Benzene, an Unexpected Binding Unit in Anion–π Recognition: The Critical Role of CH/π Interactions

We report high-level ab initio calculations (CCSD(T)(full)/CBS//SCS-RI-MP2(full)/aug-cc-pwCVTZ) that demonstrate the importance of cooperativity effects when Anion–π and CH/π interactions are simultaneously established with benzene as the π-system. In fact, most of the complexes exhibit high cooperativity energies that range from 17% to 25.3% of the total interaction energy, which is indicative of the strong influence of the CH/π on the Anion–π interaction and vice versa. Moreover, the symmetry-adapted perturbation theory (SAPT) partition scheme was used to study the different energy contributions to the interaction energies and to investigate the physical nature of the interplay between both interactions. Furthermore, the Atoms in Molecules (AIM) theory and the Non-Covalent Interaction (NCI) approach were used to analyze the two interactions further. Finally, a few examples from the Protein Data Bank (PDB) are shown. All results stress that the concurrent formation of both interactions may play an important role in biological systems due to the ubiquity of CH bonds, phenyl rings, and anions in biomolecules.