Alkylation of C_(60) by 4-Alkyl NADH Analogs via Photoinduced Electron Transfer

摘要

The photochemical reaction of C_(60) with 1-benzyl-4-tert-butyl-1,4-dihydronicotinamide (t-BuBNAH), yields tert-butylated C_(60) anion (t-BuC_(60)-) selectively under irradiation of visible light in deaerated benzonitrile. The studies on the quantum yields, triplet-triplet quenching experiments and direct detection of transient spectra of the radical ion pair in laser flash photolysis have revealed that the photochemical reduction proceeds via photoinduced electron transfer from t-BuBNAH to the triplet excited state of C_(60) (~3C_(60)*). Fast C-C bond cleavage in t-BuBNAH~(.+) produced in the electron transfer occurs to give t-Bu~. which is coupled with C_(60)~(.-) to yield t-BuC_(60)~- and BNA~+. The mono-alkylated C_(60) anion (C_(60)(CMe_2COOMe)~-) is also obtained in the photochemical reaction of C_(60) with RBNAH (R = CMe_2COOMe). On the other hand, the selective one-electron reduction of C_(60) to C_(60)~(.-) is attained through photoinduced electron transfer from RBNAH (R =i-Pr) and 1-benzyl-1,4-dihydro-nicotinamide (BNAH) to ~3C_(60). The mechanistic difference between the selective photochemical alkylation and the one-electron reduction of C_(60) is discussed based on the difference in the cleavage mode of RBNAH~(.+) depending on the R group.