O_2~- GENERATION IN C_(60)-PHOTOSENSITIZED OXIDATION OF NADH AND AN ANALOGUE BY OXYGEN

摘要

Visible light irradiation of poly(vinylpyrrolidone) (PVP)-solubilized C_(60) in water in the presence of NADH and molecular oxygen results in the formation of superoxide anion (O_2~(dot -)), which was detected with use of 5-diethoxyphosphoryl-5-methyl-l-pyrroline-N-oxide (DEPMPO) as a O_2~(dot -)-trapping agent. Formation of O_2~(dot -) having a characteristic g// value of 2.18 was also evidenced by the direct observation with use of a low-temperature ESR technique at 77 K. Photoinduced O_2~(dot -) formation was also observed for the N-methyl-2-pyrrolidone (NMP) solution of C_(60) and 1 -benzyl- 1,4-dihydronicotinamide (BNAH) in the presence of O_2, whereas C_(60) radical anion (C_(60)~(dot -)) was formed in the absence of O_2 under otherwise the same experimental conditions. These results suggest that C_(60)~(2-) formed in the photoinduced electron-transfer reduction of C_(60) by BNAH acts as an electron donor to molecular oxygen to give O_2~(dot -) in NMP.