Photochemical reactions between C60 and aromatic thiols, protonation of C60 via photoinduced electron transfer

Photochemical reactions between C-60 and aromatic thiols via electron transfer from aromatic thiols to the excited triplet state of C-60 (C-3(60)*) have been studied by means of laser flash photolysis. In polar benzonitrile, accompanied by the decay of C-3(60)*, the rise of the anion radical of C-60 (C-60(.-)) was observed for thiols, phenols, and disulfides with NH2 substituents. In the case of aminobenzene disulfide, the cation radical was observed at the same time as C-60(.-), which decayed by back electron transfer. For aminobenzenethiols, the free thio radical was observed, indicating fast deprotonation of the cation radicals of thiols. By the repeated laser-pulse irradiation of C-60 in the presence of the aminobenzenethiols, the characteristic absorption bands of the monoadduct with C-60 were observed, suggesting that the monoadduct is formed via electron transfer followed by consecutive radical coupling and protonation reactions. The rate constant of protonation of C-60(.-) was also determined, which supports the proposed reaction mechanism.