PRIMARY PHOTOCHEMICAL PROCESSES IN FAC-CLRE(CO)3L2 (L=4-PHENYLPYRIDINE AND 4-CYANOPYRIDINE) - A STEADY-STATE AND FLASH PHOTOCHEMICAL STUDY OF REACTION-PRODUCTS AND INTERMEDIATES

The photochemistry of fac-ClRe(CO)3L2, L = 4-phenylpyridine and 4-cyanopyridine, has been investigated by monochromatic steady-state and flash photolyses between 400 and 229 nm. Two parallel photoprocesses, the photogeneration of the emissive MLCT state and the photoredox dissociation in {ClRe(CO)3L+, L .-} products, have been observed with both compounds. A third photoprocess, namely, the photogeneration of a Re(I)-ligand biradical, has been observed only in photolyses of the 4-phenylpyridine complex. While this Re(I)-ligand biradical reduces Cu(II)(TIM)2+ to the corresponding Cu(I) species, no such reaction is undergone by the MLCT state. Differences between the electronic structures of these complexes, shown by extended Huckel MO calculations, were related to their intrinsic photochemical behavior.