Small Molecules in C_(60) and C_(70): Which Complexes Could Be Stabilized?

摘要

The recent syntheses of complexes involving some small molecules in opened fullerenes and those of hydrogen molecule(s) inC_(60) and C_(70) are accompanied in the literature by numerous computations for endohedral fullerene complexes which copewith the problem of the stability of these complexes. In this contribution, stabilization energies of endohedral complexes ofC_(60) and C_(70) with H2, N2, CO, HCN, H2O, H2S, NH3, CH4, CO2, C2H2, H2CO, and CH3OH guests have been estimated usingsymmetry-adapted perturbation theory, which, contrary to the standard DFT and some other approaches, correctly describes thedispersion contribution of the host-guest interactions. On the basis of these calculations, the endohedral complexes with allthese guests were found stable in the larger fullerene, while the C_(60) cage was found too small to host the latter fourmolecules. Except for H2 and H2CO, a stabilization effect for most guests in the C_(60) cage is about 30 kJ/mol. For H2 andH2O guests, a typical supramolecular effect is observed; namely, the stabilization in the smaller cage is equal to or largerthan that in the larger C_(70) host. Except for the water molecule where the induction interaction plays a non-negligiblerole, in all complexes the main stabilization effect comes from the dispersion interaction. The information on the stabilityof hypothetical endohedral fullerene complexes and physical factors contributing to it can be of importance in designingfuture experiments contributing to their applications.