A comparative study of interplay effects between the cation-π and intramolecular hydrogen bond interactions in the various complexes of methyl salicylate with Mn+, Fe2+, Co+, Ni2+, Cu+, and Zn2+ cations

Abstract

The interplay among two important noncovalent interactions involving aromatic ring is studied by means of density functional theory (DFT) calculations on complexes of methyl salicylate with Mn+, Fe2+, Co+, Ni2+, Cu+, and Zn2+ cations. The energetic, geometrical, spectroscopic, topological, and molecular orbital descriptors are applied to evaluate the strength of the cation-π and intramolecular hydrogen bond (IMHB) interactions. These outcomes are compared with the parent molecule of methyl salicylate and the corresponding results of benzene (BEN) complexes with the cited cations as a set of reference points. Based on the energetic conclusions, for the double-charge cations, the simultaneous presence of these interactions enhances the strength of the cation-π, while for the mono-charge cations, the reverse process is observed. On the other hand, for both type of the cations (mono- and double-charge), the coupling of noncovalent interactions reduces the strength of the IMHB in the studied systems. The computations in this study are discussed with the Bader theory of atoms in molecules (AIM), the natural bond orbital (NBO) analysis, and the frontier molecular orbital (FMO) theory.