Contribution of the Basal Planes to Carbon Basicity:  An Ab Initio Study of the H₃O⁺−π Interaction in Cluster Models

The contribution to carbon basicity of π−cation interactions in aromatic systems has been investigated in this work by carrying out ab initio calculations on various cluster models. According to various levels of theory, the mono-, bi-, and tridentate H 3 O + −benzene complexes present a binding enthalpy in the gas phase of about −28 kcal/mol showing intermolecular contact through unconventional hydrogen bonding between H 3 O + and the π-cloud of benzene. The interaction energies calculated for other cluster models (pyrene−benzene−H 3 O +, coronene−H 3 O +, and a C 54 H 18 −H 3 O + cluster) indicate that the size of the basal plane has a slight influence on the strength of this π−cation interaction, whereas the presence of the π−π contacts reinforces the electrostatic interaction with the H 3 O + cation. These theoretical results support experimental data on the ability of the basal planes to contribute to carbon basicity and suggest that π−cation interactions may play an important role in the surface chemistry of carbon materials.