Regulating function of alkali metal on the strength of OH⋯O hydrogen bond in phenol-water complex: Weak to strong and strong to weak

Quantum chemical calculations have been performed for the complexes of phenol and M-substituted phenol (M = Li, Na, K) with water to investigate the regulating function of the M atom on the strength of OH⋯O hydrogen bond. The results show that the presence of the M atom in the phenol ring enhances the hydrogen bond with water as the proton donor but weakens the hydrogen bond with water as the proton acceptor. The regulating effect of alkali metal confirms to the order of Li < Na < K. Natural bond orbital and aims in molecules analyses have been carried out to unveil the regulating mechanism of the M atom. It is demonstrated that the M effect is realized through the hyperconjugation and electrostatic induction interactions.