Near-IR absorption spectra for the C70 fullerene anions

Abstract : C70, like C60, can exist in a number of oxidation states including C70(1-), C70(2-), C70(3-) and C70(4-). We have discovered unique visible and near-IR absorption transitions which appear upon reduction of C70. These transitions are observed upon one, two, three and four-electron electrochemical reductions of C7O- In contrast to C60, however, the electronic properties of C70 are less well understood. In particular, previous theoretical studies of C7O(l-) failed to predict the existence of the near-IR transition we observe in the spectrum of C70(1-). In this paper, in addition to presenting the, heretofore unreported, spectra of the various C70 anions, we attempt a first-order explanation of the energies and intensities of the various spectral absorptions; this explanation is based on the published molecular orbital diagram for neutral C70 and a structural distortion that we suggest occurs upon reduction of C7O.