Molecular and electronic structure of some bowl-shaped unsaturated hydrocarbon molecular systems, possible precursors of C60 fullerene

Abstract

The AMI calculations of hydrocarbon molecules C20H10 (1) and C30H10 (2) and anions C20H15−4 (3) and C30H15− (4) have been performed with the full energy optimization of the geometric parameters. The chosen topology of the carbon framework of the studied compounds is identical to the topology of the corresponding carbon fragments of C60 fullerene. Analysis of the structure of the frontier orbitals of systems1–4 demonstrated that the tendency of the C20H10 molecule to form sandwich π-complexes of the η5-type with transition metal atoms is small; however, this tendency is significantly larger than that of C30H10. Moreover, the exclusion of the five-membered cycle of bowlshaped unsaturated hydrocarbon molecules and anions from the conjugated system (as a result of the conversion of five framing C atoms to saturated carbon centers) favors the stabilization of their η5-type π-complexes with M(C5H5) species. The stability of these complexes must approach the stability of classical sandwich complexes of the ferrocene type. The results obtained have been extrapolated to polyhedral C60 and C70 carbon clusters.