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

Redox reactions of C-60, C-120, 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 C-120 shows ESR behavior similar to C120O in the first electron transfer at 260 K characterized by the single ESR line of R2C60- fullierdes. 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 C-60 cages in the dimer. The stability of radical ions of the C-60 dimers under study increases with the number of chemical bonds between both fullerene cages (C-120 < C120O < C120OS). NIR absorption of the fullerene anions generated in the first voltammetric double peak (lambda(max) = 1020 nm for C-120, lambda(max) = 940 nm for C120O, lambda(max) = 1020 nm for C120OS) is dominated by both the mono- and dianionic structures comparable to R2C60 monoanions (C-120 and C120O) and R4C60 (C120OS) fullerene anion spectra, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.