Triplet Properties and Photoinduced Electron-Transfer Reactions of C120, the [2+2] Dimer of Fullerene C60

Abstract

Photophysical and photochemical properties of a [2+2] fullerene dimer, C120, have been characterized by laser flash photolysis. By laser irradiation to C120, a triplet−triplet absorption band appeared at 700 nm. From triplet energy-transfer reactions with some energy acceptors, photophysical properties of C120, including triplet energy, extinction coefficient, and quantum yield of the intersystem crossing process, were estimated. Reduction of C120 in the ground state by tetrakis(dimethylamino)ethylene resulted in decomposition into C60•- and C60. Photoinduced electron transfer from N,N,N‘,N‘-tetramethyl-1,4-phenylenediamine to triplet-excited C120 was confirmed by the observation of a transient absorption band due to the radical anion of C120 at 1020 nm. Electron-transfer rates between triplet-excited C120 and various electron-donors were explained by the semiempirical Rehm−Weller relation. Oxidation of triplet-excited C120 was also observed by employing tetracyanoethylene as an electron-acceptor.