Two contrary effects of electron transfer on the structures and stability of dimetallofullerenes

Extensive density functional theory calculations were performed on dimetallofullerenes M2@Cn (n = 72, 76, 78, 80, and 84). The calculated results demonstrate that the two metallic atoms always tend to separate as long as possible inside fullerene cage. The transferred electrons from the encaged atoms can stabilize those unstable cages by modifying their electronic structures, meanwhile they generally destabilize the cages by modifying their geometrical structures. The two contrary effects of electron transfer determine the structure and stability of a dimetallofullerene, and the bonding of encaged metallic atoms toward the cage does not play an important role unexpectedly.