PHOTOREDUCTION OF FERRIC-TETRAPHENYLPORPHYRIN IN OXYGEN-CONTAINING SOLVENTS REVEALED BY RESONANCE RAMAN AND ABSORPTION-SPECTROSCOPY

Photoreduction is observed for Fe-III(TPP)CI (TPP is tetraphenylporphy rin) in some oxygen (O)-containing solvents under anaerobic conditions using resonance Raman (RR) and absorption spectroscopy. This process is found to be initiated by visible light in the 390-450 nm region, Th e coincidence of RR and absorption spectra of photoinduced species and of chemically reduced ones reveals that the final product of photored uction is the high-spin Fe-II(TPP)L complex, where L = THF (tetrahydro furan), DMF (dimethyl formamide) or 1,4-dioxane. Such a photoreduction is not observed under anaerobic conditions for the Fe-III(TPP)CI comp lex in benzene, pyridine or CH,CI,, nor in the abovementioned solvents under aerobic conditions. No photoreduction is observed for Fe-III(OE P)CI (OEP = octaethylporphyrin). A mechanism for the photoinduced phen omenon observed for Fe-III(TPP)CI in O-containing solvents under anaer obic conditions is proposed.