Cation-π versus anion-π interactions: a comparative ab initio study based on energetic, electron charge density and aromatic features

Several complexes of benzene with cations and hexafluorobenzene with anions have been optimized at the MP2/6-31++G**, B3LYP/6-31++G** and HF/6-31++G** levels of theory. Different aspects of the cation-π interaction have been compared to those of anion-π, including changes in the aromaticity of the ring upon complexation, charge-transfer effects using the Merz–Kollman charges and the contribution of dispersion energies by comparing the complexation energies computed at the B3LYP and MP2 levels of theory.