HIGH-NUCLEARITY MIXED-VALENCE MAGNETIC CLUSTERS - THEORETICAL-STUDY OF THE SPIN COUPLING IN THE C-60(2-) FULLERIDE ION

The problem of delocalization of a pair of electrons over the fulleren e C-60 is considered, with the aim of elucidating the nature of the gr ound spin state, as well as the structure of the low-lying energy leve ls 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 deloca lization, is developed. The influence of these electronic parameters o n the spectrum of the low-lying energy levels is discussed. We find th at the ground state is always a spin singlet, whatever the relative va lues of these parameters are. (C) 1998 Elsevier Science B.V.