Mechanisms of Electrochemically‐Induced Retro‐Cyclopropanation Reactions of Fullerene Derivatives Using Digital Simulations

Abstract

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.

Methanofullerenes from Macrocyclic Malonates

“…The elucidation of the electrode mechanism evidenced by the CV experiments is beyond the scope of this paper, however, and will be the subject of forthcoming publications. [28] …”

Electrochemically Induced Retro‐Cyclopropanation Reactions

“…The proposed mechanism was similar for all the compounds and involved two main chemical reactions in a reversible-square scheme. [69] Figure 17 (a) shows the CV for a 0.1 m THF solution of 5. Three main reduction processes were observed, the first two being reversible and the third one chemically irreversible, in agreement with previous results obtained using other solvents.…”

“…[69] The study was conducted with different C 60 derivatives in which the addends result in different electrochemical responses. They range from the non-electroactive addend in 5 to the electroactive and highly interacting unit in spiromethanofullerene 28.…”

“…This feature, and the general shape of the curve, was reminiscent of a bi-electronic slow electron-transfer process. [69,74] The simulation shown in Figure 18 (b) was made using the mechanism shown on top of the figure. This diagram was proposed based on the new experiments and the data previously reported.…”

Coordination Programming of Photofunctional Molecules

“…Figure 5 a shows a cyclic voltammogram of 1 · BF 4 (0.45 mM) in 0.1 M Bu 4 NBF 4 −CH 2 Cl 2 at 203 K, which revealed two reversible waves at E 0' = 0.48 V and 0.62 V vs. Ag + /Ag. The waves were assigned to the Cu II /Cu I couples of the o - and i -isomers, respectively, because a bulky substituent around the Cu center destabilized the Cu II square-planar geometry, thereby shifting the redox potential in the positive direction [ 56 , 57 , 58 , 59 ]. A differential pulse voltammogram yielded an abundance ratio ( i -Cu I : o -Cu I = 30:70) consistent with that determined using 1 H-NMR spectroscopy ( Figure 5 b).…”