Zinc(II) and mercury(II) iodide complexes containing 2-pyridinealdoxime compound: synthesis, characterization, crystal structure determination and DFT study

Two novel mononuclear complexes of [Zn(paoH)2(pao)]2[ZnI4] (1) (paoH is 2-pyridinealdoxime or pyridine-2-aldoxime and pao is 2-pyridinealdoximato) and [Hg(paoH)I2] (2) were prepared from the reactions of ZnI2 and HgI2 salts with 2-pyridinealdoxime ligand, respectively, in methanol. The empirical formulae of these complexes were established by elemental analyses (CHNO). Subsequently, these complexes were characterized by 1H NMR, 13C{1H}NMR, IR and UV–Vis spectroscopic techniques. Moreover, the crystal structures of these complexes were characterized using single-crystal X-ray diffraction. The X-ray crystallographic analyses reveals that the structure of 1 consists of two [Zn(paoH)2(pao)]+ cationic parts and one [ZnI4]2− anionic part. In the cationic parts, the Zn(II) cation has a distorted octahedral coordination environment by six nitrogen atoms from two 2-pyridinealdoxime and one 2-pyridinealdoximato ligands, and in the anionic part, the Zn(II) cation has a distorted tetrahedral coordination environment with four iodide anions. Also, in complex 2, the Hg(II) cation has a distorted tetrahedral coordination environment by two nitrogen atoms from two 2-pyridinealdoxime ligands and two iodide anions. Furthermore, the crystal packing diagram of both complexes is stabilized by intermolecular π···π interactions (in 1 and 2) and intermolecular O–H···O (in 1 and 2), C–H···O (in 1) and O–H···I (in 2) hydrogen bonds. The density functional theory calculations are carried out for the evaluation of the studied structures. The TD-DFT calculations, NBO analysis, complex stability by binding energy and Wiberg bond indices analysis for complexes have been performed by DFT calculations.