5 .501 6.11 .517 [diketone]=0.00973M(0.102%T), [VP]=0.00998M(0.331%T), [C14]=6.10x10-4M, 4.5M Dioxane in benzene solvent, 313nm, 30.0°, g.c. condition set 5. Intersystem Crossing Yield for DiBzPr Table 20: Ketone [1,3-pentadiene] cis 4isc M cis+trans 0.0506 M DiBzPr 0.535 .0261 1.02 0.0650 M Ac 0.535 .0266 1.00 Benzene solvent, 313nm, 30.0°, g.c. condition set 8. 148 Table 21. 4Dis for DiBzPr run 1 run 2 [diketone] 0.00985M 0.00988M [tetradecane] 0.000536M 0.000609M [diethylphthalate] 0.0304M 0.0304M avg. ratio, diketone/phthalate , unirradiated 1.658 1.373 irradiated 1.522 1.246 % conv of ketone 8.20% 9.25% area Ac/area Cl4 0.615 0.627 % conv to Ac 6.69% 7.73% % conv ketone/% conv Ac 1.23 1.20 Benzene solvent; 313nm; 30.0°; g.c. condition set 5; h.p.1.c. conditions neutral alumina: 2' x 1/8", 700psig, methylene chloride. Max . Table 22. 4Dis for DlePr [diketone] 0.0101M [tetradecane] 0.00128M [di-n-propyl phthalate] 0.0836 avg. ratio, diketone/phthalate unirradiated 1.02 irradiated 0.771 % conv of ketone 24.4 Area Ac/area Cl4 0.701 % conv to Ac 17.8 % conv ketone/% conv Ac 1.37 4.5M Dioxane in benzene solvent; 313nm; 30.0°; g.c. condition set 5; h.p.1.c. conditions Porasil 1000pft, 2' x 1/8", 50% stroke, 60:40 hexane/methylene chloride 149 Table 23: Stern-Volmer Data for DiBth Run 1 411=0.434, kqt=82.5M‘1sec'1, Lamp intensity=0.00503E/hr [Q] area Ac 4°/4 [Ac] x102M area C14 x104M 0.0 2.62:0.04a 10.1 0.393 2.17 1.22 8.38 0.787 1.66 1.58 6.41 1.57 1.23 2.13 4.75 2.36 0.896 2.92 3.46 3.15 0.748 3.50 2.89 3.93 0.604 4.34 2.33 VP Actinometer (average from three tubes) 0.0 1.28:0.04 4.94 [diketone]=0.0101M(0.0745%T), [VP]=0.00957M(0.346%T), [c141=1.93x10'4m, benzene solvent, 313nm, 30.0°, g.c. condition set 5. Run 2 4II=0.423, qu=77.6, Lamp intensity=0.00761 E/hr [Q] area Ac 4°/4 [Ac] x102M area C14 x104M 0.0 2.68:0.05a 14.9 0.468 1.80 1.49 10.0 0.936 1.47 1.82 8.17 1.87 1.18 2.27 6.56 2.81 0.819 3.28 4.55 3.74 0.678 3.96 3.77 4.68 0.570 4.71 3.17 VP Actinometer (average from three tubes) 0.0 1.48:0.10 [diketone]=0.0101M(0.0745%T), _ -4 g.c. condition set 5. a. average from three tubes 8.23 [VP]=0.0115M(0.279%T), M, benzene solvent, 313nm, 30.0°, 150 Tabel 24: Effects of Varying Concentrations of Dioxane on 4 for DiBth 11 Run 1 [Dioxane] area Ac [Ac] 4 M area C 3 II 14 x10 M 0.0 0.793t0.01a 0.917 0.427 0.500 0.771 0.891 0.415 1.00 0.917 1.06 0.493 2.00 0.874 1.01 0.470 3.00 0.881 1.02 0.474 4.00 0.968 1.11 0.521 5.00 1.00 1.16 0.538 VP Actinometer (average from three tubes) 0.0 0.39010.03 0.451 [diketone]=0.01023M(0.0720%T), [VP]=0.00944M(0.351%T), 4 [C14]=5.78x10- M, benzene solvent, 313nm, 30.0°, g.c. condition set 5, lamp intensity = 0.00154 E/hr Run 2 [Dioxane] area Ac [Ac] 4II M area C 3 14 x10 M 0.0 1.25:0.04a 1.10 0.376 1.5 1.46 1.28 0.439 2.5 1.61 1.41 0.484 3.5 1.67 1.47 0.502 4.5 1.78 1.56 0.535 6.0 1.48 1.30 0.445 7.0 1.50 1.32 0.451 VP Actinometer (average from three tubes) 0.0 0.927:0.06 0.814 [diketone]=0.0101M(0.0745%T), [VP]=0.0177M(0.141%T), _ -4 [0141—4.39x10 M, benzene solvent, 313nm, 30.0°, g.c. condition set 5, lamp intensity = 0.00158 E/hr a. average from three tubes 151 Table 25: Intersystem Crossing Yield for DiBth Ketone [1,3-pentadiene] ‘ cis 4. M cis+trans 15c 0.0496M DiBth 0.985 0.0272 1.02 0.0542M Ac 0.985 0.0267 1.00 Benzene solvent, 313nm, 30.0°, g.c.condition set 8 Table 26: 4 . for DiBth D13 run 1 run 2 [diketone] 0.0102M 0.0101M [tetradecane] 0.000578M 0.000439M [diethylphthalate] 0.0679 0.0629 avg. ratio, diketone/phthalate unirradiated 1.30 1.51 irradiated 1.18 1.33 % conv of ketone 9.23 11.9 area Ac/area Cl4 0.793 1.25 % conv to Ac 8.99 10.9 % conv ketone/% conv Ac 1.03 1.09 Benzene solvent; 313nm; 30.0°; g.c. condition set 5; h.p.1.c. conditions, 2' x 1/8" Corasil x 1000pft, 400psig, methylene chloride 152 . . Max . used to determine ¢Dis and 4Dis are presented in Tables 26 and 27. 5 . DiBth The Stern-Volmer data for this diketone are presented in Table 28. The observed qu value is 45.131.4M-lsec-l. The effects of various concentrations of dioxane and Max pyridine on 4II are presented in Tables 29 and 30. 4II was observed to be 0.55:.03, and the average 4II observed for all experiments was 0.37:.03. 6. DipEtBt The Stern-Volmer data for this diketone are presented in Table 31. The observed qu value is 371110 M-lsec-l. The effects of various concentrations of dioxane on 4II Max II 0.28:.01 and the average 4II observed in the Stern-Volmer experiments was 0.27:.03. The data used to are presented in Table 32. 4 was observed to be Max II determine 4isc are shown in Table 33. The data used and 4 to determine 4Dis are shown in Table 34. 7. le4pEthBt The Stern—Volmer data for this diketone are presented in Table 35. The observed qu values for acetOphenone and 1-pheny1but-3-en-1-one are 14925 M-lsec”l and 165:2 M-lsec-l. The effects of various concentrations of dioxane and pyridine on the 4Ac and 4pEtAc are reported Max . Max in Tables 36 and 37. 4AC and 4pEtAc be 0.36:.03 and 0.11:.01. The average ¢Ac and ¢pEtAc experiments were were observed to observed in the Stern—Volmer and 4Max 153 Table 27: 4M?x for DiBzEt D15 [diketone] 0.0100 M [tetradecane]. 0.00128 M [diethylphthalate] 0.103 M avg. ratio, diketone/phthalate unirradiated 0.841 irradiated 0.655 % conv of ketone 22.1 area Ac/area Cl4 0.790 % conv to Ac ' 20.2 % conv ketone/% conv Ac 1.09 4.5 M Dioxane in benzene solvent; 313nm; 30.0°; g.c.condition set 5; h.p.1.c. conditions, 2' x 1/8" Porasil 1000pft, 50% stroke, 40:60 hexane/methylene chloride 154 Table 28: Stern-Volmer Data for DiBth Run 1 4II=0.367, qu=46.5M’lsec“l, Lamp intensity=0.0007l9E/hr [Q] area Ac 4°/4 [Ac] x102M area C14 x104M 0.0 2.06:.07a 7.29 0.467 1.72 1.20 6.09 0.933 1.53 1.35 4.78 1.87 1.17 1.76 4.14 2.80 0.872 2.37 3.09 3.73 0.742 2.78 2.63 4.67 0.659 3.13 2.33 VP Actinometer (average from three tubes) 0.0 1.37:.09 4.85 [diketone]=0.0103M(0.0706%T), [VP]=0.0125M(0.250%T), [c14]=1.77x10'4M, benzene solvent, 313nm, 30.0°, g.c. condition set 6. Run 2 ¢II=0.379, qu=43.7M’lsec'l, Lamp intensity=0.000981E/hr [Q] area Ac 4°/4 [Ac] x102M area C14 x104M 0.0 1.62:.05a 10.30 0.524 1.26 1.29 8.01 0.105 1.08 1.50 6.87 0.210 0.892 1.82 5.67 0.315 0.691 2.35 4.39 0.419 0.549 2.96 3.49 0.524 0.500 3.24 3.18 VP Actinometer (average from three tubes) 0.0 0.910i.01 5.79 [diketone]=0.0100M(0.0762%T), [VP]=0.00963M(0.344%T), [C14]=3.18x10-4M, benzene solvent, 313nm, 30.0°, g.c. condition set 6. a. average from three tubes 155 Table 29: Effects of Varying Concentrations of Dioxane on 4 for DiBth II Run 1 [Dioxane] area Ac [Ac] 4II M area Cl4 x104M 0.0 1.33:0.07a 6.04 0.374 1.00 1.70 7.72 0.478 2.00 1.74 7.90 0.489 3.00 1.88 8.54 0.528 4.00 1.95 8.85 0.548 5.00 2.09 9.49 0.587 6.00 2.04 9.26 0.573 VP Actinometer (average from three tubes) 0.0 1.00:0.07 4.54 [diketone]=0.0101M(0.0743%T), [VP]=0.0182M(0.133%T), 4 [C14]=2.27x10- M, benzene solvent, 313nm, 30.0°, g.c. condition set 6, lamp intensity = 0.00116 E/hr Run 2 [Dioxane] area Ac [Ac] 4II M area Cl4 x104M 0.0 1.11:0.04a 5.82 0.372 1.00 1.26 6.60 0.423 2.00 1.45 7.60 0.486 3.00 1.53 8.02 0.513 4.00 1.43 7.49 0.480 5.00 1.51 7.91 0.506 6.00 1.51 7.91 0.506 VP Actinometer (average from three tubes) 0.0 0.63:0.06 3.30 [diketone]=0.0100M(0.0762%T), [VP]=0.00951M(0.348%T), 4M, benzene solvent, 313nm, 30.0°, [C14]=2.62x10 g.c. condition set 6, lamp intensity = 0.00125E/hr a. average from three tubes 156 Table 30: Effects of Varying Concentrations of Pyridine on 4 for DiBth II Run 1 [Pyridine] area Ac [Ac] 4II M area Cl4 x104M 0.0 0.401:.004a 4.03 0.399 0.0255 0.447 4.49 0.445 0.0511 0.464 4.66 0.461 0.0766 0.491 4.93 0.488 0.102 0.481 4.83 0.478 0.128 0.520 5.22 0.517 0.153 0.560 5.62 0.557 VP Actinometer (average from three tubes) 0.0 0.295:.01 2.96 [diketone]=0.0101M(0.0743%T), [VP]=0.0213M(0.0943%T), [C14]=5.02x10-4M, benzene solvent, 313nm, 30.0°, g.c. condition set 6. Run 2 [Pyridine] area Ac [Ac] 4 M area C 4 II 14 x10 M 0.0 0.338:.03 3.95 0.334 0.253 0.421 4.93 0.416 0.507 0.544 6.36 0.538 0.760 0.527 6.17 0.521 1.27 0.527 6.17 0.521 VP Actinometer (average from three tubes) 0.0 0.306t.04 3.58 [diketone]=0.00990M(0.0782%T), [VP]=0.0239M(0.0707%T), _ -4 [C141-5.85x10 M, benzene solvent, 313nm, 30.0°, g.c. condition set 6, lamp intensity=0.000642E/hr a. average from three tubes 157 Table 31: Stern—Volmer Data for DipEthBt Run 1 411:0.253, qu=364M'lsec’l, Lamp intensity=0.00935E/hr [Q] area pEtAc 4°/4 [pEtAc] x102M area C18 xlO4M ‘ 0.0 1.89:0.02a 17.30 0.469 0.679 2.79 6.21 0.938 0.432 4.38 3.95 1.88 0.246 7.71 2.25 2.81 0.171 11.1 1.56 3.75 0.127 14.9 1.16 4.69 0.105 18.0 0.961 VP Actinometer (average of three tubes) 0.0 1.23:0.09 (area Ac/area C14) 14.1 [Ac] [diketone]=0.0101M(0.0243%T), [VP]=0.0100M(0.330%T), 4M, [C14]=5.72x10-4M, benzene solvent, [C18]=5.72x10 313nm, 30.0°, g.c. condition set 4, actinometer g.c. condition set 5. Run 2 4II=0.258, kqt=383M-lsec-l, Lamp intensity=0.00928E/hr [Q] area pEtAc 4°/4 [pEtAc] x102M area C18 x104M 0.0 3.82:0.04a 17.5 0.181 2.34 1.64 10.7 0.363 1.79 2.14 8.22 0.725 0.979 3.90 4.50 1.09 0.749 5.10 3.44 1.45 0.581 6.58 2.67 1.81 0.482 7.93 2.21 VP Actinometer (average of two tubes) 0.0 1.79:0.03 (area Ac/area C14) 19.2 [Ac] [diketone]=0.0106M(0.0202%T), [VP]=0.0227M(0.0807%T, [C18]=2.87x10-4M, [C14]=5.35x10-4M, benzene solvent, 313nm, 30.0°, g.c. condition set 4, actinometer g.c. condition set 5. 158 Table 31: (cont'd.) Run 3 4II=0.313, qu=365M-lsec-l, Lamp intensity=0.00732E/hr [Q] area pEtAc 4°/4 [pEtAc] x102M area C18 x104M 0.0 1.46:0.03a 17.21 0.231 0.829 1.75 9.78 0.462 0.513 2.84 6.05 0.924 0.338 4.31 3.99 1.39 0.242 6.02 2.85 1.85 0.184 7.92 2.17 2.31 0.156 9.35 1.84 VP Actinometer (average of three tubes) 0.0 0.864:0.025 (area Ac/area C [diketone]=0.0200M(0.000636%T), [C18]=7.37x10 313nm, 4 condition set 5 a. average from three tubes 14) [VP]=0.0206M(0.102%T), M, [cl4]=8.59x10‘4M, benzene solvent, 30.0°, g.c. condition set 4, actinometer g.c. 14.8 [Ac] 159 Table 32: Effects of Varying Concentrations of Dioxane on 4II for DipEthBt Run 1 [Dioxane] areangtAc [pEtAc] 4 M area C 4 II 18 x10 M 0.0 1.33:.09a 10.6 0.277 1.00 1.34 10.7 0.279 2.00 1.20 9.58 0.250 3.00 1.25 9.98 0.260 4.00 1.36 10.86 0.283 5.00 1.18 9.42 0.246 6.00 1.15 9.18 0.240 VP Actinometer (average from three tubes) 0.0 1.221.04(area Ac/area C ) [Ac]=0.00102M 14 [diketone]=0.0103M(0.0226%T), [VP]=0.0185M(0.129%T), [C18]=4.99x10-4M, [cl4]=4.20x10‘4 313nm, 30.0°, g.c. condition set 4, actinometer g.c. M, benzene solvent, condition set 5, lamp intensity = 0.00196E/hr Run 2 [Dioxane] area pEtAc [pEtAc] 4II M area C 4 18 x10 M 0.00 0.705:0.006a 6.20 0.245 1.00 0.726 6.39 0.253 2.00 0.605 5.32 0.210 4.00 0.709 6.24 0.247 5.00 0.769 6.77 0.277 6.01 0.764 6.72 0.266 VP Actinometer (average from three tubes) 0.0 0.524:.04(area Ac/area C ) [Ac]=0.000665M 14 [diketone]=0.00998M(0.0254%T), [VP]=0.0174M(0.145%T), [018]=5.50x10'4m, [cl4]=6.35x10"4 313nm, 30.0°, g.c. condition set 4, actinometer g.c. M, benzene solvent, condition set 5, lamp intensity = 0.00117E/hr a. average from three tubes 160 Table 33: Intersystem Crossing Yield for DipEthBt Ketone [1,3-pentadiene] cis 4isc M cis+trans 0.0551 M DipEthBt 0.526 .0332 1.06 0.0583 M Ac 0.526 .0313 1.00 cis/(cis+trans) unirradiated diene = 0.00200, benzene solvent, 313nm, 30.0°, g.c. condition set 8. Table 34. 4Dis for DipEthBt Run 1 Run 2 [diketone] 0.0103M 0.00998M [octadecane] 0.000499M 0.000550M [diethylphthalate] 0.188M 0.188M avg. ratio, diketone/phthalate unirradiated 1.24 1.11 irradiated 1.10 1.03 % conv of ketone 11.7 6.85 area pEtAc/area C18 1.33 .705 % conv to pEtAc 10.3 6.22 % conv ketone/% conv pEtAc 1.14 1.10 Benzene solvent; 313nm; 30.0°; g.c. condition set 4; h.p.1.c. conditions, 2' x 1/8" Corasil 1000pft, 400psig, methylene chloride 161 Table 35: Stern-Volmer Data for le4pEthBt Run 1 4 =0 241 4 =0 0661 k r =1531~4'1s.ec‘l k r =166M,"1sec'l Ac ' 'pflflk: ' '<;Ac ' (IPNNBn [Q] area Ac (4°) ' area PhBten (4°) [Ac] x102M area C14 Q Ac area C14 ¢ PhBten x104M 0.0 4.95:0.2a 2.63:0.1a' 19.1 0.540 2.95 1.68 1.61 1.63 11.4 1.08 1.97 2.51 0.928 2.83 7.60 2.16 1.14 4.34 0.600 4.38 4.40 3.24 0.825 6.00 0.401 6.56 3.18 4.32 0.579 8.54 2.23 5.40 0.462 10.7 1.78 VP Actinometer (area Ac/area Cl4=4.36i.08a,[Ac]=0.00168M), PetAc(area PetAc/area C18=2.1910.1a, [pEtAc]=0.000466M), [diketone]=0.0102(0.0315%T),[VP]=0.0104(0.316%T), [C14]= 1.93x10-4M,[C18]=l.33x10-4M, benzene solvent, 313nm, ambient temperature, g.c. condition set 5, lamp intensity=0.0108E/hr Run 2 _ 4 =0 263 4 =0 0718 k r =144M-lsec-l k r =163M"1.«=.ec"l Ac ' 'peum: ' ’