Sumanenetrione anions generated by electrochemical and chemical reduction

The electrochemical reduction of sumanenetrione by cyclic voltammetry showed stepwise multielectron reduction. Cyclic voltammograms of the stepwise first and second one-electron reduction exhibited reversible waves with associated reduction potentials that were almost equivalent to those of C₆₀. EPR studies of the chemically generated monoanion and dianion of sumanenetrione, in conjunction with theoretical calculations, revealed their structures. The radical anion exhibited C₃v symmetric spin delocalization over the entire bowl structure. The radical anion exhibited several absorption bands covering the whole visible to near-IR region. The nature of excitations was assigned by SAC/SAC-CI SD-R calculations. The dianion has a singlet ground state with a large energy gap between the singlet and triplet states. The dianion, too, has C₃v symmetry with delocalization over the bowl structure. The major contributing structure of the dianion is the closed-shell configuration rather than the open-shell biradical configuration.