Bonding in exohedral metal–fullerene cationic complexes

Abstract

We present a systematic theoretical study of the exohedral interaction between singly positively charged metal (M) atoms and the C₆₀ fullerene in [M–C₆₀]⁺ complexes. Calculations have been carried out by means of the density functional theory. We have considered alkali (Li, Na and K), alkaline-earth (Be, Mg and Ca) and first period transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) interacting with C₆₀ in different positions: on top of a ring (pentagon or hexagon), a bond (hexagon–hexagon or hexagon–pentagon) and a C atom. A detailed topological analysis of the electronic density reveals metal–C₆₀ exohedral interaction of the ion-induced dipole type, with the positive charge localized on the metal atom and with increasing covalent character for the heavier transition metals. An energy decomposition analysis allows us to quantify the different contributions to the bonding in each complex, being dominant the polarization one. A simple ion-induced dipole model explains the main features of the interaction.