LOW-LYING ELECTRONIC EXCITED-STATES OF BUCKMINSTERFULLERENE ANIONS

We report Pople-Pariser-Parr (PPP) calculations of the energies of the lowest electronically excited states of six C60 anions ranging from the monoanion to the hexaanion. Multiplicities up to septet are included. The results for the monoanion are compared with the existing absorption spectrum. The stability of various anions and the possibility of obtaining them by electrochemical reduction are discussed. In most of the species studied, we find a remarkable density of electronic levels close to the electronic ground state. This density is due to the existence, in neutral C60, of a triply degenerate lowest unoccupied molecular orbital (LUMO), together with a close-lying LUMO+1 of the same degeneracy.