Thermal stability of the endohedral fullerenes NaC60, NaC70, and PaC60 - art. no. 045421

Nitrogen and phosphorus atoms enclosed in fullerenes keep their atomic grou nd-state configuration, and no charge transfer or covalent bonding to the c age occurs. These systems can be dissolved in organic solvents and reacted with addends without losing the atomic character of the guest atom. In this paper, we present a detailed study of the annealing behavior of NaC60, NaC 70, PaC60, and of some NaC60 adducts. The disintegration of these systems, as recorded by electron paramagnetic resonance measurements, occurs in the temperature range between 400 K and 600 K. The results are in qualitative a greement with potential energy calculations and confirm the proposed escape mechanism that proceeds via bond formation of the trapped atom with the ca ge. It is found that other combinations of group-V elements with fullerenes , e.g., NaC84, PaC70, and AsaC(60) are not stable at room temperature. The escape mechanism and the possibility of disabling this path are discussed.