Comparative Investigation on Non-IPR C68 and IPR C78 Fullerenes Encaging Sc3N Molecules

Publisher Website
Google Scholar
Abstract
A computational study on the experimentally detected Sc3[email protected]68 cluster is reported, involving quantum chemical analysis at the B3LYP/6-31G* level. Extensive computations were carried out on the pure C68 cage which does not conform with the isolated pentagon rule (IPR). The two maximally stable C68 isomers were selected as initial Sc3[email protected]68 cage structures. Full geometry optimization leads to a confirmation of an earlier assessment of the Sc3[email protected]68 equilibrium geometry (Nature2000, 408, 427), namely an eclipsed arrangement of Sc3N in the C68 6140 frame, where each Sc atom interacts with one pentagon pair. From a variety of theoretical procedures, a D3h structure is proposed for the free Sc3N molecule. Encapsulated into the C68 enclosure, this unit is strongly stabilized with respect to rotation within the cage. The complexation energy of Sc3[email protected]68 cage is found to be in the order of that determined for Sc3[email protected]80 and exceeding the complexation energy of Sc3[email protected]78. The cage−core interaction is investigated in terms of electron transfer from the encapsulated trimetallic cluster to the fullerene as well as hybridization between these two subsystems. The stabilization mechanism of Sc3[email protected]68 is seen to be analogous to that operative in Sc3[email protected]78. For both cages, C68 and C78, inclusion of Sc3N induces aromaticity of the cluster as a whole.