Photoinduced Electron Transfer from Aromatic Aldehyde Hydrazones to Triplet States of C60 and C70; Electron-Mediating and Hole-Shifting Systems

Abstract

Abstract Photoinduced electron transfer of fullerenes such as C60 and C70 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 C60/C70–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)–C60/C70–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 C60/C70, to AAH.