Photoinduced Electron Transfer and Electron‐Mediating Systems of [60]Fullerene and Triphenylamine Derivatives in the Presence of Viologen Dication in Polar Solvent

Photoinduced electron‐transfer processes between fullerenes (C 60 ) and three triphenylamines (TPA's) including bis(tolylaminophenyl)cyclohexane in the absence and presence of hexylviologen dication (HV 2+ ) and 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) have been studied by the transient absorption method in the visible and near‐IR regions. Electron‐transfer takes place initially from TPA's to the triplet states of fullerenes ( 3 C 60 * ), giving the radical anions of fullerenes (C 60 − ) and the radical cations of TPA's (TPA + ). The rate constants and efficiencies of electron transfer are quite high, because of the high electron‐donor abilities of TPA's as their low oxidation potentials indicate. On addition of HV 2+ to the C 60 and TPA systems, the electron‐mediating process from C 60 − to HV 2+ occurs, yielding the viologen radical cation (HV + ). In the further addition of BNAH, which acts as a sacrificial donor, steady‐state concentration of HV + was accumulated during continuous photoirradiation and persisted for a long time.