Chemical bond inside a fullerene cage: is it possible?

The geometries, electronic structures, and hyperfine coupling constants of azafullerene C₅₉N (a π-electron radical) and its derivatives, C₅₉NH and endofullerene H@C₅₉N, were calculated at the B3LYP level of the density functional theory. Analysis of calculated potential energy profiles along trajectories of the motion of encapsulated hydrogen atom from the center of the fullerene sphere toward different atoms of C₅₉N revealed formation of a chemical bond between the H atom and a carbon atom that is involved in the 6,6-bond with the N atom and bears the most part of the π-electron spin density. The C—H endo-bond length is 1.12 Å, the bond dissociation energy being equal to 26.4 kcal mol⁻¹. The C—H exo-bond involving the same carbon atom is 0.02 Å shorter than the endo-bond, the bond dissociation energy being much higher (78.4 kcal mol⁻¹).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 51–54, January, 2005.