Endohedral complexes of C58 cage with H2 and CO

Ab initio Hartree–Fock (HF) calculations were carried out to determine the structures and energies of the endohedral complexes of C₅₈ cage with H₂ or CO. It was demonstrated that the formation of these complexes is endothermic with destabilization energies of 3.3 kcal/mol for H₂ and 18.6 kcal/mol for CO. Furthermore, the H₂ and CO molecules have different orientations in the C₅₈ cage, namely, the orientation of the molecular axis of the former is normal to the face of the 7-member ring, while that of the latter is parallel to that face. In addition, the H–H bond of the H₂ molecule is shortened inside the cage, whereas the length of the C–O bond remains unchanged.