In situ ESR/UV–vis–NIR spectroelectrochemistry of C60 and its dimers C120, C120O and C120OS

Redox reactions of C60, C120, C120O and C120OS in tetrabutylammonium tetrafluoroborate/o-dichlorobenzene solutions of high purity are studied by simultaneous measurement of UV–vis–NIR and ESR spectra during electrochemical reduction in dependence on the dimeric fullerene structure. It was found that C120 shows ESR behavior similar to C120O in the first electron transfer at 260 K characterized by the single ESR line of R2C60− fullerides. C120OS anions exhibit a sharp ESR line (linewidth 0.04 mT) with the characteristic feature of R4C60 anions indicating a strongly perturbed icosahedral symmetry of both C60 cages in the dimer. The stability of radical ions of the C60 dimers under study increases with the number of chemical bonds between both fullerene cages (C120<C120O<C120OS). NIR absorption of the fullerene anions generated in the first voltammetric double peak (λmax=1020 nm for C120, λmax=940 nm for C120O, λmax=1020 nm for C120OS) is dominated by both the mono- and dianionic structures comparable to R2C60 monoanions (C120 and C120O) and R4C60 (C120OS) fullerene anion spectra, respectively.