Stability of endo- and exohedral complexes of all-boron fullerene B-40

In a recent publication [Nature Chemistry, 6, 727 (2014)] the synthesis and properties of a new all-boron fullerene analog, B-40, have been reported, and a possibility of utilizing the B-40 molecule as a hydrogen storage has been postulated. Therefore, in this contribution we study the stability of endo- and exohedral complexes with the hydrogen molecule and several other small molecules, such as N-2, H2O, and CO2. The examination of binding and interaction energies obtained by symmetry-adapted perturbation theory and by supermolecular approaches shows that among the studied endohedral complexes only the one with H-2 inside the cage is possibly weakly stabilized by the complexation, while all other molecules clearly exhibit too large repulsion, which cannot be counterweighted by attractive components of the interaction energy. An addition of the zero-point vibrational correction to the H-2@B-40 binding energy changes the balance of the attractive and repulsive contributions in favor of repulsion, so that finally also this endohedral complex is thermodynamically unstable at zero Kelvin. The exohedral minima are stable in all the cases, and are mostly bound by dispersion.