Porphyrin-like rare earth metal complexes ([CO2H-APPC)Gd]Cl2) are a kind of promising PDT agents due to their very long absorption wavelength at near IR region (770nm). In this paper, the generation of singlet oxygen during photoirradiation of porphyrin-like rare earth metal complexes 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 augmented the ESR signal intensity. The rate of production of singlet oxygen was dependent not only upon the concentration of [(R-APPC)RE]Cl2 and the time of irradiation but also on the oxygen content of the reaction mixture. Different central metal ions and different substituents affected the rate of generation of singlet oxygen dramatically.

Key words: PIPERIDINE P, PHOTOSENSITIZATION, ELECTRON SPIN RESONANCE, PORPHYRIN, NITRO-OXY RADICAL, SINGLET OXYGEN