Photoinduced electron transfer between fullerenes (C 60/C 70) and disubstituted naphthalenes using laser flash photolysis

Abstract

Photoinduced electron-transfer processes between fullerenes C 60/C 70 and disubstituted-naphthalenes have been studied by laser flash photolysis. Quantum yields ( Φ et T) and rate constants ( k et) of electron transfer from naphthalenes to the excited triplet states of C 60 ( 3 C 60 ∗ ) and C 70 ( 3 C 70 ∗ ) have been determined by observing the transient absorption bands in the wide wavelength VIS/NIR regions. The observed Φ et T and k et values depend significantly on the nature and position of the substituents. The k et values are seen to correlate well with the free energy changes (Δ G et) for the electron transfer reactions on the basis of Rehm–Weller relation. Addition of pyridine (Py) enhanced significantly the rates and efficiencies of photoinduced electron transfer process of dihydroxy-naphthalenes (DHN). However, the effect of Py in the dimethoxy-naphthalenes (DMN) is far less than that of DHN. In the presence of octylviologen (OV 2+), electron-mediation occurs from C 60 − to OV 2+ to generate OV +.