Influence of accompanying anions on supramolecular assembly and coordination geometry in HgII complexes with 8-aminoquinoline: experimental and theoretical studies

Abstract

To investigate the effect of counterions on crystalline networks, we have designed and synthesized a series of Hg^II complexes, [Hg(8-aq)Cl₂] (1), [Hg(8-aq)Br₂] (2) and [Hg₅(8-aq)₂I₁₀]_n (3), via a reaction between 8-aminoquinoline (8-aq) with HgX₂ (X = Cl, Br, I). They have been characterized by elemental analyses, IR, ¹H- and ¹³C-NMR spectroscopy and two of the compounds (X = Br and I) have been structurally determined by single crystal X-ray diffraction analysis. These studies revealed that compound 2 is mononuclear with the metal centre exhibiting a distorted tetragonal geometry while compound 3 is a one-dimensional coordination polymer where the bridging iodide ligands and the metal centres exhibit distorted tetragonal and octahedral geometries. The non-covalent interactions responsible for the crystalline network of 2 and 3 have been studied using theoretical methods by means of dispersion-corrected density functional theory (DFT-D) calculations. The binding energies associated with the different non-covalent interactions indicate hydrogen bonds, stacking and X⋯X interactions govern the network formation of complexes 2 and 3.