Mechanisms of electrochemically-induced retro-cyclopropanation reactions of fullerene derivatives using digital simulations

Three C(60) derivatives, 1, 2 and 3, have been studied by cyclic voltammetry (CV) under high vacuum in anhydrous tetrahydrofuran (THF). The CV behavior was essentially similar to that already observed for other cyclopropanated fullerene derivatives. After the second reduction processes all compounds undergo a chemical reaction that generates another electroactive species. This "new" chemical species is likely to be the compound with the cyclopropane ring open. Differences in CV behavior were observed for the different addends. Electrochemical data obtained at different scan rates for a given potential window, were fit with the BAS digital simulation program, DigiSim. The purpose of this study was to probe the proposed mechanisms and to obtain reliable estimations of the kinetic constants for the homogeneous chemical reactions taking place during the CV experiments. Calculations at the PM3 level lend additional support to the conclusions derived from digital simulations. The proposed mechanism is similar for all the compounds and involves two main chemical reactions in a reversible square scheme.