The electrochemical reduction of sumanenetrione by cyclic voltammetry showed stepwise multi-electron reduction. Cyclic voltammograms of the stepwise first and second one-electron reduction exhibited reversible waves with associated reduction potentials which 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 exhibits C3v symmetric spin-delocalization over the entire bowl structure. The radical anion exhibited several absorption bands covering the whole visible to near IR regions. The nature of excitations was assigned by the SAC/SAC-CI SD-R calculations. The dianion has a singlet ground state with a large energy gap between the singlet and the triplet states. The dianion also has C3v symmetry with delocalization over the bowl structure. The major contributing structure of the dianion is the closed-shell rather than the open-shell biradical configuration.
2014 The Chemical Society of Japan