Computational study of N@C60, P@C60, and As@C60

Semiempirical and density functional theory structural calculations on Group V atom-endohedral complexes are reported. While reports, in some instances contradictory, on the structure of N@C-60 have appeared in the literature, this is the first computational study that includes both phosphorous and arsenic as endohedral atoms. Potential energy functions for all complexes are also reported. The calculations indicate that, as the atoms are translated towards the cages, weak covalent bonds external to the cage are possible. There is a significant difference between the potential surface for the nitrogen complex and that of either phosphorous or arsenic. The nitrogen surface is repulsive for movement of the endohedral atom off-center. The curves for the other atoms are essentially flat with displacement. The potential curves have also been calculated for the reaction products of the complexes with azides. Similar potentials, as a function of endohedral atom displacement, were observed. The relative experimental stabilities of the complexes are understood on the basis of these data.