Effects of Trimethylpyridine Addition on forward and backward Electron Transfer between Triplet States of C60/C70 and 2-Naphthols

Abstract

Photoinduced electron-transfer processes between C60/C70 and 2-naphthols have been studied by nanosecond laser flash photolysis. Quantum yields (ΦetT) and rate constants (ket) of electron transfer from naphthols to the excited triplet states of C60 and C70 have been determined by observing the transient absorption bands in the wide wavelength (UV−vis/NIR regions), where the naphthoxy radicals, triplet states, and anion radicals of fullerenes appear. Both ΦetT and ket were increased by the addition of trimethylpyridine (Py), indicating that Py promotes the electron-donor ability of naphthols. The C60•-/C70•- decay with second-order kinetics in the absence of Py, suggesting charge recombination of free ion radicals. In the presence of Py, on the other hand, the initial decays of C60•-/C70•- obey first-order kinetics, suggesting that back electron transfer takes place within the ion radicals bridged via Py.