Efficient photoinduced electron transfer between C60/C70 and zinc octaethylporphyrin studied by nanosecond laser photolysis method

Abstract

Photoinduced electron-transfer processes between C 60 or C 70 and zinc octaethylporphyrin ( ZnOEP ) have been studied in polar solvents with the nanosecond laser flash photolysis method, observing the transient absorption spectra in the visible and near-IR regions. By the predominant excitation of ZnOEP with 532 nm laser light the transient absorption bands of 3 ZnOEP * decayed, accompanied by the appearance of the transient absorption bands of [Formula: see text] and [Formula: see text]. By the predominant excitation of C 60 and C 70 with 610 nm laser light the decays of [Formula: see text] and [Formula: see text] were observed, accompanied by the appearance of [Formula: see text] and [Formula: see text]. The electron transfer rate constants (k et ) and the quantum yields (Φ et ) of [Formula: see text] and [Formula: see text] formation via 3 ZnOEP * and [Formula: see text] or [Formula: see text] have been evaluated. These values increase with the solvent polarity; in polar benzonitrile these values are higher than for other porphyrins such as zinc tetraphenylporphyrin. The back electron transfer rate constants were evaluated from the decays of [Formula: see text] and [Formula: see text], which also show a solvent polarity dependence.