Photoinduced electron transfer from aromatic aldehyde hydrazones to triplet states of C60 and C70;: Electron-mediating and hole-shifting systems

Photoinduced electron transfer of fullerenes such as C-60 and C-70 in the presence of aromatic aldehyde hydrazones (AAH's) has been studied by the nanosecond laser photolysis which measures the transient absorption spectra in the visible and near-IR regions. Electron-transfer takes place from AAH's to the triplet states of fullerenes; the rates and efficiencies of electron transfer are strongly affected by the electron-donor ability of AAH's as evaluated by their oxidation potentials. The absorption bands of the radical cations of AAH's appeared in the near-IR reagion, indicating that the radical-cation center (hole) delocalizes in the entire region of each AAH. On addition of a viologen dication to C-60/C-70-AAH, the electron of the anion radical of fullerenes moves to viologen dication yielding the viologen radical cation. In the systems of octaethyl porphyrinatozinc (ZnOEP)-C-60/C-70-AAH, the hole shift was observed from the radical cation of ZnOEP, which was produced by photoinduced electron transfer from the triplet state of ZnOEP to C-60/C-70, to AAH.