High nuclearity mixed-valence magnetic clusters:: theoretical study of the spin coupling in the C602- fulleride ion

The problem of delocalization of a pair of electrons over the fullerene C-60 is considered, with the aim of elucidating the nature of the ground spin state, as well as the structure of the low-lying energy levels in this mixed-valence molecule C-60(2-). A model that considers the Coulomb interactions between the two extra electrons, as well as the two single-electron transfer processes involved in the electron delocalization, is developed. The influence of these electronic parameters on the spectrum of the low-lying energy levels is discussed. We find that the ground state is always a spin singlet, whatever the relative values of these parameters are. (C) 1998 Elsevier Science B.V.