Investigation of the kinetics of electron transfer processes involving fullerenes at liquid–liquid interfaces using scanning electrochemical microscopy: evidence for Marcus inverted region behaviour

Abstract

Electron transfer (ET) reactions between the anions of fullerenes (C₆₀ and C₇₀) in chlorobenzene (PhCl) and Fe(CN)₆³⁻ in an aqueous phase have been investigated using scanning electrochemical microscopy (SECM). Salts of the anion ClO₄⁻ were added to each phase to control the interfacial potential drop and maintain charge neutrality during the ET process. The rate constants of ET between C₆₀⁻ and Fe(CN)₆³⁻ were similar to those between C₇₀⁻ and Fe(CN)₆³⁻. Although the measured ET kinetics were found to depend on the interfacial potential drop, the rate constant for the oxidation of the fulleride anion (reduction of aqueous Fe(CN)₆³⁻) decreased when the ClO₄⁻ concentration in the aqueous phase increased, even though this corresponds to an increase in driving force. It is suggested that this could be due to inverted region behaviour predicted by Marcus theory.