Cation− π interactions of bare and coordinatively saturated metal ions: contrasting structural and energetic characteristics

Abstract

In the present work, we address an apparent disparity in the structural parameters of the X-ray structures and theoretical models of cation−π complexes in biological and chemical recognition. Hydrated metal ion (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) complexes with benzene (cation−π) are considered as model systems to perform quantum mechanical calculations in evaluating the geometrical parameters and interaction energies of these complexes. The computations disclose that there is a variation in the structural parameters as well as in the interaction energies of these complexes with the multiple additions of water molecules. The distance between the cation and the π-system increases with the addition of water molecules, delineating the influence of solvent or the neighborhood atoms on the structural parameters of cation−π systems present in crystal structures.