A B3LYP and MP2(full) theoretical investigation on the cooperativity effect between cation–molecule and hydrogen-bonding interactions in the O-cresol complex with Na+

The B3LYP/6-311++G∗∗ and MP2(full)/6-311++G∗∗ calculations are carried out on the binary complex formed by an O-cresol moiety and a Na+ cation or two O-cresol monomers, as well as the ternary system that contains a Na+ cation and two O-cresol units. The cooperativity effects between the cation–molecule (Na+⋯O and T-shaped Na+⋯π) and hydrogen-bonding (H⋯O and T-shaped H⋯π) interactions are investigated. The result shows that the distance RNa⋯O in ternary system increases when compared to the binary complex while the value of RNa⋯π, RH⋯O or RH⋯π in ternary conformation decreases. The cooperativity effect is observed in the conformations formed by the moderate Na+⋯π, H⋯π and H⋯O interactions, while the anti-cooperativity effect is present in the complex with the strong Na+⋯O cation–molecule interaction, as one of the coexistent non-covalent interactions in a ternary system. The nature of the cooperativity effect is revealed by the atom in molecule (AIM) and electron density shifts methods.