Generation of long-lived radical ions through enhanced photoinduced electron transfer processes between [60]fullerene and phenothiazine derivatives

Photoinduced electron transfer processes between fullerenes ( C-60) and four phenothiazine derivatives ( PTZs) in the absence and presence of hexylviologen dication ( HV2+) have been studied by the transient absorption method in the visible and near-IR regions. Electron-transfer takes place from PTZs to the triplet states of fullerenes ( C-3(60)*) giving the radical anion of fullerenes ( C-60(center dot-)) and the radical cations of PTZs ( PTZ(center dot+)). The rate constants and efficiencies of electron transfer are quite high, because of the high electron-donor abilities of PTZs as elucidated by their low oxidation potentials. On addition of HV2+ to the C-60 and PTZ systems, the electron-mediating process occurs from C-60(center dot-) to HV2+, yielding the viologen radical cation ( HV center dot+). In the presence of a sacrificial donor, HV center dot+ persisted for a long time.