Electrochemical investigations of singly and doubly bridged imino[60]fullerenes

Abstract

The electrochemical properties of four singly bridged (1-4) and one doubly bridged ( 5) N-substituted imino[60]fullerenes have been investigated with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The substituents on the imino nitrogen are methoxycarbonylmethyl (1, 2, 5), 4-(pentafluorophenoxycarbonyl)phenyl (3), and 4-(succinimidoxycarbonyl)phenyl (4). [6,6]-Bridged structures (2) with closed and [5,6]-bridged structures (1, 3, 5) with open transannular bonds were compared for the first time. Whereas C 60 and 1-4 exhibit four successive, reversible reduction peaks in terms of an EEEE mechanism, a chemical reaction followed the cathodic reduction of 5 to 5 Ϫ . This effect is particularly clear in the DPV, where all subsequent reduction peaks were doubled. This can be explained by an ECEEE mechanism, in which 5 after the first E reduction undergoes a chemical transformation into one or two new species, which are further reduced in EEE processes. In the anodic oxidation of 1-5 a two-electron transfer was confirmed. In sharp contrast to all other fullerene derivatives, a quasireversible oxidation of 4 could be observed. To our knowledge, this is the first report of a quasireversible electrochemical oxidation for C 60 mono adducts. The reduction potentials exhibit good linear relationships with the calculated LUMO energy levels. Significantly, compared to C 60 , the reductions of the [6,6]-bridged derivative 2 as well as of the doubly [5,6]-bridged compound 5 occur at more negative potentials, whereas those of the singly [5,6]-bridged compounds 1, 3, 4 are found at less negative potentials.

Calculation of the two-step reduction potentials of some quinones in acetonitrile

“…1 and 2). Since a molecule in the oxidized form accepts electrons to be converted to its reduced form, the observed relationship between electrode potential and energy of LUMO is reasonable, as discussed before in the literature [8,10,15,[38][39][40][41][42][43]. The respective regression equations for the first and the second electron transfer steps are E 1 Q (exp.)…”

Cyclic voltammetric, computational, and quantitative structure–electrochemistry relationship studies of the reduction of several 9,10-anthraquinone derivatives

“…Since a molecule in oxidized form accepts electrons and converts to its reduced form, the relation between electrode potential and energy of lowest unoccupied orbital level (LUMO) is reasonable. The relation between energy of highest occupied molecular level (SOMO) of molecule in reduced form and electrode potential is also justified since the molecule in its reduced form has already gained electron, as discussed before [35,36,57,[64][65][66][67], and for the sake of simplicity, we limited ourselves to a single level of theory, namely, B3LYP/6-31G * based on the data given in Table 5.…”

Discrete Fulleride Anions and Fullerenium Cations

“…88 In keeping with their delocalized charges, the first oxidation potentials of C 60 , C 70 , C 76 , and C 78 follow the same trend as their first ionization potentials (7.61, 7.58, 7.10, and 7.05 eV, respectively). 89,90 In contrast to reduction, the oxidation of fullerenes typically becomes easier upon derivatization, 59,80,91,92 particularly with bis(silyl) derivatization, 93 but no cations have been characterized.…”