CHEMISTRY OF SINGLET OXYGEN .8. ESR STUDI ES OF SINGLET OXYGEN GENERATED BY PHOTOSENSITIZATION OF PORPHYRIN-LIKE RARE-EARTH COMPLEXES

Porphyrin-like rare earth metal complexes ([(R-APPC)RE]Cl-2) are a kin d of promising PDT agents due to their very long absorption wavelength at near IR region (770nm). In this paper, the generation of singlet o xygen during photoirradiation of porphyrin-like rare earth metal compl exes was detected by the formation of 2,2,6,6-tetramethylpiperidine-N- oxide radical (TEMPO) using ESR spectroscopic techniques. Sodium azide diminished the ESR signal intensity, whereas deuterated solvents augm ented the ESR signal intensity. The rate of production of singlet oxyg en was dependent not only upon the concentration of [(R-APPC)RE] Cl-2 and the time of irradiation but also on the oxygen content of the reac tion mixture. Different central metal ions and different substituents affected the rate of generation of singlet oxygen dramatically.