Photochemical reactions between C₆₀ and aromatic thiols. Protonation of C₆₀ via photoinduced electron transfer

Photochemical reactions between C₆₀ and aromatic thiols via electron transfer from aromatic thiols to the excited triplet state of C₆₀ (³C₆₀*) have been studied by means of laser flash photolysis. In polar benzonitrile, accompanied by the decay of ³C₆₀*. the rise of the anion radical of C₆₀ (C₆₀^•-) 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 C₆₀^•-, 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 C₆₀ in the presence of the aminobenzenethiols, the characteristic absorption bands of the monoadduct with C₆₀ 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 C₆₀^•- was also determined, which supports the proposed reaction mechanism.