By means of ESR, we studied the photosensitization of porphyrin-like rareearth metal complex [(CO2H-APPC)Gd]Cl2. By using 4-oxo-TEMPO as a probe and through its spin elimination, the production of cation free radical [(CO2H-APPC)Gd]^+ in [(CO2H-APPC)Gd]Cl2 photosensitization was established and moreover it might be promoted by using BNAH as a reducing agent. Through trapping O2^- and .OH with DMPO and measuring the ESR spectra of the spin adducts of [DMPO-O2^-] and [DMPO-OH], the O2^- and .OH were found to be definitely generated. These results showed the presence of oxygen radicals in [(CO2H-APPC)Gd]Cl2 photosensitization, and shed light on the type I mechanism.

Key words: PHOTOSENSITIZATION, ELECTRON SPIN RESONANCE, PORPHYRIN, FREE RADICALS