Theoretical study of neutral and charged Sc n≤2–(benzene) m≤3 clusters

Abstract

Interactions of benzene molecules with scandium atoms, Scn≤2–(C6H6)m≤3, in the gas phase were studied by means of density functional theory. All-electron calculations were performed using the B3LYP hybrid functional in concert with 6-311+G(d,p) orbital basis sets for the Sc, C, and H atoms. Multiple-decker sandwich (MDS) structures are identified as the ground states for Scn≤2–(C6H6)m≤3, where the ligands are attached to the metal through Sc–C bonding, formed between the 3d electrons and the π-clouds of the benzene rings. Significant distortion is produced on the absorbed benzene molecules by the metal–ligand bonding. Rice ball structures also appeared, but they were found at higher energies, in such a way that essentially MDS isomers may emerge in the molecular beams. Even the low number of valence electrons (3d24s1) of the Sc atom; sextuple coordinations are formed, but they show different Sc–C bond lengths, diminishing the symmetry of neutral and charged clusters. The estimated ionization energies, in near agreement with experimental data, and electron affinities, suggest delocalization of the valence electrons through the network of 3d–π bonds of Sc1,2–(C6H6)m≤3. The binding energies decrease with the absorption of more benzene molecules, and in some cases increase as more metal atoms are added to the cluster.