-—-—' I arm-:- .- ---r 1_-.& ..~.1 I EA 7.1 -~ “‘3 I-_! ..... i "--£VLI--_I This is to certify that the dissertation entitled Internal Conversion Vs. Photochemistry in Pentammine and Bis(2,2'Bipyridine), (4-Acy1pyridine) Ruthenium (II) Complexes. Photodisproportionation of Penta- carbonyl (4-Acylpyridine) Tungsten(0) Complexes in the Absence of an Entering Ligand. presented by Nicholas Leventis has been accepted towards fulfillment of the requirements for Ph.D. degree in Chemistry (BMW yjor profeyor Date 10/18/85 MS U is an Affirmative Action/Equal Opportunity Institution 0-12771 RETURNING MATERIALS: )V1531_] Place in book drop to remove this checkout from 4:22;;2221. your record. FINES will be charged if book is returned after the date stamped below. INTERNAL CONVERSION VS. PROTOCHEMISTRY IN PENTAAMMINE AND BIS(2,2'BIPYRIDINE), (4-ACYLPYRIDINE) RUTRENIUM(II) COMPLEXES. PHOTODISPROPORTIONATION OF PENTACARBONYL (4-ACYLPYRIDINE) TUNGSTEN(0) COMPLEXES IN THE ABSENCE OF AN ENTERING LIGAND. By Nicholas Leventis AN ABSTRACT OF A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Che-iatry 1985 I '1“) ’lr’ 4‘ V“ i i, A s. .‘._. _ ABSDMEH IlflIIILCBIWflBmfllVS.I‘Dmflfllflflfiflflfll mum AND BIS(2,2'BIPYRIDINE). (Q-EYIPYRIIHB) MIIIKII) W. PIUNIHSHIIQIEKIMIHIIOFFIIDMMRINHI 0&iflflfl"!flflflfl)1flflflflllfln OUIEBIEBIN ‘fllllflflnnllflfANllflifllfllLRNHD. BY Nicholas Leventis This dissertation primarily concerns the estimation of the rate of the Internal Conversion of an upper Internal Ligand excited state to lower excited states in inorganic complexes. As representative examples, various Ruthenium penteammine and bis(2,2'bipyridine) complexes were chosen. The rate of the Internal Conversion of the Internal Ligand ns‘ excited state of coordinated pyridyl ketones was estimated by varying the reactivity of the pyridyl ketones towards the Norrish Type 11 Internal Ligand photochemical cleavage. so that for sufficiently low reactivity of the coordinated pyridyl ketones, the Internal Conversion competes with the Type II cleavage. It was found that the rate of the Internal conversion of the ns‘I Internal Ligand excited state in [Ru(NHs)s(4-pyridyl ketone)]3* is 5‘4.0 107 sec“, and in cis—[Ru(hipy)z(4-pyridyl ketone)2]3’ is 2.9 10° sec’l; (bipy = 2,2'bipyridine). The higher rate of the Internal Conversion in the bis(2,2'bipyridine) complexes was explained in terms of poor orbital overlap between the n orbital localized on the pyridyl ketone oxygen and the non- bonding d orbitals of Ruthenium on one hand, but, on the other hand, favorable orbital orientation and overlap between the n orbital of the pyridyl ketone oxygen and the 2,2'bipyridine I system. Efforts to transfer the same approach for the Internal Conversion rate estimation in Pentacarbonyl (4-pyridyl ketone) Tungsten(0) complexes failed, due to a fast photochemical reaction of these complexes, to yield W(CO)s and cis-W(CO)4(4-pyridyl ketone)2. This reaction has been overlooked in the chemical literature so research was concentrated on the elucidation of the mechanism by which this reaction takes place. It was found that, in the absence of any 4-pyridyl ketone in the irradiated solution (solvent: benzene or methylcyclohexane), two mechanisms seem to proceed simultaneously both at short or long irradiation wavelengths (490 or 410 nm, respectively): an associative one, presumably from the MLCT lowest excited state, and a dissociative one from the higher LF state which leads primarily to.4-pyridyl ketone photodissociation. The W(C0)s intermediate attacks a ground state molecule from which it abstracts a CO molecule to give W(CO)s and a W(CO)4(4- pyridyl ketone) intermediate that eventually finds a 4- pyridyl ketone molecule in the solution to give cis- W(CO)4(4-pyridy1 ketone)2. The presence of 4-pyridy1 ketone in the irradiated solution quenches the tetracarbonyl product formation more efficiently at longer irradiation wavelengths‘ (Xsrr>400 nm) than at shorter irradiation wavelengths (Air: 400 nm). At higher energy irradiations (~400 nm), loss of CO becomes competitive with 4-pyridy1 ketone loss, and another mechanism through the direct formation and trapping of a W(CO)4(4-pyridy1 ketone) intermediate becomes important; the main reaction path, though, remains the one through loss of 4-pyridyl ketone. To my parents, Spyro and Efrosini Leventis II First and foremost, I want to thank Professor Peter J. Wagner for his encouragement, support and understanding throughout the years of ”hard work”. I believe that his honesty and words of wisdom made me not only a better chemist but a better human being as well. I want to thank the past and the present members of Wagner’s group for their friendship. Here, I want to mention Young C. Chung, a very special friend from Dr. Leroi’s group; our long talks, either philosophical, political or scientific, were always enjoyable. I want to acknowledge my parents. Words cannot express my thanks to them. My cousin, Nicholas T. Leventis: who set the standards in the family which I tried to push further. My friend, John E. Spatharas: the only real friend I have left in Greece. Finally, I would like to thank the Chemistry Department of Michigan State University for financial support, research assistantships and the use of its facilities. Thanks also to the NSF for research assistantships administered by Dr. Wagner and to Ethyl Corporation and Yates Memorial for Summer Fellowships administered by the Chemistry Department of Michigan State University. III LIST OF mus LISTOFFIGIBS.......... INTRODUCTION . . . . . . . . . . . . ELECTRONIC TRANSITION AND PHOTOCREMISTRY IN TRANSITION METAL COMPLEXES. . . . PROTOCREMISTRY OF RUTEENIUM(II) COMPLEXES . RESONANCE RAMAN SPECTROSCOPY 0F TRANSITION METAL COMPLEXES O O O O O O O O O PROTOCREMISTRY 0P TUNGSTEN CARBONYLS. KINETICS. . . . . . . . . . . . . RESEARCH GOALS. . . . . . . . . RESULTS. 0 O O O 0. O O O O O O O O O PROTOREDUCTION OF KETONES BY TETRARYDROFURAN. RUTRENIUM COMPLEXES . . . . . . . . . Ruthenium Pentaammine Complexes. Ruthenium 2,2'bipyridine and 1,10- phenanthroline Complexes . . . Ruthenium Porphyrines. . . . . Spectroscopic Studies. . . . Raman Studies. . . . . . . . . Intramolecular Photoreduction. IV 2222 IX XVII 10 11 16 22 24 24 33 33 35 37 38 50 54 Photoproduct Identification Quantum Yield Studies . . . . . . . Quenching Studies . . . . . . Ruthenium 2,2'bipyridine and Ruthenium- Osmium 2,2'bipyrimidine bridged complexes. Compound Preparation and identification Spectroscopic Studies . . . . Raman Studies . . . . . . . . . . . . Photochemistry of Tungsten Carbonyls . . Compound Preparation and Identification Ligands . . . . . . . . . . . Pentacarbonyl Tungsten(D) Complexes Spectroscopic Studies. Photochemical Studies. . . . . . . . . . Photoproduct Identification, Mass Balance, and Cross-coupling Experiments Comparison of the Photobehavior of H(CO)5(4VP) with Other Pentacarbonyl Complexes of Tungsten-Stability of the Photoproduced Tetracarbonyl Complexes. . . Quantum Yield Studies . . . . . . . . . Quenching Studies . . . . . . . . . A Energy Transfer Quenching . . . 5; Reaction Quenching . . . . . . Ag Emission Quenching. . . . . . . a Chemical Quenching. . . . . . . 5; Reaction Quenching. . . . . . . g; Emission Quenching. . . . . . . Page 55 6O 65 75 75 81 82 82 82 83 86 86 86 97 102 106 106 106 106 115 115 117 Page Intermediate Trapping Experiments . . . . . 117 DISCUSSION . . . . . . . . . . . . . . . . . . . . . 127 PHOTOREDUCTION 0F KETONES BY TETRAHYDROFURAN. . . 127 PYRIDYL KETONE PENTAAMMINE AND DIS(2,2'BIPYRIDINE) . . . . . . . . . . . . . . . 128 RUTHENIUM(II) COMPLEXES . . . . . . . . . . . . . 128 Absorption and Emission Studies. . . . . . . Raman Studies. . . . . . . . . . . . . . . . . 130 Photochemical Studies. . . . . . . . . . . . . 131 RUTRENIUM 2,2'BIPYRIDINE AND RUTRENIUM-OSMIUM 2,2'BIPYRIDINE BRIDGED COMPLEXES. . . . . . . . . 150 TUNGSTEN CARDONYLS. . . . . ... . . . . . . . . . 150 Electronic Absorption and Emission Spectra . . 151 Photochemistry of W(CO)5(4VP). . . . . . . . . 152 SUMMARY . . . . . . . . . . . . . . . . . . . . . 176 SUGGESTIONS FOR FURTHER STUDY . . . . . . . . . . 177 EXPERIMENTAL . . . . . . . . . . . . . . . . . . . . 180 INSTRUMENTATION . . . . . . . . . . . . . . . . . 181 CHEMICALS . . . . . . . . . . . . . . . . . . . . 182 Solvents . . . . . . . . . . . . . . . . . . . 182 Internal Standards . . . . . . . . . . . . . . 185 External Standards . . . . . . . . . . . . . . 185 Quenchers. . . . . . . . . . . . . . . . . . . 186 Actinometers . . . . . . . . . . . . . . . . . 186 Eetones. . . . . . . . . . . . . . . . . . . . 187 Pyridyl Eetone Hydrochloride Salts . . . . . . 193 VI Page Nitrogen Coordinating Ligands. . . . . . . . . 194 Photoreduction Products. . . . . . . . . . . . 195 Type II Products . . . . . . . . . . . . . . . 196 Ruthenium Complexes. . . . . . . . . . . . . . 196 Pentaammine Pyridine Ruthenium(II) Tetrafluoroborate and the Pyridine Substituted Derivatives . . . . . . . . . . 197 Diaquo cis-bis(2,2‘bipyridine) Ruthenium(II) Dichloride. . . . . . . . . . 201 Aqueous cis-bis(l,lO-phenanthroline) Ruthenium(II) Dichloride. . . . . . . . . . 202 Synthesis of Monocarbonyl Tetraphenylporphyrinato Ruthenium(II) . . . 211 Synthesis of bis(4-pheny1-l-(4- pyridyl)butanone) Tetraphenyl Porphyronato Ruthenium(II). . . . . . . . . 212 Synthesis of bis(4- phenyl- -1- (4- pyridyl)butanone) octaethylporphyrinato Ruthenium(II) . . . . . . . . . . . 213 Synthesis of Carbonyl Pyrazino Tetraphenylporphyrinato Ruthenium(II) . . . 215 Synthesis of Carbonyl (Carbonyl Pyrazino Tetraphenylporphyrinato Ruthenium(II)) Tetraphenylporphyrinato Ruthenium(II) . . . 215 Osmium Complexes . . . . . . . . . . . . . . . 217 Aqueous cis-bis(2, 2' bipyridine)0smium(II) Chloride. . . . . . . . . . . . . . . . 217 Aqueous bis(l,10- phenanthroline)0smium(II) chloride. . . . . 218 Ruthenium-Osmium 2,2'bipyridine Bridged, Mixed Ligand Einuclear Complexes. . . . . . 218 Tungsten Complexes . . . . . . . . . . . . . . 221 Pentacarbonyl (4-substituted-pyridine) Tungsten(0) Complexes . . . . . . . . . . . 221 VII Photoproduct Isolation and Identification cis-Tetracarbonyl bis(l-(4- pyridyl)pentanone) Tungsten(0). . . . Hexacarbonyl Tungsten(0). . . . . . . . . METHODS AND TECHNIQUES. . . . . . . . . . . Preparation of Samples . . . . . . . . . . . Photochemical Glassware Irradiation Tubes . . . . . . . . . . . . Stock Solutions and Photolysis Solutions. Degassing Procedures. . . . . . . . . . . Irradiation Procedures. . . . . . . . . . Analysis of Samples. . . ... . . . . . . . Identification of Photoproducts . . . . . Gas Chromatography Procedures . . . . . High-pressure Liquid Chromatography Procedures. . . . . . . . . . . . . . . Actinometry and Quantum Yield Determination. Valerophenone Actinometry . . . . . . . Uranyl Oxalate Actinometry. . . . . . . . Potassium Reineckate Actinometry. . . . Absorption Spectra . . . . . . . . . . . . . Emission Spectra . . . . . . . . . . . . . LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . APPENDIX . .'. . . . . . . . . . . . . . . . . . . . . . VIII Page 226 226 227 228 228 228 228 229 229 229 230 230 232 233 233 236 237 238 242 242 243 252 Table Table Table Table Table Table Table Table Table Page Entering group concentration effects on photosubstitution of N(CO)s(pip) in benzene at 25°C. . . . . . . . . . . . . . 14 Quantum Yields for Photoreactions of W(CO)5L Complexes. . . . . . . . . . . . . 15 Results from the Intermolecular photoreduction of pyridyl ketones by THE. . . . . . . . . . . . . . . . . . . . 32 UV-Visible Absorption Spectral Data for some Pyridyl ketones and their Ruthenium Complexes. . . . . . . . . . . . 40 Emission Data for Some Ligands and Their Ruthenium Complexes. . . . . . . . . 48 Mass Balance Experiment for styrene and 4AP been produced in the Type II cleavage of cis- [Ru(bipy)2(4phap)z](nr.)z. . . . . . . . . 57 UV-Visible absorption data of [Ru(NHs)s(4PhBP)](BF4)2. cis- [Ru(biPY)2(4PhBP)2](BF4)2. [Ru(NRa)s(4EsterBP)](BF4)2 and cis-[Ru(bipy)2(4EsterBP)2](BF4)2 upon irradiation at 313 nm. . . . . . . . . . . 49 Quantum Yields and qu values for 4PhBP, 4EsterBP, 4PhBP.HCl, 4EsterBP.HCl and the corresponding Ruthenium Complexes. . . . . . . . . . . . 61 Results from Stern-Volmer quenching of butyrophenone by Ruthenium(II) complexes. . . . . . . . . . . . . . . . . 75 IX Table Table Table Table Table Table Table Table Table Table Table Table Table 10. 11. 12. 13. 14. 15. 16. 17. 18. 20. 21. 22. Page UV-Visible Absorption' data of mononuclear and binuclear 2,2'bipyrimidine complexes . . . . . . . . 78 Emission data of mononuclear and binuclear 2,2'bipyrimidine Complexes . . . 80 Carbonyl Compounds of Tungsten(O) and the Abbreviations Used . . . . . . . . 84 Absorption and Emission Data for the Tungsten Carbonyls . . . . . . . . . . . . 87 Mass balance experiments for Pentacarbonyl 4-valery1pyridine Tungsten(O) Photolysis . . . . . . . . . . 96 Cross-Coupling Experiments for W(CO)s(4VP) .and W(CO)5(4BP) Irradiated Together . . . . . . . . . . . . . . . . . 97 Formation Quantum Yield Data for cis- N(CO)4(4VP)2 from N(CO)s(4VP). . . . . . . 102 Photoproduct and Emission Quenching from N(CO)5(4VP) . . . . . . . . . . . . . 109 cis-W(CO)4(4VP)2 formation Stern-Volmer Quenching by 4VP for 1 it: > 400 and Alrr>475nl.............. 115 >Effect of Added Butyrylpyridine on Photoproduct Formation with Visible Irradiation of N(CO)5(4VP) . . . . . . . . 122 Relative Reactivities of Various Phenyl Eetones, Pyridyl Ketones and the Corresponding Pyridyl Eetone Hydrochloride Salts. . . . . . . . . . . . 132 Rate Constants for Quenching of Triplet BP by Various Ruthenium Complexes in Acetonitrile . . . . . . . . . . . . . . . 135 Pyridyl Proton Chemical Shifts in Free Pyridyl Eetone Ligands, Their Hydrochloride Salts and Their Ruthenium Complexes. . . . . . . . . . . . . . . . . 136 Table Table Table Table Table Table Table Table Table Table Table Table Table 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. Type for II th Fragmentation Hydrochloride Pentaammine, Porphyrine Ruthenium(II) the Pyridyl Eetones. 2,2'Bipyridine Complexes Quantum Yields Salts, and of Lifetime Data for Ruthenium Complexes. Comparison of the Ruthenium Complexes. Rates Quantum of H-abstraction Internal Complexes. Conversion and Rates of of Ruthenium Yields of Type II Products of Various Pentaammine Response Factors for Various Compounds . Balance in acetonitrile. . . Experiment Photoreduction of Acetophenone Double Reciprocal for DTHF vs. for the by THF [THF]"1 in the Photoreduction of acetophenone by THF 0 O O O O O 0 Double Reciprocal for THFCBaCN vs. [THFl‘l in the Photoreduction of Acetophenone by THF. . . . . . . Double Reciprocal for DTHF vs. [THF]'1 in the Photoreduction of 4- acetylpyridine by THF. . . . . . . Double Reciprocal for THFCHaCN vs. [THFI'1 in the Photoreduction of 4- acetylpyridine by THF. . . . . . . . . Double Reciprocal for DTHF vs. [THFJ‘1 in the Photoreduction of Benzophenone by THF 0 O O O O O O O O O O O 0 Double Reciprocal for THFCHaCN vs. [THF]q in the Photoreduction of Benzophenone by THF. . . . . . . . . Double Reciprocal for DTHF vs [THF]"1 in the Photoreduction 4- benzoylpyridine by THF . . XI of O Page 138 139 140 144 235 253 254 256 257 258 259 260 261 Table Table Table Table Table Table Table Table Table Table 37. 38. 39. 40. 41. 42. 43. 44. 45. Double Reciprocal for THFCH30N vs. [THFJ'1 in the Photoreduction of 4- benzoylpyridine by THF . . . . . . . . Stern Volmer Data for 4-phenyl-l-(4- pyridyl) butanone. . . . . Stern Volmer data for 4-Phenyl-l-(4- pyridyl)butanone hydrochloride Concentration Dependence of the Quantum Yield of the Type II cleavage of 4- Phenyl-l-(4—pyridy1)butanone . . . . Concentration Dependence of the Quantum Yield of the Type II reaction of 4- Phenyl-l-(4-pyridyl)butanone hydrochloride. . . . . . . . . . Independent Quantum Yield Determination for the Type II Cleavage of Pentaammine 4-Phenyl-l-(4-pyridyl)butanone Ruthenium(II) Tetrafluoroborate. . . . Quantum Yield and Stern Volmer data for Penaammine 4-Phenyl—l-(4- pyridyl)butanone Ruthenium(II) Tetrafluoroborate. . . . . . . . . . . Quantum Yield and Stern Volmer Data for cis-bis(2,2'bipyridine) bis(4-Pheny1-l- (4-pyridyl)butanone) Ruthenium(II) Tetrafluoroborate. . . . . . . . . . . Concentration Dependence of the Quantum Yield of the Type II Cleavage of Pentaammine 4-Phenyl-l-(4- pyridyl)butanone Ruthenium(II) Tetrafluoroborate. . . . . . . . . . . Concentration Dependence of the Quantum Yield of the Type II cleavage of cis- bis(2,2'bipyridine)-bis(4-Phenyl-1-(4- pyridyl)butanone) Ruthenium(II) Tetrafluoroborate. . . . . . . . . . . XII Page 262 263 264 265 266 267 268 269 270 271 Table Table Table Table Table Table Table Table Table 46. 47. 48. 49. 50. 51. 53. 54. Stern-Volmer data for the cis- bis(2,2'bipyridine)- bis(4-Phenyl-1-(4- pyridyl)butanone) Ruthenium(II) Tetrafluoroborate Using Complex Concentration 0.010 M. Mass Balance Styrene and 4- acetylpyridine Produced from the Type II Cleavage of cis-bis(2,2'bipyridine)- bis(4-Phenyl-1-(4-pyridyl)butanone) Ruthenium(II) Tetrafluoroborate. Quantum Yield and Stern-Volmer Data for the Type II Cleavage of n-buty1-4-[(4- pyridy1)carbonyllbutyrate. . . . Independent Quantum Yield Determination for the Type II Cleavage of the n- butyl-4-[(4-pyridyl)carbonyl]butyrate. Quantum Yield and Stern-Volmer Data for the Type II Cleavage of n-butyl-4-[(4- pyridy1)carbonyllbutyrate Hydrochloride. . . . . . . . . . . Quantum Yield and Stern-Volmer Data for the Type II Cleavage of Pentaammine n- butyl-4-[(4-pyridyl)carbonyllbutyrate Ruthenium(II) Tetrafluoroborate. . Independent Quantum Yield Determination for the Type II Cleavage of Pentaammine n-buty1-4-[(4-pyridy1)carbonyllbutyrate Ruthenium(II) Tetrafluoroborate. . . . Stern-Volmer Data for the Type II Cleavage of Cis-Bis (2,2'bipyridine) bis(n-butyl-4-[(4-pyridyl)carbony1]- butyrate) Ruthenium(II) Tetrafluoro- borate . . . . . . . . . . . . . . . . Determination and Concentration Dependence of the Quantum Yield of cis- bis(2,2'bipyridine)-bis(n-butyl-4-[(4- pyridyl)carbonyllbutyrate) Ruthenium(II) Tetrafluoroborate. . . XIII Page 272 273 274 275 276 277 278 279 280 .1219. Table 55. Stern-Volmer Data for the Quenching of Butyrophenone by Pentaammine 4- acetylpyridine Ruthenium(II) Tetrafluoroborate. . . . . . . . . . . . . 281 Table 56. Stern-Volmer Data for the Quenching of Butyrophenone by cis-bis (2,2'bipyridine)bis(4-acetylpyridine) Ruthenium(II) Tetrafluoroborate. . . . . . 282 Table 57. Stern-Volmer Data for the Quenching of Butyrophenone by cis-bis(1,10- phenanthroline)bis(4-acetylpyridine) Ruthenium(II) Tetrafluoroborate. . . . . . 283 Table 58. Determination and Concentration Dependence of the Quantum Yield of the Type II Cleavage of Ruthenium Tetraphenylporphyrinato bis(4-phenyl-1- (4-pyridy1) butanone). . . . . . . . . . . 284 Table 59. Determination of the Quantum Yield of the Type II Cleavage of Ruthenium Octaethylporphyrinato bis(4-phenyl-1- (4-pyridyl)butanone) . . . . . . . . . . . 285 Table 60. Data fer the Calculation of the Response Factors of Various Compounds vs. Benzene for the HPLC Analysis. . . . . 286 Table 61. Mass Balance Experiment for the Irradiation of Pentacarbonyl 1-(4- pyridy1)pentanone Tungsten(0). . . . . . . 288 Table 62. Comparative Mass Balance Experiment for the Irradiation of Pentacarbonyl 1-(4- pyridy1)pentanone Tungsten(0). Degassed Normally and Under Carbon Monoxide . . . . 1 289 Table 63. Quantum Yield Data for Pentacarbonyl l- (4-pyridyl)pentanone Tungsten(O) Photolysis at 490 nm . . . . . . . . . . . 290 Table 64. Quantum Yield Data for Pentacarbonyl l- (4-pyridyl)pentanone Tungsten(O) Photolysis at 410 nm . . . . . . . . . . . 291 XIV Table Table Table Table Table Table Table Table Table Table Table Table Table Table 65. 66. 67. 68. 69. 7o. 71. 72. 73. 74. 75. 76. 77. 78. Concentration Dependence of the Quantum Yield of W(CO)5(4VP) Photolysis at A = 490 nm . . . . . . . . . . . . . . . . Concentration Dependence of the Quantum Yield of N(CO)5(4VP) Photolysis at A = 410 n. O O O O O O O O O O O O O O O O O Stern-Volmer Data for W(CO)5(4VP) irradiated at 490 nm . . . . . . . . Stern-Volmer Data for N(CO)5(4VP) Irradiated at 490 nm . . . . . . . . . Stern-Volmer Data for the N(CO)5(4VP) Emission Quenching . . . . . . . . . . Stern-Volmer Quenching Data for the cis-N(CO)4(4VP)2 Formation from W(CO)5(4VP) at [complex] = 0.00508 M . Stern-Volmer Quenching Data for the Emission from W(CO)5(4VP) at [Complex] = 0.00508 M. . . . . . . . . . . . . . Stern-Volmer Data for N(C0)s(4VP) Emission Quenching . . . . . . . . . . . Stern—Volmer Data for W(CO)5(4VP) Irradiated at 410 nm . . . . . . . . . Stern-Volmer Data for W(CO)5(4VP) Irradiated at 410 nm . . . . . . . . . . Stern-Volmer for W(CO)5(4VP) Irradiated at 410 nm. . . . . . . . . . . . . . . . Chemical Quenching Stern-Volmer Data for H(CO)s(4VP) Irradiated at A > 400 nm . . . . . . . . . . . . . . . . . . . Chemical Quenching Stern-Volmer Data for N(CO)5(4VP) Irradiated at 1 ) 475 Stern-Volmer Data for W(CO)5(4VP) Emission Quenching by 4AP. . . . . . . XV Page 292 293 294 295 296 297 298 299' 300 301 302 303 304 305 Table Table Table Table Table 79. 80. 81. 82. 83. Stern-Volmer Data for N(CO)s(4VP) Emission Quenching by 4VP. Intermediate Trapping Data for N(CO)5(4VP) Irradiated at A > 400 nm . Intermediate Trapping Data for N(CO)s(4VP) Irradiated at A > 475 nm . Thermal and Photochemical Behavior of cis-N(CO)4(4VP)2 in the Absence and in the Presence of 4BP. . . . . . . . . . Data for the Thermal Reaction of cis- W(CO)4(4VP)2 with 4BP. . . XVI Page 306 307 309 311 312 Figure Figure Figure Figure Figure Figure Figure Figure LIST OF FIGURES Simplified molecular orbital diagram of a ds pyridyl ketone complex. - -- Double reciprocal plots for .nrur‘l and Qrurcuscu‘l vs. [THF]'1 in the photoreduction of acetophenone by THF in acetonitrile. Double reciprocal- plot for Oorur'l vs. [THF]‘1 in the photoreduction of acetophenone by THF in benzene. Double reciprocal plots for Oprar‘l and .THPCH3CN-1 vs. [THF]"1 in the photoreduction of benzophenone by THF in acetonitrile. Double reciprocal plots for Oornr’l and Orurcuscu'l vs. [THF]'1 in the photoreduction of 4- acetylpyridine by THF in acetonitrile. Double reciprocal plots for Oornr" and Qrurcuacu’l vs. [THF]"1 in the photoreduction of 4-benzoy1pyridine by THF in CHacN. Absorption spectra in acetonitrile of 4PhBP, 4PhBP.HCl, [Ru(NHa)s(4PhBP)](BF4)2 and cis- [Ru(bipY)2(4PhBP)z](BF4)2. Absorption spectra in acetonitrile of 4EsterBP, 4EsterBP.HCl, [Ru(NHa)s(4EsterBP)](BF4)2 and cis- [Ru(bipY)2(4EsterBP)2](BF4)2. XVII Page 26 27 28 29 30 45 46 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 9 10 11 12 13 14 15 16 17 18 19 20 Absorption spectra in CH2C12 of RuTPP(4PhBP)2 and RuOEP(4PhBP)z. Emission spectra of 4PhBP, 4PhBP.HC1, cis-[Ru(bipy)2(4PhBP)2](BF4)2 and [Ru(biPY)3](BF4)2. Emission spectra of 4EsterBP, 4EsterBP.HCl, cis- [Ru(bipy)2(4EsterBP)2](BF4)2 and [Ru(bipY)3](BF4)2. Absorption and emission spectra of 2,2'bipyridine and 4,5-diazaf1uorene. UV-Visible absorption spectra lupon 313 nm irradiation of [Ru(NH3)5(4EsterBP)](BF4)2 and [Ru(NH3)s(4PhBP)](BF4)2 in acetonitrile. Effect of ketone concentration on the Type II products quantum yield for 4PhBP and 4PhBP.HCl irradiated at 313 nm in acetonitrile. Effect of concentration of Ruthenium complex on quantum yield for [Ru(NH3)5(4PhBP)](BF4)2, cis- [Ru(bipy)2(4PhBP)2](BF4)2 and cis— [Ru(bipy)2(4EsterBP)2](BF4)2 Effect of concentration of RuTPP(4PhBP)2 on the quantum yield for the Type II cleavage of the ligand. Stern-Volmer plots for 4PhBP and for 4PhBP.HCl in acetonitrile. Stern-Volmer plots for 4EsterBP and 4EsterBP.HC1 in acetonitrile. Stern-Volmer plots for [Ru(NHs)s(4PhBP)](BF4)2 and for cis- .[Ru(bipY)2(4PhBP)2](BF4)2 in acetonitrile. Stern-Volmer plots for [Ru(NH3)s(4EsterEP)](BF4)2 and for cis-[Ru(bipy)z(4PhBP)z](BF4)2 in acetonitrile. XVIII Page 47 51 52 53 58 62 63 64 66 67 68 69 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 21 22 23 24 25 26 27 28 29 3O 31 32 33 Stern-Volmer plot for butyrophenone quenched by [Ru(NH3)s(4AP)](BF4)2. Stern—Volmer plot for butyrophenone quenched by cis- [Ru(bipY)2(4AP)2](BF4)2. Stern-Volmer plot for butyrophenone quenched by cis- [Ru(phen)2(4AP)2](BF4)2. spectra of Absorption and emission N(CO)5(4VP) in benzene and methylcyclohexane. Absorption spectra of cis- W(CO)4(4VP)2 in benzene and methylcyclohexane. Infrared spectrum of cis- W(CO)4(4VP)2 in a EBr pellet. Carbon-13 nmr spectra of cis- W(CO)4(4VP)2 in CeDe. Proton nmr of cis-N(CO)4(4VP)2 in Cst and CDCls. Absorption spectra of W(CO)5(4VP) in methylcyclohexane upon irradiation with A>400 nm. Absorption spectra of N(CO)5(4VP) in benzene upon irradiation with A>400 nm. Carbon monoxide saturated sample. .Absorption spectra of W(CO)5(4Cpr) in methylcyclohexane and in benzene upon irradiation with A>400 nm. Carbon-13 nmr spectra of W(CO)s(4szy) before and after irradiation in benzene-de. Carbon-l3 nmr spectra of W(CO)5(4VP) before and after irradiation in benzene-do. XIX Page 72 73 74 89 91 92 93 94 99 100 101 103 104 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 34 35 36 37 38 39 40 41 42 43 Carbon-13 nmr spectra of N(CO)s(4BP) before and after irradiation in benzene-ds. Effect of concentration of N(CO)5(4VP) on the cis-W(CO)4(4VP)2 formation quantum yield. Irradiation at 410 nm in benzene. Effect of concentration of W(CO)5(4VP) on the cis—W(CO)4(4VP)2 formation quantum yield. Irradiation at 490 nm in benzene. Stern-Volmer plots for W(CO)5(4VP) irradiated at 410 nm in benzene. Three different complex concentrations. ' Stern-Volmer plot for W(CO)5(4VP) irradiated at 490 nm in benzene. Cis-W(CO)4(4VP)2 formation quenching by anthracene. [W(CO)5(4VP)] = 0.0105 M. Stern-Volmer plots for W(CO)5(4VP). [Complex] 0.00508 M. Cis— N(CO)4(4VP)2 formation and emission quenching by anthracene in benzene. Stern-Volmer plots for W(CO)s(4VP). [Complex] 0.000897 M. Cis- N(CO)4(4VP)2 formation and emission quenching by anthracene in benzene. Stern-Volmer for the emission quenching of W(CO)5(4VP) by anthracene in benzene. [Complex] = 0.0000829 M. Stern-Volmer plots for cis-W(CO)4(4VP)2 formation from W(CO)5(4VP) in benzene, quenched by free ligand (4VP). Stern-Volmer emission quenching plot of W(CO)5(4VP) by 4A? in benzene. XX Page 105 107 108 110 111 112 113 114 116 118 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 44 45 46 47 48 49 50 51 52 53 Stern-Volmer emission quenching plot of W(CO)5(4VP) by 4VP in benzene. Thermal reaction 'kinetics of cis-W(CO)4(4VP)2 with 4BP in benzene. Product distribution after irradiation of W(CO)5(4VP) in the presence of 4BP in benzene. Airr)400 nm. Product distribution after irradiation of W(C0)s(4VP) in the presence of 4BP in benzene. Alrr>475 nm. Variation of the concentration of cis-W(CO)4(4BP)2 produced upon irradiation of H(CO)5(4VP) in benzene with Airr>400 nm, in the presence of 4BP. Stern-Volmer plots for W(CO)5(4VP) in benzene. Total tetracarbonyl product cis-W(CO)4(4VP)2, cis- N(CO)¢(4BP)2 and cis- W(CO)4(4VP)(4BP) formation quenching 'by free ligand (48?). Internal ligand nt"I excited state of cis-[Ru(bipy)2(4-pyridy1 ketone)2]2+ complex. Jablonski diagram for the cis- [Ru(bipy)2(4-pyridyl ketone)2]2+ complex. MLCT and LF transitions in W(CO)s(4VP). Simulation of equation 61 for the Stern-Volmer quenching by 4VP of cis-W(CO)4(4VP)2 formation from N(CO)5(4VP) at various kL/kco values. The experimental points shown have the same meaning as in Figure 42. XXI Page 119 120 123 124 125 126 146 149 164 174 IHHIQMMHIGN Electronic Transitiongiggnd Photochemistry in Transition Metal Complexes. The excited state behavior of transition metal complexes having at least one conjugated ligand (i.e., ligand with low lying antibonding orbitals) has been explained adequately by considering three types. of electronic transitions: The Internal Ligand (IL), the Ligand Field (LF) and the Metal to Ligand or Ligand to Metal Charge Transfer (MLCT or LMCT) transitions. Figure 1 is a simplified molecular orbital diagram of a de pyridyl ketone complex in a Cav field which illustrates the three types of electronic transitions,1 in the case where the MLCT transition is the lowest one. The internal ligand (IL) transitions involve electronic redistribution localized on the ligand and reaction patterns must involve ligand structural changes, reactions with other substrates, etc. similar to those of the free ligands. This is a relatively unexplored area of transition metal photochemistry. 11* TT*___ n* n* eg-nr—— -—- eg 99 * *- TT TT __ TT*» TT* LF -——'MLCT «41 —+ Bali +1, _ 129 +— + ’11—‘29 -——-—--41. n + 11 "ii-— 11+ ”.1.”— Figure 1. Simplified molecular orbital diagram of a d6 pyridyl ketone complex:.A. pyridyl ketone; B. orbitals resulting from the mixing of metal and antihonding ligand orbitals,t1-back bonding is not considered; C. metal orbitals in the presence of a distorted octahedral field; D. crystal field approximation of d orbitals. The ligand field (LF) or d-d transitions involve only d-orbitals of the metal and are localized mainly on it. These transitions are insensitive to solvent polarity or ligand substituents. The photochemistry originating from the LF excited states is dissociative in nature. In Figure l for example, electron transfer from the t2; non-bonding orbitals to the a; antibonding orbitals weakens the bonds between the metal and its ligands with resulting ligand dissociation. Finally, the metal-to-ligand or ligand-to-metal charge transfer transitions (MLCT or LMCT, respectively) whose occurrence depends upon the origin of the excited electron have energies which depend both on the nature of the transition metal and on the nature of the ligands and are affected by the solvent polarity. These transitions do not involve any bond weakening so. the corresponding excited states are not dissociative in nature (see below). A closer look reveals that these transitions leave an oxidized metal center and a reduced ligand, so it is not surprising that these transitions cause important red-ox reactions of the complexes. Wrighton, for example, reported2 the reduction of 4—acety1pyridine (4AP) to l-(4-pyridyl)ethanol in fee- [Re(CO)3(4AP)zCl] by MLCT excitation in the presence of triethylammine. Whittenaa, on the other hand, has opened the way to a water-splitting reaction using tris- (2,2'bipyridine) Ruthenium(II) complexes as sensitizers which participate in a red-ox reaction originating from the 4 MLCT excited state. Finally, the possibility of photodissociation from the MLCT excited states has been underlined first by Zink3 who attributed the potential reactivity of the MLCT excited states to different ligand properties in the excited state compared to those in the ground state. More recently, Gray‘ explored the possibility the MLCT states favor an associative substitution pathway. No clear-cut proof has been presented though on MLCT excited states photodissociative properties. Although d-d transitions are insensitive to solvent and to ligand substituents, MLCT transitions are greatly affected by those factors. In some cases, by varying the ligand substituents and/or the solvent, the excited state sequence can be tuned so that the lowest excited state is either the MLCT or the LF, with dramatic results on the photochemistry of the complexes. In this work, emphasis has been given first to Internal Ligand reactions in pentaammine and polypyridyl complexes of Ruthenium as well as pentacarbonyl complexes of Tungsten, and second, to the excited state sequencing and characterization of the Ruthenium pentaammine and polypyridyl complexes. A brief account of the photochemistry of Ruthenium complexes is followed by a summary of the Resonance Raman spectroscopy by which the excited state sequencing of the Ruthenium complexes has been achieved. Next, an introduction to the photochemistry of Tungsten carbonyls follows. Finally, a description of the excited state kinetics shows how kinetic parameters and mechanistic conclusions for transition metal complexes are extracted from experimental data. The Introduction concludes with the research goals. Photochemistry of Rmthenium(II) Complexes. Interest in the photochemistry of Ru(II) complexes has been considerable in recent years5'5v7'3 and has been spurred by the discoveries that excited states of certain Ru(II) aromatic amine complexes can undergo either energy transfer9 or electron transfer with the appropriate substrates.1° There have been assigned four types of electronic transitions, i.e., charge transfer to solvent (CTTS) and Ligand Field (LF), in the case of [Ru(NHs)s]‘-’*,11'12 as well as Metal to Ligand Charge Transfer (MLCT) and Internal Ligand (IL), in the cases of [Ru(NHa)s(py-x)]2* and cis-[Ru(bipy)2(py-X)2]2* (pr-x = substituted pyridine). The latter two are more intense and obscure the other two transitions.13 The presentation to follow starts with the photochemistry of the ammine complexes of Ruthenium in relation to the excited states involved and continues with the photochemistry of the polypyridyl complexes. Special emphasis is given always to the internal ligand reactions. Aqueous solutions of [Ru(NH3)s]2* at pH=3 irradiated at Airr>3l3 nm, yield both oxidation (0Ru(III)) = 0.03 1 0.01) and equation, i.e., photosubstitution (an = 0.26 i 0.01) $1818 absor aquec fioth baud COOft 6 both wavelength independent, attributed to the population of a common excited state, presumably LF in character, as the result of irradiation in this region.H For Airr<280 nm, light absorption is directly into the CTTS state, and oxidation is dominant. Residual photoaquation has also been seen, either as a result of interconversion from the CTTS states into the LF states or alternatively to direct absorption into LF bands obscured by more intense CT bands. Photolysis of the pyridine complex [Ru(NHa)s(py)]2+ in aqueous solution at wavelengths shorter than 334 nm gives both photoaquation and photooxidation. The major absorption band in this region is the IL 1->1‘ transition of the coordinated pyridine but the products are formed from other states, perhaps produced by internal conversion/intersystem crossing from the initially populated IL configuration. At longer irradiation wavelengths, no photooxidation is detected, only photoaquation and a low quantum yield (~10‘4) exchange of pyridine hydrogens with solvent hydrogens. The latter reaction has been explained in terms of the MLCT state, while the ligand labilization has been proposed to originate from a LF state, populated by internal conversion from the initially formed MLCT state.12»15-1° Since the LF states are much less affected by substituents on pyridine than are the MLCT stateslz, choice of an appropriate electron-withdrawing group should give a lowest energy MLCT state. Complexes like [Ru(NH3)s(4-acetylpyridine)]2* and [Ru(NHa)s(isonicotinamide)lat, with Anax(utcr) longer than 531’! the ”PI Co: St Ru di fu 7 ~460 nm, are significantly less reactive than [Ru(NHa)s(py)]2* when irradiated at their Anax(cr), with wavelength dependent O values as much as three orders of magnitude smaller. This pattern suggests that the crossover point between complexes with a lowest energy LF state and those with a lowest energy MLCT state comes when Anax(xtcr> is ~460 nm. Finally, the only example of an Internal Ligand reaction for the Ruthenium Pentaammine system involves the Type II cleavage of 3- and 4-va1ery1pyridine coordinated to Ruthenium(II) according to equation (1).17 313 O [Ru(NHslsNM“ I” -----::——>[Ru(NHs)sN@—< l“ t N (1) CHsCN The quantum yields corrected for partial absorption of light by the ligand are unaffected by the coordination to the Ruthenium center. This permits an estimation of an upper limit to 108 sac‘1 for the rate of the internal conversion of the nr‘ IL excited state to lower LF and MLCT states.17 Another large class of Ruthenium complexes includes the Ruthenium polypyridyl complexes, the chemistry of which started with the synthesis of [Ru(bipy)3]X2.nH20 by Bursta111° (bipy = 2,2'bipyridine) in 1936, but it attracted little interest until 1959 when Paris and Brandtl’ discovered its visible-region luminescence at 77° K. After further research, a large amount of evidence accumulated ‘13 in .II at and iro from luminescence lifetime studies of [Ru(bipy)3]2* that strongly supported a d1‘20'21'22'23-24 heavy-atom perturbed25 spin forbidden process as the basis for the observed phenomenon. [Ru(bipy)3]2*, once thought to be photochemically inert, has been provenN-z'“28 to be photochemically active, giving products according to equation (2). hr [Ru(biP¥)s]Xs ----- ) [(bipY)sRuX(bipy))X ----> [(biPY)aRuX2] + bipy (2) For the salt [Ru(bipy)a](NCS)2, O in dichloromethane was measured as 0.068 at 25°C. The proposed mechanism“8 is: initial excitation leads to a charge-transfer state largely triplet in character. The CT state undergoes thermal activation to give a d-d excited state. The d-d state undergoes further thermal activation by loss of a pyridyl group to give a five coordinate intermediate, which captures a sixth ligand (either solvent or an anion held close to the activated metal .centar by ion-pairing) or chelate ring closure to return to [Ru(bipy)3]2*. The apparent photochemical stability of [Ru(bipy)a]2+ in water has been attributed to a consequence of the dominance of chelate ring closure and not of an inherently low photochemical reactivity. In related complexes, photochemical substitution in cis-[Ru(bipy)2(py)2]2+ i(py=pyridina) has been shown to be of synthetic value29 and both photochemical cis 0:5! 1:01 we thic Elie that late reac me In llu{ cis (----> trans isomerization and 0104- oxidation have been observed for cis-[Ru(biPY)2(Hzo)2]2*.3° Internal ligand photochemical reaction from cis- [Ru(bipy)2X2](BF¢)2 complexes has been reported by Whitten and Zarnegaral'32 when X=4-stilbazole. No photodissociation of these complexes was observed. Coordinated 4-stilbazole isomerizes in a wavelength dependent manner. Long wavelengths of irradiation produces MLCT excited states which behave like the radical anion of 4-stilbazole with cis- to trans- isomerization being more efficient. Short wavelengths yield a cis- to trans- ratio very similar to that of the free ligand. Finally, the red-ox properties of the MLCT excited states of Ruthenium polypyridyl complexes have been investigated extensively with respect to the water splitting reaction. Nhitten33 demonstrated that visible wavelength irradiation of some samples of the complexes cis- [Ru(bipY)2(4,4'-(ROOC)2bipy)lat (R=dihydrocholesterol and octadecyl) under special experimental conditions, causes photoinduced cleavage of H20 into H2 and 0;. Thus, attention was focused on other possible candidate complexes like bis(2,2'bipyridine) Ruthenium(II) complexes possessing a third, strong-field bidentate ligand for continuing studies in this area. Species like [Ru(bipy)2(phen)]2*.3"3s [Ru(bipy)2(bipy-)l2+ 3"37 and [Ru(bipy-)a]2+ 36 (phen=l,lO-phenanthroline, bipym=2,2'- 10 bipyrimidine) have been reported. Utilization of these and related complexes in the water splitting reaction revealed certain advantages over the classical [Ru(bipy)3]2+ cemplex (higher quantum yields for H2 evolation, etc.).3° Certain binuclear species like [Ru(bipy)2(bipym)Ru(bipy)z]‘* have been reported3°i37 and they have been studied with respect to their red-ox and emission properties.37 After one electron oxidation, an Intervalence-Transfer absorption band appears, the intensity of which allows an estimate for the extent of delocalization («2), which was found to be small, supporting the suggestion that electronic coupling between sites is weak.39 Only very recently, binuclear complexes have been reported that they can carry the water splitting reaction with efficiencies claimed higher than those obtained with [Ru(bipy)a]2*.‘° Resonance Raman Spectrogcopy of Trgnsition Metml Complexem. Resonance enhanced Raman spectroscopy has proved to be a powerful tool in obtaining excitation profiles of transition metal complexes, thus elucidating which transitions are responsible for the broad and intense CT absorptions.‘1 The innovation in the field came in 1979 when Woodruff reported‘2»‘3 the Raman spectrum of the MLCT excited state of [Ru(bipy)a]2*. This spectrum is identical to the spectrum reported by Wrighton“ four years later for fac-[Re(CO)a(bipy)Cl], and both are almost identical to the 2,2'bipyridine anion radical Raman spectrum.‘3 The ["U 11 implications of these results are overwhelming. It proves that the electron is localized on one bipy ligand in the MLCT excited state. The question rises: what makes the electron discriminate against the two bipy molecules and localize on the third one, despite the fact that the MLCT excited state of [Ru(bipy)3]2* is long lived and, therefore, delocalization would have plenty of time to occur? On the other hand, [Ru(bipy)3]2* in 1:1 (v/v) water/glycol mixtures, above and well below the glass-forming temperature, led to a disappearance of the discrete frequencies observed in liquid solutions and replacement by a broad scattering.‘5 The latter fact has been taken as evidence that charge localization takes place rapidly in the solutions but is inhibited in rigid media. Photochemistry of Tungsten Cambonyls. The primary photochemical step for most metal carbonyls is the loss of a carbon monoxide molecule.‘° The discovery of the photosensitivity of Group VI hexacarbonyls in 195141.49 opened the route for the preparation of many pentacarbonyl species by the photochemical substitution of CO by some donor (eg. pyridine, PPha, pentene).“9 Many early50'51'52'53 and recent54-55'55-57 reports concern the nature of the intermediates after photolysis of the parent hexacarbonyls in solution and in rigid glasses, employing either steady state or flash photolysis techniques. It seems that the pm {50: con: pho .,su bel nit Spa 30 ei ab 1‘1 ‘14 12 primary photoproduct is W(CO)5 which coordinates weakly with a ground state molecule through the carbonyl oxygen as in (CO)5N-OC-W(CO)5.55'55 Since this thesis concerns pyridyl complexes of Tungsten, an extensive review of the photochemistry of pentacarbonyl- and tetracarbonyl- (substituted pyridine) Tungsten(O) complexes is presented below. Complexes of the general formula W(CO)5L, where L is a nitrogen donor ligand, have interesting and interrelated spectroscopic and photochemical characteristics. They luminesce is both rigid glasses at 770K53'59'50 and in solution at 298°K,°3'59 the emission having been assigned to either a 3E ---> 1A1 ligand .field (LF) transition or a W ---> L Charge Transfer (MLCT) transition. The electronic absorption spectra suggest that as L becomes more electron withdrawing, the MLCT state lowers in energy and, for some ligands (eg. 4-acetylpyridine: 4AP. 4-cyanopyridine: 4Cpr), it crosses below the LF state, thus becoming the lowest- lying state.°° The identity of the lowest excited state has been shown to be of primary importance when the complex photosubstitution reactivity is investigated. Complexes with W ----) L CT lowest excited state are less reactive towards photosubstitution compared to the complexes with LF lowest excited state,°° in analogy to previous findings for [Ru(NH3)5L]2+ complexes.14:16 13 In general, complexes of the type ”(CO)5L are supposed to react according to Scheme 1. Adamson and Lees M W(CO)5 + L (3a) hv W(CO)5L ------ > Cev-[W(CO)4L] + co (3b) Cs-[W(CO)4L] + CO (3c) reported,61 based on room temperature flash photolysis data, that the primary photoproduct from W(CO)s(4AP) is the same obtained from W(C0)e and they assigned the structure W(CO)sS (S=Solvent). The Cs-[N(CO)4L] species seems also to exist based on IR data.55 Cs-[W(CO)4(pyridine)] is formed and has been detected after short wavelengths of irradiation (229 and 254 nm) in an Ar matrix at 100K. No experimental evidence has ever been collected for the Csv-[N(CO)4L] species. Its existence has only been suggested; and since the only tetracarbonyl Tungsten(O) complexes ever isolated are of the cis- geometry, it has been proposed"2 that Gov. geometry can rearrange to the Cs‘ one so that the final 14 product is always the cis-disubstituted tetracarbonyl product and not the trans. A very important point here is that all the experiments described in the literature concern irradiations of W(CO)5L in the presence of L or another entering group like 1-pentene or ethanol as an intermediate trapper. The photochemistry of W(CO)sL in the absence of an entering ligand has been assumed complicated63 and never carefully studied. In order to verify the mechanism of Scheme 1 for CO substitution in W(CO)5L accounting for cis- W(CO)4L2 formation, Wrighton investigated the entering group concentration effects on photosubstitution in N(CO)s(pip’°‘ (pip=piperidine) and his results are displayed in Table 1. Table l. Entering group concentration effects on photosubstitution of N(CO)s(pip) in benzene at 25°C. Entering group, (H) Product A trr,nl Relative Q.Y. piperidine, 0.025 cis-N(CO)c(pip)z 366 1.10 piperidine, 0.25 cis-N(CO)¢(pip)z 366 1.00 piperidine, 1.00 cis-N(CO)¢(pip)2 366 0.98 l-pentene, 0.025 W(CO)s(l-pen) 436 0.94 l-pentene, 0.25 W(CO)s(l-pen) 436 1.00 l-pentene, 1.00 W(CO)s(l-pen) 436 1.09 Nrighton6‘ considered that there is no entering group concentration effect on substitution quantum yields and he thought that this is consistent with a dissociative type of It of ob Hr It so ph th ll f0 15 mechanism for the photosubstitution of both C0 and L in W(CO)5L. Internal ligand photochemical reaction, as in the case of cis-[Ru(bipy):(4-styry1pyridine)2]2*.31:32 has been observed in N(CO)s(4—styry1pyridine) too.65 According to Nrighton, this reaction is an example of a photoassisted reaction.66 The photoreactions of W(CO)s(Pyridine) and N(CO)5(4-styrylpyridine) in 3.66 M l—pentene, isooctane solvent have been compared. The data demonstrate that photosubstitution of the pyridyl group can be attenuated by the provision of another chemical decay. path: energy migration from the coordination sphere to the ligand followed by independent reaction of the ligand. The quantum yields for cis-trans isomerization of the 4-styrylpyridine seem to account for most of the loss in substitution yields. Equations (4), (5), (6) and (7) of Table 2 demonstrate the fact. 1gb}; 2. Quantum Yields for Photoreactions of N(CO)5L Complexes' in; 436 nm "(60):?! --------- ) W(CO)s(l-pent) 0.63 (4)0 436 nm W(CO)spy --------- ) cis-"(CO)¢(PY)2 0.002 (5)c 436 nm N(CO)s(t-4-styPY) --------- > "(CO)s(l-pent) 0.16 (6)° 436 nm N(CO)s(t-4-stypy) --------- > H(CO)s(c-4-stypy) 0.49 (7)D 'py = pyridine, l-pent = l-pentene, 4-stypy = 4-styry1pyridine. .0 measured at room temperature in the presence of 3.66 M 1-pentene. isooctane solvent. ‘0 for formation of cis-"(CO)¢(py)a at room tem erature i °f 0'25 M PYridine in isooctane. p n presence 16 The cis-W(CO)¢L2 complexes have been prepared utilizing equation 3b, as has been explained above, by photolyzing W(CO)5L in the presence of LAM-3'"68 When L is a substituted pyridine, the spectral data show that the W ---> py CT state moves smoothly to lower energy with more electron-withdrawing substituents on the pyridine, while the ligand field states are essentially insensitive to these changes.°7 The 2980K emission centered in the 550-700 nm region is sensitive to the nature of the pyridyl ligand substituents and emission quantum yields range from 1.0 x 10“ to 56 x 10“.68 The W -—--> L CT state is virtually unreactive; eg. cis-W(CO)4(4eformylpyridine)2 undergoes photosubstitution with a 436 nm quantum yield of ~0.0007. Complexes having LF lowest excited state are very photosubstitution labile; eg. for L = 3,4-dimethylpyridine, 4-ethylpyridine, or pyridine the photosubstitution of L in cis-W(CO)4L2 occurs with a 436 nm irradiation quantum yield of ~0.4.°° Kinetics. In order to elucidate the excited state processes in a certain photochemical reaction, it is necessary to make quantitative measurements of the Quantum Yields, excited state lifetimes, and rate constants of the different processes originating from the excited states. 17 A simple mechanistic scheme which can fit any unimolecular photochemical reaction originating from the triplet state is as follows: amsuLz. be GS ------ > 188‘ creation of singlet excited state OtisC) lES‘ -------- > 383‘ Intersystem Crossing of excited singlet to triplet state kr 388' ------ > intermediates s Intermediates --------- > Products; e: efficiency with which intermediates yield products Rs 388' ------ > GS radiative decay to CS (phosphorescence) ks 388' ------ > GS radiationless decay to CS he 388' + Q ------ ) GS bimolecular deactivation process (quenching) GS = Ground State ES = Excited State The quantum yield of a product is .(prwadu<:t) = .(IEBC))(¢XFN:pr11du<:t) ; (8) where P(product) is the probability that the triplet state yields the product versus any other process. 18 In the absence of an externally added quencher: P(product) = --------------- (9) In the presence of an externally added quencher Q: P(product) = ----------------------- (10) kr + kp + lid “1" kq[Q] Therefore, the Quantum Yield in the absence of a quencher is: “a _ . kr - (13¢)xax —————————————————— (11) kr+kp+kd In the presence of a quencher: O = 0(xsc)x¢x ----------------------- (12) kr + kp + kd 4" kqlol The Stern—Volmer equation70 is obtained from (11) and (12): 00/0 = 1+qu [0] . (13) r is the lifetime of the excited state and is defined as r = (kr + kp + ka)‘1 (14) From equation (13), a plot of 90/. versus [Q] gives a straight line with a slope qu. The value of kq is known 19 for triplet quenchers in various solvents71'72'73 and the value of r is easily determined. If the excited triplet state reacts intermolecularly with another substrate to give intermediates which decay either to CS or to products, Scheme 2 is modified to Scheme 3. Scheme 3 hv GS ------ ) ES .(xsc) 188'“I -------- > 388’ kr 385' + S ------ > Intermediates; S: Substrate reacting w1th the excited state a Intermediates ------ > products; a: efficiency with which intermediates yield products l-s Intermediates ------ > GS + S kp 4* Rd 388‘ ----------- > GS kq 3ES* + Q ------ > GS + Q The product Quantum Yield in the absence of a quencher is: G kr[S] “(product) = .(ISC) --------------------- (15) krIS] + kp + ka 20 Eq. (15) and the product quantum yield in the presence of external quencher is: .(product) - O WWW wig) . W + .244 OH DTHF THFCH3CN l-Phenyl-l-(Z- p—(Z-tetrahydrofuryl) acetophenone tetrahydrofuryl) acetophenone pinCCOl ethanol Benzophenone, 4—acetylpyridine and 4-benzoylpyridine were irradiated in acetonitrile only and were found to yield THFCHaCN in parallel to DTHF production. None of the products was isolated quantitatively. The phenyl and pyridyl ketones studied were irradiated at 313 nm in acetonitrile (0.1 M) with varying concentration of THF (hydrogen donor). All runs were analyzed for DTHF and for THFCHaCN. Plots of 0'1 products vs. [THFJ'1 (Double reciprocals) for both products analyzed are shown on Figures 2-6. The intercept of these double reciprocal plots is equal to Onax'l, i.e., the quantum yield for the photoreduction of the corresponding ketone at infinite hydrogen donor concentration while the slope over the intercept is equal to the ka/kr value of the triplet excited state of the ketone under study (kr is the same as defined in Scheme 3 of the introduction; ka includes both kc and kp constants of Scheme 3). Table 3 shows the intercepts as Casx'l values as well as the ka/kr values for each ketone studied for both products analyzed, together with the number of points used from each figure to draw the best line. Octahydro-2,2'bifuran usually gives a good linear correlation where 2-(2-tetrahydrofuryl)acetaldimine proved difficult to analyze; several points usually do not 26 T I I I I I I r 0.2 0.4 0.6 0.8 /.0 [2 I .4 [.6 [THF1'] (M_1) 1 (O) and®-l F9:- e fl 1"”. Jr‘ ‘1: T, ' - q 1 u e 2 Double CLlr ccal p1< s fox-(DUMP TleCH3LN , . -1 . . _ .- . . .. - (D) vs. [InF] 1n the pootoreouction of aretoimenone by THF in acetonitrile. 27 DTHF 180- [60‘ I40- 120« I00~ 8C)« 60- 4(7‘ 2C}- Ix) 219 .319 419 51) [anl‘l (M'l) Figure 3. Double reciprocal plot for(I)B%HF ([25) vs. [THF]—1 in the photoreduction of acetophenone by THF in benzene. 28 80- I. II (171 ' I 0 7C21 1. 1. 1. D U 60‘ 50 I I I 0.2 0.4 0.6 d8 Lb /.2 AZ: [Turi'l (m“) Figure 4. Double reciprocal plots f°r(I>DIHF ((:)) and(I)TEFCH3CN ([:]) vs. [THF].1 in the photoreduction of benzophenone by THF in acetonitrile. 29 0.2 0.4 0'6 (58 170 Al? [THF]“ (M-ll . ' -l -1 Figure 5. Double rec1proca1 plots f0r(I>DTHF ((:)) andTHFCH3CN ([:]) vs. [THF].l in the photoreduction of 4—acety1pyridine by THF in acetonitrile. 30 O (151 O O 4cn9« O O C] 300« 2001 100‘ I as <14 as < .>~o>«uooanon .nuewoa m use a ”scan ozu Mo ouco>< .Auxou uouv segues assumes has; vouuottoo sew-«vaoaoosfiamusuonvmnsnuoalmVlwnzon=ou=h .consuamuw.ulocv>:ouoo n amp: 2 o~.o u .ocoLux_ um v . ~ uwm w M." ma” m o.~ mm~ 20n=u cm ocuvanqumoucomnv m mw.v m.mm . n ~m.> mud zonzo cw oewvwcmadaaoo w mm.o ~.Nm zoozo ca ococozaoacom a in is . mo.o H No.~ ~.~ H m.>N ocoucom em e um.~ c.me e ~o.c H hm.~ m.~ H ~.m~ zonro cm ococoso0uou< summon co txxamii a-..mw nuance co txwmm .-..mw Lucas: coals: umwawmwmw mmmmm nomawmme sunsets quconox .mzh an success umuwnma ho newuostLOuocm so~=oo~0lnouc~ emu loam saunas: .n ounce LO LO even after a very short time of irradiation (about 0.5 hr.). Free ligand which was not present before irradiation was detected by g.c. analysis; after much longer irradiation times, octahydro-2,2'bifuran and 2-(2- tetrahydrofuryl)acetaldimine were detected, consistent with a free ligand reaction. The same reaction carried out in water using the same concentrations as in acetonitrile gave no free ligand and no photoreduction products even after prolonged irradiation (130 hrs.). gmthenimm Complexes. A full list of all the ligands used and their hydrochloride salts, their syntheses as well as their purification procedures, where applicable, are given in the experimental section. Pyridyl ketones and their hydrochloride salts were kept in the dark at room temperature. No decomposition problem was encountered. Rmthenium, Pentaammine Complexes. They were prepared by the procedure shown in Scheme 5.15.15 34 Scheme 5. reflux [Ru(NHs)s]C13 + HCl > [Ru(NH3)sCl]C12 AgzO, CF3COOR [Ru(NH3)sC1]C12 in H20 Under Argon l) Zn-Hg 2) py-X 3) NHe-BFs v [Ru(NH3)5(PY‘X)](BF4)2 Reduction and complexation were accomplished in a continuous process as is described in detail in the Experimental Section. Pentaammine pyridyl complexes are sensitive to long exposure to the air so they were prepared under -Argon. Complexation results in color change of the reduced Ru(II) (deep yellow) to deeper yellow for pyridine and 4- cyanopyridine or to deep purple for all the other complexes. The absorption spectrum (look under spectroscopic studies) is dominated by the strong MLCT transition in the visible 35 region with characteristic extinction co—efficients in the area of 10000 M'1 cm’l. Further verification of the compound identity is given by the proton nmr spectra.76 All complexes were isolated as the tetrafluoroborate salts. In the IR spectra of all the compounds, we see the strong absorption band of the tetrafluoroborate group in the region of 1200-900 cm‘l.77 Free ligand present in the complexes was less than 0.01% by g.c. Ruthenium 2,2'bipyridine and 1,10-Phenanthroline Complexes. They were prepared by the procedure shown in Scheme 6.78.79 Scheme 6. RCl/Hzo K3[RuCle] > [bidenH][Ru(biden)Cla] H20 pH ~ 1.1 2 biden l) DMF/reflux 2) MeOH/H20,ref1ux 3) LiCl 1 cis-[Ru(biden)2Clz]-nH20 l) H20/MeOH,py-X reflux 6 hrs. 2) NHeBFs V cis-[Ru(biden)2(PY‘X)2](BF4)2 biden = bidentate ligand: 2,2'bipyridine, 1,10-Phenanthroline 3 ll 1 for biden 1.10-Phenanthroline 2 for biden 2,2'bipyridine :3 ll 36 Reflux in DMF brings the bidentate ligand operating as counter cation in the first complex into the first coordination sphere with simultaneous reduction of Ru(III) to Ru(II). Recrystallization from water/methanol 1:1 (v/v) follows which gives the deep brown solution of [Ru(biden)2Cl(H20)]* which is precipitated as cis— [Ru(biden)2C12].nH20 by the addition of excess LiCl and removal of solvent. This retains one or two water molecules depending on the bidentate ligand (look at Scheme 6).73'79 The two chlorine atoms can easily be removed from the first coordination sphere and the his (pyridyl) complexes can be prepared. The relatively long reflux needed is probably due to the low solubility of the cis-[Ru(biden)2C12].nH20 complexes. All the bis(2,2'bipyridine)-bis(substituted pyridine) Ruthenium(II) complexes are orange-yellow in color and their visible absorption spectrum is dominated by the strong MLCT absorptions with extinction coefficients in the region of 10000-14000 M'l cm‘l. Further verification of the complex identity is given as in the case of their pentaammine . counterparts by the proton nmr spectra. [Ru(bipy)s](BF4)2 gives a clean proton nmr spectrum of 2,2'bipyridine where one can distinguish each proton separately. The proton nmr of cis-[Ru(bipy)2(py-x)2](BF4)2, though, exhibits a complicated aromatic region similar to cis-[Ru(bipy)2C12].2H20. Diastereomeric placement of the two 2,2'bipyridines renders them magnetically unequivalent 37 with different chemical shifts. All complexes were isolated as the tetrafluoroborate salts. In the IR spectra of all the compounds, we see the BFa' absorption (1200-900 cm’l).77 Free ligand present in the complexes was less than 0.013 by g.c. uthenimm Porpmyrines. Ruthenium Porphyrines were synthesized by the procedure given in Scheme 7.30-31-82 flamyLl- reflux in toluene Porphyrine + Rua(CO)iz a: RuPorphyrine(CO)(solvent) under Argon . l) hv,pyrex filter in Benzene/THF ligand,ref1ux in Benzene 2) Ligand RuPorphyrine(CO)(ligand) RuPorphyrine (ligand): Porphyrine = Tetraphenyl Porphine or Octaethyl Porphine. Solvent = THF in the case of Tetraphenylporphine and CHaOH in the case of Octaethylporphine. From the first step, RuPorphyrine(CO) is isolated where the sixth coordination position of Ruthenium is occupied by a solvent molecule such as THF originating from the purification procedure (column chromatography and recrystallization).3° This weak ligand can easily be replaced by reflux of RuPorphyrine(CO)(THF) with the desired ligand in benzene. Bidentate ligands like pyrazine can form d1. of ex Ru ah re ca re pr Ru ad 5C 50 at 11'6 8C Cc ft Cc It 38 dimers when added in half stichiometric amount of monomers of the type RuPorphyrine(CO)(pyrazine) when added in large excess. To replace CO and prepare complexes of the type RuPorphyrine(ligand)2, we modified the literature method by which RuPorphyrine(pyridine)2 has been prepared.3°-32 CO is removed photochemically in the presence of pyridine. In our case, the pyridyl ketone ligands are photochemically reactive, so RuPorphyrine(CO)(solvent) was irradiated in the presence of THF so the highly reactive intermediate RuPorphyrine(THF)2 is presumably formed and subsequently added to the free ligand. The desired RuPorphyrine(ligand)2 is immediately formed. Decisive proof about the compound identity has been given by proton nmr and IR spectra. Spectromcopic Studies. Ruthenium Complexes are absorbed on the surface of old, scratched glass. Glassware treated in hot water-alconox solution 3-4 times, for 24 hrs. each time, becomes foggy and absorbs the complexes, in some cases leaving the solution almost colorless. The absorbed complex seems to be very well bound on the surface and washings with solvent are not adequate to remove it; it can be removed only with concentrated hydrochloric acid. In order to make solutions for quantitative measurements, including extinction coefficient determinations as well as quantum yield measurements and Stern-Volmer studies, it is necessary to use new glassware. 39 Table 4 displays the absorption maxima and the extinction coefficients for all the compounds studied, together with literature values when data are available. For the calculation of the molecular weight of the pentaammine and bis(2,2'bipyridine) Ruthenium Complexes used to measure the extinction coefficients, it was assumed no water of crystallization, even though in the IR spectra of all these complexes a broad strong absorption is always observed in the 3500-3000 cm"1 region, characteristic of the O-H stretching vibration. For the pantaammine complexes, this IR band is not conclusive about the existence of crystallization water since N-H vibrations are expected in the same region overlapping with O-H vibrations. Nevertheless, the error in the worst cases of low extinction coefficients and low complex molecular weight is less than 7%, assuming two water molecules are co-crystallizing with the complex. Figures 7, 8 and 9 display the absorption spectra of some pyridyl ketone ligands, their hydrochloride salts, and the corresponding Pentaammine, bis(2,2‘bipyridine) and Porphyrine Ruthenium complexes. Pentaammine complexes do not emit either at room temperature or at 77°K.85a In Table 5, emission maxima are listed.in parallel with the triplet energies in kcal/mol for all the complexes which emit. When a vibrational structure is present in the emission spectrum, the triplet energy reported corresponds to the highest energy peak. Those compounds for which the only emission spectra given are in 40 Avg MN.: New AL: owl: man :3 no.3 mew co zoo: wovw $538 mom ammo: m.~om Z Ammmv: mdmm O O Ammvm v cow o~duudcouooo ozsson~umwmavin.v Avg 35.8 mmm :2 92; mum ”to: 8323.. 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Absorption spectra in acetonitrile of 4PhBP (- ---) at 7.4 1074 M, 4PhBP.HC1 (~~--) at 5.2 10-4 M, -5 3)5 4)2 ( ) at 6.8 10 M and A cis-[Ru(bipy)2(4Pth)2](BF4)2 (— - —) at 1.2 10‘ M. [Ru(NH (4PhBP)](BF 46 2 >. A.) -.-4 U) C 5" 1. P... CO U -r-'l A.) O. c: () I ‘ f". I fir —I' 300 400 500 Wavelength, nm Figure 8. Absorption spectra in acetonitrile of 4EsterBP ( ----- ) -4 at 7.8 10‘4 M, 4EsterBP.HCl c ~.~) at 5.5 10 M, ( ) at [.2 10-4 M and [Ru(NH3)5(4EsterBP)](BF‘4)2 . -4 c13—[Ru(bipy)2(4EsterBP)2](BFA)2 (- - r) 231 1.-2 10 M- .2 cm N.~ om AHHV “AHV z m-os 0.8 on meanesco acmnlgnae an A- - -V Nflamza4vam03m .N in sammataasm ccma "AHHV “AHV : msofi q.m on A 47 E: .Lom:o~m>w3 n88 V Nfimmcmevmmesm mo meHcoHco mcoasznme ca mcoooam ceaoqcomg< .0 ocawflm . . . . . . . - . _ a . . _ _ . . A H s ——_—‘_.-_.._—- o Klgsuou [ejiido . 'lells ~nII-Avuw 'e. a :1:§ we.~§ .h ‘ tans e ‘w-hl‘ 'hv-heb‘ - N ‘5... has“ Cole‘s £91-0‘...‘ ‘48 v.m¢ ~.mv m.o> m.ob m.mm v.06 m.mm «.mm o.mm ammo mum ammo Non mum own one: nee wwv: mme vov mmv moo omv «no wow «we mmv mum vac mmv nmv owv «we owe com com com con can com com com com eh he he be be be he he be ob =Oum\zoo: =OuM\=out acuM\=ODz =OuM\=ooZ mouM\=ovz =0uM\=ouz =oLM\=ooz :ouM\=ooz =OuM\:ooz :OuM\=ooz «Assay.«xtouamevaAssnnvsma-nso ~A.Ammv.«aameaeeuAsaaavam.-aLu uo=.mmsounme mascummv ~o=.mm£mv mange ococosauowownum.q some sang ~0l\~oom .sm In. use A cemeewlu I: .couusuwoxe so .9 «cosaom vcsonloo .uoxoassoo Issuance: cause on: noun-«a one. no. once scan-«nu .n oases 49) m.bv m.h¢ h.wv m.wv o.mv o.mv v.on N.om c.mv h.mv o.mv «.mv man new mom mam one: can ommc Nam bmm bum mmm NNw mum mam: 5mm mum: can mum can ovv ovo ovv owe owv com cue ode o~v cav man owe be 65 he 55 be be so he mean: Loan: Loan: sous: =OuM\=ovz =OLM\=ODZ =OuM\=ooz =Oaw\:oot ZOuM\=oot EOuM\=oot hzbotlm uses: «1.8mv.nflcogao=mm ~A.hmv_aficogavxssngv=m_ .mymmv_laoeavalsa2scam. ~A.umc.aasaanc=m_ am.amv_~Aamvuamnwavsm_unwo ~Avmmv_mamavuaammnvsm.|owo 50 methanol/ethanol glass at 770K do not emit at room temperature. Figures 10 and 11 display the emission spectra of some pyridyl ketone ligands, their hydrochloride salts and the corresponding Ruthenium complexes, used in intramolecular photoreduction studies for direct comparison. All emission spectra are uncorrected. Figure 12 displays the absorption and emission spectra of bis(2,2'bipyridine) and 4,5-diazaf1uorene; the implications and conclusions extracted from these spectra are discussed later in the Discussion Section. Esme-.2 511112158- Ground and lowest excited state (MLCT) resonance Raman spectra were recorded for almost all the Ruthenium complexes cited in Tables 4 and 5. Most of the Ruthenium complexes which contain 2,2'bipyridine give excited state resonance Raman spectra identical to the one obtained for [Ru(bipy)3]2*.42'43 Cis-[Ru(bipy)2(py)2]2+ gives a mixture of excited state spectrum (Raman scattering from cis- [Ru(III)(bipy)(bipy;)(py)2]2*) and ground state spectrum.86 Cis-[Ru(bipy)2(4AP)2]2* exhibits only a ground state spectrum containing contributions of both 2,2'bipyridine and 4-acetylpyridine. 1,10-Phenanthroline complexes (without 2,2'bipyridine) do not give‘ excited state spectra even in the case of [Ru(phen)3]2*, the MLCT excited state of which is known to 51 Relative Emission 400 500 600 700 800 Wavelength, nm Figure 10. Emission spectra of 4PhBP (— - —), 4PhBP.HC1 F—), Cis—[Ru(bipy)2(4PhBP)2“8174)2 ( ----- ), [Ru(bipy)3](BF[‘)2 (u-u.), at 77 °K in l:l (v/v) ethanol/methanol glass. Concentrations between 10—5 and 10-4 M. Excitation at 300 nm. 52 E \ E \. o \ s k. C \. E \ \ \ 1 \ X \. \. \\~ 460 590 600 700 800 Wavelength, nm Figure 11. Emission spectra of 4EsterBP (- — —), 4EsterBP.HC1 (——-—). cis—[Ru(b1py)2(4EsterBP)2](BF4)2 ( ----- ) and [Ru(bipy)3](BF‘4)2 ( ------ ) at 77 °K in 1:1 (v/v) ethanol/methanol glass. Concentrations between 107‘5 and 10—4 PL Excitation at 300 nm. 53 2 4‘ I I I I ' I I 1 l ' l l I ' u I Q ' l S H : ll '1 D n g, s: ' n , ‘ < ' H ‘ w l '1 f I 7 h .1 I 1" g I . , \ \ w. . If” y K o ‘ a 3 ll ”I‘ y‘ 1 l a 'd l V ' ’7 I- o a , I I3 1 a 61+ ‘ I l I I! . o 3 1 .. . . l | _ . U \ n F. l ' ' '\ G 3 . . , ~. :- .u-4 l 1 I \ n 3 ' I . , 2 O 1 I l ' \ ~< I l " I l ‘ “ g l l , \ H. l l fl I | l \. tn ' l l \' P\ l, I ‘ \.\ I ‘ I ‘ ' l l \ c l l ' ,\ ‘ ' | ' | - - 7' ‘ '\. ‘ l l ' I \ ‘ \l‘ " l ' I ' I“\. ‘1 ‘ ’I | ~._ _ ‘ - - \J I I l 0 ‘ T U I T v I 200 300 400 500 600 700 Wavelength. nm Figure 12. Absorption spectra in acetonitrile of bipy ( ) at 1.2 10-4 M and 4,5-diazafluorene (- — —) at 8.3 10-5 M. Emission spectra of bipy ( ----- ) and 4,5-diazaf1uorene ( ------ ) in 1:1 (v/v) ethanol/methanol glass at 77 °K. Concentrations in the range of 10"5 to 10-4 M. Excitation at 300 nm. be 54 be long lived.87 Instead, they give spectra identical to the ground state spectrum. The Pentaammine 4-acetylpyridine Ruthenium(II) complex gives a spectrum88 similar to the 4-acetylpyridine anion radical while the Pentaammine pyridine88 or 4-cyanopyridine Ruthenium(II)89 complexes exhibit scattering only from the ground state. Conclusions drawn from the Raman data are given in the discussion section. Intramplecmlmr Photoredmction. The Intramolecular Type II photoreduction of efree pyridyl ketones, pyridyl ketone hydrochloride salts and of pyridyl ketones coordinated to a Ruthenium center were studied. The Ruthenium complexes studied were the pentaammine, the 2,2'bipyridine and the tetraphenyl- or octaethylporphyrine ones. The intermolecular quenching effect of the [Ru(NHa)s(4AP)](BF4)2, cis—[Ru(bipy)2(4AP)2](BF4)2 and cis- [Ru(phen)2(4AP)2](BF4)2 complexes on the intramolecular photoreduction of butyrophenone was also studied. These results have been used, as shown in the discussion section, in order to make corrections on the coordinated ketone lifetimes, taking into account the bimolecular self- quenching effect of the Ruthenium complexes. 55 Photoprodmct Identifipmtion. The following five reactions were investigated with respect to the photochemical Type II fragmentation of the coordinated pyridyl ketone and compared with the photochemical data from the free pyridyl ketone ligand and its hydrochloride salt (see below). 313 nm _ R NH ) (4PhBP)](BF )2 --------- > [Ru(NHs)s(4AP)](BF¢)2 + (20) [ II( 3 ‘ ‘ CRsCN ©—\ 313 nm cis-[Ru(biPY)a(4PhBP)a](BF4)2 -------- ) CRsCN cis-[Ru(biPY)s(4PhBP)(4AP)](BFo)z + ‘<:>fwg (21) 313 nm RuPorthyrin(4PhBP)a --------- > RuPorphyrine(4PhBP)(4AP) + <:>rw§ (22) CHaCls 313 nm 0 [Ru(NHa)s(4EsterBP)](BIN): ------------ > [Ru(NHo)s(4AP)](BF¢)2 + M (23) CRsCN O 313 nm cis-[Ru(bipy):(4EsterBP):](BFc)a -------- > cis-[Ru(bipy):(4EsterBP)(4AP)](BF¢)2 CHsCN cis-[Ru(bipY)a(4EsterBP)(4AP)](BFa): + if g_;; (24) All the irradiations were performed at 313 nm. All the starting complex concentrations were 0.02 M. Solvents are shown for each reaction separately. Irradiation times 56 varied widely. For a 5-10% conversion, reaction (20) needs 15-20 hrs.; reaction (21) needs 20-25 hrs.; reaction (22) needs 10 days; reaction (23) needs 30-35 hrs. and reaction (24) needs 7 days. Styrene produced from (20), (21) and (22) becomes apparent by its characteristic odor and was identified from its gas chromatographic retention time, by comparing to an authentic sample. N-butylacrylate produced from (23) and (24) was identified from its chromatographic retention time by comparison to an authentic sample as well as by gc/ms. A sample of cis-[Ru(bipy)z(4EsterBP)2](BF4)2 was analyzed before and after irradiation for n-butylacrylate. No gc peak corresponding to n-Butylacrylate was present before irradiation, while after irradiation a peak was present which gave the same mass fragmentation pattern given by a neat sample of n-butylacrylate. All Ruthenium complexes were tested after irradiation for ligand dissociation and in no case was any pyridyl ketone ligand or photoproduced 4-acetylpyridine found in the bulk solution. An experiment to measure the 4AP produced and compare it with the amount of styrene formed failed to give quantitative release of the coordinated photoproduced 4AP. According to Whitten, he was able to remove quantitatively the coordinated 4-stilbazole molecules from cis- [Ru(bipy)2(4-stilbazole)2](PFs)2 by refluxing the complex in 57 n-butyronitrile in the presence of triphenyl phosphine for 24 hrs.32 Efforts to repeat Whittenfs experiment with cis- [Ru(bipy)2(4PhBP)2](BF¢)2 gave the results displayed in Table 6. In the best case, it was possible to obtain only 35% as much 4AP as styrene. I;§13_§. Mass Balance Experiment for styrene and 4AP been produced in the Type II cleavage of cis-[Ru(bip¥)a(4PhBP)al(BF¢)a.' Reflux solvent time,(hrs.) [styrene],(M) [4AP],(M) acetonitrile 24 - 0.00168 0.000590 n-butyronitrile 24 0.00164 0.0000743 '[complex] 8 0.02 M, [PPhs] = 0.2 M. Finally, in agreement with previous observations,85c pentaammine complexes bleach while bis(2,2'bipyridine) complexes remain unaffected by prolonged irradiations. Figure 13 illustrates this phenomenon for the two pentaammine Ruthenium complexes studied. The bleaching (loss of optical density) becomes less effective as the amount of a quencher, like ethyl sorbate, increases. Table 7 summarizes the data from Figure 13. No products have been isolated. 58 . . __.-’ H. ~‘ - ’ §.~. . ,-\J- k. Optical Density ”-- I I I I 300 400 SC” 600 700 Wavelength, nm Figure 13. UV-Vis. absorption spectra upon 313 nm irradiation of 1.0 10-4 M [Ru(NH3)5(4EsterBP)](BF4)2 (top frame) and 5 7.5 10- M of [Ru(NH (4PhBP)](BF4)2 (bottom frame) in 3)5 acetonitrile. (.u- ): 2 hrs irradiation, 0.00920 einstein. (---9: 6 hrs irradiation, 0.0287 einstein. Table . UV-Vis absorption data of [Ru(NRs)s(4PhBP)](BF4)z. cis-[Ru(bipy)a(4PhBP)a](BFh)s. [Ru(NRs)s(4EsterBP)](BFh)z and cis-[Ru(bipy)z(4EsterBP):l(BF4)s upon irradiation at 313 nm. Complex Time of irr. Amount of light limes, (A) Asia (hrs.) (einstein) [RU(NHs)s(4PhBP)](BFc)z' 0 0.0 (507) 0.790 0.082 2 0.00920 (596) 0.056 0.086 6 0.0287 (593) 0.047 0.084 cis-[Ru(bipy)z(4PhBP)](BF.)2b 0 0.0 (422) 0.336 0.342 6 0.0287 (422) 0.256 0.313 12 0.0829 (422) 0.251 0.311 [Ru(Nlis)s(4EsterBP)](BF4)2c 0 0.0 (507) 1.002 0.123 2 0.00920 (601) 0.172 0.107 6 0.0287 (603) 0.137 0.093 cis-[Ru(bipy):(4EsterBP)](BI-“4):d 0 0.0 (456) 0.370 0.339 6 0.0287 (456) 0.374 0.349 12 0.0829 (456) 0.374 0.341 ' 7.5 10'9 M in acetonitrile. ° 2.6 10‘5 M in acetonitrile. c 1.1 10" M in acetonitrile. ‘ 2.8 10‘5 M in acetonitrile. ID 60 Quantum YieldfiStudies. Quantum yields for photoproduct formation were obtained by irradiation of the appropriate samples at 313 nm in a ”merry-go-round” apparatus at room temperature using Valerophenone actinometry. Photoproduct quantum yield from cis-[Ru(bipy)2(4EsterBP)2](BF4)2 and from RuPorphyrine(4PhBP)2 were obtained using 0- methylbutyrophenone and o-methylvalerophenone actinometry9° due to long irradiations necessary to build measurable amounts of product. Table 8 displays the Quantum Yields measured and Figures 14, 15 and 16 demonstrate the effect of varying ketone (or complex) concentration on the Quantum Yields. Free pyridyl ketone Quantum Yields according to previous observations°54'°1 increase linearly by increasing the ketone concentration while hydrochloride salt quantum yields seem to be insensitive to concentration variation.83d Quantum Yields of Type II cleavage from Ruthenium Pentaammine and 2,2'bipyridine complexes seem to be very strongly sensitive to complex concentration with a decrease in the quantum yield under conditions where all the light at 313 n. is absorbed by the complex (o.n.>2). This observation implies an intermolecular quenching effect, thus justifying the experiments of quenching of butyrophenone by Ruthenium Complexes described under "Quenching Studies” below. 61 Table 8. Quantum Yields and kg 7 values for 4PhBP, 4EsterBP, 4PhBP.HCl, 4EsterBP.HCl and the corresponding Ruthenium Complexes.‘ Compound k 1 1) kg r‘I 4PhBP 0.42: 9.74 t 0.54! 4PhBP.HCl 0.093c 2.05h [Ru(NHs)s (4PhBP)](BF4)2 0.014 t 0.001 6.89 1' 0.98 (4.99 i 0.01)‘ cis-[Ru(bipY)2(4PhBP)2](BF4)2 0.0072 t 0.0001 3.44 .+. 0.30 4EsterBP 0.41 i 0.04 167 1' 12.5 4EsterBP.HClf 0.096 31.5 i: 1.2 [Ru(NHs)s(4EsterBP)](BFI): 0.0051 1:0.0008 68.3 (52.6)1 cis-[Ru(bipY)2(4EsterBP)2](BF4)2 0.0017 i:0.0001 23.6 1:0.01 RuTPP(4PhBP)2b 0.000203 RuOEP(4PhBP)2b 0.000220 ‘All compounds 0.020 M in acetonitrile (unless otherwise noted) irradiated at 313 nm. t’Methylene chloride solvent. “Estimated from Figure 14 for [4PhBP] = 0.020 M and for [4PhBP.HCl] = 0.020 M. ' “Average of two runs. '[4EsterBP] = 0.021 M. f[4EsterBP.HCl] = 0.030 M. ‘[4PhBP] = 0.040 M, 2 runs. h[4PhBP.HCl] = 0.040 M, 1 run. ‘For nudaers in parentheses, see text: eq. 25. 62 e 0.57 . e 0.4« ' O O e 0.3« e 0.2- 0" ‘ D i I I m I I 0.51 ' 0.03 ' 0.05 ' 0.07 [ketone], (M) Figure 14. Effect of ketone concentration on the Type II products quantum yield. Ketones irradiated at 313 nm in acetonitrile. (.): 4PhBP; (I): 4PhBP.HCl. (O) and (D) correspond to quantum yields corrected for partial light absorption by the ketone. 63 . A Do was: Nastabasaeseéi. .8 Ba .23 aleszalaeevaea.eé.ae .AOV aleaezbasmmsé new name» ashamed co xoaqsoo Esacozusm mo :ofiumsucoocOo co soouwm .mH shaman sz ._xalaeeaa ems. nae was and flu mu D D AV .8 O Q 0 AV 0 a. no .01 AV is AV mosxawv O 0 AV Tma 64 .NAmmcmqum05m we mamas Essence one Cu accommoccoo AAGVV .AAHVV ecmmafi one we owm>moao HH same one new mama» Esuemsc one so NAmmcmqvmmesm mo cowumsucoocoo mo ooowmm .oH shaman lee ._Nlaaeaeoaeaeaeaueaaa_ woo 5.0 4‘ 65 Quenching Studies. Stern-Volmer quenching of the Type II cleavage was performed by the 313 nm irradiation of constant concentration (see Table 8) of the pyridyl ketones, pyridyl ketone hydrochloric salts, Pentaammine pyridyl ketone Ruthenium(II) complexes as well as of the cis- bis(2,2'bipyridine)-bis(pyridyl ketone) Ruthenium(II) complexes with varying concentrations of . quencher as described in the experimental section. The Quencher used was ethyl sorbate which is a diene (classical triplet quencher) miscible with acetonitrile in any proportion. Conversions to products were usually kept below 10%, and the qu values reported (Table 8) usually come from duplicate runs. Figures 17 and 18 compare the Stern-Volmer plots of the pyridyl ketones and the pyridyl ketone hydrochloride salts in the cases of 4PhBP and 4EsterBP, respectively. Figures 19 and 20 compare the Stern-Volmer plots for the Pentaammine pyridyl ketone and the cis-bis(2,2'bipyridine)- bis(pyridyl ketone) Ruthenium(II) complexes for the same two ketones. The Stern-Volmer plots of Pentaammine pyridyl ketone Ruthenium(II) complexes exhibit an unusual phenomenon: they have intercepts lower than unity, while the slopes are quite reproducible. The slope/intercept values vary widely;‘ qu values reported on Table 8 are the slope values only. The numbers in parentheses cited next to these values are the qu values calculated through the modified 66 02 ' 0?: ‘ 36 [ethyl sorbate], (M) Figure 17. Stern Volmer plots for 4PhBP ((:)) and for 4PhBP.HCl ([:]) in acetonitrile. 67 <1>° 6.. I e 5- 4.. .3; II D 2‘ I r I... 0.02 0.04 0.06 0.08 0.70 0.72 074 0.70 [ethyl sorbate], (M) Figure 18. Stern Volmer plots for 4EsterBP ((:)) and 4EsterBP.HCl ([:]) in acetonitrile. 68 (19° 5-1 0 4" O I I Cl I 3.. fl 24 ' I s ,9 I", 0'1'0'3 T05 ' 0'7' [ethyl sorbate], (M) Figure 19. Stern Volmer plots for {Ru(Nig)5(4PhBP)](BF4)2 (O) and for cis—[Ru(bipy)2(4PhBP)2](BF4)2 (D) in acetonitrile. 69 Figure 20. 0.62 ' 0.64 ' 0.66 [ethyl sorbate], (M) Stern Volmer plots for [Ru(NH3)S(4ESterBP)](BF4)2 (C1) and for cis—[Ru(bipy)2(l+EsterBP)2](BFA)2 (O) in acetonitrile. 7O Stern-Volmer relation (25) for each point of the Stern- Volmer plots (Figures 19 and 20) individually and averaging. l-O°/. [Q] kg!’ (25) Stern-Volmer quenching studies were also performed using as quenchers the [Ru(NHa)s(4AP)](BF4)2, cis- [Ru(bipy)2(4AP)2](BF4)2 and cis-[Ru(phen)2(4AP)2](BF4)2 complexes to quench the intramolecular Type II photoreduction of butyrophenone. The purpose of this experiment was double. First was to verify that there is an intermolecular triplet energy transfer from the pyridyl ketones to another complex molecule, thus explaining the decrease in the quantum yield of the intramolecular Type II cleavage of coordinated pyridyl ketones with increasing complex concentration. Secondly was to prove that the photoreduction from the Ruthenium complexes comes from complexed ligand only and that any free ligand, even though not detectable by g.c., is completely quenched by the relatively high concentration (0.02 M) of the Ruthenium complex. Butyrophenone concentration in all these experiments was high (0.5 M) in order to absorb most of the light at 313 nm while the concentrations of the Ruthenium complexes were kept low. It was found that Ruthenium complex concentrations up to 0.005 M were enough to quench 60-80% of the photoreduction. Quantum yields always were corrected for the fraction of the light absorbed by the 71 ketone. Details are given in the experimental section. Figures 21 and 22 display both the uncorrected and the corrected Stern-Volmer plots for the quenching of butyrophenone by [Ru(NH3)s(4AP)](BF4)2 and by cis— [Ru(bipY)2(4AP)2](BF4)2, respectively. As can be observed from Figure 22, the intercepts of the corrected Stern-Volmer plots in the case of cis—[Ru(bipy)2(4AP)2](BF4)2 quencher are consistently higher than unity. Figure 23 displays the effect of cis- [Ru(phen)24AP2](BF4)2 on the butyrophenone photoreduction; it was though that 1,10-Phenanthroline, due to its extended conjugation relative to 2,2'bipyridine, can serve as a representative model to elucidate the ruthenium complexes’ quenching trend, going from 2,2‘bipyridine to Tetraphenylporphyrine and Octaethylporphyrine, comparing this way the quantum yield ,found for the Type II photoreduction of RuTPP(4PhBP)2 and of RuOEP(4PhBP)2 with the quantum yield found for [Ru(bipy)24PhBP2](BF4)2. qu values calculated from the corrected curves for each complex are cited in Table 9. f—i 72 ‘ 0602 r 0.604 ' oboe ' oboe l[Ru(NH3)5(4AP)](BFA)2 1. (M) Figure 21. Stern Volmer plot for butyrophenone quenched by [Ru(Nl‘l3)S(5AP)](BFA)2 . (O): uncorrected curve. (.): curve corrected for partial light absorption by the ketone. ‘ 73 F l i (1)0 ¢ . 8‘ O A 7- £3 6.. o 5. A I 0.602 I 0.604 0.606 [ cis—[Ru(bipy)2(hAP)2](BFA)2 ]. (M) Figure 22. Stern Volmer plot for butyrophenone quenched by cis— Ci5‘[RU(biPY)2(“AP)2“31:45 . Two runs. (0) and (A): uncorrected curves; (.) and (A): curves corrected for partial light absorption by the ketone. 74 919° 0.0'0/ 0.603 r (2605 cis-[Ru(phen)2(AAP)2](BF;)2 ], (M) Figure 23. Stern Volmer plot for butyrophenone quenched by cis-[Ru(phal)2(4AP)2](BF4)2 . (O): uncorrected curve; (.): curve corrected for partial light absorption by the ketone. 75 Table 9. Results from Stern-Volmer quenching of butyrophenone by Ruthenium( I I) complexes . Quencher Intercept slope(qu) slope/intercept [Ru(NHs)5(4AP)](BFI)2 0.97 400 412 cis—[Ru(bipY)z (4AP): ] (at. )2 1.42 527 371 1.40 365 261 cis-[Ru(phen)z(4AP)2](BFq): 0.78 203 p 260 Ruthenipg 2,2'bipyripidipe and Ruthenium-Osmium 2,2'bipyrimidingfi bridged Complexes. Compound Preparation gnd Identification - Spectroscopic Studies. Ruthenium(II) tris (2,2'bipyrimidine) Chloride was synthesized by the route shown on Scheme 8, a modification of the literature procedure.36 &flmne£L l) 3 bipym, DMF RuCla ) [Ru(bipyl)3]C12 2) bipym, Eton/320 bipym = 2,2'bipyrimidine 76 [Ru(bipy)2(bipym)](BF4)2 and [Ru(phen)z(bipym)](BF4)2 were synthesized from cis-[Ru(bipy)2Clz].ZHzO or cis- [Ru(phen)2C12].H20 by refluxing these complexes in the presence of 5 molar excess of 2,2'bipyrimidine in 1:1 (v/v) water/methanol. Osmium Complexes (cis-[03(bipy)2C12].H20 and cis- [0s(phen)2Clz].H20) were synthesized by the literature procedure according the Scheme 9.92 Sdm:329. thdu: NikOsCls > [Os(biden)zClz ]Cl DMF ' sodium dithionite in water J. [Os(biden)zclz]'HzO biden = bidentate ligand (2,2'bipyridine or 1.10-Phenanthroline). Bimetallic complexes were synthesized according to Scheme 10. 77 Saba-349. l) reflux in 1:1 (v/v) HzOVMeOR [Ru(biden)z(bipym)](BFs)z + 1.5[Os(biden)zClzl'HzO 9 2) NHcBFk [Ru(biden):(bipym)0s(biden)2](BF4)4 bhkm bidentate ligand (2,2'bipyridine or 1,10-Phenanthroline). 2,2'bipyrimidine. bipy- Detailed synthetic procedures for all the complexes prepared are given in the Experimental Section. The compounds were identified by their Infrared Absorption Spectra, showing all the characteristic absorptions of the coordinated ligands. Further verification of the compounds identity is given by the comparison of their UV-Vis. absorption spectra as well as their emission spectra with the ones cited in the literature. The absorption maxima usually match well with the literature reported ones, eventhough the extinction coefficients were found somewhat lower. Table 10 summarizes our results in comparison to the literature ones when data are available. Here again, as for the Ruthenium Complexes of the previous section of this chapter, we assume no water of crystallization in the calculation of the extinction 78 8...: e as «on :- Amman V age can a. ascends emu .A.mne_«AaoeaeaoA-sasav«Asasnesm_ A.o~ o.~e paw Asap v «we own .msn .man ..a.. can .oom .mmn ..a. Aves H.ne use Amman e use :2 1: SN $.88 98“ emu :- can a. . .nxgos n.ne ecu Ammsn~e new .A.uav_«AsazpeaoA-sasae«Reassesm. A.c~ me.oe «an A.°~ mm.ue mac Avevn V mom can a. Aves ms.ce mom “accuse sfle can a. Aenmsmv n.ms~ .n.pn..nx.o~ n~.ne mow Anemone new .A.anv_«AsawaeaeAIAauav«Asauaesm. «we a. Amuse v o.~mm can a. Aunsmne New Ancomue m.-~ «A.uae_A-sasae~xcoeae=m_ Aves no.se one nee a. Amman e use pa..nx.o~ mz.~e nae Aeoseqv new man :- “sesame m.ne~ «A.uae_A-sauavuxsaznesm_ $2 3.8 So :53 v «3 A.o~ os.oe use Anew» v use . .HA.°~ me.~V am" can a. 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For some of the compounds cited in the literature, it has been proven that they retain a variable number of water molecules in their crystal structure. It is noteworthy that for some of the mixed ligand bimetallic complexes, the extinction coefficients found are substantially lower than expected for charge transfer transitions, a fact probably due to the purification procedure (Column Chromatography on a cation exchange Sephadex column eluting with NHqBFq aqueous solution) combined with the small scale preparation which tend to give products containing substantial amounts of NHqBFc. Nevertheless, when literature data are available, it can be seen that the .ratios of the extinCtion coefficients at the absorption maxima found in this work match well with the corresponding ratios from the literature, fact taken as further verification of the complex identity. Finally, Table 11 displays the emission data of the complexes studied. Eggpn Studieg. Ground and lower excited state (when applicable) Raman Spectra have been recorded by Y. C. Chung for all the compounds listed in this section. Tris (2,2'bipyrimidine) Ruthenium(II) chloride shows clear evidence that its peculiar absorption spectrum is the 82 contribution from two distinct MLCT states, one being in resonance at the 442 nm cw excitation wavelength, the other being in resonance 364 nm cw excitation. Employment of pulsed excitation from the Nd-YAG laser at 440 nm and 354.7 nm reveals new peaks which have been attributed to scattering from the complex having one of the 2,2'bipyrimidine ligands in the MLCT state: [Ru(III)(bipym)2(bipym*)]2*. Differences again . in the relative peak intensity and the appearance of two new peaks at 1255 and 1362 our1 to the red of the excitation line at 354.7 nm have been attributed to different upper electronic states being in resonance with the MLCT excited state of the [Ru(bipym)3]2+ when the two pulsed excitation wavelengths were employed. Similar behavior has been demonstrated for most of the 2,2'bipyrimidine complexes under this section of this chapter. Complete experimental description and interpretation of the Raman spectra with respect to their significance in the resolution of the absorption and emission spectra can be found in Y. C. Chung, Ph.D. Thesis, Michigan State University, 1985. Photochemistry of Tungsten Carbonyls. Qpppound Prepggption gnd Identification. Ligands. The ligands used were either commercially available or synthesized (4-valerylpyridine, 4- butyrylpyridine and 4-acety1pyridine) by the Grignard 83 reaction using 4-cyanopyridine and n-butyl bromide, n-propyl bromide or methyl iodide, respectively. Verification of the product identity comes from the spectroscopic data for each compound, a detailed list of which can be found in the experimental section of this thesis. All complexes synthesized along with their abbreviations are listed in Table 12. Pentacarbonyl TunggtepLQ) Copplexes. These complexes were synthesized from Hexacarbonyl Tungsten(O) according to the classical Strohmeier method. Scheme 11 shows the general synthetic route to prepare these complexes.“"69 SdMnn LL hv, pyrex filter Ligand W(CO)s 4% W(CO)5(THF) > W(CO)5(Ligand) THF,Aw THF replaces one photochemically removed CO molecule and THF is subsequently, after the end of the irradiation, substituted by -a better ligand, like the substituted pyridines used. THF has to be dry, otherwise, a white precipitate appears during the first minutes of irradiation, presumably W(CO)5(R20) and the reaction fails. The absence of the pyridyl ligand in the irradiation step is essential for two reasons. First, some pyridyl ketones are photochemically reactive and, second, this method, as has been reported,°9 leads to replacement of only one CO molecule and formation of Pentacarbonyl Tungsten(O) 84 voovz «Am>¢vvfioovxumso on evenness aaeoaznomxom on ausumnsa Aoaseutsaastosasuvvaua asaoasaoatsoaumsu Aaseemxooez Aoe couamasa moqseuusamstuao>uev ascentooauaua Ammvvaoovz on counussk Aoswvwahmahuhusmlvv ahsonzmomusom Asazoeemaooez Ace couuucse Aoczvucsaocasouev Haaoasaoauaem Assumevmxoovz on amuumnsa Amauewtsassouqumuev masonsaoasaoa Aoszsozvmxoovz on amswuasa Aouaawuouflaousussasmav sauoasaoauaoa Aaouna< use can Ace aosuuasa so measoaaao ascentao .NH msnam 85 complexes. Purification is achieved by column chromatography and, when possible, recrystallization. All the complexes studied are yellow solids, except Pentacarbonyl [l-(4-pyridy1) pentanone] Tungsten(O) which is a deep orange oil. They all decompose at temperatures ranging between 70 and 130°C yielding brown-reddish oils. Only Pentacarbonyl (4-cyanopyridine) Tungsten(O) seems to be stable since it can be recovered after melting. Nevertheless, all these complexes give interpretable mass spectra, including the molecular ion peak; the rest of the spectrum is dominated by the ligand fragmentation pattern as well as peaks corresponding to the original complex losing successive CO molecules. Proton and Carbon-l3 nmr spectra are also conclusive about the complex identity. Finally, visible light absorption spectra match precisely the spectra cited in the literature for those of the complexes having been synthesized before by other researchers. 86 Spectroscopic Studies. Absorption and emission spectra were recorded in both benzene and methylcyclohexane for all the compounds studied. Table 13 lists the absorption and emission data. Figure 24 displays representative absorption and emission spectra for Pentacarbonyl [l-(4-pyridyl)pentanone] Tungsten(0). In agreement with previous observations for a solvent- sensitive, MLCT lowest excited state, all the complexes’ absorption spectra show a solvent dependent long wavelength feature. In the less-polarizable methylcyclohexane, a separate peak is observed at the long wavelength side of the solvent insensitive peak at approximately 402 nm; the two merge as one moves to the more- polarizable benzene.°°'69 Emission was recorded in fluid solution at room temperature. Eventhough emission maxima tend to be insensitive to solvent polarity, the emission spectrum oVerall becomes broader in the less polar methylcyclohexane with a broad shoulder on the blue side of the maximum emission. linhminmflufl.8hmfies Photoproduct Identification. Mass Balance and Cross- coupling Experiments. Irradiation of four freeze-pump-thaw, degassed and hermetically sealed W(CO)s(4VP) solutions in both benzene and methylcyclohexane at 313 nm, 410 nm or 490 nm resulted in change of the solution color from orange-yellow to deep 87 m.nv N.nv o.m¢ m.nc p.0v ooo a. mum cum ova an ”mm «mm own am «No «No ova A. nNm «an as one A. Asmmmo new «on an Auo no. 2-. new on” a. onv A. 385 v3. own as «money now Agog mov won as one an Aouvmv nov Nan A. one A. onmmv oov NMM :- Anmvmo woe mmm~ «an no Amodmv ace :3va vov «no no one a. Ao_~me Noe menu «an :- vagueness... osowsoa oesxoso~050u>AuOI ”EON—~00 osoonoHo>o~>Auom ocouson onsxuso~o>ouhzuol ususson ossxoao~o>0u>nuom amounum Amnvoaaooe: Asazoevnmooe: Asaunevnmoov: Aoszuozemmooe: Am<¢o.xooe: Auom\~suxvuu la .xle .IIIIlulnnuummwmuwmmlunluuul. Anlautvflua Aqu—lxflv I“ all.“ (111mmdmmumNMQ. ua0>~om nasomloo .auhnonhso sou-mash one so» sad: soda-«mu one sowumhoan< . A smash 88 .nqomw u 83.—seals» .3. Nov as conduuuxm - m.av m.av o.av «Na ova :- nma «Na aoNN oNNN «vows 3v «name aov «on as onv 4a Avnamv Nov man as «moot mnv sons aov 05.533053550- econ-son $35 203: 89 2 :n m 1 ,m n m | n I H' >. ' 5 u \ .9; |‘ g" c \ _ r“ Q) \ ,~”\_ 1.. (I) C: t I \ '-. m 1 -‘ I I" \\ S. :6 l I, \.\ 1. a U | I' '\ a , Y2 é? l I \i l I .‘ I ” '\. \ , x \ \ / ~ " \3 X \ \‘ix 0 .sao 450 560 660 760 800 Wavelength, nm Figure 24. Absorption spectra of W(CO)S(4VP) in benzene at 2.3 10-4 M ( ) and in methylcyclohexane at 1.4 10-4 M (- - -). Emission spectra of W(C0)5(4VP) in benzene ( ————— ) and in methylcyclohexane ( ~--~). Concentrations between 10_5 and 10-4 M. 90 red. HPLC analysis gave two product peaks. The first product was initially identified as W(C0)s by comparing its HPLC retention time with an authentic sample. At longer conversions, upon longer irradiation, a white product precipitated out of solution. It was collected and identified as W(CO)s by mass spectrometry. Finally, a C-13 nmr spectrum of this product gives a peak at 191 ppm downfield from TMS, identical to the peak given by a neat sample of H(CO)s. The product responsible for the color change was isolated by column chromatography/recrystallization (for details, look at the experimental section) and identified as cis-Tetracarbonyl bis[l-(4-pyridy1)pentanone] Tungsten(O) (cis-W(CO)4(4VP)2). Figure 25 displays the absorption spectrum of the compound in both benzene and methylcyclohexane; these spectra are identical to the spectrum reported by Lees for cis-W(CO)4(4- benzoylpyridine)2.‘5a Figure 26 displays the Infrared spectrum of this compound, consistent with the assignment of the cis-geometry.9‘ The peak at 1695 cm"1 corresponds to the two equivalent ketone carbonyls of the ligands, while the strong peaks at 1990, 1880, 1855, and 1810 cm'1 correspond to the 00’s coordinated to Tungsten. Figure 27 displays the proton decoupled Carbon-l3 nmr spectrum; two peaks of equal intensity appear at 205 and 213 ppm. As has been reported’s, peripheral carbonyls coordinated to zero valent metal centers appear between 180 and 220 ppm, while bridging 91 -__-——---d I J Y OpticaL Densit 500 Wavelength. nm Figure 25. Absorption spectra of 1.9 10_4 M cis-W(CO)4(4VP)2 in benzene (-————Q. (— - -): absorption Spectra of cis-W(CO)4(4VP)2 in methylcyclohexane. .uwHHoa umx m CH mAm>qvqfloovzumwu we Essmumam emsmuwcH .om osswwm A Eu .smneaco>m3 00w: 8vs 86‘ 8Q\ 80w 8am 000m. 8am. 80v 92 commwcsh cu umumcwcuooo m.oo r Hzconumu occumx / 93 .mAumumvuo A>\3v N H mcwcwmucou colocmucmn cw NAm>vvvoov3umwo we Esmuumam as: nonconamo .NN augusa Egg on OO~ . owm 1...... 1.11.1, visageiaeéii _ ...1..............._d £1.11... \_ n :OhMmo .oo macho: m .ooumao hasewaaaln . . __ mconumu “ Hmowumaus _ M. mconamo asowaxauo 94 .Asouuonv maono cam Aneuv ovlmcmucmn cw NAm>qquoov3lmwu mo sauuumam he: cououm .mm muzmwm Baa .mw .0 . m , m w m M. 1. .. .. .4 “N \xlIIII m _ 1 m u 890 . . m p 2 w fl m m q m o n w o r _ L [— p b F L . _ L h b _ L L » _ L \l . . q r 411_ . . . m u once M . H u m n u n u n m zm>qquovzumfiu 4 w w D m 9S carbonyls appear between 220 and 240 ppm. Thus, any kind of bridging is excluded. Trans-geometry is also excluded since all four carbonyls would be identical and, therefore, only one signal for the coordinated carbonyls would be observed in the C-13 nmr spectrum. Finally, Figure 28 provides further verification that the ligand is not involved in any internal ligand photochemical reaction, but it is transferred from the reactant (W(CO)5(4VP)) to the product (cis-W(C0)¢(4VP)2) intact. Table 14 gives the mass balance data for irradiation (lirr>400 nm) of Pentacarbonyl [l-(4-pyridyl)pentanone]- Tungsten(O) in benzene in two cases, i.e., degassed normally with four freeze-pump-thaw cycles and under 2 atm. of carbon monoxide. In the latter case, the sample remains yellow and W(CO)5 is formed as a white precipitate. Parallel irradiation of an almost equimolar solution of W(CO)5(4VP) ,and W(CO)5(4BP) in benzene resulted in the formation of three products besides W(CO)5 as analyzed by HPLC. Two of these correspond to the Tetracarbonyl products observed in the irradiation of each compound separately. The middle product, formed in a yield equal to the sum of the yields of the other two products, corresponds probably to cis-W(CO)«(4VP)(4BP). Table 15 summarizes these results. <96 .voususol uos u .so_~¢tas as cos-snout. . .IGSVA 52‘ o monoc.o . «neoooo.o «Ado.o In. a In. peso.o .u- . smmooo.o usso.o --- --- -u- pmsc.° .n- momeo.o mmuoo.o memo°.o nu. .uu .n. muso.a nu. qwnoo.o unnoo.o ossoo.o I- I- -l «88... Ass ..m>¢~ Axe ._.Aoovsa Axe ._«As>ee.aooezeu.so_ Axe ._As>vv.fiooes_ soda-«vsusa scams emolu- vOusuvsusu so: coo mus N some: OH mom sequsuvsssm souus van-us vausmvsssm so: .3 modusavsusw suaus one-so veaswvsuhm so: mmmmmummnmwummm souusuvosuu scams ode-us vouomvssum so: an”; .oashuouonm onsououssh convuu>A~>Lo~s>uv gaseousosaaum so» nasalwsoaxo oceans: and! . n ounce 97 Table 15. Cross-Coupling Experiments fOr W(CO)s(4VP) and "(CO)5(4BP) Irradiated Together.‘ Area W(CO)5(4VP): 446173 Area W(CO)5(4BP): 656522 Area cis-"(GO)4(4VP)2: 19274 Area cis-W(CO)4(4VP)(4BP): 49735 Area cis-"(CO)4(4BP)2: 30617 ‘HPLC analysis, detector at 402 na; l.1rr > 400 nm; results after irradiation. The l:2.5:l.5 ratio of the tetracarbonyl products represents statistical ratio since the two reactants were in 121.5 ratio initially. Comparison 2;; the Photobehavior of "(CO)5(4VP) with other Pentacarbonyl Complexes of Tungsten Stability of the Photoproduged Tetracarbonyl Complexes. Two methods were employed to verify that other complexes like W(CO)5L, where L is a substituted pyridyl ligand, behave photochemically similarly to W(CO)5(4VP). The first method is to compare the UV-Visille absorption changes of the complexes under visible light irradiation. The seCond method involves comparison with 98 each other of the C-13 nmr spectra of the complexes before and after irradiation. Figure 29 displays the absorption changes of an Argon bubbled degassed W(CO)s(4VP) solution in methylcyclohexane upon visible light (lirr>400 nm) irradiation. An isosbestic point, probably due to cis-W(C0)¢(4VP)2 appears at 525 nm only at the beginning of the reaction. The early loss of this isosbestic point is probably due to a photooxidation reaction of cis-W(CO)4(4VP)2. 0n the other hand, cis- W(CO)4(4VP)2 in a four freeze-pump-thaw cycle degassed and hermetically sealed nmr tube does not bleach upon long exposures to room light and does not lose any of the C-13 nmr signals. W(CO)5(4VP) irradiated in 1:1 (v/v) benzene/methanol or in CO saturated benzene solution gives no long wavelength isosbestic points. Figure 30 displays this behavior in CO saturated benzene solution; a new isosbestic point appears at 318 nm with the simultaneous increase of the W(C0)e absorption maximum at 290 nm. Finally, Figure 31 exhibits the behavior of W(CO)5(4Cpr) in Argon degassed benzene and methylcyclohexane. Certain of the compounds were dissolved in benzene containing 1-2.53 (w/v) Chromium trisacetylacetonate (shiftless relaxation reagent),95'°° degassed and sealed in an nmr tube. Carbon-13 nmr spectra were recorded before and after irradiation of the tubes with visible light (Xirr>400 99 2 t=0 t=0.25 3‘ / '~—'\. 0" \ m l . 5 - \ a J '1 .‘_.t=0.5 . .-I 1 .I .‘ ...... ' 8 I \. °H ’ , . .. \ u ¢ /" o. . ‘3‘ ' . .' '. \ O I. - '. . 1 [5 3‘ i Izi; ” “ \‘ \t=1 .\ s I ‘ ‘l\ .f ll, \\ \ \i ‘.‘\ .‘J l” ‘\ \ .'.\ \‘Al” \ \ 1. . [=1 . S \\ \ -.,\,\ \ °' \ \ \ \ t=2 \ .x,‘.‘.\ \\\ ‘2 \ \h. 8 \“\. ‘3 ..... C= \‘\, .............. \'\.‘ $5,”. 0 y ..... r ...... "i." '- ‘ 4-“. 400 500 600 , Wavelength, nm Figure 29. Absorption spectra of 2.0 10-4 M W(CO)54VP in methylcyclohexane upon irradiation with DAOO nm. Argon bubbled degassed sample. Time (t) in minutes. 100 24 Optical Density 7 ”3.89.1" -' )- 300 460 560 660 Wavelength, nm Figure 30. Absorption spectra 01 2.1 10-4 M W(CO)5(4VP) in benzene upon irradiation with )\>400 nm. Carbon monoxide saturated sample. Time (t) in minutes. Optical Density Optical Densirv 101 0.5 0.25. 0.0 i “ 1.0 ‘ t=S sec sm%\\\\ t=lO sec g,«1%,‘\\ t=15 sec 0.5 T 0.0 I , ' - 300 400 500 600 Wavelength, nm 7CN9 Figure 31. Absorption spectra of about [.4 10_4 M W(OO)§4CNPY) S in methylcyclohexane (top frame) and 5.0 10- M in benzene (bottom frame) upon irradiation with A>4OO nm. Argon bubbled degassed samples. 102 nm). Figures 32, 33 and 34 display the results obtained. After irradiation, all the compounds studied show a peak at 191 ppm due to photogenerated W(CO)e along with the peaks at 205 ppm and 213 ppm due to cis-Tetracarbonyl bis(substituted pyridine) Tungsten(O) complexes. Quantum Yield Studies. Solutions of Pentacarbonyl [l-(4-pyridyl)pentanone] Tungsten(O) in benzene and methylcyclohexane (0.050 M) were irradiated at 410 nm and at 490 nm, and the duantum yields of cis-Tetracarbonyl bis[l-(4-pyridy1) pentanone] Tungsten(O) formation were measured by two methods: First by HPLC analysis and second by the product visible light absorption at 600 nm. Details about both methods are given in the experimental section. Uranyl oxalate actinometry97 was used for the 410 nm irradiation while Potassium Reineckate98 actinometry was employed for the 490 nm irradiation. Results are summarized in Table 16. Table 16. Formation Quantum Yield Data for cis-W(CO)4(4VP)2 from H(CO)s(4VP). Solvent: benzene' methylcyclohexaneb Irradiation wavelength (mm): 410 490 410 490 cis-W 00 4VP : 0.0657 0.000658 0.0285 0.0000408 ' [H(CO)5(4VP)] = 0.0504 M. b [W(CO)5(4VP)] = 0.0501 M. 103 .mAumumvso A>\3v N~ mewewmucoo ovuocwucon ”ucozom .5: 05322:: 53323.; sebum "meat a3 “cowumfivouuw ouowon "oemsu ecuuom .AsaumquAoov3 mo ocuomqm he: mfiuconsmu .Nm ossmwm can .0 on o2 0.: 02 F . — . p p p . - . . . _ _ L . s _ - o... 3.. E15? . sagsczisifm 104 SO 260 150 100 I l-s n__L.‘_ 1LLI- 200 V 150 160 5‘0 5 - PP'“ Figure 33. Carbon-13 nmr spectra of W(CO)S(4VP). Bottom frame: before irradiation; top frame: after irradiation with A>400nm. Solvent: benzene—d6 containing 1% (w/v) Cr(acac)3. 105 1110 U 1.- _ - J- -1... 200 I $0 100 50 T 200 l 50 100 50 " 50 PP'“ WuiLPMWfi ' MW Utanmwwmmwiwa . M r l T ' ' r * T T Figure 34. Carbon-13 nmr spectra of W(CO)S(4BP). Bottom frame: before irradiation; top frame: after irradiation with A>4OO nm. Solvent: benzene—d6 containing 1% (w/v) Cr(acac)3. 106 Because cis-W(CO)4(4VP)2 is sparingly soluble in methylcyclohexane, its extinction coefficient at 600 nm has been measured only in benzene; therefore, in order to calculate the quantum yields in methylcyclohexane, methylcyclohexane had to be replaced by benzene after irradiation. The formation quantum yield depends on ground state concentration in benzene, as displayed in Figures 35 and 36. D uenching Studies. Energy Transfer Quenching l>|>| l—' gggction Qggnching W(CO)5(4VP) was irradiated at 410 and 490 nm in benzene in the presence of varying concentration of anthracene. The formation of cis-W(CO)4(4VP)2 was quenched as shown in Figures 37, 38, 39 and 40. A; Emission Quenching The emission from W(CO)s(4VP) is quenched by anthracene. The samples were excited at 420 nm and the emission spectrum was recorded from 500 to 800 nm. As baseline, we chose the 800 nm end of the spectrum. The intensity of the emission for various anthracene concentrations was considered to be proportional to the Emission Quantum yield. In two cases, after the Stern- Volmer plots for emission quenching had been obtained, the same tubes were irradiated at 490 nm and identical (within 107 .wcmncon cw E: o~< um :OwumflvmssH .caoflh Esucmsc sewumEcOW NAm>3qAOQV3ImHo of co €>$m883 we :owumwucoocoo mo momuwm .mm 0.3m; .75 yasemaei 8.... . cm. 0.9 on p p b b p b p b p s b h L 10‘ .ocoucon cw e: 003 so cowumwcowwH .vaowa 5353 53953 NE>3quov3lmwu of co Agcvmsovz mo cofiouueoocoo wo uummum .om 95mg .75 . 75.11.2093 D b h Chow P b . h h pm‘ b b P L- 8‘ n r m h Ohm b b L D .82 8 m .88 .83 76 109 experimental error) Stern-Volmer slopes were obtained from the photoproduct quenching experiments. Figure 37 displays product quenching for irradiation at 410 nm of various W(CO)5(4VP) concentrations. Similarly, Figures 38, 39, 40 and 41 display the emission and the photochemistry at 490 nm irradiation quenching, in parallel when applicable, for various ground state complex concentrations. Finally, Table 1? summarizes the quenching results. Table 17. Photoproduct and Emission Quenching from H(OO)5(4VP)'. IVCO 4VP M 7 art Irradiation at 410 nm 0.0105 27.5b 0.00364 38.5b 0.00104 44.8b Irradiation at 490 nm and emission Quenching 0.0105 372b 0.00508 164b 0.00508 156b 0.000897 564b 0.000897 530c 0.0000829 576$ ‘ 4VP = l-(4-pyridyl)pentanone 5 product (cis-WKGO)¢(4VP)2) quenching c emission quenching, excitation at 420 nm. 110 (Do (I) / 3.. A 2.. A /x D /,l l/ v I-‘l r9 062 . 0&4 006 [anthrarenol, (M) Figure 37. Stern Vthfi' plots for W(CO)5(4VP) irradiated at 410 nm in benzene. (O): [complex]=0.0105 M; (A): [complex]: 0.00364 M; ([j ): [complex]=O.OOlOl4 M. 111 26*; (1>C> 15‘ [0‘ [a I ' 7.02 ' 0.224 a'os [anthracene], (M) Figure 38. Stern Volmer plot for w«13%¥AVP)irradiated at 490 nm in benzene. Cis-W(CO)4(4VP)2 formation quenching. [W(CO)54VP]=O.OIOS M. 112 0.005 0.007 0.009 [anthracene] , (M) 0.001 0.003 Figure 39. Stern Volmer plots for W(CO)S(4VP); [W(CO)5(4VP)]= 0.00508 M. ( [25): cis—W(CO)4(4VP)2 formation quenching, irradiation at 490 nm in benzene. ( O ): Emission quenching, excitation at 420 nm. 113 0.002 ' 0.004 9 0.006 [anthracene], (M) Figure 40. Stern Volmer plots for W(CO)S(4VP); [W(CO)S(4VP)]= 0.000897 M. (O ) : cis-\«I(CO)4(4VP)2 formation quenching, irradiation at 490 nm in benzene. ( . ) : Emission quenching, excitation at 420 nm. 114 1 016:. l ‘1 l ‘7 0.002 0.004 0.006 [anthracene], (M) Figure 41. Stern Volmer for the emission quenching of W(CO)S(4VP) in benzene. [W(CO)S(4VP)]=O.0000829 M. Excitation at 420 nm. 115 g Chemical Quenching 4-valerylpyridine (4VP) quenches both photochemistry and luminescense from W(CO)5(4VP). _1 gggction Qgenching At 4-valery1pyridine concentrations in the range of 0.001-0.007 M, we obtained the results displayed in Figure 42, for cis-W(CO)4(4VP)2 formation quenching at both long (ltrr>475 nm) and short (lirr>400 nm) wavelengths of irradiation. Higher 4-valery1pyridine concentrations (0.1- 0.8 M) were found to suppress the reaction completely; no tetracarbonyl product is produced. It is important to note that the quenching plots obtained at long and short wavelengths of irradiation have different slopes which are given in Table 18. Table 18. cis-W(CO)«(4VP)2 formation Stern-Volmer Quenching by 4VP for A in > 400 and x irr > 475 nm.‘ slope,(M'1) l in > 400 nm 282 A in > 475 m 732 ‘ solvent benzene, [W(CO)5(4VP)] = 0.02 M. 116 0.002 ' 0&4 ' 0.006 1 00'08 [A—valerylpyridine], (M) Figure 42. Stern Volmer plots for W(CO)S(4VP) in benzene. Cis-W(CO)A(4VP)2 formation quenching by free ligand (4VP). (O ): [W(CO)5aoo nm. (0 ): [wcm <4vp>1=0.0200 M. A. >400 nm. S irr (A ): [14(00)5(4vp)]=0.020z. M, Airr>475 nm, 117 5; Emission Qggnching Figure 43 displays the Stern-Volmer quenching by 4AP of the emission at 623 nm of W(CO)s(4VP) excited at 420 nm. The slope was calculated as 2 M‘l. Figure 44 displays the emission quenching results for the same compound by 4VP. The excitation wavelength for the latter experiment was 410 nm. The area under each peak was taken as proportional to the emission intensity. The emission spectra were traced and the emission peaks were cut off and weighted. The slope was calculated as 1.2 M‘l. Interggdigte Trappigg_§xperigent§ The above experiments show that free ligand quenches the cis-W(CO)4(4VP)2 formation but they do not prove that this is because 4VP traps an intermediate, returning the starting material. As a matter of convenience (easily analyzed products by HPLC), l-(4-pyridyl)butanone (48?) was used to trap the intermediates coming from W(CO)5(4VP). Short (lirr>400 nm) and long (Airr>475 nm) wavelength irradiation of W(CO)s(4VP) in the presence of 1-(4-pyridyl) butanone (48?) yield W(CO)s(4BP) as the main product. Two additional peaks in the HPLC analysis appear where the peaks of cis-W(CO)4(4VP)(4BP) and cis-W(CO)4(4BP)2 appeared in the cross-coupling experiments. Control experiments proved that cis—"(CO)4(4VP)2 reacts thermally in a first-order reaction (Figure 45) with l-(4-pyridy1)butanone to give the mixed 118 I .012 T 0.4 F 0.6 0,8 [4-acety1pyridine]. (M) Figure 43. Stern Volmer emission quenching plot of W(CO)5(4VP) by 4AP in benzene. [W(CO)S(4VP)]=1.41 10‘4 M. Excitation at 020 nm. 119 V I I I I Y 1 1 I I I I 0.2 0.4 . 0'0 ' ‘ 08' [4—Valerylpyridine], (M) T ‘ V Figure 44. Stern Volmer emission quenching plot of W(CO)S(4VP) by 4VP in benzene. [W(CO)S(4VP)]=6.7 10-I3 M. Excitation at 410 nm. 120 .00 ON newsumwoquB .2 ammoo.ou_mmqa uz ommooo.ou~NAm>qquouv3lmon .ocmscon cw mmq new: NAm>qVquov3ImHo mo mofloocwx consumes massage .mq ossmwm Amouscwev megs Om? . 00F. - pm 0 .3 I U ) I _ .3 n... .m. I. Tc. .1. .1. . M M r a mo 0. m 0 O ( ( I O 9) v) . bl hi .3 n n ( ( z ) rl. Fl 1.. 8 U 10 . I. (\ .3 n. 31 8 I ( .00 121 pyridyl ligand Tetracarbonyl complex. The rate constant of this first order reaction is calculated as the slope of Figure 45 and was found 1.65 10“3 min'l. Table 19 displays the concentrations of cis-W(CO)4(4VP)(4BP), cis-W(CO)¢(4VP)2 and cis-W(C0)4(4BP)2 which have been produced in parallel to the concentrations of W(CO)s(4BP). Figures 46 and 47 display the variations in the concentration of W(CO)5(4BP), cis-W(CO)4(4VP)2 and cis- W(CO)4(4VP)(4BP) produced at various 48? concentrations at 11rr>400 and lirr>475 nm, respectively. Figure 48 displays the concentrations of cis-W(CO)4(4BP)2 produced at various 48? concentrations at lirr>400 nm. Figure 49 displays the Stern-Volmer quenching plots _ of total tetracarbonyl formation by 48? at both 11rr>400 and Axrr)475 nm. The slopes were calculated as 516 and 1378 M‘l, respectively. .122 Ilonv < .oamsssamOI as: use oqnauooaov ausvosm u .: v-o~ uo saws: ea oceausuusoosoo «sevens a .una.-a assuage pso~Io~o~ comm>oun use hunchol mu>o=G= .I: mva as .ou: o.mN .ms coca as .ac: w “some“; msuessv 0a unsomusomoua use av~om> ammo moss nsouuwu «henna ouswssosnas Us» susosmu monusssa a“ pousmpossa Am>evnAoov3 :m z ouo.c anewasnom osowsum masseuse sonata-salouoohu anon - em.o m.m moo.e es.o nm.o m.e e.e m.n o.m~ m.su sseo.e sm.o e._~ ~.o oe.o ss.e ~.m o.o ~.m n.- ~.m~ memeo.e e._ m.- .o sv.o 5.. ~.m e.e ~.s 0.x“ «.mm ~mveo.e e.~ m.m_ no m~.o ~.~ e.v ~.o o.~s ~.m~ e.m~ menco.e w.n 2.x“ .e s~.o m.w v.e _._ n.n~ e.N~ s.- anueo.o m.v ~.~N ea mo.e v.~ e.n ~.~ e.m~ _.m m.s cm_ee.e n.e «.mw .o .e ~.N m.~ ~.m m.e~ ..m n.m sseeo.e o.~s e.sn o o o o o.- e.sn o o o nee. eeex apex oevx neon see. new. use. apex cow“ ._.seoenaoansue .esoe. e_~Aenee.Aooc3-a.u_ e.xe>ecxemee.xooez-neu_ ._nAe>ee4.ooc3-asu_ n.8eaqenAooe3_ z._snv_ ..Ae>eceaooez co eosscseenns oneness :31: sense-non seasoneosoec no oesvenss~snswan eoee< co sconce .m~ u_eup 123 99 O . 1 . 20- [j [Tungsten Product] x 103 , (M) —3 0 O A l 1 A 0 A A O BAA 8 A 1 Y 1 '20 ' ' '40 9610' [4-Butyry1pyridine] x 103 . (M) Figure 46. Product distribution after irradiation of W(CO)S(4VP) in the presence of 4BP in benzene. [W(CO)S(4VP)]=O.0202 M. Irradiation with )\::>4OO nm. ( A ): cis—W(CO)4(4VP)(4BP). (D ): wwmsmap). (Q ): cis—W(CO)4(4VP).). 124 L 3.01) .1 m U1 '0 1.11.1 A D C] [Tungsten Product] x 10 “\J I QAA A .....C?.n.. n A 4; 2.0 4.0 ' ' (30' [4—Butyrylpyridine] x 103 , (M) Figure 47. Product distribution after irradiation of W(CO)S(4VP) in the presence of 4BP in benzene. [W(CO)S(4VP)]=O.0202 M. Irradiation with A>47S nm. (A ): cis-W(CO)4(4VP)(4BP). ([3 ): W(CO)5(4BP). ( O ): cis-W(CO)A(4VP)2- 125 (48oz) . (M) e: o l 1 A [cis-W(CO) 4 O Y T I I V I Y I I I '20 '40 '60 3 [4-Butyrylpyridine] x 10 . (M) Figure 48. Variation of the concentration of cis-W(CO)4(4BP)2 produced upon irradiation of W(CO)S(4VP) in benzene with )\.:>-4OO nm, in the presence of 4BP. [W(CO)5(4VP)]=O.0202 M. 126 616' 0.0'01 ' 0.003 I 00105 ' 0.007 [4—Butyrylpyridine] . (M) Figure 49. Stern Volmer plots for W(CO)S(4VP) in benzene. Total tetracarbonyl product (cis—W(CO)4(4VP)2, cis-W(CO)4(4BP)2 and cis-W(CO)4(4VP)(4BP) ) formation quenching by free ligand (4BP). (A ): [w(00)5(4vp)1=0.0202 M, Am>475 nm. ( Q ): [w(00)5(4vp)]=0.0202 M, Am>400 nm. nnynmsnxl PhMUKedmndonInflehmnmthz1k¢g§§gtgflm1m.99 Tetrahydrofuran proved to be an unsatisfactory hydrogen donor, giving maximum quantum yields for octahydro- 2,2'bifuran (DTHF) well below 0.25, the statistical value expected if THF is involved only in a hydrogen abstraction process (Table 3). It is assumed that the lower quantum yield results from electron transfer quenching1°° by THF of the excited triplet ketone. 03* 00— " H Ph—C-CEs + Q ----> [Ph-C-Clla + (O) 1 ———-—> 0.3. (26) 6+ It is interesting though that 2-tetrahydrofuryl radical reacts with, acetonitrile solvent to give 2-tetrahydrofury1 acetaldimine (THFCH3CN). This product seems to be formed at the expense of DTHF in Scheme 12. Schemelz OH OH [THF- + Ph-C-CHs] ----> 9 + Ph—C-Clh ----> coupl. and disprop. (fibCN NH THF [I CH3f=N ----> //C THF (fib \jg:> (THRflbCN) 127 128 The fact that the quantum yields of DTHF are larger than the quantum yields of THFCHaCN in phenyl ketones, while the opposite happens in the pyridyl ketones, has to do with the relative reactivity of the corresponding ketones (Table 3). The more reactive phenyl ketones yield higher steady- state concentration of 2-tetrahydrofury1 radicals, with the result that bimolecular coupling dominates over the reaction with solvent. In any case, it would be interesting to further investigate this unique example of CHaCN reacting with radicals. Further studies using THF as a hydrogen donor in the photoreduction of complexed pyridyl ketones were interrupted at this point after the irradiation of Pentaammine 4- acetylpyridine Ruthenium(II) complex in the presence of THF led to pyridyl ligand decomposition. . mgl Eetme Pests-inc and bis(2,2'bimidime) Ruthenium(II) gggglexes. Absogption and Emission Studies. [Ru(NHs)s(4AP)]2*, [Ru(NHs)s(4PhBP)12*, [Ru(NHa)s(4EsterBP)]2*, etc. complexes show a characteristic broad MLCT absorption at ~510 nm in acetonitrile.”1 The increased absorption at 313 nm compared to the free ligand hydrochloride salts is probably due to underlying LF transitions. Comparison of the extinction coefficients of [Ru(NHa)s(4AP)]2* and [Ru(NHa)s(MeINic)]2* at 313 nm gives a small difference (17 M'1 cm‘l) due to the pyridyl ketone nr‘ 129 transition, since esters do not have low-lying nt‘ transitions.”2 This e value is low compared with the extinction coefficient at 313 nm of 4PhBP.HCl which is 104 M"1 cm‘1 (Table 4) and is due to nt‘ absorption. It proves though that a portion of the 313 nm irradiation populates the n!"l excited state of the pyridyl ketone ligand. These complexes do not emit either at room temperature or at 770K.85a The corresponding bis(2,2'bipyridine) complexes cis- [Ru(bipy)2(4AP)2)]2*, cis-[Ru(bipY)2(4PhBP)2]2* and cis- [Ru(bipy)2(4EsterBP)2]2+ show intense CT absorption below 500 nm. The extremely high absorptions (z~7.5 103 M"1 cm'l) at 313 nm are due only partially to underlying LF transitions and mainly to the bipy ligand. 2,2'bipyridine coordinated to Ruthenium is forced to be planar. 4,5— Diazafluorene, because of its structure, forces the two pyridine rings into the same plane and it should be an adequate model for the planar 2,2'bipyridine. Its absorption spectruma‘ is red shifted compared to that of 2,2'bipyridine,83 absorbing strongly at 313 nm (c~6.4 103 M‘1 cur1 compared to free bipy: c ~83 M'l cm'l, in acetonitrile). 0n the other hand, the emission spectra of the two compounds (bipy and 4,5-diazafluorene) are identical (Figure 12). This fact suggests a planar conformation for the 2,2'bipyridine in the excited state, in analogy to bipheny1.1°3 The 0—0 emission band of 2,2'bipyridine is also 4-5 Kcal/mol red shifted compared to 4PhBP and 4EsterBP 130 (Table 5, Figures 10 and 11). This fact, combined with the emission spectra of cis-[Ru(bipy)2(4AP)2]2’, cis- [Ru(bipy)2(4PhBP)2]2* and cis-[Ru(bipy)3]2*, allows the conclusion that the 1* orbital of coordinated 2,2'bipyridine lies lower energetically than that of the pyridyl ketone ligands. Raman Studies. [Ru(NHa)s(4AP)]2+ gave excited state Raman spectrum while [Ru(NHa)s(py)]2* did not, consistent with Ford’s model”1 for a MLCT lowest excited state for the first complex and a LF lowest excited state for the second one.”1 cis-[Ru(bipy)2(4AP)z]2+ failed to show MLCT excited state scattering, probably due to short lifetimes of the excited states created by 355 nm_ excitation, while cis- [Ru(bipy)2(py)2]2* gave the expected Ru ---> bipy CT excited state scattering.3° These results might be interpreted by Woodruff’s model .of a localized MLCT excited state or combined with the fact that [Ru(phen)3]2* does not exhibit excited state Raman spectrum,1°‘ to suggest that the species observed by Raman are not the MLCT excited states but some intermediates (probably produced from the MLCT excited state and returning to it so no permanent change is observed) having monocoordinated 2,2'bipyridine. 1,10-Phenanthroline, due to its structural rigidity, recombines to the metal 131 center in the picosecond time scale, beyond the limits of the nanosecond instrumentation used. Photochemical Studies. As we stated in the Introduction, the Type II reaction can be used to monitor the rate of internal conversion of the IL upper excited states to the lower ones in coordination compounds. _. It was found that in [Ru(NH3)s(4VP)]2+ the internal conversion is slow to compete with Type II cleavage of the coordinated 4VP.17 Two types of pyridyl ketone ligands were investigated: one with reactivity comparable to or higher than 4VP so it could be applied to the cis-[Ru(bipy)2Lz]2+ case where possible deactivation to the energetically lower- lying bipy might enhance kic, and one of lower reactivity, which possibly would compensate for the failure of the bimolecular photoreduction of coordinated 4AP. Table 20 compares the reactivities of some phenyl ketones with reference to valerophenone. 4PhBP and 4EsterBP were prepared and their 1“}, and kr values are also presented in Table 20. The values for the corresponding hydrochloride salts are also included in Table 20. r values are calculated from qu values assuming kg = 1x1010 M‘1 sec‘1 for ethyl sorbate in acetonitrile.“59 kr values for the pyridyl ketones and their hydrochloride salts were calculated as kr=1/r assuming kd<~oa sconce. . .unfl .uoz u .uOuo: oowxuusuo ano~cs .uco>—on o~«m»«60uou< o .nc~ .uos .a=o>~0o oceans: . to :5 :2 2.." 82.3.3.3 .od :2 86 WE e._ .2 a; $6 23 :2 8... 2929:. .22: .2 8.— 9%: «.8 c.4n.mw soo~ nm.w uL\UVIAHMz :28 :2 a." 8:5; .662 82 8.2 0.2 va.m one" mN.m \ Im M2 12.... :2 ma... 8:23 .8... :2 8.. o 86 .2 as w 0 an.-ouavao~ as an_-ooav.- s cacao: ea.-uonvpo~ s: aasuuoav~- s cacao: nasoounvaA ex ea.-ooov~- 5 ocean: .sa_sm sewsoumoowvhx cacao: «avmwxm uswvsoaaossou «Au use cocoon: ~>e2u>m .sOGOuon assent ssomws> up sawdusauusom o>mus~o= .m» ounce 133 logical assumption since 0:: for the two ketones as well as for the corresponding hydrochloride salts studied (4PhBP, 4EsterBP and 4PhBP.HC1, 4EsterBP.HCl) are mutually equal, so the term kr/(kr + ka) in equation 11 has to be one. According to Table 20, 4-butyrylpyridine would be a good candidate ligand for a slow Type II reaction, but photoproduced ethylene has not been possible to be analyzed reproducibly.35‘ Despite the photochemical instability of [Ru(NRa)s(4AP)]2+ in the presence of THF, [Ru(NHa)s(4PhBP)]2*, [Ru(NH3)s(4EsterBP)]2*, cis- [Ru(bipy)2(4PhBP)2]2* and cis-[Ru(bipy)2(4EsterBP):12* did not undergo photoinduced ligand dissociation in acetonitrile during the irradiation periods employed. Pentaammine complexes upon long irradiations tend to bleach, a fact which has to be attributed to oxidation rather than to dissociation85h since no free ligand is detected. No corresponding phenomenon was observed with the 2,2'bipyridine complexes. The Ruthenium porphyrines, RuTPP(4PhBP)2 and RuOEP(4PhBP)2, were also photostable since no free ligand was detectable after long irradiation. Quantitative ligand liberation from the 2,2'bipyridine complexes could not be achieved even after reflux with PPhs in n-butyronitrile as reported by Whitten.32 Therefore, we concentrated on measurements of free olefin formation from the Internal Ligand Type II cleavage. 134 The Type II product quantum yields increase slightly with increasing concentration in the case of the free pyridyl ketones because of solvation of the biradical by the pyridyl nitrogen (Figure l4).856'91 The corresponding hydrochloride salts are insensitive to ketone concentration85d (Figure 14). With the Ruthenium complexes, the picture is quite different (Figures 15 and 16). At low complex concentrations, the olefin quantum yield progressively increases, reaches a maximum, and then decreases as the complex concentration increases further. This behavior correlates with the absorption of light at 313 nm by the corresponding complex.‘ At the concentration point where all the 313 nm radiation is absorbed, a bimolecular quenching process starts lowering the quantum yield. Ruthenium complexes were proven to be good triplet excited ketone quenchers. They were found to quench Type II cleavage of butyrophenone (Figures 21, 22 and 23; Table 9). The lifetime of butyrophenone is 1.34 10'7 sec,105 so kq values for the Ruthenium complexes (Table 21) are calculated using the relation kq = qu/(l.34x10‘7). 135 Table 21. Rate Constants for Quenching of Triplet BP by Various Ruthenium Complexes in Acetonitrile. Ruthenium Complex kq (M‘1 sec“) [Ru(NHs)s(4AP)](BFk)2 3x109 cis-[Ru(bipy)z(4AP)z](BFK): 2x109 cis-[Ru(phen)2(4AP)2](BFk): 2x109 It is obvious from Table 21 that Ruthenium complexes quench the ns' excited ketones very efficiently. The diffusion control limit is about 2x101° M"1 sec‘1.73 This result is what is expected for a metal ion complexed to a ligand which has an equal or lower triplet excitation energy than the ketone donor.1°7 On the other hand, it has been shown that bare .rare earth chlorides quench the Type II reaction from phenyl ketones more slowly (kq=:lO°), probably due to salvation; the solvent molecules have high excitation energies.103 It has been assumed that hydrochloride salt formation has the same effect as metal coordination in the absence of orbital mixing. It is suggested here that the 1R-nmr signal of the pyridyl protons is a useful method to compare the effect of metal coordination and protonation on the pyridyl ligand. Table 22 shows that metal coordination seems to have a similar effect on the pyridyl ketone ligand as 136 Table 22. Pyridyl Proton Chemical Shifts in Free Pyridyl Eetone Ligands, Their Hydrochloride Salts and Their Ruthenium Complexes. Compound Solvent . . 6 H’s o- to Nitrogen H’s m- to Nitrogen 4PhBP , 00013 8.76 7.65 4PhBP.HCl 00013 9.11 8.28 020 ’ 8.82 8.20 [Ru(NHs)s(4PhBP)]2+ 020 8.35 7.28 cis-[Ru(bipY)2(4PhBP)212* 020 8.85 8.42 RuTPP(4PhBP)2 Cabs 3.40 5.51 RuOEP(4PhBP)2 Cst 1.59 5.15 4EsterBP CDCla 8.81 7.75 4EsterBP.HCl CDCla 9.10 8.39 020 8.88 8.33 [Ru(NHs)s(4EsterBP)]2’ 020 8.60 7.52 cis-[Ru(bipy)2(4EsterBP)2]2+ 020 8.89 8.55-8.45 CDCla 9.05 8.54 137 hydrochloride salt formation, in the cases of the 2,2'bipyridine complexes, while in the pentaammine complexes the pyridyl proton chemical shifts seem to correlate better to the free pyridyl ketones. No conclusion can be drawn for the Ruthenium porphyrines since the pyridyl protons are shifted upfield by the ring current of the porphyrine. In any case, since complexation does not cause any dramatic change in the chemical shifts of the pyridyl protons, we accept that pyridyl ketone ligand hydrochloride salts are reasonable models for the Ruthenium complexes. Multiplying the 0(11) of each Ruthenium complex by the ratio (R) of the extinction coefficients at 313 nm of the Ruthenium complex to the corresponding ligand hydrochloride salt, we obtain the corrected quantum yield of the Ruthenium complex for partial light absorption by the ketone chromophore. Table 23 compares the observed and the corrected quantum yields of all the complexes studied. 1 values for the Ruthenium complexes studied in this thesis (Table 8) have been calculated accepting 1x10lo M'1 see"1 as the kq value for ethyl sorbate in acetonitrile,ase using the relation 7 = qu/(l.0x101°) and have been corrected for the bimolecular self-quenching effect of Ruthenium complexes mentioned above; in other words, (kr+kd) values .represent the sum of the rate constants of chemical reaction and decay of the Ruthenium complexes if no bimolecular quenching was taking place and have been .ovusoamu oeouhmuol sq smouus~os 2 c~o.o sou oss sodas soeuuhasuoa on» annexe suuhuasouoos s“ vases-co newscasossoo 2: ho Gama-50s : 30.0 3 vsasossoo .vouwu Auaiv 8:0: Ina—:39 quasar-0&3 on» =< a 138 «mod 28.0 me 806 $86 no 806 mecca-me mmod «Noocé N2 «36 oweood mm .520 «Sod em mood So... a... «mod mean—e sson‘ 2.8 m use“ 2.3 ~— sson‘ ss‘ 2 sso‘ oa‘ ~— 2:. aoxo~mloo g lflwfludllowll lslmxloawl :sm occuom 522:3. 52352. 92052. 532:3. 8: 33.5. .150 an... oe«3.§3n.~.~ s3 oil—.33.. 23:33. Tags»; of .«o 09.0380 SCI-5.35:: «cusses—son. use 053533.”...N Jews-mousse. .316 amusemzoosvzz of so.— nEo: I558 session.- : 05 .MN 033. 139 calculated from (28), which has been derived from (27). 1‘1 and (kr+ka) values are cited in Table 24. “l r = kr + kc + kq [complex] (27) kr + kn = 7'1 -ka [complex] (28) Table 24. Lifetime Data for Ruthenium Complexes.a Ruthenium Complex 1/7°,(sec‘1) 0.02xkq (kr + kd)¢,(sec‘1) [Ru(NHa)5(4PhBP)]2+ 1.4x109 6.0x107 l.3x10° cis-[Ru(bipY)2(4PhBP)212* 2.9x109 4.0x107 2.9x109 [Ru(NH's)!’(48sterBP)]“-’+ 1.5x10a 6.0x107 9.0x107 cis-[Ru(bipy)z(4EsterBP)2]2* 4.2x108 4.0x107 3.8x10° ‘ 7'1 values concern 0.02 M solutions of the corresponding complex in acetonitrile. b Fnallhbbeit C From Equation 28. As it is noted in Table 23, the corrected quantum yield of [Ru(NHa)s(4PhBP)]2* is approximately equal to the quantum yield of 4PhBP.RCl, while the corrected quantum yield of [Ru(NHa)s(4EsterBP)]2* is about 3.6 times lower than the quantum yield of 4EsterBP.HCl. What keeps the quantum yield low even after correction for partial light absorption by 140 the ketone chromophore are probably both concentration self- quenching and a competing Internal Conversion process. Table 25 compares the quantum yields of [Ru(NHa)s(4PhBP)]3* and [Ru(NRa)s(4RsterBP)]3* with the quantum yields of [Ru(NHa)s(4-Va1erylpyridine)]2*, [Ru(NHa)s(p-methyl-4-butyry1pyridine)]2* and [Ru(NHa)sr- methyl-4-butyrylpyridine)13*, which are taken from reference 17. Table 25. Comparison of the Quantum Yields of Type II Products of Various Pentaammine Ruthenium Cmmflemes. complex .(I!) _ korr [Ru(NH'a)s(4PhBP)]2+ 0.014' 0.058 [Ru(NHs)s(4EsterBP)]2* 0.0051‘ 0.027 [Ru(NHa)s(Me43P)]2* ' 0.023” ' 0.099 [Ru(NHa)s(4VP)]2’ 0.019b 0.093 [Ru(NEa)s(1Me4VP)]2* 0.02m 0.096 ' Acetonitrile solutions 0.02 M in Ru complex irradiated at 313 nm. D Acetonitrile solutions 0.01 M in Ru complex irradiated at 313 nm. The Type II products quantum yield is given by equation 11: 0(1x) = Oxax[kr/(kr+kd)]; s is the probability that the 1,4-biradical (intermediate) will cleave to form anal and olefin. For para substitution, O and a are 141 constant. 0(11) for [Ru(NHa)s(4PhBP)]2* is within experimental error equal to the 0(xx) of [Ru(NHa)5(flMe4BP)]2*, [Ru(NHs)s(4VP)]2+ and [Ru(NHa)s(yMe4BP)]3*. Therefore, for 0(11) to be constant, the term kr/(kr+ka) in equation 11 has to be one or kr>>ka. In other words, for [Ru(NH3)5(4PhBP)]2*, kr = kr+ka = 1.3 10° sec‘l (Table 24). Using this value as a calculation basis, the k: and kc values of [Ru(NRa)s(4RsterBP)]3* are calculated from (31) which is derived as follows: 0 ([Ru(NH3)s(4PhBP)]‘-’*) = Rue) x «xx krlTZHexperimental) (29) 9' n 3' ll 0 (Ru complex) = .(ISC) x «xx krz 12(sxperimsntsl) (30) (31) is obtained by dividing (29) by (30): (1/12)sxperimentsl kra = kri X [92/01] x (31) (U1: )experimentsl This way, it has been calculated from (31) that R: = 6.1 107 sec"1 for [Ru(NHa)s(4BsterBP)]2*. The (kr+ks) value for this complex is 9.0x107 sec'1 (Table 24). Therefore, ks = 3.9x107 sec‘l. Assuming the same ks value for [Ru(NRs)s(4PhBP)]3', it is calculated from kr+ka = 1.3x109 sec‘1 that kr = 1.3x10’ sec'l. We started this method of calculation by assuming that kr for [Ru(NHa)s(4PhBP)]3* was 1.3x109 sec’l, and we verified this value after one cycle of calculations by obtaining the same value and a slow rate of 142 Internal Conversion (3.9x107 sec‘l). The calculated value of kc (ks = 3.9x107 seC'l) verifies the upper limit (108 sec‘l) that was set previously for the rate of the Internal Conversion of the Ruthenium Pentaammine complexes.n This value for the rate of the Internal Conversion has to be taken with caution, though, because it is about half the rate of self quenching (0.02xkq = 6.0x107 sec"; Table 24), which means that the main deactivation process is by self quenching and not by Internal Conversion. Subtraction of two large numbers (k: and 0.02xkq) from a llarge number (experimental l/r value) leaves a large uncertainty in the result. Therefore, it is suggested here that the calculated ka value for the Ruthenium pentaammine complexes to be considered as an upper limit for the Internal Conversion rather than an absolute value. For the bis(2,2'bipyridine) complexes, the picture is somewhat similar. Comparing the quantum yield of cis- [Ru(bipy)z(4PhBP)z]3* to the one of cis- [Ru(bipy)2(4BsterBP)2]3’ (Table 23), it can be seen that the quantum yield of the second complex is 3 times lower than the one of the first complex. What lowers the quantum yield has to be an increased contribution of the internal conversion (kc) in the (kr+kd) value. In order to find the exact R: and ks values for both bis(2,2'bipyridine) complexes, we assume for the moment that there is no internal conversion competing with the Type II chemical reaction from the ligand, in the case of cis- 143 [Ru(bipy)2(4PhBP)2]2*, i.e. kr>>ka. That means that for cis-[Ru(bipy)z(4PhBP)2]2*, kr = 2.9x109 sec". Using (31) where 01 is the quantum yield for cis-[Ru(bipy)z(4PhBP)2]2* and 02 is the quantum yield for cis- [Ru(bipy)2(48sterBP)2]3t, for cis-[Ru(bipy):(4BsterBP)a]3*, hr = 9.9x107 sec’l. Introducing this value in the equation kr+k¢ = 3.8x10a sec‘l, k4 = 2.8x10° sec'l. This value of ka has to be the same for cis-[Ru(bipy)2(4PhBP)2]z*, so setting kc = 2.8 10° sec'1 for cis-[Ru(bipy)2(4PhBR)2]3*, produces kr = 2.6x109 seC'l. We started this method of calculation by assuming that k: for [Ru(bipy)2(4PhBP)z]3* was 2.9x10’ sec-1, and we obtained a better estimate (k: = 2.6x109 sec'l). The cycles have to be repeated until two successive calculations of the kr value are identical (self consistent). Introducing the new R: value for cis- [Ru(bipy)z(4PhBP)2]2+ into equation (31), we obtain for cis- [Ru(bipy)2(48sterBP)2]3*, k: = 8.9x107 sec" and ks = 2.9x10' sec-1. Rd is the same for cis-[Ru(biPY)2(4PhBP)2]z* so k: for the latter complex is found to be 2.6x109 sec“1 (self consistent). kr and kc values for all four complexes are cited in Table 26. ka’s are given as kxc (rate constant for internal conversion). If the Chart values (Table 23) are used in equation 31, then the rates of the Internal Conversion are calculated as a 2.6 107 sec"1 and 2.7 10° sec"1 for the pentaammine and. bis(2,2'bipyridine) Ru(II) complexes, respectively. 144 gable 26. Rates of fl-dbstrsctiee and Rates of Internal Conversion of RutheMu Complexes. RuCowlex Mn 1:: + ka(sec“) kr(sec") kxc(sec’1) [hams )s(4PhBP)]3’ 0.014 1.3):10' 1.3 10' S 3.9x10' [Ru(lflh 18(4htorlPH" 0.0051 9.0x10' 5. 1x107 5 3.9x10" c1s-[Ru(bipy)s(4ml’)a I" 0.0072 2. 9x10“ 2. 6x10. . 2.9x10‘ cis-[Ru(bipy): (4EsterBP): 1” 0.0017 3.8x10' 8.93:107 2.93:10' In the case of the Pentaammine Ruthenium complexes, Internal conversion means deactivation from the upper IL excited state to lower-lying LP and MLCT states. In the case of the bis(2,2'bipyridine) complexes, an additional deactivation path seems reasonable; i;g;, triplet energy transfer from the nr‘ excited pyridyl ketone to lower-lying planar bipy triplets. Comparing the kxc values between the pentaammine and the bipy complexes cited in Table 26, the increased values for the bipy complexes might originate from this additional deactivation path. A final point needing comment is that in the case of cis-[Ru(bipy)z(4PhBP)z]3*, the corrected quantum yield is about 3 times higher than that of 4PhBP.HCl, while in the case of cis-[Ru(bipy)z(4BsterBP)2]2*, the two quantum yields are approximately equal. In a possible explanation, the 14S elevated value of the Ocorr of cis-[Ru(bipy)2(4PhBP)2]2+ implies an intramolecular singlet energy transfer (sensitization); flat 2,2'bipyridines absorb strongly at 313 nm, operate as antennas, collecting the light and transferring some of the singlet energy to the reacting ligand 4PhBP, resulting in a higher quantum yield than the one expected due to only partial absorption of light by 4PhBP. Experiments using [Ru(bipy)3](BF4)2 as a sensitizer failed to sensitize the Type II reaction from aliphatic ketones. The efficiency of singlet energy transfer depends on the lifetime of the singlet excited state109 and [Ru(bipy)3](BF4)2 has to intersystem cross fast due to heavy atom effect. Perhaps, if 4,5-diazafluorene is employed as a sensitizer, the results should be positive. The case of cis-[Ru(bipy)2(4EsterBP)2]2* is different. The corrected quantum yield and the quantum yield of 4EsterBP.HCl are almost identical. This fact is rather coincidental and cannot be attributed to a slow rate of Internal Conversion. Rather, it has to be attributed to the fact that ktc is about four times larger than kr for this compound (Table 26). Intramolecular singlet sensitization is expected to give quantum yields higher than the expected ones but fast Internal Conversion, competing with kr lowers the quantum yield again. In order to obtain insight into the inter-ligand energy transfer, we consider Figure 50, which displays a three* dimensional structure of the Internal Ligand nt‘ excited Figure 50. Internal Ligand nn* excited state of cis-[Ru(bipy)2(4-pyridyl ketone)2]2+ CompIex. 147 state of a bis(2,2'bipyridine)-bis(4-pyridy1 ketone) Ruthenium(II) complex. The plane of the pyridyl ring, in order to maximize I-back bonding, bisects the dihedral angle of the xz and yz planes. This arrangement places the n orbital of the carbonyl above the dxy orbital, but the distance is too large to have efficient energy transfer. It seems reasonable to assume that energy transfer to the v— orbitals of 2,2‘bipyridine has to be more efficient since these t-orbitals are directed upwards towards the n-orbital of the carbonyl. If we split the ktc into two terms, one for energy transfer to the MLCT excited state and one for energy transfer to 2,2‘bipyridine, and if we assume that the energy transfer to MLCT is equal.in the pentaammine and the bis(2,2'bipyridine) complexes ($3.9x107 sec'l, Table 26), we calculate that the energy transfer to 2,2'bipyridine is ~2.5x10° sec-1, 4 times higher than the energy transfer to MLCT, which reinforces the speculation based on Figure 50. For the Ruthenium porphyrines, the corrected quantum yields are about 3 to 7 times lower than those of 4PhBP.HCl. The difference might be due to intermolecular quenching or most probably to fast internal conversion as well as intramolecular energy transfer (quenching) from the excited ketone to the porphyrine ring. Lack of lifetime data prevented further corrections based on intramolecular quenching, eventhough there is a clear dependence of Type II products quantum yield on ground state complex concentration (Figure 16). A rather crude model for the Ruthenium 148 porphyrine complexes is the cis~[Ru(phen)2(4AP)z]2* complex which is found to quench excited ketones rapidly (Table 21). A proposed Jablonski diagram for the cis-[Ru(bipy)2(4- pyridyl ketone)2] complexes is given in Figure 51. There have been two cases in the literature where other workers have assumed slow internal conversion to explain their data, or they have given an estimate for the rate of the internal conversion. Wrighton has observed dual emission in systems like fac-[(CH3CN)Re(C0)3(phen)]+11° or fac-[ClRe(CO)3(3-benzoylpyridine)z]111 at 77°K. The short— lived emission component (~lO-20 us) is the structureless ReLCT transition, while the long-lived component (>50 us) has the same features of ‘1,10-phenanthroline or 3- benzoylpyridine emissions, and lifetimes 75 us and 1400 us, respectively. In order to explain the dual emission, Wrighton assumed slow and endothermic internal conversion from the IL excited state to the low ReLCT. Finally, Whitten speculated,32 without measuring rate constants, that kxc = 5x1012 sec"1 for cis-[Ru(bipy)2(4- stilbazole)2]2*. Sensitized isomerization of complexed 4- stilbazole was inefficient, and be attributed the direct photoisomerization of complexed stilbazole to a singlet state reaction. He concluded the above value for kxc by considering and arbitrarily correcting, for complexation, the values for fluorescence rate constant and quantum yield of trans-4-stilbazole. a m¢¥5e$_H3:L%J NAxaflnV:z_nmnu new emuwmfic wxm::_2mm .fim ouomflm .xoaoeou +9. mu m x 5331.; Eocene: 50321:. a a: ll. _ v: e .Zn .523qu llTllII .ivntsa-qqnuz 9 _ 4 3 1. w m can; mouavOLm HH same mom .5. Alannvosm AHOUWOQHwDV AUCOUQX 333.535 Allul Australia; 1 4 3:39. 1623134: n... TEES: 4 150 Ruthenium Ag,2'bipyrimidine and Ruthenium:0smium ngjbipyrigidine Bridged Complexes. All these complexes were synthesized in order to be used in resonance Raman spectroscopy. Resonance Raman Spectroscopy has proven to be a nice and relatively simple method to resolve the origin of the broad and structureless CT absorption bands of transition metal complexes. It was shown, for example, that [Ru(bipym)3]2*, under its peculiar absorption spectrum, hides two different MLCTtransitions."3 The same behavior is exhibited by the rest of the monometallic and bimetallic complexes cited in Tables 10 and 11.104 Tungsten Carbonyls. Efforts to transfer the same technique used in Ruthenium complexes (122;: estimation of Internal Conversion from IL to MLCT excited state by competition with fast internal ligand reaction) failed eventhough 148 of the light at 313 nm goes into the internal ligand nt* state, compared to only SX in the case of [Ru(NH3)s(4AP)]2* complex. This lack of an internal ligand Type II reaction is probably due to a fast Internal Conversion to lower excited states, which seem to give photochemistry of their own. In the present study, the high concentration of W(C0)s(4VP) (0.02 M) needed for Type II products observation was helpful since the initially yellow solutions of W(CO)s(4VP), upon 313 nm irradiation, rapidly turned a deep red color, a fact missed 151 by earlier workers who used less than 10" M complex concentration. These low concentrations were essential since the photochemical reaction of W(C0)sL (L = substituted pyridine) was followed by measuring changes in the visible absorption spectra of W(CO)5L. As noted in the introduction, the photochemical studies of W(CO)s (substituted pyridine), in the literature, always included an entering ligand in order to scavenge the W(CO)s and W(CO)4L intermediates. The photochemistry of this class of compounds in the absence of an entering ligand was never attempted, and it was considered complicated.63 Our results led to the stoichiometric reaction (32). by 2 W(CO)5(4VP) -----) W(CO)s + cis-W(CO)4(4VP)2 (32) Electronic Absgrption and Emission Spectra. W(CO)5(4VP) absorption spectra both in benzene and in methylcyclohexane follow the same pattern as already reported for the W(CO)5(4AP) (4AP = 4-Acetylpyridine) complex.°9 The higher energy absorption band maximum at 402 nm in benzene is essentially unshifted by variations of the solvent medium (Figure 24). The lower energy band maximum is observed at 437 nm (methylcyclohexane) and is blue shifted in benzene, appearing as a shoulder to the red of the peak at 402 nm. The absorption bands at 402 nm and 430- 437 nm have been assigned previously to a ligand field (LF) 152 1A1(e‘b22) ----) lE(e3b22a11) symmetry allowed transition and a metal-to-ligand charge transfer (MLCT) transition, respectively.°° The weak absorption maximum at ~330 nm does not shift at all when the solvent is varied. This absorption band has been previously assigned to LF transitions.°9 Room temperature emission is observed (Table 13) in agreement with previous observations.°3'59 The emission maximum does not change drastically by varying the solvent, but it does by changing the ligand. In methylcyclohexane, a short wavelength shoulder appears, the origin of which is uncertain. Due to structural and spectral similarities, W(CO)s(4VP) is expected to behave like W(CO)s4AP and the other complexes having an MLCT lowest excited state. The broad structureless emission is assigned to a MLCT emission. Photochemistry of W(CQ);(4VP). Most of the studies reported here were performed using W(CO)5(4VP) which has certain advantages over “(CO)5(4AP) or W(CO)s(4Cpr). W(C0)s(4VP) has higher solubility than both W(C0)s(4AP) and W(CO)5(4CNpY). so one can make much more concentrated solutions of the former complex in methylcyclohexane, as high as in benzene. It also proved to be ideal for HPLC analysis (short retention times of both W(CO)5(4VP) and cis-W(CO)4(4VP)2). Irradiations were performed at both 410 nm, which presumably populates the LE transition exclusively, and at 153 490 nm, where W(CO)5(4VP) absorbs 10% as much as its maximum at 402 nm in benzene. According to Adamson,69 assuming a gaussian shape for the LF absorptions, 490 nm irradiation populates primarily the MLCT excited state. The quantum yields for direct LF population are 100 and 700 times higher than at 490 nm irradiation, in benzene and methylcyclohexane, respectively (Table 16). This fact can be interpreted either as a relatively inert, independently reacting MLCT state or as an unreactive MLCT state thermally populating the higher energy, reactive LF state. The latter is the standard interpretation.53'65 0n the other hand, the quantum yields in benzene and methylcyclohexane at 410 nm irradiation are comparable (0.066 vs. 0.026, respectively; Table 16), while at 490 nm irradiation, they differ substantially. In benzene, the 490 nm quantum yield is 16 times higher than in methylcyclohexane (Table 16). Taking into consideration the absorption spectra of W(CO)5(4VP), this variation of the quantum yields is consistent with the standard model for the photobehavior of W(CO)s(substituted pyridine) complexes.53»°5 Irradiation at 490 nm populates some higher vibrational level of the MLCT lowest excited state which relaxes rapidly to the zero vibrational level of this excited state. The zero vibrational levels of the LF and MLCT excited states are closer in benzene than in methylcyclohexane, so thermal population of the LF state is more effective in benzene than in methylcyclohexane, with resulting higher quantum yields in the former solvent. 154 The small concentration dependence of the quantum yield at both short and long wavelengths of irradiation in benzene (Figures 35 and 36) probably represents two competing processes: a dissociative mechanism at all concentrations competing with an associative one at higher concentrations. According to Scheme 3, if an excited state reacts with a ground state substrate, it is expected that the reciprocal quantum yield of a product will be a linear function of the reciprocal concentration of the substrate (equation 19). At both 410 and 490 nm irradiation wavelengths,' an identical dependence of the tetracarbonyl product quantum yield on ground state complex concentration was observed, which seems to be what is anticipated if both mechanisms displayed in Schemes 2 and 3 take place simultaneously. Gray has suggested an associative mechanism as a possible reaction path of the MLCT excited states.‘ An associative process for W(CO)5(4VP) to produce W(CO)s and cis-W(CO)4(4VP)2 from an MLCT excited state requires the reaction of a long-lived MLCT state with a ground state molecule, which goes through a seven-coordinate transition state. Eventhough there are no seven-coordinate complexes of Tungsten in the +1 oxidation state it possesses in the MLCT state, there are several such Molybdenum complexes known, like [qs-CsHsMo(CO)3]2.9‘° Therefore, it seems reasonable for Tungsten to form a seven-coordinate transition state, and it is suggested here that the MLCT excited state of W(CO)s(4VP) reacts bimolecularly with the 155 ground state to give W(CO)5 and cis-W(CO)4(4VP)2. As noted in the introduction, LF states are dissociative in nature and, therefore, are anticipated to react unimolecularly. In any case, the variation of the quantum yield with complex concentration is small, especially at 410 nm irradiation, a fact indicating that the main reaction path is through a unimolecular cleavage. The identical dependence of the tetracarbonyl product formation on ground state complex concentration at both 490 and 410 nm irradiations reinforces the hypothesis that the W(CO)5(4VP) complex reacts through interconverting excited states independent or where it is irradiated, a fact verified by quenching experiments described below. Energy transfer quenching in benzene does not show a clear-cut concentration dependence of lifetime on ground state complex concentration (Table 17). Successive Stern- Volmer quenching though of emission and product formation at 490 nm irradiation gives identical lifetimes, within experimental error, at the same W(CO)s(4VP) concentration (Table 17, Figures 39 and 40). Linear Stern-Volmer plots yield qu value of 547 t 17 M‘1 at 10"3 M, and 160 i 4 M‘1 at 5x10'3 M complex concentration in benzene. Therefore, the photoreactive state for long wavelengths of irradiation and the emitting state are kinetically identical. The fact that at 410 nm irradiations the quenching plots obtained have intercepts in general higher than unity (Figure 37) might be interpreted as two excited states being 156 quenched,112 a short-lived one (presumably LF) and a long- lived one (presumably MLCT). The presentation so far implies that the two excited states interconvert but they do not equilibrate. If equilibration were taking place, the Stern-Volmer quenching plots would be identical, independently of where excitation was taking place. Lack of equilibration is most probably due to fast chemical reaction from the upper photolabile LF state. Our quenching plots of cis-W(CO)4(4VP)2 formation are similar to what Adamson obtained for the quenching of the photoexchange in W(CO)5(4Cpr) by ethanol in methylcyclohexane, implying that the same excited states are reponsible for the pyridyl ligand photoexchange reaction and the tetracarbonyl product formation. In the preceding discussion, 490 and 410 nm irradiations imply monochromatic light, which was achieved by a monochromator, while in the discussion to follow Airr > 400 nm means light including all the wavelengths above 400 nm. Correspondingly, Atrr > 475 nm means light which includes all the wavelengths above 475 nm. Since 0(410) )> 0(490), we accept the common interpretation that irradiation with a 400 nm cutoff filter gives products coming primarily from the LF state, while irradiations with wavelengths longer than 475 nm give products originating from the initial population of the MLCT excited state. As noted in the introduction, it has been speculated that excited W(CO)5L species (L is a nitrogen, oxygen or 157 phosphorous ligand) react by losing cis- or trans- CO or L,55'5°-55 and several models have been employed=*'¢’1-°-‘>:113 to explain the reactivity patterns. In our experiments, free ligand quenches cis- W(CO)4(4VP)2 formation with a good Stern-Volmer relation at both short (Airr>400 nm) and long (Air: > 475 nm) wavelengths of irradiation (Figure 42). At both wavelengths of irradiation most tetracarbonyl product seems to be formed through a unimolecular process giving a W(CO)s intermediate, which is effectively scavenged by the free ligand. Little, if any, C0 photoliberation seems to be responsible for the tetracarbonyl product formation at least for visible light irradiation. No CC has been detected by gc/ms when W(CO)5(4VP) was irradiated in benzene in the absence of any entering ligand. If tetracarbonyl product was originating from loss of CO, addition of free ligand (4VP) would enhance the quantum yield, instead of quenching it. The fact though that at Air: > 400 nm we observe less efficient quenching than at lirr > 475 nm (Figure 42) implies that at shorter irradiation wavelengths, loss of CO becomes more significant, the main reaction path for tetracarbonyl product formation remaining the 4VP loss. Further proof for the intermediacy of W(CO)s, as a primary photoproduct,61 came from trapping experiments. 4BP traps the intermediate W(C0)s, quenching the formation of cis-W(C0)g(4VP)2 (Table 19), the main product being W(CO)5(4BP). Two other tetracarbonyl products are produced: 158 cis-W(CO)4(4VP)(4BP) and cis-W(C0)4(4BP)2. The total tetracarbonyl product formation is quenched with good Stern- Volmer relation both at lirr > 400 nm and Airr > 475 nm (Figure 49). The slopes are different, with the larger slope obtained at lirr > 475 nm, consistent with the product quenching by 4VP. Figures 46 and 47 display the product distribution, taken from Table 19, at lirr > 400 nm and Airr > 475 nm, respectively. Only at low concentrations of 4BP cis-W(CO)4(4VP)2 and cis-W(CO)4(4VP)(4BP) .r. producted as major products. If loss of CO was a competitive route, cis- W(CO)4(4VP)(4BP) should always be a major product. While the concentration of cis-W(CO)4(4VP)2 decreases monotonously with increasing concentration of 48?, the concentration of cis-W(CO)4(4VP)(4BP), at Airr > 475 nm, increases then eventually decreases. At Airr > 400 nm, this behavior of the latter compound is less pronounced; the concentration of cis-W(CO)4(4VP)(4BP) is almost constant, a fact which allows the possibility that there is some CO loss and the W(CO)4(4VP) intermediate is trapped by the excess of 4BP. Another point which counts towards a minor CO loss hypothesis at Airr > 400 nm comes from Table 19. For comparable W(CO)5(4BP) formation at both Airr > 400 nm and xirr > 475 nm, the total tetracarbonyl product formation is always lower in the latter irradiation by a factor of 7-9. If we assume W(CO)5 is the major intermediate responsible for photoproduct formation, then by increasing the concentration of 4BP, the intermediate is trapped more 159 efficiently, with resulting increase in the concentration of W(CO)s(4BP). The most probable route for this intermediate to give tetracarbonyl products is to react with the ground state W(CO)s(4VP), to give W(CO)e and W(CO)4(4VP). W(CO)4(4VP) finds itself in an environment of progressively increasing concentration of 4BP, so the concentration of cis-W(C0)4(4VP)(4BP) increases, while the concentration of cis-W(CO)4(4VP)2 decreases. Then it comes a point where the concentration of 4BP becomes high enough to trap more effectively the W(CO)5 intermediate, so the concentration of cis-W(C0)4(4VP)(4BP) decreases. Small amounts of cis-W(CO)4(4BP)2 produced have to come either from the photochemical reaction of photoproduced W(CO)5(4BP) or by thermal reaction of cis-W(CO)4(4VP)(4BP) with 4BP. Figure 48 shows that despite what happens to the concentrations of cis-W(CO)4(4VP)2 and cis-W(C0)4(4VP)(4BP), the concentration of cis-W(CO)4(4BP)2 increases by increasing the concentration of 4BP. The photochemical reaction seems reasonable since the concentration ratio of the photoproduced W(CO)s(4BP) to unreacted W(CO)5(4VP) at high 4BP concentrations is 1:3. But also the thermal formation of cis-W(CO)4(4BP)2 from cis-W(CO)4(4VP)(4EP) is consistent. Control experiments (Figure 45) prove that cis- W(CO)4(4VP)2 reacts in a first order thermal reaction with 43? to give cis-W(CO)4(4VP)(4BP). This thermal reaction has been implied in the literature but the reports seem to contradict each other. Wrighton claims67 that photolysis of 160 cis-W(CO)4X2 (X = py, 4Cpr, 4szy, etc.) in the presence of PPha gives cis-W(CO)4(PPha)X. 0n the other hand, photolysis of cis-W(CO)4X2 with a bidentate ligand (L-L) like 1,10- Phenanthroline is believed to give cis-W(C0)4X(L-L) which thermally57'53 gives CiS‘W(CO)E:1. Our results suggest that the reaction is a first order thermal reaction (Figure 44) from the very beginning. 0n the other hand, cis- Mo(CO)4(CsH10NH)2 reacts smoothly1H at 40°C with L to give cis-Mo(CO)4L(CsHioNH) and then cis-Mo(C0)4L2 which reinforces the thermal reaction hypothesis. Wrighton“ investigated the effects of entering group concentration on photosubstitution in W(CO)spip (pip = piperidine) and his results are displayed in Table l. Eventhough he interpreted these results as there being no concentration effect on piperidine substitution, the trends he found parallel ours for short (lirr > 400 nm) wavelengths of irradiation (small variations in the quantum yields). Wrighton’s complex has highly reactive LF as the lowest excited state, so it is expected to behave photochemically like W(CO)5(4VP) when the latter complex is irradiated in its LF excited state. His data in Table 1 parallel ours cited in Table 19 and Figure 42. A mechanism consistent with our results requires that the W(C0)s intermediate reacts not only with free ligand but also with ground state W(CO)5(4VP) to yield W(CO)s and Cgv- or Cs-W(CO)¢(4VP). As has been proposed,62 the Civ-geometry 161 Scheme 13 H(CO)S(6VP) 490 nm 4l0 nm k k.. . k. c s é—d—z— [mm]. < k” —> [LF] —;)(..s. O 0 IC k2[C] qu[4VP| kL kCO C.S. W(CO)4(4VP) + CO H C0 + 4VP U(C0)6 + cis-U(CO)6(4VP)2 ( )5 kn: = rate of decay (including phosphorescence). kiq = rate of quenching of MLCT excited state by 4VP. krs = rate of then-a1 activation. kic = rate of internal conversion. k2 = bimolecular rate constant. ki = rate of decay of the LF excited state directly to ground state. kL = unimolecular rate constant for loss of 4VP. kco = unimolecular rate constant for loss of CO. k-co = rate constant for the coupling of the W(CO)4(4VP) intermediate with CO. ki = RL + kco. kss W(00)s + 4VP ) W(CO)s(4VP) kss ("(00): + 43? - > W(OO)5(4BP)) ksu "(00): + "(CO)s(4VP) > "(CO)6 + Cs-"(C0)o(4VP) kfsst Cs-W(CO)4(4VP) + 49? --> cis-W(CO)¢(4VP)2 ken = rate constant for the Beck Reaction. ksw = rate constant for the Eimolecular Reaction of W(CO)s with a ground state molecule. krooi = rate constant for coupling of W(CO)4(4VP) intermediate with 4VP. 162 can rearrange to the Cs, so the final product is the cis- disubstituted tetracarbonyl and not the trans. Scheme 13 indicates a possible mechanism which explains the cis-W(CO)4(4VP)2 formation. The mechanism suggests that. the two excited states (MLCT and LF) interconvert, with the LF reacting dissociatively to give primarily W(CO)s, which reacts with a ground state molecule to yield W(C0)s and Cs-W(CO)4(4VP). The latter eventually finds a free 4VP to give cis- w(00).(4vp)2. '1 In an original attempt to explain why chemical quenching Stern-Volmer plots have different slopes at Airr > 400 and lirr > 475 nm (Figures 42 and 49), it was thought that a free ligand, besides trapping the W(CO)s intermediate, quenches some excited state. The most probable excited state to be quenched by 4VP is MLCT, which has been assumed to be involved in redox reactions but to be substitution inert.1°'115'116 Scheme 14 shows a degenerate electron transfer mechanism, which accounts for MLCT quenching by free ligand. Scheme 14. '(-) kiq '(-) (CO)sW(I)(py-x) +py-x ------ > (CO)sW(I)(py-X) + py-x MHHP G.S. 163 Figures 43 and 44 prove that free ligand (4AP or 4VP) quenches the emission from the MLCT excited state but this quenching is too inefficient to explain the big difference (450 M'l) in the Stern-Volmer slopes at Airr > 400 and Xirr ) 475 nm. As mentioned above, less efficient quenching would be reasonable at lirr > 400 nm if some dissociation of CO was responsible for some Cs-W(CO)4(4VP) production, which in the presence of 4VP leads to the tetracarbonyl product. If the mechanism proposed in Scheme 13 is correct, kinetic expressions derived from it should be consistent with experimentally measurable quantities. It is reasonable to assume that thermal activation of MLCT populates lower ligand field states, responsible for loss of 4VP only, while higher energy wavelengths (around 400 nm) populate simultaneously higher ligand field states, responsible for loss of CO. Figure 52 shows this situation. Therefore, at lirr > 475 nm, k1 = kL. According to Scheme 13, irradiation at lirr > 475 nm populates the MLCT state which gives products coming from the bimolecular reaction of this state with the ground state or from the LF state which is populated thermally from the MLCT state. Equation 33 describes this situation. __‘t__ dx2__y2 .— fikin >400 nm +—— ~a—-Thermal Activation TT* +———————~————-—)\irr_::>475 nm .1 dxy fl 4"» dx2.dYZ F' ure 52 MLCT and LF transitions in W(CO)S(4VP). 1g . 165 k2[C] kTA (p O = kisc>[ + + ”‘75 k2[C]+ka2+kiq[4VP]+k1'A k2 [C]+kdz+kiq[4VP]+k'rA kic k2[C] kTA ( + (P-+ k1 +kxc+ki k2 [C]+ka2+ki q [4VP]+1(TA kn [C]+ka2+ki q [4VP]+ku kic k2[C] kTA ( + (P-+ ki +kxc+ki k2 [C]+kaz+kiq [4VP]+kn k2 [C]+kdz+qu [4VP]+k1'A kic k2 [C] k‘l‘A ( + * ' (P + ki+kic+ki k2[C]+kd2+kiq[4VP]+krA kz[C]+ku2+kiq[4VP]+krA kic kzlcl ( + .................... ] (33) ki+kic+ki k2[C]+kd2+qu[4VP]+kTA P is the probability the thermally populated LF state will give products and is best described according to Scheme 13 and Figure 52 as: kL RBNIC] P = -----——- x (34) k2+kic+ki ksn[C] + ksa[4VP] Equation 33 describes the situation the directly kale populated MLCT state will react (.(ISC) ] ) hatcl+kaa+ki.[4VP]+kri or will thermally populate the LF state In (Rise) ‘ ) , which either reacts with h [C]+kss+ku “Whit" probability P, or internally converts to MLCT with 166 k probability -—::—~ , which either reacts, ki+kic+ki or thermally populates the LF to react or repopulate the MLCT. This continuous interconversion between the two states is described by the infinite terms in 33. To simplify equation 33, let: k2[C] = A (35): Probability MLCT reacts. k2[C]+ka2+kiq[4VP]+krA kTA = B (36): Probability MLCT populates k2[C]+kd2+qu[4VP]+kTA thermally the LF state. Inc . ------ = D (37): Probability LF internally ki+kic+ki converts to MLCT state. Substituting 35, 36 and 37 into 33, one obtains equation 38. O i>475 = case) [A+ B(P+ D(A+ B(P+ D(A+ B(P+ D(A+ B(P+...] (38) Equation 38 can be written as 39. 9 m7.- 2 use) [(A+ BP)(1+BD+BZDZ+83D3+B‘D‘+...)] (39) B and D are positive and less than unity, therefore, the sun of the infinite terms of the series (l+BD+BZDZ+B303+B‘D‘+ ..... ) converges to l/(l-BD); therefore, eq. 39 becomes 40. 167 1 O was = fiisci (A+ BP)( ) (40) 1‘80 Both B and D represent efficiencies; therefore, they are both less than unity. B is expected to be much less than unity since thermal activation is slow compared with other exoergonic processes like radiative or radiationless decay to ground state. Therefore, BD<<1 so 40 becomes 41. O: .75: .(ISC) [A+ BP] (.41) Substituting back into 41, the expressions from 35, 36 and 37 one obtains, after performing the multiplications, 42. k2[C] km .leN 2 Rise)[ * P] on) . k2[C]+kaz+kiq[4VP]+kn k2[C]+kaz+kiq[4VP]+-kn Inverting 42, one obtains 43. .l>47«3‘1 z - firscil [ J on) he [C] It's? 4» k3[C]+kda+kle[4VP]+kTA Ratcl+kaa+kigl4VPl+kri Multiplying the numerator and denominator of 43 by l/[C], we obtain 44. 168 . "‘75-! 2 Rise ‘1 l 1 ) I l 0“) k8 krAP [C] 9 hICI+ha+kin4VPI+ku (CUR: [C]+hs+kie[4VP]+krs) It is obvious from 44 that by increasing l/[C], the slope decreases, as found experimentally (Figure 35). Equation 42 can be approximated by considering that the bimolecular reaction plays only a minor role at low values of [C], the main reaction path being the unimolecular reaction from the thermally activated LF state. In other words, kTAP>)k2[C]. This hypothesis is valid if one considers the quantum yield difference at 490 nm irradiation in benzene and methylcyclohexane; if the bimolecular reaction was an important component of the 0 >475 the two quantum yields should not be substantially different. Under this point of view, 42 is modified to 45. lflAP 0 i>s75 -'- «13(3) ( . ) (45) k2 [C]+kdz+qu [4VP]+kTA Substituting-34 into 45, we obtain 46. h .l>475 = .(ISC)( A In. x— IONIC] (46) ) ( 1 Its [Clfltertkiq [4VP]+hs htkic+ki ken [CltkanVP] Equation 46 in the absence of 4VP becomes: 169 lflA kL Ono'ls 3 .(ISC) ( ) ( ) (47) k2[C]+kd2+kTA kL+kic+ki Considering that kiq [4VP] is too low (Figures 43 and 44) and dividing 47 by 46, one obtains the Stern-Volmer equation for quenching by free ligand (4VP). ken (F/O) 1>475 = l + [4VP] (48) ksu[C] The slope of 48 at [complex] = 0.02 M is 732 n-I, therefore, ken/ken = 15. At Airr>400 nm, we have to take into consideration that two processes might give products; loss of CO (kco) and loss of 4VP (kL). The quantum yield is given by 49. 4 ¢ l > ' be In [C] kn " fixsc>[r+ (p, ( + ki+krc+ki kaICl+ksa+RIQI4VPl+kTA hatcl+kaa+kiqtevrl+kra kic ( k2[C] kra kic + (P + ---------- ki+kic+ki ka(C]+kez+kie[4VP]+kn k2[C]+kaz+kiq[4VP]+kn ki +kic+ki kzIC] kn kic + (p + ——-——---- k2[C]+kaz+kiq[4VP)+k1A k2[C]+kaz+kie(4VP]+kn k1 +kic+ki hIC] ( + kitcl*kla*klef4vpl+k74 ] (49) 170 P is the probability with which the Ligand Field state will give products and is best described according to Scheme 13 and Figure 52 as: ice knu [4VP] kl. kill [C] P = r + x (50) ki+ksi has: [4VP]+k—co [W] In flu: but [01+]:in [4VP] kai includes both deactivation processes: internal conversion (kic) and direct deactivation of the LF excited state to ground state (ki). The infinite terms in 49 are needed to describe the fact that LF partially deactivates to the lower MLCT which thermally repopulates the LF excited state and the cycle is repeated. Substituting 35, 36 and 37 into 49, one obtains 51. o x>4oo = *186)[P+ D(A+ a[P+ AD](1+DB+DZBZ+D383+D4B4+ ....... ] (52) (1+DB+0282+0383+D4B4+ ..... ) converges to l/(l-DB), therefore, 52 becomes 53. 171 1 O DQOO = RISC) [(P + DA)("""""")] (53) l-BD DB<<1, so 53 becomes 54. 0 H400 e Crisc>[P + DA] (54) Substituting back into 54, the expressions for 35, 36 and 37, one obtains 55. k2[C] kic O 1>4oo '-'- kisci[P +( X )1 (55) k2[C]+kd2+kiq[4VP]+kTA ki+kic+ki Inverting 55 and multiplying the numerator and denominator by l/[C], one obtains 56. [01“ O M400“1 2 .(ISC)-1 (56) .2. + kgkxc [C] (k2[C]+kd2+qu[4VP]+kTA)(kl+le+ki) It is obvious from 56 that increasing l/[C] the slope decreases, as found experimentally (Figure 36). Equation 55 can be approximated by considering the fact that .410 >> 4490. In other words, the reaction originating from direct population of the LF state is much faster than 172 the reaction taking place through the MLCT state, i.e., bimolecular reaction of MLCT and thermal activation to LF state. k2[C] kic P>>( x ), so 55 becomes 57. k2[C]+kdz+qu[4VP]+kTA ki+kic+ki O i>4oo 2'- .(Iscfl’ (57) Substituting 50 into 57, one obtains 58. Res kfsstI4VP] kt ksuIC] + .“<"" = .(ISC)( ”— r ki+kai krsscI4VPl+kbcoIOOI ki+kai kszCI+kss[4VP] (58) It is assumed that kfast [4VP]>>k-co[CO] at all 4VP concentrations. This is a logical assumption since CO is a gas and, after its generation, diffuses to the vacuum space above the degassed samples, until its chemical potential is equal in the two phases. 58 reduces to 59. kco ki. ken [C] O M400 = QISC)(--“‘-—-- + x ki+kdi ki+kai kanfC]+kaa[4VP] ) (59) In the absence of 4VP, 59 becomes 60. kco kl. Oxmoc- 2 .(ISC)( -------- + ) (60) ki+kai ki+kni The Stern-Volmer equation is obtained from 59 and 60 and is given by 61. 173 kLkan (“/O) M400 3 1+ ------------------------------- [4VP,I (61) kco(ken[C]+ksa[4VP])+kLksH[C] To obtain an estimate of kL/kco, equation 61 was simulated for various kL/kco values, considering that ken/kau[C] = 732, as was found from equation 48. Figure 53 displays the situation. For kco = 0 equation 61 reduces to equation 48 for irradiation with Airr>475 nm. As the ratio kL/kco decreases, the simulated, through equation 61, lines fall between the lines obtained at Airr>475 and Airr>400 irradiations. At approximately kL/kco 2.5, the theoretical line simulates the experimental points at Airr>400 nm well. The small discrepancy is due rather to experimental error. We assumed that for Airr > 400 nm in the presence of 4VP, part of the tetracarbonyl product formation originates from loss of 4VP and part from loss of CO. This hypothesis explained the less efficient quenching of cis-W(CO)4(4VP)2 formation at Airr > 400 nm since the slope of 61 is obviously less than the slope of 49 and gave us an estimate of the relative ratio of the rate constants for CO and 4VP loss from the LF excited state. Of course, the presence of an entering ligand like 4VP or 4BP complicates the situation. CO loss in the absence of any entering ligand produces W(CO)4(4VP) which recombines with either CO or 4VP to give starting material or 174 _k._ kco.100 6.. A 5' -JL: kco20 A 4- ‘ . L‘.:4 . 3~ [km (3 ,__ .fl- 2‘ e . 103,725 / V 1.. 0.002 ' 0.004 I 0.006 ' 0.008 [WP]. 00 Figure 53. Simulation of equation 61 for the Stern Volmer quenching by 4VP of cis—W(CO)4(4VP)2 formation from W(CO)S(4VP) at various kL/kCO values. The experimental points shown have the same meaning as in Figure 42. 175 tetracarbonyl product, respectively. One might argue that cis-W(CO)¢(4VP)2, in the absence of 4VP originates from this very process which is illustrated by 62 and 63. hv W(CO)s(4VP) ------- > W(CO)s + 4VP (62) hv W(CO)5(4VP) ------- ) W(CO)4(4VP) + CO (63) Cross recombination is expected to give W(CO)s and cis- W(CO)4(4VP)2. This process though seems inprobable since presence of free 4VP would not quench the tetracarbonyl product formation. Instead, it would enhance it. The only precedent dispropotionation reaction 32 has in the literature is the reaction 64: hv 2 W(C0)s(PPh3) ------ > W(CO)s + cis-W(C0)4(PPh3)2 (64) suggested by not elaborated by link.117 In conclusion, the synthesis of cis-W(CO)4L2 by irradiation of W(CO)sL with UV light in the presence of L is still valid since, even if we assume that all tetracarbonyl products originate from a W(CO)s intermediate, the photoproduced W(CO)s reacts further to form W(CO)sL so that the yield of the final product is increased. In cases though where the ligand L is reactive under UV light irradiation (like 4VP which gives the Type II reaction), in order to make cis-W(CO)4L2, one has to irradiate W(CO)sL 176 with visible light in the absence of L, limiting the chemical yield to 50* but avoiding ligand side photoreactions. Summary. The results described in this thesis indicate that for the Ester-pyridyl ketone ligand in pentaammine or bis(2,2'bipyridine) Ruthenium(II) complexes, internal conversion to lower excited state competes directly with the chemical reaction from the nt‘I Internal Ligand upper excited state. This competition allows an accurate estimation of the rate of the internal conversion. In the case of the bis(2,2'bipyridine) complexes, we obtained some evidence that an inter-ligand communication may exist. Possibly singlet energy transfer from 2,2‘bipyridine to coordinated pyridyl ketones and triplet energy transfer from the coordinated pyridyl ketones to 2,2'bypyridine. The case of Tungsten carbonyl complexes is different. Internal Conversion is much faster than chemical reaction. Lower excited states (LF and MLCT) give distinct photochemistry. Research towards this direction forced us to introduce a new mechanism for cis-W(CO)4L2 formation. This product comes from W(CO)sL primarily not by loss of CO (at least for irradiations at wavelengths longer than 400 nm), as was believed, but by loss of L and subsequent attack of the W(CO)5 intermediate on a ground state molecule. It appears that the classical photoexchange reaction 177 hv W(C0)5L + X ------- > W(CO)sX + L and the Tungsten Tetracarbonyl formation hv 2 W(CO)5L ---) W(CO)3 + cis-W(CO)4L2 follow the same mechanism. Sgggestions for Further Stggy. The problem of the bimolecular photochemical reaction of the coordinated pyridyl ketone ligandw remains. A reactive hydrogen donor-like sodium succinate should be a good candidate for intramolecular photoreduction of coordinated 4-Acetylpyridine. Another direction would be to move to complexes having LF lowest excited state, but because of geometric and bonding reasons, photodissociation would be avoided. A good candidate would be trans- [Rh(cyclam)(4PhBP)2](BF4)2 (cyclam = l,4,8,ll- Tetraazacyclotetradecane).118 Thus, a direct comparison between IL ----> MLCt and IL -—--> LF Internal Conversion rates would be made. The Tungsten carbonyls open a new chapter in the possible carbonyl exchange reactions between coordinatively unsaturated carbonyls and coordinatively saturated ones. It would be interesting to see in other systems like Fe(CO)s, irradiated with PPhs and yielding Fe(CO)3L2,119 if the mechanism followed is Mechanism I or Mechanism II, according to our model. 1 8 Mechanism 1. hu,L Fe(CO)s --------- > Fe(CO)4L + C0 hv Fe(CO)4L --------- > Fe(CO)3L + CO L Fe(CO)3L --------- > Fe(C0)3L2 Mechani§m_ll. hml. Fe(CO)5 ) Fe(C0)4L + C0 by Fe(CO)4L > Fe(CO)4 + L Fe(C0)4 + Fe(C0)4L > Fe(CO)s + Fe(CO)3L Fe(C0)aL + L ———————— > Fe(C0)3L2 A more careful study at high entering ligand and W(CO)sL concentrations would elucidate any minor bimolecular mechanism taking place in parallel to the dominating unimolecular process. A nice experiment to prove any bimolecular process involving the MLCT excited state would be to find an efficient quencher with intermediate triplet energy between LF and MLCT excited states. High concentrations of this quencher would quench all reactions originating from the LF excited state. By varying the complex concentration, a plot of 1/9 vs. l/[complex] for tetracarbonyl product formation at long wavelength irradiation would be linear. It would be easier to perform 179 this experiment in methylcyclohexane since the spacing between the two excited states is larger than in benzene and the thermal activation would be slower. 180 nxnmummmnu. Instrumentation All compounds were identified on the basis of their physical and spectroscopic properties using the instruments described below. Nuclear magnetic resonance spectra (nmr: Proton and Carbon-l3) at 250 MHz were obtained with a Bruker WM-250 MHz Fourier Transform Nuclear Magnetic Resonance Spectrophotometer. All chemical shifts (6) are reported in parts per million (ppm) downfield from tetramethylsilane (TMS). All coupling constants (J) are reported in Hz. Infrared absorption spectra (IR) were determined either on a Perkin Elmer model 2838 or on a Perkin Elmer model 599 spectrophotometer. All absorptions are reported in wavenumbers (cm‘l) and are characterized as broad (b), strong (s), medium (m) and week (w). Low resolution mass spectra (ms) were determined on a Finnigan 4021 Gc-Ms at an ionization potential of 70 eV for electron impact ionization. Melting points (mp) were 181 182 determined with a Thomas Hoover capillary melting point apparatus. All melting points are uncorrected. Elemental analyses were performed by Spang Microanalytical Laboratory, Eagle Harbor, Michigan_ 49951. Absorption spectra were measured with a Varian Cary 21 spectrophotometer, courtesy of Dr. Chang (all t are reported in units of M‘1 cm’l). Emission spectra were measured on a Perkin Elmer MPF-44A fluorescence spectrophotometer equipped with a differential corrected spectra unit and Hitachi phosphorescence accessory. Preparative scale separations were done on a Varian Aerograph model 920 gas chromatograph fitted with a thermal conductivity detector. Analytical scale separations were done either on a model 1200 Varian Aerograph fitted with a flame ionization detector or on a High Pressure Liquid Chromatography system composed of two model 110A Beckman pumps, 3 DuPont Instruments column compartment fitted with an injection port, and a model LC-75 Perkin Elmer spectrophotometric detector. Relative peak areas were determined using an infotronics CRS 309 Computing Integrator for gas chromatographic analysis or a model 3380 Hewlett Packard recorder-integrator for HPLC analysis. Chemicals Solvents Benzene: 3.5 liters of thiophene-free benzene (Fischer Scientific or Mallinckrodt Chemical Co.) was stirred over 183 several changes of concentrated sulfuric acid (300 nm) until the sulfuric acid remained colorless. The benzene was washed first with distilled water (2 x 300 ml), then with saturated sodium bicarbonate (3 x 300 ml) until a white precipitate no longer formed. It was then washed with distilled water (2 x 200 ml) and dried over anhydrous magnesium sulfate. It was refluxed over phosphorous pentoxide overnight and distilled through a one meter column packed with stainless steel helices; the first and last 300 ml being discarded: bp = 80.0°C. '4 Acetonitrile: Aldrich Gold Label acetonitrile was used as received. Acetonitrile (Fischer Scientific Co.) was purified according to the procedure of O’Donnell.12° Analytical grade acetonitrile was distilled from 10 g anhydrous sodium carbonate and 15 g potassium permaganate, made slightly acidic with concentrated sulfuric acid, decanted from the precipitated ammonium sulfate and distilled through a half meter column packed with stainless steel helices: bp = 82°C. Methylcyclohexane: Methylcyclohexane (Fischer Scientific, Eastman Chemical Co.) was purified according to the procedure of Foster.121 Methylcyclohexane (500 ml) was stirred over several changes of concentrated sulfuric acid (100 ml) until the sulfuric acid remained colorless. It was washed with distilled water (3 x 200 ml), saturated potassium carbonate (3 x 100 ml), distilled water (2 x 100 ml) and dried over anhydrous potassium carbonate. It was 184 distilled through a 30 cm Vigreaux column over lithium aluminum hydride; the first and last 50 ml being discarded: bp = 101°C. Tetrahydrofuran: Tetrahydrofuran (Fischer Scientific, EM Science or Mallinckrodt Chemical Co.) was purified according to a procedure cited in Organic Smtbesesfizz Tetrahydrofuran (1.5 l) was refluxed over 10 g cuprous chloride overnight and distilled through a 30 cm Vigreaux Column, then it was distilled three times over lithium aluminum hydride; the first and the 1... lox being discarded: bp = 66°C. Ethanol: Ethanol was refluxed overnight over sodium metal and distilled; the first and last 10% being discarded: bp = 78°C. Methanol: Methanol (Mallinckrodt SpectAR and J. T. Baker Spectrophotometric grade) was used as received. Dichlorgmethgng: Dichloromethane (Fischer Scientific Co.) was distilled over lithium aluminum hydride; the first and the last 10% being discarded: bp = 39.5°C. Hexane: UV grade Hexane (Burdick & Jackson Laboratories, Inc.) was used as received. Mixed Hexane (EM Science) was purified by washing with sulfuric acid in a manner similar to benzene, dried with anhydrous sodium sulfate, magnesium sulfate or potassium carbonate and distilled over calcium hydride; the first and the last 10- 203 being discarded: bp = 69 : 2.5°C. 185 Ethyl Acetate: UV grade Ethyl Acetate (Burdick & Jackson Laboratories, Inc.) was used as received. Internal Standards n-hexadecane (C16): was available from previous work. n-tetradecane (C14): n-tetradecane, pure grade was obtained from Phillips Petroleum Co. and used as received. n-tridecane (013): was available from previous work. p-dichlorobengene (gaggl: was obtained .from Matheson Coleman & Bell Chemical Co. and used as received. Methyl bengggtg: was obtained from Aldrich Chemical Co. and used as received. Externgl Standards gggtophgnpne: acetophenone (Fischer Scientific Co.) was passed through an. alumina column and then fractionally distilled through a 30 cm Vigreaux column; the first and last 208 being. discarded. Pure acetophenone (>99.SX by g.c.) was obtained by subsequent spinning band distillation. n-heptadecane (017): was obtained from Chemical Samples Co. and used as received. entacarbon l- 4-acet l ridine Tun stem 0 : See below. 186 Quenchers Ethyl sorbate: ethyl sorbate was used as received from Aldrich Chemical Co. Anthracene: Anthracene (blue-violet fluorescence) was used as received from Matheson Coleman & Bell Chemical Co. 4-Vglerylpyridine: See below. Actinoggterg Vglerophenone: was prepared by the Friedel Crafts acylation of benzene by valeryl chloride by Dr. B. P. Giri. o-methylvalerophenone: was prepared earlier by Dr. C. P. Chen.9° o—methylbutyrophenone: was prepared earlier by Dr. C. P. Chen.°° Potgssiu! Reineckate: was prepared from the ammonium Reinecke’s salt ([(NHtCr(NH3)2(SCN)4].HzO - Aldrich Chemical Co.) according to the procedure of Adamson.°a The ammonium Reinecke’s salt (10 g, 28.2 mmol) was dissolved in 50 ml of warm (40-50°C) water. Solid potassium nitrate (28.5 x 1.5 mmol) was added followed by cooling over ice and filtration. The product was recrystallized from a warm, 5% potassium nitrate solution in water, washed with 2 ml of cold water and dried over phosphorous pentoxide under vacuum. All the operations were carried out in dim red light. UV—Vis. Ann: 392 nm, broad absorption between 480 and 580 nm; IR (KBr): 3600-2800 (b.s), 3310 (s), 3200 (3), 2240-1800 (b.s), 1605 187 (s), 1395 (s), 825 (w), 710 (s), 520 (m), 480 (m), 352 (s) cm“. Uggnyl nitrgtg: uranyl nitrate (U02(N03)2.6H20) - Analytical reagent was used as received from Mallinckrodt Chemical Company. Ketones _cetophenone: See above. Benzophenone: received from Aldrich Chemical Co. and recrystallized twice from petroleum ether; mp., 49-50°C. l-phenyl-l-butanone; butyrophenogg:123 n-butyl bromide (59 g, 0.43 mol) in 80 ml of ether was added to a well- stirred mixture of 11.7 g (0.48 mol) of magnesium turnings and 30 ml of anhydrous ether; when the reaction was completed, 25 g (0.24 mol) of benzonitrile in 100 ml of ether was added, and the reaction mixture was refluxed for 7 hrs. Then 200 ml of 10 M HCl was added and reflux continued for another 12 hrs. At the end of the period, the reaction mixture was cooled and transferred to a separatory funnel where the ether layer was collected. The water layer was washed three times with ether and the ether extracts were combined with the original ether layer which subsequently was washed with water followed by saturated potassium carbonate solution; dried with anhydrous potassium carbonate. Ether was removed under reduced pressure and the slightly yellow product was fractionally distilled twice to give 16.9 g (46*) product which was >99.QX pure by gc., bp = 188 117°C (9.3 Torr); UV (CHaCN) Ammx 277 nm (t 954), 317.5 nm (a 56), £313 = 54.50 M"1 cm“; H-nmr (CDCla): (6) 1.0 (t,38), 1.5-2.0 (qui,28), 2.9 (t,2H), 7.4-7.6 (m,3H aromatic), 7.9-8.1 (m,2H aromatic); m/e (rel. int.): 148 (28), 106 (12), 105 (100), 77 (8), 55 (2); IR (C014): 3090 (w), 3070 (w), 2965 (s), 2940 (m), 1694 (s), 1601 (m), 1451 (s), 1414 (w), 1370 (m), 1360 (m), 1214 (s), 1180 (m), 900 (w) cm’l. gzgcetylpyridine; 4AP: was obtained from Aldrich Chemical Co. and vacuum distilled before use or was prepared by the method described by Rosemary Bartoszek, Ph.D. Thesis, Michigan State University, 1981. 4-beggoylpyridine; 4szy: was obtained from Aldrich Chemical Co. and recrystallized three times from petroleum ether prior to use; mp., 72°C. l-(4-pyridyl)but§none (4-butyrylpyridine); 4BP:12‘h125 A solution containing 59 g (0.48 mol) of n-propyl bromide in 80 ml of anhydrous ether was added dropwise to a well- stirred mixture of 11.7 g (0.50 mol) of magnesium turnings and 30 ml of anhydrous ether. After the reactions subsided, a solution containing 25 g (0.24 mol) of 4-cyanopyridine in 60 m1 of anhydrous ether and 40 ml of benzene was added to the stirred solution over 5 min. The resultant mixture was refluxed with stirring for 7 hrs. At the end of the period, 200 m1 of a 10 M hydrochloric acid solution was added slowly with cooling, and reflux was continued for another 12 hrs. Then, upon cooling, the solution was made basic with solid 189 potassium carbonate and solid potassium hydroxide. Filtration removed the precipitated salts which were washed with ether. The aqueous solution was extracted with ether until the ether extracts were colorless. The ether extracts were combined, washed three times with 30 m1 saturated potassium carbonate solutions, one time with 30 ml of a saturated salt solution, and dried with anhydrous potassium carbonate. Ether was removed under reduced pressure to leave a brown oil which was distilled three times under vacuum to give 6.4 g (188) of product which was >99.93 pure by gc. UV (methylcyclohexane) has: 279 nm (a 3390); H-nmr (C0013): (6) 1.01 (t,3H), 1.78 (hext,28), 2.97 (t,2H), 7.74 (dd,2H aromatic), 8.80 (dd,2H aromatic); m/e (rel. int.) 149 (M,25), 121 (27), 106 (100), 78 (93), 51 (79); IR (CCla): 3075 (w), 3030 (w), 2970 (s), 2940 (w), 1700 (s), 1412 (s), 1271 (m), 1217 (m), 1206 (s), 1063 (w), 990 (w), 900 (w) cm". 1-(4-pyridy11pentanone (4-valerylpyridine); 4VP:12“'125 was synthesized by the method used for l-(4-pyridyl)butanone using 79 g (0.58 mol) of n-butylbromide, 14 g (0.59 mol) of magnesium turnings and 30 g (0.29 mol) of 4-cyanopyridine. The synthesis gave a brown oil which was distilled four times under vacuum to give 15 g (328) of the product which was >99.QX pure by gc. bp., 140-141°C (10 Torr); UV (methylcyclohexane) Amax 279 nm (t 2892); H-nmr (Cst): (6) 0.81 (t,3H), 1.20 (hex,2H), 1.52 (qui,2H), 2.44 (t,2H), 7.33 (dd,ZH aromatic), 8.58 (dd,2H aromatic); (CDCla): (6) 0.80 190 (t,3H), 1.25 (hex,2H), 1.55 (qui,2H), 2.85 (t,2H), 7.59 (dd,2H aromatic), 8.63 (dd,2H aromatic); C-nmr (C500; 2.5x Cr(acac)3 added): (a) 13.9, 22.5, 25.9, 38.4, 121, 142.9, 151.1, 199.1; IR (0014): 3080 (w), 3030 (w), 2960 (s), 2935 (s), 1705 (s), 1595 (w), 1555 (w), 1410 (s), 2269 (m), 1222 (m), 1210 (m), 1070 (w) cm’l; m/e (rel. int.): 164 (M+l,100), 121(62), 106(66), 78(18), 51(11). 4-phenyl-l-(flrpyrigyl)bg£gnone; 4PhBP: A solution containing 43.8 g (0.22 mol) of 1-bromo-3-phenyl propane (Aldrich Chemical Co.) in 80 m1 of anhydrous ether was added dropwise to a well-stirred mixture of 5.35 g (0.22 mol) of magnesium turnings and 30 ml of anhydrous ether in a flame- dried, three-neck, round bottom flask equipped with a mechanical stirrer. The reaction was assisted to start by traces of iodine. After the vigorous reaction subsided, the reaction mixture was refluxed for 10 hrs. under argon until all the magnesium had been consumed. Then a solution containing 20.8 g of 4-cyanopyridine in 200 ml of 3:2 (v/v) anhydrous ether - benzene was added to the stirred solution upon cooling over 5 min. The resultant mixture was refluxed with stirring for 12 hrs. At the end of the period, 200 ml of a 10 M hydrochloric acid solution was poured slowly with cooling. Reflux was continued for another 24 hrs. Then, upon cooling, the solution was made basic by addition of solid potassium carbonate. Filtration removed the precipitated salts which were washed with ether. The aqueous solution was extracted with ether until the ether 191 extracts were colorless. All the ether solutions were combined, washed three times with 30 m1 saturated potassium carbonate solution and dried with anhydrous potassium carbonate. Ether was removed under reduced pressure to leave a brown oil which was fractionally distilled under vacuum to give a yellow solid. This product was dissolved in benzene, decolorized with decolorizing carbon and precipitated by the addition of pentane and cooling in the refrigerator for 24 hrs. to give 22.4 g (458) of white flakes. (Pure product was also obtained by a.'spinning-band distillation following the first fractional distillation). mp., 323-3900; bp., 156~157°C (11.6 Torr); uv (cases) i... 280 nm (t 2078), £313 = 124 M’1 cm"; nmr (00013): (6) 2.08 (qui,2H), 2.72 (t,2H), 2.96 (t,2H), 7.1-7.3 (m,5H aromatic), 7.65 (dd,2H aromatic), 8.76 (dd,2H aromatic); IR (CClo): 3040 (w), 3010 (m), 2920 (b,w), 2840 (w), 1690 (s) cm‘l; m/e (rel. int.): 225(M,16), 205(20), 104(100), 91(46), 78(32), 65(14), 51(32). g;bgtyl-4-[(4-pyridyl)carbonyl] butyrate; 4EsterBP: was prepared from the enamine125'l27 derivative of 4- acetylpyridine which was added to n-butyl acrylate (Aldrich Chemical Co.). 4-Acety1pyridine (10 g, 0.0826 mol); pyrrolidine (30 g, 0.422 mol, 5 molar excess) and a catalytic amount of p- toluene sulfonic acid (0.2 g) were dissolved in 150 m1 of purified (as described above) benzene and refluxed for 24 hrs. with continuous removal of water (dean stark). Benzene 192 and excess pyrrolidine were removed under reduced pressure and the resulting oil was diluted with 80 ml of acetonitrile. n—Butyl acrylate (16 g, 1.5 molar excess) was added and the solution was refluxed for 24 hrs. with a drying tube on the top of the condenser. Then 30 m1 of an aqueous solution containing 14 g of sodium acetate and 14 g of an 80% acetic acid solution was added. The resulting solution was refluxed for another 2.5 hrs. At the end of the period, 100 m1 of water was poured into the solution and addition of a large excess of solid potassium carbonate resulted in the separation of two phases. The lower water layer was washed several times with ether and the ether extracts were combined with the upper organic layer. The solution was dried with anhydrous potassium carbonate and the ether was removed under reduced pressure. Distillation under vacuum gave a slightly brown oil collected between 150 and 200°C. .This oil was passed through an Alumina column (Alumina Activated 80-200 mesh: dimensions: 20 cm x 1 cm; solvents: eluent, 100 ml hexane followed by 853 hexane, 15X ethyl acetate) collecting 10 m1 fractions. In the first 60 ml, there were only impurities. Between 100 and 150 ml, there was found only product. Analysis of the fractions was performed by gas chromatography (gc column C at 210°C). All solvents were removed and the product was distilled under vacuum once more to give 0.82 g (48). bp., 163-164°C (11 Torr); UV (CH3CN) lmmx 274.5 nm (e 1884), e313 = 112 M’1 cm‘l; H-nmr (00013): (a) 0.92 (t,3H), 1.38 (hex,2H), 1.61 193 (qui,2H), 2.07 (qui,2H), 2.45 (t,2H), 3.09 (t,2H), 4.10 (t,2H), 7.75 (dd,2H aromatic), 8.81 (dd, 2H aromatic); IR (0014): 2965 (s), 2938 (s), 2875 (m), 1718 (s), 1703 (s), 1405 (s), 1218 (s), 1202 (s), 1150 (m), 1065 (m), 1048 (m), 812 (m) cm’l; m/e (rel. int.): 249 (M,4), 175 (23), 147 (25), 121 (12), 106 (100), 85 (21), 78 (61), 51 (37). Pyridyl getone Hydrochloride Salt; Both hydrochloride salts were prepared by bubbling hydrogen chloride gas through an ether solution of the pyridyl ketone. The salts were purified by repeating recrystallizations from methylene chloride and n-pentane until a colorless product was received. The final product was washed with ether and dried under vacuum. 4-phenyl-l-(4-pyridyl)butanone hydrochloride; 4PhBP.HCl: mp., l30-l3l°C, decomposes; UV (CHaCN) Ammx 275 nm (e 1238), £313 = 104 M‘1 cm'l; (CH2012) Ammx 274 (t 2734), £313 = 166 M‘1 cm‘l; H-nmr (020): (6) 8.82 (d,2H,J=6.l), 8.20 (d,2H,J=6.4), 7.23-7.12 (m,5H), 3.07 (t,2H,J=7.0), 2.61 (t,2H,J=7.6), 1.96 (qui,2H,J=7.0); IR (KBr): 3190 (w), 3090 (m), 3062 (s), 3029 (s), 1700 (s), 1593 (s), 1487 (s), 1223 (m), 1192 (m), 790 (s), 744 (s), 695 (s) cm'l. gzbgtYl-4-(4-pyridy1)carbonyl butyrgte hydrochloride; 4EsterBP.HCl: mp., 137-138°C, decomposes; UV (CH30N) Ass: 271 nm (E 2941), £313 = 82 M"1 cm‘l; H-nmr (D20): (6) 8.88 (d,2H,J=5.8), 8.33 (d,2H,J=5.8), 4.00 (t,2H,J=6.4), 2.41 (t,2H,J=7.3), 1.94 (qui,2H,J=7.0), 1.50 (qui,2H,J=7.0), 1.23 194 (hex,2H,J=7.3), 0.77 (t,3H,J=7.3); IR (KBr): 3050 (w), 2960 (w), 1725 (s), 1700 (s), 1593 (s), 1491 (s), 1381 (m), 1280 (s), 1228 (s), 1178 (s), 1078 (m), 800 (s), 745 (s) cm'l. Nitrogen Coordinatinngiggnds Methyl-(4-pyridy1)forggte (Methyl plsonicotingte); MeINic: was obtained from Aldrich Chemical Co. and was distilled under reduced pressure; the first and last 10% being discarded. 4-Cygnopyridine; 40pr: was used as ’received from Aldrich Chemical Co. [ELE;§ipyridineL bipy: was used as received from Aldrich Chemical Co. 1,10-Phengnthroline, ,gonohydrate; phen: was used as received from J. 1. Baker Chemical Co.. EEEEQipyrigidine; bipyg: was used as received from Alfa Products. Tetraphenylporphyrige; TPP: was used as received from Aldrich Chemical Co. Octgethylporphyrine; OEE: was obtained from Dr. Chang and was used without any further purification. Pyrazine; 222: was used as received from Aldrich Chemical Co. 4,5-Diazaf1uorene: was used as obtained from Dr. W. R. Cherry; University of Louisiana. 195 Photoreduction Products In the photoreduction of acetophenone by THF99, the following products were identified by gc/ms: Octahydro-2,2'bifuran: m/e (rel. int.): 142 (0.7), 97 (0.5), 84 (2), 73 (0.9), 72 (4), 71 (100), 70 (39), 55 (3), 43 (30), 42 (5), 41 (12), 40 (3). E;(E-tetr§hydrofuryl) acetaldimine: One molar solution (2.8 m1) of acetophenone in 1:1 (v/v) THF/CHacN was degassed and irradiated for two days at 313 nm. The product was isolated by preparative gas chromatography using a U-shaped trap containing CD013 and kept in a mixture of acetone/dry ice; nmr (CD013): (6) 2.00-1.88 (m,4H), 2.19 (s,3H), 2.62 (s,lH; the size of this peak descreases by addition of 020), 3.85-4.00 (m,3H); m/e (rel. int.): (by gc/ms) 71 (81), 44 (5), 43 (100), 42 (4), 41 (37), 40 (23). 1-phenyl 1-(2-tetrghydrofgryl) ethgnol: m/e (rel. int.): 192 (M,l), 121 (100), 105 (8), 77 (4), 71 (26), 43 (30). p-(E-tetrghydrofuryl):gcetophenone: m/e (rel. int.): 147 (2), 122 (31), 121 (6), 107 (100), 103 (4), 80 (3), 79 (60), 78 (14), 77 (34), 53 (3), 51 (9), 45 (3), 43 (ll), 40 (2). Acetophenone pingcol: Identified by comparison of the g.c. retention time to an authentic sample which had been synthesized and purified by Dr. M. J. Thomas. 196 Type 11 Products n-butylggcrylggg: A 0.02 M solution (2.8 m1) of cis- [Ru(bipy)2(4EsterBP)2](BF4)2 in acetonitrile was degassed and irradiated for a week at 313 nm. The photoproduced n- butyl acrylate was identified by comparison of the g.c. retention time to an authentic sample (obtained from Aldrich). Its identity was also verified by gc/ms. Photochemically Prodgcegf n-bgtylgcrylggg: m/e (rel. int.): 113 (0.23), 99 (1.32), 85 (6.39), 73 (35), 69 (1.44), 57 (4.5), 56 (44), 55 (100). n-butyl acrylate obtained. from Aldrich: m/e (rel. int.): 129 (M,0.38), 113 (0.34), 99 (1.38), 85 (6.5), 73 (41), 69 (1.58), 57 (5.9), 56 (56), 55 (100). Egthenig! Complexes Chloropgntggggine Ruthenigg(11) dichloridg; Ru NH 01 Cl :123'129 Hexaammine Ruthenium(III) trichlor- ide (Strem Chemical, Inc.) (20 g, 6.5 mmol) was dissolved in 70 ml of 6 M hydrochloric acid solution with warming. The solution was refluxed for 4 hrs., during which a yellow precipitate formed. The mixture was cooled and filtered. The precipitate was washed first with 10 ml of 6 M hydrochloric acid solution then with 5 m1 of methanol and was dried under vacuum to give 1.25 g (663) of bright yellow crystals. IR (KBr): 3600-3000 (b,s), 1618 (m), 1300 (s), 800 (m) cm’l. 197 Pentagmminepyridine Ruthenium(II) tetrafluoroboggte Egg the pyridinegggbstituted derivatives: These complexes were synthesized by a modification of Ford and Taube’s methods.15'75 General synthetic procedure: Silver oxide (158 mg, 0.683 mmol) was dissolved in 4 m1 of distilled water by the dropwise addition of trifluoroacetic acid with stirring. Chloropentaammine Ruthenium(III) dichloride (200 mg, 0.683 mmol) was added. The resultant mixture was stirred, then digested (heated to boiling to complete the precipitation of silver chloride). After 20 min., the precipitate was filtered then washed with two 5 ml portions of distilled water. The filtrate was diluted to 25 ml with distilled water and placed in an addition funnel. The pyridyl ketone ligand, in 3-10 molar excess, was flushed with argon in a 3- neck 100 m1 round bottom flask covered with aluminum foil. Methanol (2 ml) was added to improve ligand solubility in the resultant aqueous solution. Granular zinc (50 g) was washed with 50 m1 of 1.2 M hydrochloric acid solution. The acid solution was decanted and 5 g of mercuric chloride was added to the zinc, which reacted immediately to give the amalgam. Water, 150 ml, and 5 m1 of concentrated sulfuric acid were added on the top and the whole mixture was stirred for 10 min. The zinc mercury- amalgam was washed with distilled water until the washings were slightly acidic, then with acetone and finally with 198 ether. It was air dried and packed into a column which was fitted to the middle neck of a 3-neck round bottom flask containing the ligand. The other two necks were stoppered with rubber septums. On top of the zinc-mercury amalgam column (reduction column) was fitted a funnel containing the Ruthenium(III) solution, on top of which was attached another funnel containing 20 ml of distilled water. The entire system was flushed with argon for 10 min. The light yellow Ruthenium(III) solution (25 ml) was passed through the reducing column over -a period of 30 minutes, giving a deep yellow Ruthenium(II) solution which was added to the stirred ligand slowly. When the addition was completed, the reducing column was washed with two 10 m1 portions of distilled water. Stirring was continued for 30 min. and then ammonium tetrafluoroborate (144 mg, 0.683 x 2 mmol) was added directly to the flask. The resultant solution was refrigerated for a minimum of 12 hrs. The water was then removed under reduced pressure. The resultant precipitate was dissolved in the minimum amount of dry acetone and added dropwise to 500 ml of argon bubbled ether. The precipitated complex was immediately filtered. The product was purified by reprecipitation from acetone/ether repeating the method of the original complex isolation. The precipitate was dried under vacuum for 12 hrs. and stored in the dark. Pentaamminepyridine Ruthenium(II) tetrgflgoroborgte; |Ru(NH3)s(py)|(BF4)2:1°l was synthesized using 200 mg (0.683 199 mmol) of [Ru(NHa)sCl]Clz and 2 ml of pyridine (1.97 g, 0.683 x 3.7 mmol). The complex was recrystallized once from acetone/ether to yield 180 mg (60*). UV-Vis. (water) Imam 244 nm (t 3798), 407 nm, (e 4900); IR (KBr): 3700-3000, 1636, 1525-1350, 1290, 1225-925, 760, 700 cm‘l. Pentaamggne 4-acetylpyridine Rgthenium(II) tetrafluoro- borgte; [8!(Nfla)s(4AP)](BF4)2:1°1 was synthesized using 200 mg (0.683 mmol) of [Ru(NH3)501]012 and 580 mg of 4- acetylpyridine (0.683 x 7 mmol). The complex was recrystallized twice from acetone/ether to. yield 230 mg (70%). UV-Vis. (CH30N) Amax 268.5 nm (a 3696), 509 nm (a 11256), £313 = 336 M'1 cm'l; H-nmr (D20): (6) 8.60 (d,J=6.8), 7.53 (d,J=6.2), 2.52 (3); IR (KBr): 3650-3050 (b,s), 1685 (s), 1639 (w), 1590 (m), 1420 (m), 1365 (w), 1282 (s), 1200 (s), 1170 (w), 1225-925 (b,s), 1005 (s), 962 (w), 835 (w), 796 (w), 754 (w), 729 (w) cm‘l. Pentaammine methyligonicotinate Rgtheniu!(ll) tetrg; Elggroborateip [Ru(NHglg(MeINic)](BF4)z:7°r101 was synthesized using 200 mg (0.683 mmol) of [Ru(NHa)sCl]Clz and 936 mg (0.683 x 10 mmol) of methylisonicotinate. The complex was recrystallized twice from acetone/ether to yield 296 mg (87%). UV-Vis. (CH30N) Imam 264 nm (a 4044), 488.5 nm (E 11865), £313 = 319 M"1 cm'l; IR (KBr): 3700-3000 (b,s), 3360 (s), 3290 (s), 1730 (s), 1634 (m), 1606 (s), 1342 (m), 1325 (m), 1234 (m), 1200 (s), 1107 (s), 1150-850 (b,s), 761 (w), 740 (w), 675 (m), 610 (m), 573 (w) cm'l. 200 Pentaammine 4-pheny1-l-(4-pyridyl)butanone Ruthenium(II) tetrafluoroborgge; (Ru(Nfla)s(4Ph§f)1(§£i);: was synthesized using 200 mg (0.683 mmol) of [Ru(NH3)5Cl]C12 and 768 mg (0.683 x 5 mmol) of 4-pheny1-l-(4-pyridy1) butanone. The complex was recrystallized twice from acetone/ether to yield 316 mg (79X). UV-Vis. (CHaCN) luax 268 nm (e 3860), 505 nm (a 10572), £313 = 432 M‘1 cm’l; H-nmr (020): (6) 8.35 (d,28), 7.28 (d,2H), 7.25-7.10 (m,5H), 2.95-2.80 (broad,28), 2.7-2.5 (broad, 2H), 2.0-1.9 (broad,2H); IR (KBr): 3700-2900 (b,s), 1720-1557 (b,s), 1690 (s), 1680 (s), 1592 (s), 1405 (s), 1300 (m), 1200 (3), 1160-960 (b,s), 745 (w), 692 (w) cm‘l. Pentaammine n-butyl-4-[(4-pyridyl) carbonyl] ggtyrggg Ruthenium(II),tetrafluorogorgte; LRQ(N83)5(4EsterBP)IgBngg: was synthesized using 200 mg (0.683 mmol) of [Ru(NHa)sCl]Clz and 850 mg (0.683 x 5 mmol) of n-butyl-4-[(4-pyridy1) carbonyl] butyrate. The complex was recrystallized twice from acetone/ether to yield 334 mg (80%). UV-Vis. (CH3CN) Anax 266.5 nm (a 2989), 507 nm (z 8853), z-313 = 433 M‘1 cm‘l; H-nmr' (D20): (6) 8.60 (d,2R), 7.52 (d,ZH), 4.00 (t,2H,J=6.2), 3.00 (t,2H,J=5.5), 2.38 (t,Zfl,J=6.3), 1.91 (qui,28,J=6.6), 1.49 (qui,2H,J=7.0), 1.23 (hex,28,J=6.6), 0.76 (t,3H,J=6.9); IR (KBr): 3680-3020 (b,s), 2975 (m), 2870 (m), 1717 (s), 1685 (s), 1635 (s), 1592 (s), 1420 (m), 1290 (s), 1200 (3), 1230-900 (b,s), 835 (m), 750 (m), 540 (m) cm'l. 201 Pentaammine 4-cyanopyridine Ruthenium(II) tetrafluoro- borate; [Ru(NH3)s(4Cpr)](BF412:13° was synthesized using 200 mg (0.683 mmol) of [Ru(NH3)sC1]C12 and 284 mg (0.683 x 4 mmol) of 4-cyanopyridine. The complex was recrystallized twice from acetone/ether to yield 161 mg (518). UV-Vis. (water) luax 257.5 nm (a 22680), 402 nm (e 9536); IR (KBr): 3700-3000 (b,s), 2180 (s), 1691 (s), 1610 (s), 1429 (s), 1290 (s), 1200 (3), 1225-925 (b,s), 820 (w), 798 (w), 718 (w) cm‘l. Diaguo cis-bis(2,2fbipyridine) Ruthenium(II) dichloride; cis-[Ru(biQY)2C12]:§H20: was prepared by Dwyer’s method.7°'79'131 Potassium hexachlororuthenate (Strem Chemicals, Inc.) (1.15 g, 2.67 mmol) was dissolved in 6.6 m1 of 1.0 N hydrochloric acid solution. 2,2'bipyridine (1.114 g) was added and the resulting suspension was stirred for 10 days with a magnetic stirrer at room temperature in .a stoppered flask covered with aluminum foil. The brownish- orange precipitate was collected, washed with water, and air dried to yield 1.46 g of [bipyR][Ru(bipy)Cl¢].RzO. IR (KBr): 3650-3300 (b,s), 3200-2750 (b,s), 1618 (s), 1604 (s), 1583 (s), 1525 (s), 1470 (s), 1450 (s), 1431 (s), 1420 (s), 1320 (s), 1310 (s), 1268 (m), 1244 (m), 1230 (m), 1171 (s), 1160 (S), 1027 (m), 1010 (m), 990 (m), 980 (w), 919 (s), 868 (m), 774 (s), 768 (s), 725 (s), 638 (w), 622 (w), 602 (m) cm‘l. [bipyH][Ru(bipy)Cl4].H20 (1 g) was suspended in 20 ml of pure DMF and the mixture was refluxed for 3 hrs. The 202 initially formed brown solution soon turned to a deep brown- violet and finally to a deep violet color. During the last hour, most of the solvent was slowly distilled off, leaving a volume of about 5 m1. .Then the solution was cooled and suspended in cold acetone (20 m1); 894 mg of dark, almost black crystals was collected. This product was recrystallized/ reduced by suspending it in 100 ml of 1:2 (v/v) water - ethanol and refluxing until all the solid had been dissolved to form the deep .-brown cis- [Ru(bipy)2(HzO)Cl]* complex. This solution was gravity- filtered, 10 g of LiCl was added into the filtrate solution and evaporated over a stream bath down to 45 ml. The solution remained at room temperature for 16 hrs. to complete crystallization. The crystals were washed with 20 m1 of water then 10 m1 of acetone and were dried under vacuum to give 593 mg (573) of the deep purple cis- [Ru(bipy)zclz'].2nzo. UV-Vis. (CDaCN) a... 244 nm (a 31981), 297 an (t 53208) sh 288 nm, 378 nm (e 8632), 553 nm (e 9057); H-nmr (CDC13): (6) 10.32 (d,J=5.9), 8.13 (d,J=8.1), 7.99 (d,J=8.1), 7.85 (t,J=7.9), 7.66-7.55 (m), 7.47 (t,J=8.0), 6.90 (t,J=6.8); IR (KBr): 3650-3150 (b,s), 3100 (w), 3070 (w), 1618 (m), 1600 (s), 1464 (s), 1444 (s), 1420 (s), 1310 (w), 1268 (w), 1120 (w), 1018 (m), 765 (s), 760 (s), 726 (m), 650 (w) cm‘l. Agueous cis-blgil,10-Phengnthroling) _Rg£hgnigg(ll) dichlorigg;_cis-[Ru(phen22C12|.2R20:73:79 was synthesized by the same method used for cis-[Ru(bipy)2012].2820 using 1.15 203 g (2.67 mmol) of potassium hexachlororuthenate (Strem Chemicals, Inc.) and 1.328 g (2.98 mmol) of 1,10- phenanthroline monohydrate. 487 mg (34%) of the deep purple - almost black - product was obtained. UV-Vis. (CDaCN) l-ax 216 nm (1 86159), 266.5 nm (t 78476), 547 nm (c 12012) sh 460 nm; IR (KBr): 3700-3100 (b,m), 3065 (w), 3042 (w), 1517 (m), 1421 (s), 1407 (s), 1283 (m), 1247 (m), 1195 (m), 1095 (m), 1088 (m), 840 (s), 765 (m), 714 (s) cmrl. Diaquo cis-bis(2,2'bipyridine) Ruthenium(II) dichloride and aqueous cis-bis(l,10-phenanthroline) Ruthenium(II) dichloride were transformed to the cis-bis(pyridine) or bis(substituted pyridine) bis(2,2'bipyridine) (or bis(l,10- Phenanthroline)) Ruthenium(II) tetrafluoroborate salts by refluxing them for 6 hrs. in 1:1 (v/v) water/methanol solution, containing 3-5 molar excess of the pyridyl 1igand.7°v79 Addition of ammonium tetrafluoroborate and removal of all the solvents over a steam bath left the deep yellow-orange crude product which was dissolved in dry acetone, filtered, and precipitated by dropwise addition to 500 ml of ether. The product was recrystallized by dissolving it in dry acetone followed by the dropwise addition of ether until no more precipitation was observed; cooling in an ice bath completed the crystallization; the product was dried under vacuum. cis-bis(2,2;gipyridine)-bis(pyridine) #Rgtheniu5111) tetrafluoroborate; cis-[Ru bi 2 2 BFc 2:35'132 was synthesized using 100 mg (0.192 mmol) of cis- 204 [Ru(bipy)2012].2820 and 1 ml (0.98 g, 12.7 mmol) of pyridine. The complex was recrystallized twice from acetone/ether to yield 101 mg (70%). UV—Vis. (water) luau 243 (t 29700) sh 254 nm, 289.5 nm (t 67412), 338 nm (a 20364), 463 nm (t 14382) sh 428 nm; IR (KBr): 3420 (s), 3140 (s), 3049 (s), 2820 (w), 1600 (m), 1467 (s), 1445 (s), 1410 (s), 1160 (m), 1200-925 (b,s), 760 (s), 725 (s), 700 (s) cm'l. cis-bis(2,2'bipyridine)- is 4-acet 1 ridine Ruthenium- (II) tetrafluoroborate; cis-[Ru(bipyzgi4AP2g[(BF113:133 was synthesized using 86.5 mg (0.166 mmol) of cis-[Ru(bipY)2012].2H20 and 108 mg (0.166 x 2 mmol) of 4- acetylpyridine. Ammonium tetrafluoroborate (37.5 g, 0.166 x 2.2 mmol) was added. The complex was recrystallized twice from acetone/ether to yield 115 mg (783) of the product. UV-Vis. (water) 2.3x 243.5 an (t 20793) sh 254 nm, 288 nm (5 67005), 445 nm (2 14890) sh 392 nm; (CH3CN) 1.3x 244 nm (a 18467) sh 252 nm, 286 nm (t 49957), 422.5 nm (a 11280) sh 364 nm, c313 = 7588 M‘1 cm’l; H-nmr (CDacfl): (6) 2.54 (s,6H), 7.15-8.49 (m,16R), 8.9 (d,29), 9.86 (d,2fl); IR (KBr): 3650-3200 (b,s), 3070 (w), 1695 (s), 1604 (m), 1584 (w), 1465 (m), 1442 (m), 1425 (m), 1360 (m), 1260 (s), 1200- 925 (b,s), 966 (m), 830 (s), 765 (m), 735 (m), 655 (w) cm'l. cis-bis(2,2'bipyridine2-bis(4-g§gnxl-1-(4-pyridyl2 butanone) ~Ruthenium(II) tetrafluoroborate; cis- Ru bi 4PhBP 2 BFq : was synthesized using 500 mg (0.961 mmol) of cis-[Ru(bipY)2012].2H20 and 1.161 g (0.961 x 205 5.4 mmol) of 4-pheny1-1-(4-pyridy1)butanone. Ammonium tetrafluoroborate (216 mg, 0.961 x 5.4 mmol) was added. The complex was recrystallized twice from acetone/ether to yield 608 mg (613) of the product. UV-Vis. (CHaCN) A-ax 248 nm (£ 21557), 254 nm (£ 21972), 288 nm (£ 52180), 359 nm (£ 8997), 422 nm (£ 12768), 443 nm (£ 12353), £313 = 7682 M“1 cm‘l; H- nmr (020): (a) 10.10 (d,J=1.10), 8.85 (d,J=5.5, Aromatic 4PhBP), 8.42 (d,J=6.2, Aromatic 4PhBP), 8.36 (d,J=8.4), 8.28 (d,J=8.4), 8.08 (t,J=7.7), 7.91-7.84 (m), _7.77-7.68 (m), 7.36-7.25 (m), 6.97-6.82 (m), 2.85 (t,J=6.7), 2.51 (t,J=7.7), 1.91 (qui,J=6.8); IR (KBr): 3700-2900 (b,m), 1687 (s), 1605 (m), 1468 (m), 1442 (m), 1412 (m), 1170-970 (b,s), 765 (s), 728 (m), 698 (m) cm'l. cis-bis(2,2'bipyridine)-bi§(n-butyl-4-[(4-pyrigyl) carbonyl] butanoate) Ruthenium(II) tetrafluoroborate; cis; |Ru(bipy)g(4EsterBP)g|(BF4)2: was synthesized using 500 mg (0.961 mmol) of cis-[Ru(bipy)zClz].2H20 and 1.196 g (0.961 x 5 mmol) of n-buty1-4-[(4-pyridy1) carbonyl] butanoate which were refluxed in 20 m1 of 1:1 (v/v) water/n-butanol for 6 hrs. Ammonium tetrafluoroborate (216 mg, 0.961 x 2.1 mmol) was added. . The product was recrystallized twice from acetone/ether to yield 916 mg (88X). UV-Vis. (CfiacN) Ann: 293 nm (£ 64077) sh 255 nm, 365 nm (£ 10785), 403.5 nm (£ 12072), 456 nm (£ 13367) sh 483 nm, £313 é 7895 M‘1 cm'l; R- nmr (C0013): (6) 10.02 (d,J=4.8), 9.05 (d,J=5.0, Aromatic 4EsterBP), 8.54 (d,J=5.1), 8.40 (d,J=8.4), 8.29 (t,J=9.4), 8.08-7.98 (m), 7.86-7.55 (m), (all the aromatic region 206 accounts for 24 H’s), 4.05 (t,4H,J=6.6), 2.99 (t,4H,J=6.6), 2.38 (t,4R,J=7.l), 1.98 (broad m,4R,J=6.6), 1.58 (broad t,4H,J=6.6), 1.35 (broad m,4R,J=7.3), 0.90 (t,6H,J=7.3); (020): (6) 9.60 (d,J=5.l), 8.89 (d,J=5.9), 8.55-8.45 (m) , 8.34-8.25 (m), 8.17-8.00 (m), 7.10 (broad t,J=6.6), (all the aromatic region accounts for 24 R’s), 3.88 (t,4H,J=6.6), 2.98 (t,4R,J=6.6), 2.32 (t,4H,J=7.0), 1.87 (broad t,4H,J=7.3), 1.34 (broad t,4H,J=8.4), 1.08 (broad t,4H,J=7.7), 0.61 (t,6R,J=7.3); IR (KBr): 3700-3100 (b,s), 1725 (s), 1695 (s), 1635 (s), 1603 (s), 1461 (m), 1445 (m), 1418 (m), 1122 (s), 1082 (s) cm'l. cis-bis(1.10-Phenanthrolige)-bis ridine Ruthenium II tetrafluoroborate; (Ru(phen)g(21)g|(BFg)gz79 was synthesized using 50 mg (0.091 mmol) of cis-[Ru(phen)zClz].HzO and 1 m1 (0.97 g, 12.6 mmol) of pyridine. Ammonium tetrafluoroborate (19 mg, 0.091 x 2 mmol) was added. The complex was recrystallized twice to yield 55 mg (763) of the product. UV-Vis. (water)133 2.3x 224 nm (£ 57916), 265 nm (£ 75707), 316 nm (£ 9337) sh 336 nm, 415 nm (£ 11375) sh 450 nm; IR (KBr): 3650-3125 (b,s), 3050 (s), 1632 (s), 1600 (s), 1580 (m), 1480 (m), 1443 (s), 1425 (s), 1410 (s), 1339 (m), 1298 (m), 1203 (m), 1200-900 (b,s), 840 (s), 763 (s), 719 (s), 700 (s) cm‘l. cis-bis(1,10-Phenanthroligel-gig(4-gcety1pyrigine) Ruthenium(II) tetrafluoroborate; cis; Ru hen 4AP BF4 : was synthesized using 80 mg (0.150 mmol) of cis-[Ru(phen)2C12].H20 and 90.8 mg (0.150 x 5 mmol) 207 of 4-acety1pyridine. Ammonium tetrafluoroborate (32.8 mg, 0.150 x 2.1 mmol) was added. The complex was recrystallized twice from acetone/ether to yield 99.6 mg (768). UV-Vis. (water) 2.3x 222 nm (£ 66608), 263 nm (£ 70625), 415.5 nm (£ 19341) sh 434 nm; (CR3CN) luau 221 nm (£ 61195), 264 nm (£ 66534), 409 nm (£ 16375) sh 440 nm, £313 = 4813 M‘1 cm'l; nmr (CDaCN): (6) 8.9-7.6 (m,22H), 2.65 (s,6H); IR (KBr): 3650-3300 (b,s), 3240 (m), 3150 (m), 3045 (m), 1696 (s), 1429 (s), 1413 (s), 1268 (s), 1200-1000 (b,s), 840 (s), 718 (s) cm‘l. bis(2,2'bipyridine)-1,10-Phengnthroligg; Ruthenig!(II) tetrafluoroborate' Ru bi hen BF :13"135 was synthesized using 101 mg (0.195 mmol) of cis- [Ru(bipy)2C12].2820 and 97.6 mg (0.195 x 5 mmol) of 1,10- Phenanthroline monohydrate. Ammonium tetrafluoroborate (45 mg, 0.195 x 2.2 mmol) was added. The complex was recrystal- lized twice' from acetone/ether to yield 116 mg (78*). UV- Vis. (water) 1.3x 227 nm (£ 48284), 264 nm (£ 62426), 285.5 nm (£ 64260), 451 nm (£ 14426) sh 480 nm; IR (KBr): 3650- 3000 (b,s), 1625 (w), 1600 (w), 1465 (m), 1444 (m), 1425 (m), 1200-925 (b,s), 840 (m), 765 (s), 725 (m), 715 (m) cm‘l. 2,2'bipyridine-bis(1,10-Phgggnthroline) RgtheniumgII) tetrafluoroborate; [Ru(bipy)(2hen)g|(BF§)g:35 was synthesized using 200 mg (0.189 mmol) of cis- [Ru(phen)2Clz].R20 and 73.8 mg (0.189 x 2.5 mmol) of 2,2'bipyridine. Ammonium tetrafluoroborate (39.5 mg, 0.189 208 x 2.1 mmol) was added. The complex was recrystallized twice from acetone/ether to yield 71 mg (473). UV-Vis. (water) 1.3: 223 nm (£ 57063), 263.5 nm (£ 85317), 450 nm (£ 14532); IR (KBr): 3650-3175 (b,s), 3050 (w), 1629 (m), 1600 (m), 1464 (m), 1445 (m), 1426 (s), 1410 (s), 1140 (3), 1200-925 (b,s), 842 (s), 765 (s), 718 (s) cm‘l. Trig(1,10-Phenanthroline) Ruthenium(II) tetrafluoro- borate; [Ru(phen)31(BF4)2: was synthesized using 104 mg (0.194 mmol) of cis-[Ru(phen)2Clz].H20 and 193_mg (0.195 x 5.0 mmol) of 1,10-Phenanthroline monohydrate. Ammonium tetrafluoroborate (40.8 mg, 0.195 x 2.0 mmol) was added. The complex was recrystallized twice from acetone/ether to yield 101 mg (643). UV-Vis. (water) 1.3x 222 nm (£ 73495), 262 nm (£ 97816) sh 288 nm, 421 nm (£ 15037) sh 388 nm, 447 nm (£ 15681); IR (KBr): 3660-3000 (b,s), 1628 (s), 1429 (s), 1413 (m), 1390 (w), 1209 (w), 1148 (m), 1190-900 (b,s), 849 (s), 780 (w), 726 (s) cm'l. Tris(2,2'bipyridine) Ruthenium(II) tetrafluoroborate; |Ru(bipy);|(BF4)2:1°'13° was synthesized using 200 mg (0.384 mmol) of cis-[Ru(bipy)2C12].2H20 and 300 mg of 2,2'bipyridine (0.384 x 5.0 mmol). Ammonium tetrafluoroborate (100 mg, 0.384 x 2.5 mmol) was added. The volume of the solution was reduced over a steam bath until the first crystals appeared on its surface. Crystallization was induced by addition of saturated aqueous ammonium tetrafluoroborate solution. The product was recrystallized once from acetone/ether to yield 206 mg (72x) of orange 209 microcrystals. UV-Vis. (CH3CN) Anax 244 nm (£ 18513) sh 252 nm, 287 nm (£ 54895), 450 nm (£ 10273) sh’s 420 nm and 390 nm; H-nmr (020): (6) 8.41 (d,68,J=8.4), 7.92 (t,6H,J=8.1), 7.71 (d,6R,J=5.5), 7.24 (t,BH,J=7.3); IR (KBr): 3700-3000 (b,m), 1600 (m), 1461 (m), 1442 (m), 1421 (m), 1200-950 (b,s), 764 (s), 727 (m) cm‘l. Trisg2,2'bipyrigidine) Ruthenium(II) chloride; Ru bi m C1 : was synthesized by a modification of Ludi and Runziker’s method.36 Anhydrous Ruthenium trichloride (K & K Laboratories, Inc.) (100 mg, 0.482 mmol) was refluxed with 267 mg (0.482 x 3.5 mmol) of 2,2'bipyrimidine in 20 m1 of pure DMF for 12 hrs. Then DMF was distilled off until only 3 ml was left; 20 ml of cold acetone was added in portions. The dark reddish-brown precipitate (presumably cis-[Ru(bipym)2C12]; IR (KBr): 3700-3200 (b,s), 3095 (w), 3070 (w), 3040 (w), 1570 (s), 1538 (s), 1400 (s), 1190 (m), 1070 (m), 1014 (s), 820 (s), 778 (m), 740 (s), 634 (m) cm'l) was filtered, air dried and dissolved in 20 m1 1:1 (v/v) water/methanol. 2,2'bipyrimidine (76 mg, 0.481 mmol) was added and the resultant solution was refluxed for 10 hrs; then 10 ml of n-butanol was added and the solution was refluxed for another 14 hrs. LiCl (40 mg) was added and the solution was concentrated over a steam bath until the first crystals appeared on the surface of the solution; cooling completed the precipitation of the crude product which was recrystallized once from methanol/ether to yield 237 mg (763) of the product. UV-Vis (water) Aaax 246.5 nm (£ 210 38463), 331 nm (£ 10398) sh’s 360 nm, 412 nm and 452 nm; IR (KBr): 3650-2600 (b,s), 1625 (s), 1562 (s), 1543 (s), 1400 (s), 1098 (m), 1075 (m), 1020 (s), 810 (s), 762 (m), 744 (m) cm'l. bis(2,2'bipyridine) 2,2fbipyrigidine Ruthenium(II) tetrafluoroborate; (Ru(bipy)z(bipym BFq 2:35-37 was synthesized using 100 mg (0.192 mmol) of cis- [Ru(bipy)2Clz].2820 and 152 mg of 2,2'bipyrimidine (0.192 x 5.0 mmol). Ammonium tetrafluoroborate (43 mg, 0.192 x 2.2 mmol) was added. The orange product was recrystallized twice from acetone ether to yield 120 mg (84*). UV-Vis. (water) 1.3: 243.5 an (t 28046), 283 nm (£ 44754), 417 nm (£ 9995); IR (KBr): 3650-3050 (b,s), 1629 (w), 1600 (m), 1571 (m), 1542 (w), 1467 (m), 1446 (m), 1402 (3), 1200-925 (b,s), 769 (s), 750 (m), 729 (w) cm‘l. 2,2'bipyrimidine-bis(l,lO-Phengnthroline) Ruthenium(II) tetrafluoroborate; |Ru(bipzm)(phen)z|(BF4)g: was synthesized using 200 mg (0.364 mmol) of cis-[Ru(phen)2C12].H20 and 297 mg (0.364 x -5 mmol) of 2,2'bipyridine. Ammonium tetrafluoroborate (79 mg, 0.364 x 2 mmol) was added. The complex was recrystallized twice from acetone/ether to yield 192 mg (66X). UV-Vis. (water) 1.3x 222.5 nm (£ 25043), 262 nm (£ 36752) sh 290 nm, 392.5 nm (£ 6205) sh 424 nm; IR (KBr): 3650-3250 (b,s), 3140 (s), 3050 (s), 1630 (w), 1570 (m), 1542 (m), 1428 (s), 1405 (s), 1200-975 (b,s), 840 (s), 745 (m), 718 (s) cm‘l. (bis(2,2'bipyridine)-242'bipygigidine) Ruthenium(II)- bis 2 2'bi ridine Ruthenium(II) tetrafluoroborate; Ru bi bi m Ru bi 2 BFo 4:35'37'39 was synthesized using 100 mg (0.192 mmol) of cis-[Ru(bipy)zClz].2R20 and 15.8 mg (0.192 x 2 mmol) of 2,2'bipyrimidine. The mixture was refluxed in 1:1 (v/v) water/methanol for 15 hrs. Ammonium tetrafluoroborate (43 mg, 0.192 x 2.5 mmol) was added at the end of the period. The green product was recrystallized twice from acetone/ether to yield 105 mg (41X). UV-Vis. (water) laax 245 nm (£ 34203), 278.5 nm (£ 67137), 411 nm (£ 21403) with broad sh 560 nm, 609 nm (£ 5444); IR (KBr): 3650-2600 (b,s), 1635 (m), 1604 (s), 1469 (s), 1445 (s), 1403 (s), 1310 (m), 1245 (m), 1189 (s), 1200- 925 (b,s), 800 (s), 767 (s), 725 (m) cm'l. Synthesis of Monocarbonyl Tetraphenylporphyrinato Ruthenium(II);AB__1_1TPPCO('1‘HF):30‘82 In a typical synthesis, 500 mg (0.813 mmol) of Tetraphenylporphyrine and 500 mg (0.782 mmol) of Ruthenium dodecacarbonyl (Aldrich Chemical Co.) was dissolved in 50 m1 of pure and dry toluene (purified in a manner similar to benzene by Dr. C. K. Chang’s group) and refluxed under Argon for 3 days in a flask covered with aluminum foil. Toluene was removed under reduced pressure, the residue was extracted with benzene and passed through an alumina column (Fischer Scientific Co., Alumina Neutral, Brockman Activity 1, 80-200 mesh; dimensions: 10 cm x 5 cm). Blution with 212 benzene removed some green impurities, followed by elution with 4:1 (v/v) benzene/THF which eluted the red band of the product. The product was recrystallized from methylene chloride/methanol to yield 271 mg (42*) of reddish-purple microcrystals. UV-Vis. (CH2C12) A-ax 299.5 nm (£ 9959) sh 312 nm, 411.5 nm (£ 130027), 528 nm (£ 11658) sh 560, £313 = 9171 M“ cm'l; IR (KBr): 3050 (w), 3020 (w), 1955 (s), 1815 (w), 1593 (s), 1530 (m), 1485 (m), 1438 (s), 1350 (s), 1306 (m), 1205 (w), 1174 (s), 1068 (s), 1008 (s), ’830 (s), 790 (s), 749 (s), 712 (s), 696 (s), 660 (m) cm‘l. Synthesis of #§i§(4-phenyl-l-(4-pyridy1) butanone) Tetraphenylporphyrinato Ruthenium(II); ggTPP(Ph§P)2: RuTPP(4PhBP) was synthesized by a modification of the method reported for the preparation of bis(pyridine) tetraphenylporphyrinato Ruthenium(II).3° RuTPPCO(TRF) (271 mg, 332 mmol) was suspended in 200 m1 of 3:1 (v/v) THF/benzene (both purified and dried) and irradiated in room temperature for 24 hrs. with the medium pressure Hg - lamp equipped with a pyrex filter, while Argon was bubbled through the solution. After the irradiation was stopped, 150 mg (0.332 x 2 mmol) of 4-pheny1-1-(4-pyridy1) butanone was added to the solution, and all solvents were removed under reduced pressure. The product was dissolved in the minimum amount of benzene and was passed through a Silica column (J. T. Baker Chemical Co. Silica Gel, 60-200 mesh; dimensions: 35 cm x 5 cm), eluting first with 9:1 (v/v) Hexane/Ethyl Acetate. A brown band moved fast, and when it 213 was completely eluted, there were added successively 300 ml each of 1:1 (v/v) benzene/hexane, 1:1 (v/v) benzene/methylene chloride, and pure methylene chloride. The last 900 ml were combined and the solvents were removed under reduced pressure. The product was recrystallized twice from methylene chloride/benzene to yield 292 mg (723) of blue-purple fine microcrystals. UV-Vis. (CHzClz) 133x 283 nm (£ 39909) sh’s 250 nm and 308 nm, 418.5 nm (£ 144207) sh 404 nm, 507 nm (£ 25000) broad sh 532 nm, £313 = 9756 M'1 cm‘l; R-nmr (C303): (6) 8.12 (s,8R), 8.1-8.0 (m,88), 7.7-7.6 (m,12R), 7.15-7.05 (m,68), 6.9-6.8 (m,4R), 5.51 (d,4R), 3.40 (d,4H), 2.80 (t,4H), 2.00 (t,4H), 1.50 (qui,4H); IR (KBr): 3053 (w), 3024 (w), 2935 (w), 2860 (w), 1693 (s), 1599 (s), 1530 (m), 1495 (w), 1442 (m), 1350 (m), 1309 (w), 1230 (m), 1203 (m), 1178 (m), 1074 (m), 1005 (s), 794 (m), 755 (s), 718 (m), 704 (s), 672 (w) cm‘l. . Synthesis of bi§(4-phenyl-l-(4-pyridyl2 butanone) octgethylporphyringto,figthenigg(II); RuOEP‘4PhBP)g: It was synthesized by the same method as RuTPP(4PhBP)2 using 500 mg (0.936 mmol) of Octaethylporphyrine and 500 mg (0.782 mmol) of Ruthenium dodecacarbonyl. The intermediate RuOEPCO(TRF) could not be recrystallized quntitatively although enough crystals were obtained from trichloroethylene/heptane for spectroscopic identification: UV-Vis. (CHzClz) Aaax 254 nm (£ 23710), 303 nm (£ 19362), 321.5 nm (£ 19478), 392 nm (£ 249275), 514 nm (£ 16986), 547 nm (£ 41014), £313 = 18957 M‘1 cm‘l; H-nmr (00013): (6) - 214 2.65 (s,3H; in our efforts to recrystallize the compound from methylene chloride/methanol, THF was propably substituted by methanol, the protons of which give this resonance), 1.94 (t,128), 4.03 (q,8H), 9.95 (s,4H); IR (KBr): 2960, 2930, 2860, 1930, 1590, 1450, 1275, 1230, 1150, 1020, 990, 960, 845, 745 cm'l. All the compound received from the first step was dissolved in 200 m1 1:1 (v/v) THF/benzene (both purified and dried) and irradiated in room temperature for 24 hrs. with the medium pressure Hg-lamp equipped with a pyrex filter, while Argon was bubbled through the solution. At the end of the period, 200 mg (0.888 mmol) of 4-pheny1-1-(4-pyridy1) butanone was added to the solution; and all solvents were removed under reduced pressure. The product was dissolved in the minimum amount of benzene and was passed through an alumina column (Fischer Scientific Co., Alumina Neutral, Brockman Activity I, 80-200 mesh; dimensions: 10 cm x 5 cm), eluting with benzene. A yellow band moved fast followed by the blue-purple band of the RuOEP(4PhBP)2, leaving brownish impurities on the top of the column. There was obtained 129 mg (133) of the product. UV-Vis. (CH2012) 133x 285 nm (£ 41095), 401.5 nm (£ 85085), 498 nm (£ 14558), 524.5 nm (£ 30098), 619 nm (£ 10545), £313 = 21810 M‘1 cm‘l; R-nmr (CDCla): (6) 9.33 (3,48), 7.1-6.95 (m,63), 6.85-6.75 (m,4R), 5.15 (d,4H), 3.80 (qt,16R), 2.15 (t,4H), l.9-1.7 (m,>20H), 1.59 (d,4H), 1.40 (qui,4H); IR (KBr): 2960 (s), 2930 (s), 2870 (m), 1695 (s), 1598 (s), 215 1545 (w), 1455 (m), 1277 (m), 1235 (m), 1206 (w), 1015 (s), 960 (w), 840 (w), 750 (w), 705 (w) cm‘l. Synthesis of Carbonyl pyrazino tetraphenylporphyrinato Ruthenium(II); RaTPPCOpya: RuTPPCO(THF) (50 mg, 0.061 mmol) was refluxed overnight in 50 m1 of benzene in the presence of 1 g (12.5 mmol) of pyrazine. Color changed from purple-red to orange-red; and at the end of the period, the solution was cooled and passed through an alumina column (Fischer Scientific Co., Alumina Neutral, Brockman Activity I, 80-200 mesh; Dimensions: 10 cm x 5 cm), eluting with benzene. The orange-red band moved slowly and required between 1 and 2 1 of benzene to pass through the column. The product was recrystallized twice from benzene/pentane to yield 28 mg (56%) of orange-red microcrystals. UV-Vis. (CBHB)'3mmx 409 nm (£ 241176) sh 490 nm, 530 nm (£ 13753), 564 nm (£ 2906); IR (KBr): 3105 (w), 3055 (w), 3025 (w), 2958 (w), 2930 (w), 1961 (s), 1600 (m), 1530 (m), 1490 (m), 1445 (m), 1420 (w), 1354 (m), 1310 (m), 1210 (w), 1180 (w), 1075 (m), 1010 (s), 839 (w), 799 (s), 756 (s), 720-(s), 704 (s) cm‘l. Synthesis of Carbonyl (Carbonyl pyraaino tetraphenylporphyrinato Ruthenium(II)) tetraphenylpor- phyrinato gathenium(II); CORuTPPpyaTPPRugg: RuTPPCO(THF) (100 mg, 0.123 mmol) was refluxed in benzene overnight in the presence of 5 mg (0.063 mmol) of pyrazine. The product was dissolved in the minimum amount 216 of benzene and loaded on an alumina column (Fischer Scientific Co., Alumina Neutral, Brockman Activity 1, 80-200 mesh; dimensions: 10 cm x 5 cm), eluting first with 2 Its of benzene, followed by 300 m1 of 9:1 (v/v) benzene/methanol. The product was recrystallized once from benzene/pentane to yield 71 mg (373) of deep red microcrystals. UV-Vis. (CsRs) 133x 408 nm (£ 428198) sh 492 nm, 530 nm (£ 34987), 563 nm (£ 5574); H-nmr (C0013): (6) 8.30 (s,l6H), 7.95, 7.70-7.45 (d,m,40H), -0.56 (s,4R); IR (KBr): 3055 (w), 3025 (w), 1958 (s), 1812 (w), 1526 (s), 1595 (s), 1440 (s), 1415 (w), 1350 (s), 1304 (m), 1206 (w), 1175 (m), 1155 (w), 1129 (w), 1070 (s), 1010 (s), 830 (w), 790 (s), 749 (s), 712 (s), 695 (s), 660 (w) cm‘l. 217 W Aqueoaaacia-biaigag'bipyriaine) Osaiam(II) chloride; cia; Lga(bipy)gC12].820:°2 Ammonium Hexachloroosmate (Aldrich Chemical Co.) (500 mg, 1.094 mmol) was suspended in 11 m1 of DMF and refluxed for 1 h. with 346 mg (1.094 x 2 mmol) of 2,2'bipyridine. The solution darkened in color, was cooled, filtered and 10 ml of methanol was added. This solution was added to 500 m1 of ether and the product precipitated as brown flakes. Recrystallization from methanol/ether gave 711 mg of the product, presumably cis-[Os(bipy)2Clz]tzO. IR (KBr): 3600- 2700 (b,s), 3350 (s), 3000 (s), 2780 (w), 1603 (s), 1465 (s), 1444 (s), 1420 (s), 1312 (s), 1242 (m), 1165 (m), 1158 (s), 1070 (w), 1023 (m), 891 (m), 768 (s), 720 (s) cm'l. All material obtained from the above synthesis was dissolved in 30 m1 of 2:1 (v/v) DMF/methanol and cooled in an ice bath. Water (200 ml) was bubbled with Argon for 15 min.; sodium dithionite (0.5 g) was dissolved in it and this solution was added slowly to the DMF/methanolic solution upon cooling and stirring. The resultant solution remained in the ice bath for 15 min. while dark red-purple microcrystals precipitated. The product was washed with water, methanol, ether and air dried to yield 450 mg (708). UV-Vis. (CRaCN) 2.3x 236.5 nm (£ 22426), 297 nm (£ 40059), 385 nm (£ 7278), 460 nm (£ 6391), 555 nm (£ 7929); IR (KBr): 3650-3100 (b,m), 3090 (w), 3070 (m), 3045 (m), 1600 (m), 1590 (m), 1465 (s), 1452 (s), 1413 (s), 1250 (s), 1010 (s), 990 (m), 795 (w), 754 (s), 719 (m), 711 (m), 654 (m) cm'l. Aqaeoas bia(1,10-phenanthroline) 0smium§II) chloride; aia:[0§(phen)2012].H;Q;92 was synthesized by the same method used for the synthesis of cis-[Os(biPY)2C12].820 using 500 mg (1.094 mmol) of Ammonium Hexachloroosmate (Aldrich Chemical Co.) and 454 mg (1.094 x 2.1 mmol) of 1,10- Phenanthroline monohydrate. The first step produced 767 mg of product, presumably cis-[0s(phen)2C12]x820. IR (KBr): 3650-2850 (b,s), 2760 (m), 1625 (m), 1600 (m), 1579 (m), 1510 (w), 1460 (m), 1430 (s), 1410 (s), 1221 (w), 1095 (w), 1020 (w), 845 (s), 711 (s) cm‘l. Treatement with 200 ml of an Argon-bubbled aqueous solution containing 0.5 g of sodium dithionite, produced 518 mg (74%) of the dark purple microcrystalline product. UV-Vis. (CHaCN) 1.3x 220.5 nm (£ 92556), 266.5 nm (£ 97256), 532.5 nm (£ 16053) sh’s 460 and 640 nm; IR (KBr): 3700-3100 (b,m), 3080 (w), 3050 (w), 1645 (m), 1630 (m), 1605 (m), 1560 (m), 1498 (m), 1428 (s), 1409 (m), 1275 (s), 1194 (s), 1092 (s), 1053 (s), 911 (m), 835 (s), 730 (m), 710 (s) cm’l. Ruthenium-Osmium 2,2'bipyrimidiae bridged, mixed ligand binaglear com lexes; were synthesized essentially as described by Meyer.39 In a typical procedure [Ru(biden)2(bipym)](BF4)2 (biden = bidentate ligand: 2,2'bipyridine or 1,10-Phenanthroline) was refluxed with 1.5 molar excess of cis- 219 [0s(biden)2C12].HzO, in 25 m1 of 2:2:1 (v/v/v) water/methanol/n-butanol for 2 days. Then all solvents were removed over a steam bath and the residue was dissolved in water, filtrated and passed through a cation exchange column (Sephadex C-25; dimensions: 35 cm x 1 cm). Elution with 100 m1 of an aqueous ammonium tetrafluoroborate solution removed yellowish-brown impurities; then 100 ml of a 20% ammonium tetrafluoroborate aqueous solution eluted the green product. The eluent was evaporated to dryness, the _product was extracted with dry acetone and precipitated by addition to ether. Purification was achieved by recrystallization (twice) from acetone/ether. (bis(2,2'bipyridine)-bipyria;aine agatheniaa(II)) big; (gaggbipyriaidine) 0smium(II) tetrafluorobggate; [Ru(bipy)g- (bipym)0s(biDY)2J(BF4)4;39 was synthesized using 50 mg (0.067 mmol) of [Ru(bipy)z(bipym)](BF4)2 and 60 mg (0.067 x 1.5 mmol) of cis-[0s(bipy)2Clz].HzO to yield 38 mg (408) of the product. UV-Vis. (water) 2.3x 243 nm (£ 13788) sh 250 nm, 283.5 nm (£ 23372), 417 nm (£ 5665) sh’s 396 nm, 500 nm and 560 nm, 623 nm (£ 731); IR (KBr): 3700-3000 (b,s), 3320 (w), 3110 (w), 1608 (w), 1440 (s), 1295 (m), 1300-890 (b,s), 770 (m), 730 (w), 670 (w), 664 (w) cm‘l. bis(2,2'bipyridine2-bipyrimidine RutheniaaLlIl) 91a; (1,10-Phenanthroline) Osmium(II) tetrajlaaraaorate; Ru bi 2 bi m Os hen BF4 4; was synthesized using 51 mg (0.068 mmol) of [Ru(bipy)2(bipym)](BF4)2 and 66 mg (0.068 mmol) of cis-[Os(phen)zClz].R20 to yield 51 mg (513) of the 220 green product. UV-Vis. (water) 133x 264 nm (£ 18302) sh 280 nm, 410 nm (£ 5951), 631 nm (£ 1453); IR (KBr): 3075 (w), 1640 (w), 1605 (m), 1545 (w), 1469 (m), 1450 (m), 1433 (m), 1407 (s), 1200-900 (b,s), 845 (m), 769 (s), 752 (m), 732 (w), 720 (m) cm'l. bis(l,10-Phenanthroline)-2L2'bipyriajdine Ruthenium(II) bis(2,2'bypyridine) Osmium(II) tetrafluorobgrate; Ru hen 2 bi m 0s bi BF4 4; was synthesized using 53 mg (0.067 mmol) of [Ru(phen)2(bipym)](BF£)z and 44 mg (0.067 x 1.1 mmol) of cis-[Os(bipy)2012].820 to yield 42 mg (43%) of the green product. UV-Vis. (water) 133x 261 nm (£ 43248) sh 280 nm, 407 nm (£ 12096) sh’s 510 nm and 560 nm, 629 nm (£ 2799); IR (KBr): 3660-3000 (b,s), 1632 (w), 1608 (w), 1428 (s), 1184 (m), 1230-865 (b,s), 845 (m), 769 (m), 724 (m), 708 (w) cm“1. bis(l,lO-Pheaanthroline)-2,2'bipyrimidine Ruthenium- (II)) bis(l,10-Phenanthroline) 0smium(II) tetrafluoroaarate; Ru hen bi m 0s hen BFq 4; was synthesized using 50 mg (0.063 mmol) of [Ru(phen)2(bipym)](BF4)2 and 44 mg (0.063 x 1.1 mmol) of cis-[Os(phen)2Clz].R20 to yield 30 mg of the product (29x). UV-Vis. (water) Xmax 222 nm (£ 102083), 262 nm (£ 126304), 392 nm (£ 22610) sh’s 412 and 560 nm, 623 nm (£ 2230), 766 nm (£ 1259); IR (KBr): 3680-3150 (b,s), 3080 (m), 1630 (w), 1603 (w), 1579 (w), 1430 (s), 1415 (m), 1184 (w), 1200-900 (b,s), 845 (s), 720 (s) cm‘l. 221 Igggflemgzgghaua Pentacarbonyl (4-substituted-pyridine) Tungsten(O) Complexaa; were synthesized by the classical method of Strohmeier.‘9 In a typical synthesis, 1.41 g (4 mmol) of Hexacarbonyl Tungsten(O) (Alfa Products) was dissolved in 150 ml of dry THF and under continuous Argon bubbling through the solution irradiated for 2 hrs. with a Ranovia 450 watt medium pressure Rg-lamp equipped with a Pyrex filter.- The solution turned yellow and at the end of the irradiation period, 4.0 to 4.2 mmol of the ligand was added, dissolved in 5 ml of dry THF. The solution turned immediately to reddish-brown. Solvents were removed under reduced pressure and the residue was dissolved in the minimum amount of benzene or ethyl acetate and chromatographed on alumina (Look for the column specifications under each .separate compound.). Solid products were recrystallized from petroleum ether. Pentacarbonyl (4-acetylpyridine) Tungsten(O); W(CO)5(4AP);‘5°v69 was synthesized using 1.41 g (4 mmol) of Rexacarbonyl Tungsten(O) and 485 mg (4 mmol) of 4- acetylpyridine. The product was chromatographed _once on alumina (Alumina Activated, Alcoa, Type F-20, mesh 80-200; dimensions: 35 cm x 5 cm) eluting with 4:1 (v/v) benzene/hexane. The yellow band was' collected and the product was recrystallized once from petroleum ether to yield 908 mg (513) of the yellow W(CO)5(4AP). mp., 114°C, decomposes; Vis. (CeHs) 133x 402 nm (£ 9210) sh’s 430 nm and 222 332 nm, £313 = 2308 M‘1 cm’l; (methylcyclohexane) 1.3: 404 nm (£ 8244) sh 332 nm, 441 nm (£ 8109); R-nmr (0383): (6) 8.03 (dd,2H,J=5.2,1.7), 6.40 (dd,ZR,J=4.9,1.5), 1.76 (s,3H); C-nmr (CsHs; 1% (w/v) Cr(acac)3 added): (6) 25.9, 122.8, 142.2, 156.8, 194, 199.2, 202.2; m/e (rel. int.): 444 (7), 417, 338 (10), 360 (4), 351 (15), 332 (18), 295 (11), 267 (32), 121 (73), 106 (85), 78 (93); IR (KBr): 2075 (s), 2200- 1750 (b,s), 1695 (s), 1414 (s), 1360 (m), 1333 (w), 1265 (s), 1212 (m), 960 (w), 824 (m), 597 (s), 564 (m), 372 (s) cm‘l. " Pentacarbonyl Methyl-(4-pyridyl) formate Tungsten(O); W(CO)5(MeINic); was synthesized using 1.41 g (4.0 mmol) of Rexacarbonyl Tungsten(O) and 596 mg (4.0 mmol) of methyl isonicotinate. The product was chromatographed on alumina (Alumina Activated, Alcoa, Type F-20, mesh 80-200; dimensions: 35 cm x 5 cm) eluting with 3:2 (v/v) benzene/petroleum ether. The yellow band was collected and used without any further purification. Received 102 mg of product (5.5:). mp., 110°C, decomposes; Vis. (Gene) 133: 402 nm (£ 8483) sh 332 nm, £313 = 1983 M'1 cm‘l; (methylcyclohexane) 1.3x 405 nm (£ 9549) sh’s 430 nm and 332 nm; C-nmr: (CsRs; 1x (w/v) Cr(acac)3 added): (6) 52.6, 124.8, 156.7, 163.9, 199.1, 202.3; m/e (rel. int.): 461 (5), 352 (9), 295 (5), 266 (15), 240 (8), 212 (10), 184 (13), 137 (37), 106 (100), 78 (68); IR (KBr): 2970 (s), 2943 (s), 2065 (5), 2100-1775 (b,s), 1730 (s), 1430 (m), 1410 (s), 1285 223 (s), 1260 (s), 1224 (m), 1135 (s), 1110 (s), 855 (w), 795 (s), 764 (s), 700 (m) cm'l. Pentacarbonyl (4-benaoy1pyridine) Tungsten(O); W(CQ)§(4Bapy);°9 was synthesized using 1.41 g (4 mmol) of Rexacarbonyl Tungsten(O) and 732 mg (4 mmol) of 4- benzoylpyridine. The product was chromatographed once on alumina (Alumina Activated, Alcoa, Type F-20, mesh 80-200; dimensions: 35 cm x 5 cm) eluting with 9:1 (v/v) benzene/hexane. The yellow band was 'collected and recrystallized once from petroleum ether to yield 863 mg (433) of the W(CO)s(4szy). mp., 127°C, decomposes; Vis. (C383) Anax 403 nm (£ 9424) sh’s 430 nm and 332 nm; (methylcyclohexane) 1.3x 405 nm (£ 8082) sh 332 nm, 435 nm (£ 7106); H-nmr (cone): (6) 8.00 (dt,ZH,J=4.9,1.5), 6.49 (tt,28,J=7.6,1.5), 6.00-5.95 (m,5H); C-nmr (0383; 13 (w/v) Cr(acac)3 added): (6) 124.9, 130.2, 134, 135.7, 144.3, 156, 192, 198.3, 202; m/e (rel. int.): 508 (4), 480 (4), 452, 425, 354 (30), 296 (16), 268 (52), 240 (30), 212 (43), 184 (60), 105 (100), 77 (48); IR (KBr): 2075 (s), 1990 (s), 1965 (s), 1865 (s), 2150-1750 (b,s), 1664 (s), 1460 (m), 1428 (m), 1284 (s), 950 (w), 945 (w), 845 (w), 700 (m), 650 (m) cm‘l. Pentacarbonyl (4-cyanopyridine) Tungsten(O); W(CO)§(4Cpr);°3'°° was synthesized using 1.41 g (4 mmol) of Hexacarbonyl Tungsten(O) and 416 mg of 4-cyanopyridine. The product was chromatographed on alumina (Alumina Activated, 224 Alcoa, Type F-20, mesh 80-200; dimensions: 35 cm x 5 cm) eluting with 9:1 (v/v) benzene/petroleum ether. The yellow band was collected and the product was recrystallized once from petroleum ether to yield 508 mg (30%) of the yellow W(CO)5(4Cpr). mp., 107.5-108.5°C; Vis. (CsHs) A332 404 nm (£ 7364) sh’s 330 nm and 430 nm; H-nmr (0383): (6) 7.67 (dd,J=5.2,1.8), 5.73 (dd,J=5.0,1.8); C-nmr (CDC13): (6) 114.9, 121.2, 127.1, 157.1, 198.1; m/e (rel. int.): 428 (2), 372 (2), 344 (7), 316 (4), 288 (4), 261 (6), 104 (100), 77 (40); IR (KBr): 2065 (s), 2200-1750 (b,s), 1484 (w), 1445 (m), 1355 (w), 1220 (w), 1155 (w), 822 (w), 755 (s), 700 (m) cm'l. Pentacarbonyl 1-(4-pyrigy1) butanone Tungsten(0); w CO 48?); was synthesized using 1.41 g (4 mmol) of Hexacarbonyl Tungsten(O) and 597 mg (4 mmol) of 4- butyrylpyridine. The product was chromatographed once on alumina (Alumina Activated, Alcoa, Type F-20, mesh 80-200; dimensions: 35 cm x 5 cm) eluting with 3:2 (v/v) benzene/petroleum ether. The yellow band was collected and the product was recrystallized from petroleum ether to yield 930 mg (49%) of the W(CO)5(4BP). mp., 81.2-82.2°C; Vis. (CsHs) Ann: 402 nm (£ 8967) sh’s 430 nm and 332 nm; (methylcyclohexane) Aug: 405 nm (£ 7305) sh 332 nm, 438 nm (£ 7069); R-nmr (0383): (6) 8.10 (dd,28,J=5.0,1.4), 6.51 (dd,2H,J=4.0,1.5), 2.12 (t,2H,J=7.0), 1.51 (hex,ZH,J=7.3), 0.81 (t,3R,J=7.3); C-nmr (Cans; 1x (w/v) Cr(acac)3 added): (6) l4, 17, 40, 123, 143, 157, 196, 199, 202; m/e (rel. 225 int.): 473, 445, 417, 389, 352 (8), 268 (17), 240 (10), 212 (14), 184 (19), 149 (24), 121 (25), 106 (100), 78 (65); IR (KBr): 2970 (s), 2940 (s), 2888 (m), 2075 (s), 2200-1750 (b,s), 1696 (s), 1420 (s), 1405 (m), 1363 (s), 1272 (s), 1241 (s), 1220 (m), 1209 (s), 1000 (s), 903 (w), 818 (s) cm'l. Pentacarbonyl [1-(4-pyriayl) pentaaonej Tungsten(O); "(C0);(4VP); was synthesized using 1.41 g (4 mmol) of Hexacarbonyl Tungsten(O) and 685 mg (4.2 mmol) of 1-(4- pyridyl) pentanone. The product was chromatographed on alumina (Alumina Acid, Brockman Activity I, mesh 80-200; dimensions: 35 cm x 5 cm) twice; the first time, it was eluted with Hexane until a yellowish impurity had been completely removed, followed by 85:15 (v/v) Hexane/ethyl acetate which eluted the yellow-orange product. The second time it was passed through the column, it was eluted with 85:15 (v/v) Hexane/ethyl acetate until the yellow W(CO)s(4VP) had been completely eluted. All solvents were removed under reduced pressure to yield 660 mg (34:) of a thick oil which was identified as W(CO)5(4VP) based on its spectra data. Vis. (CsRs) 133x 402 nm (£ 8534) sh’s 430 nm and 332 nm, £313 = 2220 M'1 cm‘l; (methylcyclohexane) l-ax 405 nm (£ 8353) sh 332 nm, 437 nm (£ 7664), £313 = 2206 M'1 cm'l; H-nmr (Cst): (6) 0.86 (t,3H), 1.23 (hex,28), 1.52 (qui,23), 2.23 (t,3H), 6.59 (dd,2H), 8.17 (dd,2H); (00013): (6) 0.98 (t,3H), 1.44 (hex,28), 1.74 (qui,2H), 2.98 (t,2H), 7.70 (dd,28), 9.02 (dd,2H); C-nmr (Cst; 2.53 (w/v) 226 Cr(acac)3 added): (a) 14, 23, 26, 38.4, 122.8, 142.9, 156.8, 196.7, 199.4, 202.5; (CD013; 2.5x (w/v) Cr(acac)3 added): (a) 13.5, 22, 25.8, 38.4, 123, 143, 156.8, 197, 198, 202; IR (0014): 2950 (s), 2915 (s), 2850 (m), 2060 (s), 1900 (s), 1700 (s) cm‘l. Photaprnduct Isolation and Identification cis-Tetracarboayl 4§1a(1-(4-pyrid 1 entanone Tun sten 0 aia:W(CO)4(4VP12: About 1 g of pentacarbonyl l-(4-pyridy1)pentanone Tungsten(O) was dissolved in 25 m1 of purified benzene, transferred to eight elongated test tubes and degassed with four freeze-pump-thaw cycles. The tubes were flame sealed and irradiated for four days with visible light above 400 nm (Look at the "methods and techniques" part of the experimental section of this thesis.). Then tubes were opened, benzene was removed under reduced pressure and the residue was dissolved in 3 m1 of ethyl acetate and chromatographed on alumina (Alumina Acid, Brockman Activity I, mesh 80-200; dimensions: 35 cm x 1 cm) eluting first with 85:15 (v/v) hexane/ethyl acetate until all the unreacted W(CO)5(4VP) (yellow band), and all the W(CO)3 (moving with the front of the solvent), having been produced in parallel to the product had been removed followed by 1:1 (v/v) hexane/ethyl acetate which eluted the 'red band of the product. All solvents were removed under reduced pressure and the product was isolated as dark red needles after 227 recrystallization from ethyl acetate-hexane. The product was dried under vacuum to give about 260 mg (about 20%). mp., sublimes above 260°C; Vis. (CsHs) 2.3: 490.5 nm (£ 8798) sh 390 nm; £soo = 2834 M'1 cm‘l; (methylcyclohexane): broad absorption in the visible region with maximum around 520 nm, broad sh around 620 nm; H-nmr (Cst): (6) 0.81 (t,3H), 1.17 (hex,2H), 1.48(qui,29), 2.21 (t,29), 6.72 (dd,28), 8.44 (dd,28); (CD013): (6) 0.95 (t,3H), 1.40 (hex,28), 1.70 (qui,28), 2.95 (t,2H), 7.65 (dd,2H), 8.90 (dd,2H); C-nmr (Cst; 1x (w/v) Cr(acac)3 added): (a) 13.9, 22.5, 26, 38.4, 122.8, 142.9, 155.7, 197, 205.5, 213; (cnc13; 2x (w/v) Cr(acac)3 added): (a) 13.9, 22.5, 26, 39. 122.9, 142.9, 156, 198, 204.8, 213; IR (KBr): 2955 (m), 2930 (m), 2870 (m), 1990 (s), 1880 (s), 1855 (s), 1810 (s), 1695 (s), 1605 (s), 1410 (s), 1220 (w), 1200 (m), 980 (w), 840 (w), 790 (w) cm'l; Elemental Analysis Data: Calculated for WCzsNszsOs: (X) C, 46.31; N, 4.50; H, 4.21; W, 29.55. Found: C, 45.93; N, 4.47; R, 4.14; W, 27.08. Rexacarbonyl Tungsten(O): Rexacarbonyl Tungsten(O) precipitated partially out of concentrated (~0.05 M) benzene or methylcyclohexane solutions of W(CO)5(4VP) after prolonged irradiation. In one case, it was collected and identified by its mass and Carbon-13 nmr spectra by comparison with an authentic sample obtained from Alfa Products. 228 Photoprodaced “(00);: C-nmr (CeDs): (6) 191; m/e (rel. int.): 352 (36), 324 (7), 296 (32), 268 (100), 240 (50), 212 (60), 184 (66). W(00)e obtained froa AlfaProducta: C-nmr (CeDs): (6) 191; m/e (rel. int.): 352 (97), 324 (18), 296 (19), 268 (61), 240 (31), 212 (54), 184 (100). lumbomlsndfhxtmflmnm gzggggniancfl'gggfles Photochaaical Glasswaaa: Class A pipets, Class A volumetric ware and Pyrex syringes with chrome-plated brass needles were used to prepare sample solutions for photolysis. A11 glassware was cleaned by rinsing with acetone, then distilled water, followed by boiling in a distilled water solution of Alconox Laboratory Glassware Detergent for one hour then pouring out the hot solution and changing for five times the distilled water in the container, followed again by boiling in fresh sample of distilled water for one hour with subsequent changes of the distilled water for another five times. All glassware was dried at 140°C in an oven used only for photochemical glassware. Irradiation Tubes: Photolysis tubes (13 x 100 nm Pyrex culture tubes) were cleaned in a manner identical to the photochemical glassware. The necks were drawn out to the desired length by rotation in an oxygen flame. 229 Stock Solutions and Photolysis Solatioaa: A Sartorious Model 2403 balance (accurate to i 0.001) was used to weight the desired amount of substrate into a volumetric flask which was then diluted to volume with the appropriate solvent. Solutions were used directly or by pipetting an appropriate aliquot into another volumetric flask and diluting to volume. Qagassing_Procedaaaa: A 5 m1 syringe was used to fill the irradiation tubes with 2.8 m1 of the appropriate solution. The tubes were attached to a vacuum line on a manifold fitted with 12 stopcocks using one-hole rubber stoppers (size 00). For room temperature emission studies, the test tubes were attached to the vacuum line on another manifold using ground joints, sealing being ensured by) the use of high-vacuum silicon grease. All samples were degassed by four freeze-pump-thaw cycles (for emission studies the cycles were six): frozen by the cold vapor over the surface of liquid nitrogen followed by slow immersion into it, pumped for 10-20 minutes at 5 x 10 Torr. then allowed to thaw by standing in air. At the end of the final cycle, the tubes being frozen, were sealed with an oxygen torch under vacuum. Irradiation Procedures: Photochemical studies involved the use of four different irradiation apparati. Three of these involved the use of Ranovia 450 watt medium-pressure mercury lamps cooled by quartz immersion wells which were placed inside a "merry-go-round" apparatus (7 mm slit 230 width). The entire apparatus was placed inside a large crock filled with distilled water. All tubes were irradiated in parallel to ensure that each received an equal amount of light. Three different filter solutions were employed. Filter A. To isolate the 313 nm region, an aqueous filter solution of 0.001 M potassium chromate and 1x potassium carbonate was used. Filter 8. To cut all the light below 400 nm while equally transparent at all longer wavelengths, an aqueous filter solution of 1 M sodium nitrite was used. Filter C. In order to cut all the light below 475 an an aqueous filter solution of 0.05 M potassium chromate and 1% potassium carbonate was used. The fourth apparatus was a 1000 watt Hg-Xe lamp in line with a Dausch & Lomb high-intensity grating monochromator (catalog No. 33-86-76) (Filter D) held 3 cm from the quartz window of a jar containing a merry-go-round apparatus with windows on the outside of sample holders. Aaalysiagof Saaples laaatification of paatoproducts: Photoreduction products using THF as a hydrogen donor were identified by their mass spectrometric data (gc/ms). The alkene photoproducts of phenyl ketones, phenyl ketone hydrochloric salts and pentaammine or bis(2,2'bipyridine) Ruthenium complexes (styrene and n-butyl 231 acrylate) were identified by comparison with the gas chromatographic (gc) retention times of authentic samples. Styrene becomes apparent from its characteristic odor, while n-butyl acrylate was also identified by gc/ms. Cis-tetracarbonyl bis(4-va1erylpyridine) Tungsten(O) being produced by the irradiation of Pentacarbonyl (4- valerylpyridine) Tungsten(O) was isolated (see above) and identified based on its spectral and elemental analysis data. Rexacarbonyl Tungsten(O) produced with Tetracarbonyl bis(4-va1erylpyridine) Tungsten(O) upon irradiation of pentacarbonyl (4-va1derylpyridine) Tungsten(O) was identified by its HPLC retention time, by its characteristic carbon-l3 nmr resonance peak at 191 ppm, and its mass spectrum. Cis-tetracarbonyl bis(4-acy1pyridine) Tungsten(O) produced from W(CO)5(4AP), W(CO)5(4szy) and W(CO)5(4BP) were identified from the carbonyl peaks in the carbon-13 nmr spectrum by comparison of the spectrum before and after irradiation; the photochemical reactions in these cases were carried out, in four freeze-pump-thaw cycle degassed and flame-sealed nmr tubes originally attached to ground glass Joints. Ligand Fragmentation: Samples after irradiation were checked for ligand fragmentation by the comparison of the gc or HPLC retention time with an authentic sample. 232 Gas Chromatography Procedaaaa: On column, sample injections of 0.2 to 0.4 microliters were made into 1/8 inch diameter aluminum columns using nitrogen as the carrier gas. The hydrogen flow rate was 30 ml/min and the air flow rate 300 ml/min. The following columns were employed: Colaan A: 19.43 FFAP, Chromosorb P 60:80 DMCS, 3O m1/min (Nitrogen flow rate); 8’ x 1/8"; 140°C Column, 200°C injector, 280°C detector (styrene analysis);. 120°C Column, 200°C injector, 280°C detector (n-butyl acrylate analysis); 180°C column, 200°C injector, 280°C detector (acetophenone analysis); 190°C column, 200°C injector, 280°C detector (0- methyl acetophenone analysis). Column 8: 53 QF-l, 1.253 Carbowax 20 M, Chromosorb G 60:80 DMCS acid washed, treated with MeaSiNRSiMea; 25 ml/min (Nitrogen flow rate); 8’ x 1/8"; 140°C column, 200°C injector, 280°C detector (acetophenone analysis); 130°C column, 200°C injector, 280°C detector (4-acetyl pyridine analysis); 98°C column, 230°C injector, 250°C detector (2-(2-tetrahydrofuryl) acetaldimine analysis); 105°C column, 230°C injector, 250°C detector (octahydro-2,2'bifuran analysis). Column 0: 53 SE-30, Chromosorb W 60:80 DMCS acid washed; 30 ml/min (Nitrogen flow rate); 5’ x 1/8"; 210°C column, 250°C injector, 280°C detector (4-pheny1-1-(4- pyridyl) butanone and n-buty1-4-[(4-pyridyl) carbonyl] butanoate analysis). 233 Column D: 193 FFAP, Chromosorb G 60:80 DMCS; 30 ml/min (Nitrogen flow rate); 12' x 1/8"; 175°C column, 230°C injector, 290°C detector (2-(2-tetrahydrofuryl) acetaldimine analysis); 200°C column, 230°C injector, 290°C detector (octahydro-2,2'bifuran analysis). ‘ High-Pressure Liquid Chromatography Procedures: Through an injector accessory, sample injections of 20 microliters were made into a 25 cm normal phase silica column using mixtures of UV-grade Hexane and Ethyl Acetate as mobile phase, pushed through the column by two high-pressure pumps; the ratio of the solvents was automatically set by a microprocessor. The following column was employed: Column E: Ultrasphere Si 5um (Altex Scientific, Inc.); 25 cm x 4.6 mm; 1.5 ml/min (carrier solvent flow rate); 35°C column temperature; 853 Hexane, 153 Ethyl Acetate, detector at 270 nm (Pentacarbonyl(4-Butyrylpyridine) Tungsten(O) and Cis-Tetracarbonyl bis(4-valerylpyridine) Tungsten(O) analy- sis); 953 Rexane, 53 Ethyl Acetate, detector at 290 nm (Rexacarbonyl Tungsten(O) analysis). Actinometry and Quantum Yield Determination Internal standards were used for all analyses except the following cases in which external standards were employed: a) Analysis of 4-acety1pyridine being produced from cis-bis (2,2'bipyridine)-bis (4-phenyl-l-(4-pyridy1) butanone) Ruthenium(II) tetrafluoroborate. 234 b) Analysis of Hexacarbonyl Tungsten(O) being produced from Pentacarbonyl (4-Va1ery1pyridine) Tungsten(0). c) One Stern-Volmer experiment, quenching Pentacarbonyl (4-Va1ery1pyridine) Tungsten(O) with anthracene. No particular standard was used for photochemical experiments in benzene analyzed by HPLC with the detector at 270 nm; the solvent (benzene) played the role of a standard. No standard was necessary for experiments analyzed by visible light absorption at 600 nm. For the experiments analyzed by gc or HPLC, the photoproduct concentration was determined using the ratio (area of product/area of internal (or external) standard). A detector response factor (RF) was determined to account for the difference in molar response for each compound. The response factor is the reciprocal slope of the plot of concentration ratio of compound to standard versus area ratio of compound to standard. Response factors are listed in Table 27. Product concentrations are determined from (65). When the solvent (benzene) was used as internal .Kproduct) = RF x [Standard] x (area of product/area of standard) (65) standard, the response factor determined (RFoss) is the product of the real. Response factor (RF) times the concentration of benzene. i.e., RFoss = RF x [benzene]; [benzene] is constant since benzene is the solvent. M Internal (external) standard: Compaund analyzed p-dichlorobenzene: p-dichlorobenzene: methyl benzoate: methyl benzoate: n-tridecane: n-tetradecane: n-hexadecane: n-hexadecane: n-hexadecane: n-heptadecane: benzene: benzene: benzene: acetophenone: benzene: benzene: RF octahydro-2,2'bifuran 1.0' 2-(2-tetrahydrofuryl) acetaldimine 1.2' octahydro-2.2'bifuran 1.08P TRFCR:CN 1.3' n-butyl acrylate 2.22 styrene 1.57 acetophenone 2.25 o-methyl acetophenone 2.0° 4-acety1pyridine 3.01 4-acetylpyridine 3.06‘ cis-W(CO)¢(4VP)2 0.0126 cis-W(CO)4(4VP)(4DP) 0.0126” cis-H(OO)4(4DP)2 0.00554 "(00): 0.0355 4VP 0.0255 48? 0.0257 ' The response factor was calculated by the formula RF = (No. of carbons of standard)/(No. of carbonds of compound); carbons single bonded to oxygen counted as one half; carbons double bonded to oxygen not counted at all. ° Compound not available. W(CO)£(4VP)2. RF considered equal to the one measured for cis- 236 Valerophenone Actinoaetry; was used for product quantum yield determinations at 313 nm irradiations. For extremely long 313 irradiations (one week or more; cases of cis- [Ru(bipy)2(4EsterBP)2](BFd)2, RuTPP(4PhBP)2 and RuOEP(4PhBP)2), o-methyl valerophenone and o-methyl butyrophenone were used as actinometers.9° A 0.1 M solution of the actinometer in benzene containing a known concentration of Rexadecane (internal standard) was irradiated simultaneously with the desired compound in the merry-go-round apparatus and analyzed in Column A or E. Photoproduct quantum yields were determined from (66). The quantum yields for 0.1 M valerophenone, 0.1 M o-methyl valerophenone and 0.1 M butyrophenone are 0.33, 0.016, and 0.0014 mol/einstein, respectively.°° In some experiments, [product] .(product) = X Q.Y.(of actinometer) (66) [product from actinometer] the quencher was absorbing part of the light; an absorbance correction was made by multiplying Oproduct by the following quantity based on Beer's Law: ([quencher] £313 quencher + [ketone] £313 ketone) ([ketone] £313 ketone) 237 When the reacting compound (ketone) concentration is low and therefore does not absorb all the incident irradiation, a correction has to be made again by multiplying the photoproduct quantum yield by the quantity (68) based also on Beer’s Law. [l-T(actinometer)l/[l-T(ketono)l (68) Photoreduction Quantum Yields were determined by the irradiation of a constant aliquot of stock ketone solution in the presence of a hydrogen donor. The absolute quantum yields of photoproduct formation were determined by adding various aliquots of stock donor solution to a constant aliquot of stock ketone solution and diluting to volume. The tubes were prepared, irradiated and analyzed in the usual manner. A plot of (Oproductr1 versus [hydrogen donorl'1 yields a line in which the slope divided by the intercept equals kd/kr. Type II quantum yields were determined by analyzing for the alkene or for the acetophenone. Uranyl Oxalate Actinoaetry;°7 was used for cis- W(CO)4(4VP)2 quantum yield determination at 410 nm irradiation. An aqueous solution (2.8 ml) with precisely known concentrations of uranyl nitrate and oxalic acid (in the range of 0.01 M and 0.05 M, respectively) was irradiated in parallel to the Pentacarbonyl (l-(4-pyridy1) pentanone) Tungsten(O) samples, while another sample was kept in dark 238 as blank. Oxalic acid is consumed photochemically in the presence of Uranyl nitrate sensitizer according to the equation (69): ha 8000-0003 -> 00 + 002 + 820 (69) The oxalic acid consumed was determined by titration of both the blank sample and the irradiated sample with a standardized potassium permaganate solution (~6.0 x 10’3 M). Potassium permaganate reacting with 020424- decolorizes. Titration was completed when the pink color of potassium permaganate remains in the titrated solution. The quantum yield for the oxalic acid consumption upon irradiation at 410 nm is 0.56 mol/einstein and photoproduct quantum yields were determined from (70): ibroduct = [product]/[oxalic acid consumed] x 0.56 (70) Potassium Reineckate Actinometry“B was used for the cis-tetracarbonyl (1-(4-pyridyl) pentanone) Tungsten(O) quantum yield determinations at 490 nm irradiations. An aqueous solution (2.8 ml) of the potassium Reinecke’s salt (about 0.01 M) was irradiated in parallel to the pentacarbonyl (l-(4-pyridyl pentanone) Tungsten(O) samples while another sample was kept in dark as blank. Potassium Reinecke’s salt photoreleases SCN' according to the equation (71): 239 KCr(NHs)2(SCN)4 > Cr(Nfls)z(SCN)3R20 + KSCN (71) After the irradiation, 10 ml of an aqueous ferric nitrate solution (about 0.1 M) containing perchloric acid (0.5 M) was added to the actinometer solution (and to the blank). The totally released SCN' forms a red 1:1 complex with Fe(III), the concentration of which was determined spectrophotometrically at 450 nm. (£ FeSCN complex at 450 nm = 4.3 x 103 M'1 cm‘l). The concentration of the photoreleased SCN' is found as the difference between the irradiated and the blank sample. The quantum yield for the SCN' photoreleased upon irradiation at 490 nm is 0.305"8 and photoproduct quantum yields were determined from (72): Chroduct = [productJ/[photoreleased SCN‘] x 0.305 (72) Complex disappearance quantum yields were determined by comparing the complex with the internal (or external) standard area ratios of the solutions before and after irradiation. The factor R, given in (73), when multiplied by the original complex concentration and the result subtracted from the original complex concentration, gives the change in complex concentration (74) from which the disappearance quantum yield is calculated. 240 [(area of complex)/(area of standard)].tcor irradiation = R (73) [(area of complex)/(area of Standard)]bafora irradiation [CO-plex]ortsinal - R x [ca-plex]ortsinal = [complex] (74) Concentration Dependence of quantum yields were determined by two methods. Either by using an actinometer in parallel to the tubes irradiated containing varying concentrations of the substrate or by normalization when the quantum yield at one point (concentration) was known from another experiment. The normalization factor (NF) is given in (75): NF = (Quantum yield of the Photoproduct at the concentration of known Q.Y.)/(Physical property of the photoproduct at the concentration of known Q.Y.) (75) The Quantum Yield at any other concentration is given by (76): Physical Property is either (photoproduct/standard) Quantum yield of the photoproduct at any concentration = NFx(Physica1 property of the photoproduct at this concentration) (76) area ratios for gc and HPLC analysis or Corrected Absorbance for visible light absorption analysis. The Corrected Absorbance of the photoproduct at 600 nm method was applied in cis-W(CO)¢(4VP)2 analysis and is valid for low conversions: it is based on the equation (77): 241 A(600)corrected = A<600)after irradiation " A(600)before irradiation (77) In the normalization method, the sample with the concentration of known quantum yield from an independent experiment plays the role of actinometer. Stern Volaer Stadiaa Photoprodact Qaenchiag. For the pyridyl ketone Norrish Type II. fragmentation studies or for the pentacarbonyl (l-(4-pyridy1) pentanone) Tungsten(O) disproportionation studies, a constant aliquot of stock ketone (or Tungsten complex) solution was pipetted into several volumetric flasks. Varying aliquots of stock quencher solution were also pipetted into the flasks and diluted to volume. For the pyridyl ketone hydrochloride salts and for the pyridyl ketone Ruthenium complexes Norrish Type II fragmentation studies, solubility reasons prevented us from making stock solutions so the appropriate amount of the pyridyl ketone salts or the Ruthenium complexes were weighted directly into the volumetric flasks which, after the addition of the quencher solution and dillution to volume, gave the final solution for irradiation. Tubes were prepared, degassed, irradiated, and analyzed the way described before. The slope of O°/O versus [Quencher] gave qu for the reacting state. ‘ gaiaaion Qaanchiag. Samples of known concentration of pentacarbonyl (l-(4-pyridy1) pentanone) Tungsten(O) in 242 benzene were prepared as described for emission studies; emission spectra were recorded for each sample and the peak intensity was taken to be proportional to the emission quantum yield (09-). The slope of Opn°/Oua versus [Quencher] gave qu for the emitting state. Absorption Spectaa Absorption Spectra were taken using 10 mm matched quartz cells. A Beckman recording quartz spectrophotometer with Gilford accessories was used to determine the extinction coefficients at 313 nm and to analyze runs with visible light absorption at 600 nm. Full spectra were recorded on a Varian Cary 21 UV-Vis. spectrophotometer. Eaiaaion Spectra Emission Spectra at room temperature were obtained using 13 x 100 mm Pyrex culture tubes degassed as described. Emission Spectra at 77°K were taken using a quartz dewar for liquid nitrogen. Sample solution concentrations were in the range of 10" to 10-5 M. A fast-turning chopper was used to cut short-lived emissions. Triplet energies in kcal/mol were calculated from the wavelength (3) by the formula (78): E(T) = 2860/l (nm) (78) LIST 0? W 243 10. 11. 12. 13. LIST OF mums V. Balzani and V. Carassiti, "Photochemistry of Coordination Compounds", Academic Press, London, 1970, Chapter 5. S. M. Fredericks, M. S. Wrighton J. Am. 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Zarnegar, D. G. Whitten J. Am. Chem. Soc. 1971, 9?, 3776. P. P. Zarnegar, C. R. Bick, D. G. Whitten J. Am. Chem. Soc. 1973, 95, 4367. 246 33. D. G. Whitten Acc. Chem. Res. 1980, 13, 83. 34. G. A. Crosby, W. H. Elfring, Jr. J. Phys. Chem. 1976, 80, 2206. 35. R. A. Krause Inorg. Chim. Acta 1977, 22, 209. 36. M. Hunziker, A. Ludi J. Am. Chem. Soc. 1977, 99, 7370. 37. E. V. Dose, L. J. Wilson Inorg. Chem. 1978, 17, 2660. 38. S. Tazuke, N. Kitamura Pure&App1. Chem. 1984, 56, 1269. 39. K. A. Goldsby, T. J. Meyer Inorg. Chem. 1994, 23, 3002. 40. J. n. Petersen, w. R. Murphy, Jr., R. Sahai, K. J. Brewer, R. R. Ruminski Coord. Chem. Rev. 19$, 64, 261. 41. R. S. Drago, "Physical Methods in Chemistry", W. B. Saunders Co., Philadelphia, 1977, Chapter 6. 42. R. F. Dallinger, w. H. Woodruff J. Am. Chem. Soc. 1979, 101, 4391. 43. P. G. Bradley, N. Kress, B. A. Rornberger, R. F. Dallinger, W. H. Woodruff J. Am. Chem. Soc. 1981, 103, 7441. . 44. W. K. Smothers, M. S. Wrighton J. Am. Che. Soc. 1983, 105, 1067. 45. E. Krausz Chem. Phys. Lett. 195, 116, 501. 46. R. W. Thompson, A. P. Garratt J. Chem. Soc. 1934, 524, 1817. 47. W. Strohmeier, K. Gerlach Chem. Ber. lml, 94, 398. 48. W. Strohmeier, D. von Robe Chem. Ber. l$1, 94, 164. 49. W. Strohmeier Angew. Chem., Int. Ed. Engl. 134, 3, 730. 50. R. N. Perutz, J. J. Turner J. Am. Chem. Soc. 1975, 97, ’ 4791. 51. J. K. Burdett, M. A. Graham, R. N. Perutz, M. Poliakoff, A. J. Rest, J. J. Turner, R. F. Turner J. Am. Chem. Soc. 1975, 97, 4805. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 247 J. J. Turner, J. K. Burdett, R. N. Perutz, M. Poliakoff Pure &App1. Chem. 1977, 49, 271. D. R. Tyler, D. P. Petrylak J. Organomet. Chem. 1981, 212, 389. R. Bonneau, J. M. Kelly J. Am. Chem. Soc. 1”, 102, 1220. G. Boxhoorn, A. Oskam, T. M. McHugh, A. J. Rest Inorg. Chim. Acta 1990, 44, L1. G. Boxhoorn, G. C. Schoemaker, D. J. Stufkens, A. Oskam, A. J. Rest, D. J. Darensbourg Inorg. Chem. 1990, 19, 3455. J. M. 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K. Sandros, H. J. L. Backstrom Acta Chem. Scand. 1m, 16, 956. W. G. Herkstroeter, G. L. Hammond J. Am. Chem. Soc. 1%, as, 6534. P. J. Wagner, I. E. Kochevar J. Am. Chem. Soc. 1%, 90, 2232. P. J. Wagner Acc. Chem. Res. 1971, 4, 168. P. Ford, D. F. P. Rudd, R. Gaunder, H. Taube J. Am. Chem. Soc. 1&8, 90, 1187. - ~ R. G. Gaunder, H. Taube Inorg. Chem. 1970, 9, 2627. N. N. Greenwood J. Chem. Soc. 1%9, 3811'. F. P. Dwyer, H. A. Goodwin, E. C. Gyarfas Aust. J. Chem. 1%3, 16, 42. B. Bosnich, F. P. Dwyer Aust. J. Chem. 1%, 19, 2229. B. C. Chow, I. A. Cohen Bioinorg. Chem. 1971, 1, 57. W. Sovocol, F. R. Hopf, D. G. Whitten J. Am. Chem. Soc. 1972, 94, 4350. A. Antipas, J. W. Buchler, M. Gouterman, P. D. Smith J. Am. Chem. Soc. 1978, 100, 3015. R. H. Linnell, A. Kaczmarzyk J. Phys. Chem. 1%1, 65, 1196. K. Kloc, J. Mlochowski, Z. Szulc Reterocycles 1977, 9, 849. Rosemary Bartoszek, Ph.D. Thesis, Michigan State University, 1981; (a) page 111; (b) page 56; (c) page 65; (d) page 87; (e) page 93; (f) pages 30 and 90; (g) page 104; (h) page 104. Y. C. Chung, N. Leventis, P. J. Wagner, G. E. Leroi J. Am. Chem. Soc. 1%, 107, 1416. In EtOH-MeOH glass (4:1 v/v) at 77°K 9.79us: J. N. Demas, G. A. Crosby J. Am. Chem. Soc. 1971, 93, 2841; in methylene chloride at 298°K 0.19us: see ref. 125. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 2’49 Y. C. Chung, N. Leventis, P. J. Wagner, G. E. Leroi J. Am. Chem. Soc. 1985, 107, 1414. Y. C. Chung, Ph.D. Thesis, Michigan State University, 1985. P. J. Wagner, 0. P. Chen J. Am. Chem. Soc. 1976, 98, 239. P. J. Wagner, G. Capen M01. Photochem. 1m, 1, 173. D. A. Buckingham, F. P. Dwyer, H. A. Goodwin, A. M. Sargeson Aust. J. Chem. 1%4, 17, 325. Y. C. Chung, N. Leventis, P. J. Wagner, G. E. Leroi Inorg. Chem. 1985, 24, 1966. ' F. A. Cotton, G. Wilkinson, "Advanced Inorganic Chemistry"; Wiley, New York, 1980; (a): page 1073; (3): page 845. M. H. Chisholm, S. Godleski Frog. Inorg‘. Chem. 1970, 20, 299. O. A. Gansow, A. R. Burke J. Chem. Soc. Chem. Cm. 1972, 456. - S. L. Murov, "Handbook of Photochemistry", Dekker, New York, 1973, p. 124; C. G. Hatchard, C. A. Parker Proc. Roy. Soc., (London) 1%, A235, 518; J. G. Calvet, J. N. Pitts, Jr., "Photochemistry”, Wiley, New York, 1966, p. 783. E. E. Wegner, A. W. Adamson J. Am. Chem. Soc. 1%, 88, 394. M. Tokuda, M. Hasagawa, A. Suzuki, M. Itoh Bull. Chem. Soc. Jpn. 1974, 47, 2619. J. A. Barltrop and J. D. Coyle, ”Principles of Photochemistry", Wiley, Bristol, 1978, Chapter 4, p. 112. G. Malouf, P. C. Ford J. Am. Chem. Soc. 1977, 99, 7213. P. J. Wagner, D. A. Ersfeld J. Am. Chem. Soc. 1976, 98, 4515. P. J. Wagner J. Am. Chem. Soc. 1%7, 89, 2820. Y. C. Chung, N. Leventis, P. J. Wagner, G. E. Leroi, unpublished results. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 250 P. J. Wagner, A. E. Kemppainen J. Am. Chem. Soc. 1972, 94, 7495. P. J. Wagner, A. E. Kemppainen J. Am. Chem. Soc. 1%, 90, 5896. M. L. Bhanmik, M. A. El-Sayed J. Phys. Chem. 1%5, 69, 275. P. J. Wagner, H. N. Schott J. Phys. Chem. 1%, 72, 3702. P. J. Wagner M01. Photochem. 1971, 3, 169. S. M. Fredericks, J. C. Luong, M. S. Wrighton J. Am. Chem. Soc. 1979, 101, 7415. P. J. Giordano, S. M. Fredericks, M. S.- Wrighton, D. L. Morse J. Am. Chem. Soc. 1978, 100, 2257. P. J. Wagner Mo]. Photochem. 1971, 3, 23. A. W. Adamson J. Phys. Chem. 1%7, 7.1, 798. D. J. Darensbourg, R. L. Kump Inorg. Chem. 1978, 17, 2680. V. A. Durante, P. C. Ford J. Am. Chem. Soc. 1975, 97, 6898. C. Creutz, N. Sutin Inorg. Chem. 1976, 15, 496. R. M. Dahlgren, J. I. link Inorg'. Chem. 1977, 16, 3154; footnote 29. D. B. Miller, P. H. Miller, N. A. P. Kane-Maguire Inorg. Chem. 1983, 22, 383 1 . J. Lewis, R. S. Nyhalm, S. S. Sandhu, M. H. B. Stiddard J. Chem. Soc. 1%4, 2825. J. F. O’Donnell, J. T. Ayers, C. K. Mann Anal. Chem. 135, 37, 1161. E. 0. Foster J. Chem. Phys. 1%, 37, 1020. Organic Syn theses, 46, 1 0 5 . C. R. 'Hauser, W. J. Hamphlett, M. J. Weiss J. Am. Chem. Soc. 1948, 70, 426. For physical constants, see Irene E. Kochevar, Ph.D. Thesis, Michigan State University, 1970, page 56. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 2'51 J. Gearien, E. Frank, M. Megany, C. Pohorny J. Med. Chem. 1971, 14, 552. H. N. Al-Jallo, K. B. Prasad, K. S. Al-Dulami J. Chem. Soc. (C) 1%, 2134. H. 0. House, M. Schellenbraum J. Org. Chem. 1%, 28, 34. G. R. Pettit, D. C. Fessler, K. D. Paull, P. Hofer, J. 0. Knight J. Org. Chem. 1970, 35, 1398. A. Bino, F. Cotton J. Am. Chem. Soc. 1980, 102, 608. L. H. Vogt, Jr., J. L. Katz, S. E. Wibberly Inorg. Chem. 1%, 4, 1157. R. E. Clarke, P. C. Ford Inorg. Chem. 1970, 9, 495. B. P. Sullivan, D. J. Salmon, T. J. Mayer Inorg. Chem. 1978, 17, 3334. D. V. Pinnick, B. Durham Inorg. Chem. 1984, 23, 1440. B. Bosnich, F. P. Dwyer Aust. J. Chem. 1%, 19, 2235. J. V. Caspar, T. J. Mayer Inorg. Chem. 1983, 22, 2444. G. A. Crosby, W. H. Elfring, Jr. J. Phys. Chem. 1976, 80, 2206. J. Van Houten, R. J. Watts J. Am. Chem. Soc. 1976, 98, 4853. APPBIDIX This section contains all the raw data obtained experimentally. All concentrations are reported in mole/L(M). Numbers in parentheses do not correlate well with the others And have not been considered in the calculations of the slopes of the corresponding double reciprocal or Stern- Volmer plots. - All bis(2,2'bipyridine) or bis(l,10-phenanthroline) complexes are of the cis- geometry. abbreviationa pDCB = p-dichlorobenzene ArCOOMe = Methyl Benzoate 013 = n-Tridecane 014 = n-Tetradecane 016 = n-Hexadecane 017 = n-Heptadecane EtOAc = ethyl acetate 252 253 IO \AJXME u Hoosmfim econom60u00v 7:. «as... ... H .2 838... u 33%: .2 S... n 3883383 .usu>aou oawuuwsoaoom .Oemm as m ammuoo on .A< seaufihv mm «and «.8 Nomood 81° 24.3 Sim «.moH wmuoo.o m>~.o oom.c oo.~ n.HNH mmaoo.c . meH.o mmm.o om.~ v.43 83°... 33... need an; N.mma Heacc.o mmm.o cmN.H om.o 7.82.2.3 .zoéommt . none 8.3 TEE in: 20 name some .gmma he ososesmoaeo< 4o 830208321 05 5 7.65 .9. 23.85. .5 308300: 0338 .8 033. 257 .Ahmuumoswuoo esosemaoue~s>v enmm mNH.c u H .2 NHNoe.c n Hozooom zoeeosma.0oe ~00000000e 032:0: .nm;mmeda 259 .A>uumaocduoc w:o=onmonv~o>v ”-mm m-.o u H .2 amwc.c n mezoooL~om magnufi:0umou .ooooN an a aaaaoo om .A< nou~fimv a: Mafia m.m0 00000.0 0000.0 oom.o oc.~ 0.0m Hmfico.o mmbo.o mwm.o om.~ 0.00 mudoo.o mopo.o 000.0 o0.~ 0.00 um~oo.o mumo.o mmm.o o~.0 o.m> mm~oo.o mmoo.c oc.~ oo.~ 0.00 HnHoc.o mome.o m~.H om.c .-0=00. .mzenH 0zooo0< 0000\0290 0000 .-Hm=a. 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Am.va «maoo.o Namo2o com.o oo.m Am.omv ~m~oc.o unmo.o mum.o om.~ m.¢b mm~oc.o omno.o @Hb.c ov.~ N.mb vn~oo.o Ndmo.o oo.~ oo.~ m.m> mmmoo.c mono.c 0N.~ om.c 20200200200 mzonmofimhg UZOOUL< 0006\200=0E=H 0000 2uabmaH mama“ 0.5ma ha «coacamoucom 00 00220000002000 022 02 2-2020_ .00 20000000 000 2000002002 020000 .e« vague, 261 .Ahhuolcc2uoo uaoaognouo~¢>v 0-20 002.0 0 2 .2 0000.0 0 202000002 .2 02.0 0 2002020002000000 :02 .2000200 022022002000 .00000 20 0 000200 00 .20 0022200 00 020. b.N¢N mvmcoo.o ammo.o ocm.o o°.~ b.mmm mmmooo.o mmHo.o mum.o om.~ m.vbm nmmooo.o hNHo.o «H6.o o¢.~ «.mcv mmmcoo.c bmao.o mum.o ON.H o.~mv momooc.c mmuc.c co.“ 00.2 ¢.mvv hmmoco.o mNHo.o nu.“ cm.o 2-0220. thhna 020000< aoha\mwhn mono 20mmmaa samba ..000 00 002020202000000.0. 20 00220000002000 002 02 0-20222 00 0200 000 2000002002 020000 .mm ounce 262 .200200002200 00000000002002 2-20 002.0 0 2 .2 0000.0 0 202000002 .2 02.0 n 2002020002000000ne. .2000200 022022002000 .00002 20 0 000200 00 .20 0022202 00 020. 2.020 020000.0 0200.0 000.0 00.0 0.000 000000.0 0000.0 000.0 00.2 0.020 020000.0 0200.0 020.0 00.2 0.000 000000.0 0000.0 000.0 00.2 2.200 020000.0 0020.0 00.2 00.2 0.000 020000.0 . 0020.0 00.2 00.0 2-000000000 220020020. 0200000 0000\20000020 0000 0-20202 2002. 0.h=a an 0:2v2uhndxouaonlv mo Gawaoavououogm 002 :2 2nam=HH .a> zeomoama 00% Hoooumwoom 02nson .mm 02009 263 13910 37. Stern Vol-er Date for 4-pheny1-1-(4-pyridy1) butanone. n 1.. [0] area styrene/area 014 [styrene] O’IO 0.0 0.384 0.00378 -- 0.0 0.369 0.00363 -- 0.0999 0.192 0.00189 1.96 0.200 0.130 0.00128 2.90 0.300 0.0992 0.000977 3.80 0.400 0.0633 0.000623 (5.96) 0.600 0.0526 0.000518 (7.16) 0.800 0.0402 0.000396 (9.37) '0 = Ethyl eon-bate. 313 a. (Filter A, 0.5 hrs.). (c column A at 120°C. acetonitrile solvent. [4PhBP] = 0.040 M. (014] = 0.00627 H. In. 2.. [0] area styrene/area 014 [styrene] 09/. 0.0 0.173 0.00161 -- 0.0 0.159 0.00148 --- 0.0503 0.115 0.00107 1.45 0.151 0.0723 0.000673 2.30 0.201 0.0577 0.000537 2.89 0.302 0.0358 0.000333 (4.65) 0.402 0.0332 0.000309 5.02 ‘0 = Ethyl sorbate. 313 a. (Filter A, 0.5 hrs.). (c column A at 120°C. acetonitrile solvent. [4PhBP] = 0.0401 III. [CM] = 0.00593 H. 264 .2 88:... u .32 .uau>ficu odfiuafiaouooa .o.o- 5a < unsaoo on .A.uua w .< touafimv I: «Hm .oaaauoa Hmnuu u a. mH.N mu~oo.o bm~.o Nom.c mc¢°.o No.N em~oc.c mom.o Nom.o mavo.o mm.~ HmNco.c mmN.o Hom.o moeo.c Amm.~v m¢~oc.c mmm.c HcN.° oceo.c m~.~ mmmco.o m¢m.o ooH.o Hovc.c III ~mnoo.c mov.c o.o Hovc.c III «mmoo.o cmv.o o.c cc¢o.o 05$ noggufi So 60.3\o:0.§um 00.8 mg Sonia—ES £8235032 23:33.iviRaeTTinofue 8m 3% .813, 98$ .mm «Haas 265 .2 ~m»eo.c .2 88¢... .Iu «Hm no newumuouna uaufiu Meaghan uom.vuuoouuoo one: nunowh luuaasv know uuuwm «gas ~¢HUHO anoaa .Aauuo-aaduoa oaoaonnouo~¢>v .-Hu «mace. o u H .aau>~ou odfluunaouooo .o.cu~ an < nusdoo on .A. cu: m. a .< nouaflmv an «an. «m.o mm.o vcho.c mmu.o umbmo.c m¢.o m¢.o omNoo.o mNN.o ovomo.° mv.o ov.o mmuoc.o mom.o ummmo.o :6 3.0 Snood 8A6 26 ummgoé mm.o mm.o mmuoo.c mv~.o mmo.~ oemoo.o hm.o mN.o enuoo.o mmN.o N¢c.~ awvco.o mm.o 5N.o ¢¢~oo.o ooN.o awn.c anoc.c v.23. 0 7:89.33 :0 8.33—.93: 00.3 .21 735—3 o.o:o:au:nAuhvwhhmlevsficgaaonmuv we umu>oo~o an we»? use we vHoH> launaso ona no «Codename: newuauuaeoaoo .mm manna .aa man no newumuounu uauflu Hawuuon pom vauoouuoo Ono: avacwh Incense 03» uuhwm ones .Ahhuoauauuoo uaonuaaouoaa>v “anm «mac. o u H z «upco.° u .efloa .uau>~ou ognuuficouoou .o.o- am < qaafiou om .A.uun e .< umudduv a: m m. Sod :36 @286 m3 6 336 go .o 366 mmaood m3 6 , Named mmoé «mod @286 b: .o 33.0 mm «mod 89.9 2.25.: a: .o a: .N 386 mmoé mmoé 8:56 o: .o a: A 536 36 god 028.9 . , p.36 80.: $686 auto». 0 Hocophuoa «do ocha\oaou>uu coho .nn< Hfiua.mmam¢a ..ov«uo~aoouv>g «aoauusafiHuvfiuanuevufiufianoam-v mo newuonuu HH mama 0:» mo Gama» luaaaaa on» no oonuvaunon newuauunoonoo .o¢ manna 267 .33. u o o £25883"... 882283.»: 7:. 8“... u H .2 «2.8... u .vfloa .uao>~ou ofifihufiaouooa .o.c- an 2 sundae on .A.a22ou . .2 2022225 a: mfim. mac.o oumoc.° pm~.o conc.o m~o.o mmuoo.° mN~.o oouo.o . .ocou2»a_ «go uuua\oaou2au cote «2.225.22222evuflnmzvamg a.muouon0hoaamouuoe Amuvlzflaonuzm 0:0:0u3AAahvfihhmlwvumufiuaosmlv 05.9355 mo owaeiomo HH as on» now cofluoawlhuuoa vii» Isaac—.5 asvgovnu 23 «1.3. 268 I219 42. Omaha Yield end Stern Vol-er dste for Penee-ine 4-Phenyl-l~(4-pyr1dyl)butenone Ruthen1u( II) Tetrafluoroborate. Inn 1.- [RHWHDhHPhBPHUh )2 [0] sree styrene/ares 014 [styrene] . 0,. 0.0200 0.0 0.254 . 0.00272 -- 0.0200 0.0 0.260 0.00279 --- 0.0193. 0.113 0.217 0.00210 1.31 0.0202 0.229 0.125 0.00134 2.06 0.0200 0.343 0.0931 0.000998 2.77 0.0200 0.456 0.0644 0.000691 3.99 0.0200 0.572 0.0594 0.000637 4.33 0.0201 0.666 0.0424 0.000455 (6.07) '0 2 Ethyl sorbate. 313 a. (Filter A. ~20 hrs.). cc cola-n A at 120°C. acetonitrile solvent. [014] = 0.00683 M. I = 0.214 E1‘I (Valerophenone ectinoutry). 6 ° = 0.013. b[C14] = 0.00615 M. lus_2.- [Ru(mbh (4PhBP)](BF4 )2 [0] eree styrene/ares 014 [styrene] O °/O 0.0200 0.0 0.190 0.00174 --- 0.0201 0.0 0.166 0.00152 --- 0.0201 0.0 0.153 0.00140 -- 0.0201 0.114 0.138 0.00126 1.23 0.0201 0.228 0.0911 0.000832 1.86 0.0200 0.343 0.0624 0.000570 2.72 0.0201 0.457 0.0451 0.000412 3.76 0.0200 0.571 0.0364 0.000333 4.65 0.0201 0.685 0.0301 0.000275 5.64 '0 = Ethyl sorbste. 313 n- (I‘ilter A. ~15 hrs.). 1c calm A at 120°C. acetonitrile solvent. [014] = 0.00582 M. I = 0.172 E1" (Velerophenone ectinonetry). 4 ° = 0.0090: rejected. 269 Iggle 43. Quentul Yield end Stern Vol-er Date for cis-bis(2,2'bipyridine) bis(4-Phenyl-1- (4—pyridyl)butenone) Rutheniul(11) Tetrafluoroborate. In. 1.. [Ru(bipy)2(4PhBP)2](BF4)2 [0] area styrene/eree C14 [styrene] O °/O 0.0200 0.0 0.123 0.00137 --- 0.0200 0.0 0.121 0.00135 --- 0.0200 0.114 0.0817 0.000913 1.49 0.0200 0.229 0.0692 0.000774 1.76 0.0200 0.458 0.0487 0.000544 2.50 0.0188° 0.754 0.0373 0.000392 3.47 '0 8 Ethyl sorbete. 313 ns, (Filter A. ~25 hrs.). (c coluln A at 120°C. acetonitrile solvent [C14] = 0.00712 M. I = 0.191 81“ (Velerophenone ectinosetry). 41° = 0.0071. '[Cl4] = 0.00670 H. '0' 2.. [Ru(bipY)2(4PhBP)2](ch)2 [0] area styrene/area Cl4 [styrene] O'°/0 0.0200 0.0 0.157 0.00168 -- 0.0200 0.0 0.153 0.00164 -~- 0.0201 0.114 0.0954 0.00102 1.63 0.0200 0.229 0.0902 0.000967 1.72 0.0200 0.343 0.0707 0.000758 2.19 0.0200 0.457 0.0638 0.000684 2.43 0.0201 0.572 0.0491 0.000527 3.15 0.0201 0.686 0.0411 0.000441 3.76 0.0200 0.800 0.0393 0.000421 3.94 '0 = Ethyl sorbste. 313 nl. (Filter A. ~25 hrs.). to column A at 120°C. ecetonitrile solvent. [014] = 0.00683 H. I = 0.231 El" (Valerophenone sctinouetry). O>° = 0.0072. 270 .2 2666.6. 0 «2.6662662606026266. 20m v~o.o u 0 mean aowuouwanluoa no mafia: 6066290260 0203.nvuumr lbuao=OA .2 06666.6 0 20266 0006200 022022062000 .6.662 20 0 6.0200 06 .2.006 62- .0 0022226 .0: 626. 0666.6 66266.6 0666.6 2606.6 026.6 66666.6 626.6 2666.6 626.6 60666.6 666.6 6626.6 626.6 06666.6 662.6 66666.6 626.6 66266.6 662.6 22666.6 6666.6 66266.6 662.6 66666.6 6666.6 66266.6 662.6 66066.6 0 6 20600620. 026 0000\0606620 0000 . 02.66622662606620226666 ..02006600062200202 2226262602266 066602662266206610612-26606610 0:2llooucom no ouc>oo~o an 0669 0:» mo 6202» lauuono use mo ooaovavaoa couuohucoocoo .v¢ ounce 271 .26 022066 2 6666.6 0 2020600060260266066 002 6666.6 u_. 0006 0022002200000 00 60200 0020200200 0000 002026 00200060 .620606262munmvvuahm2av=ma .0> 200026202 00222o2m 60 0020200200 “20260 2002 0 2o: 02 220 .2 66666.6 0 20266 .2000200 022022002000 .00662 20 0 000200 06 .2.000 66- .0 0022206 00 626. meco.o mmaooo.o omhc.o 2ovo.o mmoc.o mmmcoc.° wmmo.o 2omo.o nmboo.c 0622oo.c III nocmc.o mmoo.o om2co.o 602.o 2o2c.o 6°2o.o o62oo.° «02.o Nomoc.o N22o.o 2m2oo.o . 662.o ammoo.o ~22c.o om2oo.o «62.6 m2voo.o “.0 20000620. 020 0020\0000620 0020 «Axmmv26200500662>a2avsmH 0.0202ono2o02m02209 2226002000206 20000020222602060106121260000-06026-20020206622.6.660221020 20 06000020 22 0066 002 20 02026 0020000 002 20 0000000006 0022002000006 006102662 272 .2 00600.0 0 2020. .2006200 022022002000 .60662 20 0 000200 06 .2.000 62- .0 0022226 .00 626 .0206000 26026 n a. 20.0 000000.0 H 0000.0 «60.0 00000.0 00.0 bN¢000.0 0000.0 000.0 0020.0 NN.N 000000.0 6000.0 000.0 0020.0 N0.2 . 060000.0 0200.0 0N~.0 00000.0 06.2 606000.0 0N60.0 022.0 0020.0 III 00200.0 2600.0 0.0 0020.0 III «2200.0 202.0 0.0 0020.0 0\0_o 20002620. 020 0020\0002620 0020 202 62120026200£m006220200002 0.2 626.6 0022002000006 0026006 60206 02000600002200206 2226002000206 2000002022260206010612-260000106022 120020206026.6.660221020 002 002 0200 000206 00026 .00 02009 273 Table 47. Mean Balance Styrene and 4-acetylpyridine Produced fro. the Type II Cleavage of cis-bis(2,2‘bipyridine)-bia(4-Phenyl-l-(4-pyridyl)butanone) Rutheniun(ll) Tetrafluoroborate. llrllllllf 1.. area atyrene/area 014° [styrene] area 4AP/area 017c [4ARJ‘ 0.153 0.00168 0.0125 0.000590 I313 nn, (Filter A. ~25 hrs.). acetonitrile aolvent. [Ru(bipy)z(4PhBP)2l(BF0)z = 0.0200 M. .(c colu-n A at 120°C, [014] = 0.00683 H. cSanple refluxed for 24 hra. in acetonitrile in the presence of 147 a: PPha; then 0.0104 017 was added and diluted to 5.66 .1; [017] = 0.00764 M; (c colu-n B at 130°C. ’ ‘(4API = 0.000292 H ea deter-ined directly frol the [c trace; reduced to 2.8 .1 (original volune of the irradiated salple - to be directly co-parable to [styrene]) [4AP] = 0.000590 H. " area styrene/area 014° [styrene] area 4AP/area 016c [4APl‘ 0.153 0.00164 0.00117 0.0000743 .313 nl. (Filter A. ~25 hrs.). acetonitrile aolvent, [Ru(biPY)2(4PhBP)zl(BF¢)a = 0.0200 M. ”(c colunn A at 120°C. [014] = 0.00683 H. cSanple refluxed for 24 hra. in g—butyronitrile in the presence of 147 I: PPhn: then 0.0113 g 016 waa added and the ealple was diluted to 5 II with g—butyronitrile; [016] = 0.0118 M; (c colunn B at 130°C. d[4AP] = 0.0000416 M as deternined directly Iran the [c trace; reduced to 2.8 .1 (original volune of the irradiated aalple - to be directly conparable to [atyrene]) [4AP] = 0.0000743 M. 274 Table 48. Quantun Yield and Stern-Valuer Data for the Type II Cleavage of n-butyl-4- [(4-pyridy1)carbony1)butyrate. In! 1' (0] area n-butyl acrylate/area 013 [n-butyl acrylate] O>°/0 0.0 0.122 0.00228 --- 0.0 0.122 0.00228 --- 0.00353 0.0812 0.00152 1.50 0.00706 0.0598 0.00112 2.04 0.0106 0.0452 0.000845 2.70 0.0141 0.0368 0.000688 3.31 0.0176 0.0323 0.000604 3.78 0.0212 0.0267 0.000499 4.57 0.02830 0.0238 0.000441 5.17 '0 = Ethyl sorbate. 313 an. (Filter A. 0.5 hrs.). gc colu-n A at 10890. acetonitrile solvent. [4EsterBP] = 0.0204 H. [013] = 0.00842 M. °[48sterBP] = 0.0202 M. [013] = 0.00834 M. 80' 2.. [0) area n-butyl acrylate/area 013 [n-butyl acrylate] O’°/O 0.0 0.166 0.00242 --- 0.0 0.164 0.00240 --- 0.00337 0.108 0.00158 1.53 0.00673 0.0751 0.00110 2.19 0.0135 0.0522 0.000763 3.16 0.0168 0.0430 0.000628 3.84 0.0202 0.0353 0.000516 4.67 0.0270 0.0238 0.000348 (6.93) '0 = Ethyl sorbate. 313 nn. (Filter A. 0.5 hrs.). gc colunn A at 108°C, acetonitrile solvent. [4EsterBP] = 0.0208 M. [013] = 0.00658 M. I = 0.00543 81" (Valerophenone actinanetry). Ot° 0.44. 275 .pm.o u_o .Amuuoaaawuoo oaoqoaaouuda>v .-Hm mmmco.° u H .2 mmmoo.o u Hague .2 oouo.o n .mmuauameH .u:o>Hoa ufiauuwaouuou .o.mo~ am < sundae om .A.:wa oe. .< uuafiwav .a: «an. mm.o «omoo.c mmH.o pm.c momoo.c . ou~.o o Houaaauoo amassing «do ocho\uun~huoa ahusnle noun g.cuouhuan_~5:oauooA—>kuhalevHueluhuanue use we umu>ao~o HH onus on» how sawuuafiluouon vaow> lacunae anuvnomovcu .m¢ wands 276) .z muscu.o u _n~o_ .u:u>~aa onwuuchuooa Damon «a < elsuoo on .A.au£ v: .< Layaway .le nan .ouanuoa munuu u o . mo.o neeoco.o npuc.o me_.o amuo.c m~.e ammooc.o omno.° ~__.e emuo.c mm.~ . m_~ao.o «abo.c apno.o mano.c -- . «muoo.o «63.9 c.o pa~°.o -- mp~o°.o _p~.o o.o ocno.c .\. o .ouaauhua.usa-a_ _o_ _~o=.mnuouum¢_ a.N a .omo.° u ..o .Aauao-aawuo. oaocosaoso~¢>e .-~m «muo.o u n .x ohmo°.o u .ndoe .uco>_o. odwuuuaouou. .u.co~ a. e gus_oo on ....u: e. .< Lou~uae .n: n~n .ouango. daaun u a. «6.0 ~nq¢ao.o -~°.o «63.: oanc.o e~.q namaoo.a. cmuc.o o~_.o pauc.c om.“ numoo°.o -vo.o mmeo.o eono.o on 4 88°... 88.6 «as... 885 --- awmoo.o p-.a 0.0 mauo.o -u- ammoc.c «n~.c o.o nono.o .\. . .ouadzhoa.3=n-:_ ”Ho no“. .a. _~o=.magouamv_ a4 a .ovmuo~:oouv>= oueuau:n_Aaconhaoamakuxnueva uvnuxusaue uo ouu>oo~o Hm case onu now can: uol~o>ueuuum we: v~0m> Isueaao .on «anew 277 mm.¢ ¢~.¢ vm.N mm.~ mN.H 0\oo .2 mmpco.o u _m~o_ . .mmoo.c u o.. .Aauuo-aafluuu oaoaoaaouo~o>v .-~u om~.o u H .2 «omco.o u _n~o_ .u=o>~ca uflfiuawaouooa .oomoH an < nusfioo on .A.uu2 on- .< heufifime .-a mum .oaoauo. Hanan u a . nommooo.c _ mm~°.° qumo.o pmao.o m~¢ceo.o ~muo.o mp¢o.o oouo.o mbmooo.o mpmo.o m~mo.o acmo.c mmmoc°.o vuno.o mo~o.c oouo.o mm~oo.o ~m>o.o mm>oo.o oomo.o mm~oc.o ammo.o o.o ~cmo.o Nch°.o NoH.c o.o oouo.o .ouaflmuou.uanua. «go ouua HoH «2.229Haamuounmevnanmzvam. ouua noo.u:nle noun .ouagoaouoafimauuoa AHHV-swaoausm ouuuau=2_"aaoagaoafiakuaauevHuvufiauaana egg-nuance; mo ouu>oofio HH onus an“ how can: gondo>uauuam can 220“» luggage .fin manna 278 .Aauuoacafiuua oaocuzmouo~a>v auam wen u H .2 unboo.o H Huang .2 oomc.o n «Ayumv.Ammuuamuevmfinmzvsm. .u=o>fiou oawuuwao»ooa .oomQH an < casaoo ow .A.au: cm: .< umuuwav .I: Man a meoc.o b¢~oo.c memo.o mvoc.o mwaoc.c demo.o o Houauhhoa ahuanlaa «do «can ..ouauonouo=~muhuos AHHV-swaugusm o~aga»=2_Hanoauuoafiuvfiuaanvv.uvsuhuaauc unwiluounom mo oma>oofio HH ”Aha on» how newuuawihouoa vaow> lauauao uauvcoauvam .Nm Ounce 279 Tab e 53. Stern-Volaer Data for the Type 11 Cleavage of Cia-Bia (2,2'bipyridine) bia(n—buty1-4-[(4-pyridy1)carbonyl)butyrate) Rutheniua(11) Tetrafluoro- borate. Ifll 1.. area n-but.ac;xlate [Ru(bipy)2(4Eater8P)2](8F!)2 [0] area C13 [n-but.acry1ate] O‘°/0 0.0200 0.0 0.0356 0.000620 -- 0.0200 0.0 0.0360 0.000627 -- 0.0200 0.00772 0.0323 0.000562 1.11 0.0200 0.0154 0.0282 0.000491 1.27 0.0200 0.0309 0.0219 0.000381 1.64 0.0200 0.0463 0.0175 0.000305 2.05 0.0200 0.0618 0.0153 0.000266 2.35 ' 0 = Bthyl aorbate. 313 na. (Filter A. ~2 daya). (c coluan A at 108’0. acetonitrile aolvaat. [013] = 0.00784 H. lnl 2.. a -b .ac ate [Ru(biPY)2(48ater8P)2l(8?¢)a [0] area 013 [n-but.acry1ate] O’°/O 0.0200 0.0 0.0761 0.00106 - 0.0200 0.0 0.0726 0.00101 -- 0.0200 0.00799 0.0631 0.000880 1.18 0.0200 0.0160 0.0512 0.000714 1.45 0.0200 0.0320 0.0405 0.000565 1.84 0.0200 0.0559 0.0319 0.000445 2.33 ' 0 = Ethyl aorbate. 313 na. (Filter A. ~4 aolvent. [C13] = 0.00628 M. daya). 1c coluan A at 1089C. acetonitrile 280 Table 54. Deter-ination and Concentration Dependence of the Quantua Yield of cia-bis(2.2'bipyridine)-bis(n-butyl-4-[(4-pyridyl)carbonyllbutyrate) Rutheniua(11) Tetrafluoroborate.‘ area n-but 1 acr late [Ru(bipy)a(4latarBP)zl(8F¢)2 area 013 [n-butyl acrylate] 0 0.0200 0.159 0.00237 0.0016 0.0200 0.164 0.00244 0.0017 0.00995 0.263 0.00391 0.0027 0.00499 0.250 0.00372 0.0026 0.00249 0.131 0.00195 0.0013 Actinoaatry for the deter-inatioa and concentration dependence of the Quantua Yield of the Type II cleavage of cis-bis(Z.2'bipyridina)-bia(n-buty1-4-[(4-pyridy1)carbonyl]- butyrate) Rutheniua(11) tetrafluoroborate.D There were used two sets of actinoaeters. SIT 1.c Actinoaeter area o-sethzl acetoghenogg No. 016 [o-aethyl acetophenone] I 1 0.217 0.00234 1.671 2s 0.201 0.00242 1.726 2b 0.180 0.00216 1.545 Iaveraae = 1.647 81". m 2“ Actinoaeter area o-ae h ace 0 henone . C16 [o-aethyl acetophenone] I 1 0.464 0.0211 1.317 2a 0.405 0.0197 1.230 2b ' 0.419 0.0204 1.273 Iaveraas = 1.273 81". ' 313 na. (Filter A. ~7 daya). (c coluan A at 108°C. acetonitrile solvent. [C13] = 0.00670 H. I = 1.46 El“. ° It was used o-aethyl butyrophenone and o—aethyl valerophenone actino-etry. ¢ SET 1: Actinoaeter Actinoaeter Actinoaeter 0 SET 2: Actinoaeter Actinoaeter = o-aethyl butyrophenone. (c coluln A at 19090. No. No. 1: 2: [o-aethyl butyrophenone] [o-aethyl butyrophenone] 0.104 M. [C16] 0.108 M. [016] = o-aethyl valerophenone. (c coluan A at 190°C. Actinoaeter No. 1: No. 2: [o-aethyl valerophenone] (o-aathyl valerophenone] 0.104 M. [016] = 0.105 H. [016] = 0.00539 H. 0.00601 M. 281 .oaouox «Au ha nowumhoana unuwu Hawuhon how oval «no: anewuoouaoo n .2 pmmo.c u ”mac“ .2 Hom.o u Hoaoaoaaauuuaaa .uao>doa odwuuwaoaooo .ooomH an < auufioo on .A< touflflav .ac man .auatoaouosfimaauo» flame-swaoausm oafikuaafiauoouae och-lacuna; u o . mm.¢ ma.e nameo.o mmvoo.o mmac.c mmmoo.o Amv.¢v Acm.vv omeco.o meeoo.o oppo.o moaoo.c do.” o~.m mauoo.o «mmoo.o 222.9 m~m°°.c mm.“ oo.~ «fifio.c mo~o.o mm~.° H¢~co.o .. -- m-°.o mHNo.o ”an.o o.o .. .n cauc.o cumo.o cam.c o.o 53!. o o? . ....3_£82.: “£0822 30 8.5.2822 «8.. 2: c.0aouonouozamouuoe Amnvaswco£uam onwkuhmuhuooolv mew-laoucom an ococosaoaauan mo uawnocozo on» no» can: aolao>lchoum .00 «Anne 282 Table 56. Stern-Volaer Data for the Quenching of Butyrophenone by cis-bis (2.2‘bipyridine)bis(4-acetylpyridine) Ruthenium(II) Tetrafluoroborate. m 1.. [0] area PhCOClb/area C16 [PhCOCHa] [PhCOClblcorr.‘ O °/O O °/Ocorr.‘ 0.0 0.612 0.0340 0.0340 -- - 0.0 0.624 0.0347 0.0347 - - 0.00106 0.237 0.0132 0.0171 .2551 2.01 0.00210 0.157 0.00873 0.0138 3.94 2.49 0.00311 0.109 0.00606 0.0113 5.68 3.04 0.00432 0.0759 0.00422 0.00926 8.15 3.71 0.00507 0.0518 0.00288 0.00691 (11.94) (4.98) HUN 2.. [0] area PhCOCHa/area 016 [PhCOCfla] [PhCOCl-ialcorr.c O °/O O °/Qorr.‘ 0.0 1.027 0.0550 0.0550 -- --- 0.0 1.047 0.0561 0.0561 -- “-- 0.00106 0.448 0.0240 0.0311 2.32 1.79 0.00208 0.314 0.0168 0.0265 3.31 2.10 0.00323 0.206 0.0110 0.0209 5.06 2.66 0.00420 0.162 0.00868 0.0188 6.41 2.96 0.00514 0.132 0.00707 0.0172 7.86 3.23 Q = [Ru(biPY)z(4AP)zl(BFc )2. 313 nm. (Filter A). (C column A at 180°C. acetonitrile solvent. [butyrophenone] = 0.502 M. [C16] = 0.0247 M. ° 0 = [Ru(biPY)z(4AP)zl(Dl-‘o )2. 313 nm. (Filter A). gc column A at 180°C. acetonitrile solvent. [butyrophenone] = 0.502 M. [016] = 0.0238 M. 1 = 0.144 El" (Valerophenone actinometry). 0° = 0.39. Corrections were aade for partial light absorption by the ketone. n 283 .AatuoaoaHuuu oaoaoaaouoHa>v .-Hu mmmo.o u H . .onouox on» up aofiumuoaan unuwu anwuhom you moon on»: anowuoouuoo a _ .bNé u o. .HatuoaanHuoa oaoaonaouoHa>v .-Hm ammo.o u H .2 v«~o.° u HoHo_ .2 «an.o u Hoauaoaaotau=a_ .u=o>Hou uHHuuHaouoou .ooomH »a < aquoo cu .Aa toaHHuv .ac «Hm .ufivamv_«22lcuoum .bm annoy 284 48303838 oaoaufioiuafiafioamov 7:. SH H .2 ammoo.o HvHo_ .Amuunaonauon ononosnouhunnahnuoalov Huam ~v.~ H .2 «mmoo.o HvHoH . .ebmo.o u ego noun\nnnuaun noun “canana sand pom unnom an: an .aoqalnn conga unnuo ozu o» Hodgnunn nu vaunwvnuuw .uOunaocHuon an non: an: 2 mo~co.o nvfluouzu onthAuna :« «Amnamvvmmanm mo nofiunuoa n “2 $2099.: u Hvaoa 0 . .Auuuoaonuuon oconngm I0h>u§£u>£unfllo can nnonnnmoun~n>H>Aanlrov Huum mn.~ u H .2.Mbvoo.o u Hemoa .unn>~on okuodao nonahzuni .ooowu an < canaoo on .Anhnv cane .< unuawuv .an mam mowooo.c vomooc.o ammo.c vacuo.o bmaooo.o Humcoc.o mmmo.o ommno.o mm~coo.c bbuoco.c «ago.o uoc~°.o momooo.c m-ooo.o mm~o.o ammboo.o m~mooo.o «Macao.o NHN°.o goonoo.o vmmoco.o mo~oo.o mm~.o nvaoo.o ammooo.o bamooo.o o-.c amcuco.o mmuoco.o mmmcco.o vumo.o nonvooo.o e annuuunH vac noun\onnu>un noun Hunmmnmevmmhnma ..Aouoquu=2 AHmvHuanuev Ignazcnaalevnwa ouncwuhnmuoauanoznnuuos Inwnonunm mo nun>no~o Hm onus 0:» mo canflr anucnno on» no nonnnnoaon :oHunuunoonoo van nowunnfiauuuna .mm manna 285 .Ahtuo-oaHuou uneconaotaaanagao-iov .-Hu om.H u H .2 mmmoo.c u HvHo_ .uaopHou ovHuoHau unuH2220- .ooouH an < ansHoo.ou .Auhav oH- .< houHHHV .nu «Hm . omuooo.o ammoo.o amNo.o Homo.o o Honohhang «no noun\onou>ua noun Huamnamvvmuonma ..AoaoaausaaHathaauvquuHmaoamnevaHn oaaaHuaanuomH>23oouoo naHaoauam mo oua>aoHo HH onus 02» mo vHoH> nauseao on» no aoHuacHntouua .mm oHnaH 286 Table 60. Data for the Calculation of the Response Factors of Various Coapounda va. Benzene for the HPLC Analysis. Data for 8(m)s (4|?) .' W Height of H(OO)s(4IP) [W(CO)s (48?” area 4"? R!" 0.0096“ 0.00203 2.749 0.00558 0.0107“ 0.00226 2.431 0.00549 Data for 4W3 Ben: Height of 4VP [4VP] area 47? If 0.0138: 0.00339 7.281 0.0247 0.0126” 0.00773 3.384 0.0262 Data for 4IP.‘ Height of 48? [481’] area 48? RF 0.0155‘ 0.00416 6.078 0.0253 0.0109 0.0113 2.311 0.0261 late for eie-I(m)e (4")a.‘ W Height of cis-WOO); (4VP): [cu-mm). (4VP)a] area cis-”(00). (47?): RF 0.0019‘ 0.00102 13.661 0.0139 0.0027. 0.000338 33.13 0.0112 287 Data for non)..- wottht of W Height of "(00% ("(00%) acetophenone [acetophenone] area “(Wk SF 0.0111. 0.00315 0.1047” 0.0871 1.258 0.0455 0.0030. 0.00852 0.0810“ 0.0674 2.192 0.0277 ' lle analysis: detector at 270 II. EPIC coin-I D eluting with as henna. 15x ethyl acetate at 1.5 m1/ain. Detector attenuator at 64. recorder attenuator at 4. 'inlOalbensene. cin25a11>enaene. ‘ in 3mlbensene. ' W analysis: detector at 290 1.. W colt-n D eluting with 95x hex-3e. 5x ethyl acetate at 1.5 a1/ain. Benzene does not show up in the lle trace. Detector attenuator at 64. recorder attenuator at 4. 288 612- 6.. .8 2.... 6.. .3934 .33.- 3. .88.. 8 5... 2......- 6 8.8 6.1.8 3.! . .38» an» an nausea... sea...- unea one gene- eaavm we 8323.80.80 Hague e... .833 .aaeauaeaae 1880a am» he» 8 2.8.0 .— 781538- the «83598 can: am» an» x 38.0 .- .eaoaaaaoaeoe. 23:33 haze .28: done an .8333 eeoaeaaoueoa I: an nl a £33 venue as: 38a so an n .9398: «IF—3.8 an as 3e as: 83.-nee issue u .aua\~a 04 .8 8n ue 53038 .040: no .81 n8 3:: hangs .a 8:8 .e‘aanene 3. a .uanauoa 88‘ .793 30 .m .8»th .8 80 A a: A e $686 8.6 84.86 «am... 6386 5.6 8.3.8.... .3:- 8~86 .36 2886 686 «886 866 8:33.... to... I. In |.. I- 836 8... 8333.... 8.8 448485 8686 «$6 8866 2&6 8.86 626 8.2.2.9.... .8:- «886 866 3686 84.6 «:86 8.6 8.8.8.... .3:- i- I. 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(4VP)a/sree benzene: 0.00117 1.47 10" Asoo: 0.125 4.41 10" O = 6.58 10“ t 3.29 10" 801m; Hetgzlmloheggg.’ [cis-IKQQ, {121“ eree cis-fl(w)e “Wk/ores benzene: 0.000234 2.94 10“ Leon: 0.002 7.06 10" O 8 4.08 10" t 2.49 10" Actinoaetn (figteeeiul Reineckstelfi Act No. [ICrOflaHICSk] A000. blsnk A00 [sou-1......“ [W]‘.(M) 1 0.0103 1.016 2.522 5.87 10" 0.00160 2 0.0101 1.415 2.230 5.19 10" mm 3 0.00946 0.784 2.054 4.78 10“ 0.00135 4 0.0106 0.972 2.447 5.69 10“ 0.00157 5 0.0113 1.113 2.684 6.24 10“ 0.00167 6 0.0102 ' 1.405 ' 0.648' 1.51 10-0 0.00107 7 0.0104 1.240 2.737 6.37 10“ 0.00159 8 0.0100 1.338 0.623' 1.45 10“ 0.00189 9 0.0109 . 1.238 2.391 5.55 10" 0.00123 [SCU'hetsl ' 0.01” H. O [W(OO)0(4VP)] 8 0.0504 II. filter 0. -42 hrs. ' [H(co).(4vr)) 1: 0.0501 N. Filter 0. 42 hrs. ‘ loch sctinenster m irrsdisted for Mt 6 hrs., 1 a 0.0447 81". ‘ These oenoutrstions ere the ones reduced to the originsl 2.8 nl solution of the ectinonster. since in order to neesure the 808‘ photorelessed. 10 ll of s solution of "(103 b.9920. 0.1 H. contsinin‘ $10. (0.5 I) use sdded to the sctinonster so1ution sfter irrsdistion. ' These solutions were too concentrsted so they were diluted 1:5 before the sbsorption st 450 I- wss nsesured. ' ".'}A‘r i .A. 1.7 30%-. 291 Ieble 64. Onset:- Yield [lots for Pentecerbonyl l-(4-pyridy1)pentsnone M‘stenm) Photolysis et 410 m. Solvent Benzene. 0 s-W 4VP sree cis-W(OO)¢(4VP)a/eree benzene: 0.0404 5.09 10" A000: 0.634 2.24 10“ O = 0.0657 1: 0.0160 So v t ohex .' [Gil-"{le {5W}; | sree cis-W(GO)¢(4VP)a/eree benzene: 0.0140 1.76 10“ Asoo: 0.508 1.79 10" O = 0.0285 t 0.0283 ctl Oxe ete .¢ Solution 1. [Urenyl Nitrste) = 0.0102 14. [0xelic Acid] = 0.0504 M. Solution 2. [ml . 0.00651 :1. Ag; inoneter Solutigg No. V f ut l Bleak 8. 60 l 8.05 2 7. 95 [Oxalic Midlresctsd = 3.49 10-3 '4. ' [H(CO)s(4VP)] 0.0504 H. Filter 0. ~24 hrs. " [W(CO)I(4VP)] 0.0501 H. 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EU! 1.‘ [4VP] area cis-H(CO).(4VP)z/area benzene [cis-H(CO)¢C4VP)2] O’°/O 0.0 0.174 0.00219 -~ 0.0 0.172 0.00217 --~ 0.00106 0.135 0.00170 1.28 0.00318 0.0887 0.00109 2.00 0.00424 0.0797 0.00100 2.18 0.00742 0.0617 0.000777 2.81 I“! 2.c 0.0 0.272 0.00343 -- 0.0 0.291 0.00367 --- 0.00110 0.206 0.00260 1.37 0.00220 0.167 0.00210 1.69 0.00440 0.122 0.00154 2.31 0.00660 0.0933 0.00118 3.02 0.00770 0.0830 0.00105 3.40 0.00880 0.0728 0.000917 3.87 ‘ benzene solvent (standard), l-(4-pyridyl)pentanone quencher. HPLC analysis coluln D. eluting with 853 Hexane. 158 Ethyl Acetate; ” [W(CO)5(4VP)] c [H(CO)I(4VP)] 0.0201 M. Filter 8, 0.0206 M, Filter B. -6 hrs. ~9 hrs. 1.5 Ill-1n. 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