Synthesis, structural and spectroscopic characterization of zinc(ii) iodide complex with 2-[(4-iodophenyl)iminomethyl]pyridine in the solid state and solution

Abstract

The title compound [ZnI₂(L^4−I)] has been prepared using the Schiff base 2-[(4-iodophenyl)iminomethyl]pyridine (L^4−I) and ZnI₂, and crystallizes in the monoclinic space group P2₁/c (no. 14). Zinc binds two N atoms of the neutral bidentate L^4−I ligand and two iodide ions in a slightly distorted tetrahedral coordination geometry (τ₄ = 0.90). The molecular packing is mainly stabilized by intermolecular C–H⋯I hydrogen bonding and π⋯π stacking interactions. The crystal structure was determined by a scXRD measurement, and compared with the DFT-calculated molecular structure. Non-covalent intermolecular interactions were analyzed by Hirshfeld surface analysis. [ZnI₂(L^4−I)] was characterized by elemental analyses and spectroscopic techniques (UV-Vis, FTIR, and NMR). The structures of the zinc(II) complexes present in acetonitrile, dimethylsulfoxide, methanol, water, N,N′-dimethylpropyleneurea (DMPU), and dichloromethane have been studied by XAS methods. EAXFS measurements showed that the [ZnI₂(L^4−I)] complex remains in DMPU and dichloromethane solution, while the iodide ions at least partly dissociate in acetonitrile, methanol, and dimethylsulfoxide solution and completely in aqueous solution. The [ZnI₂(L^4−I)] complex, its chlorido analog, [ZnCl₂(L^4−I)], as well as the free L^4−I ligand, did not exhibit any relevant antibacterial activity against Gram-negative and Gram-positive bacterial strains.