Solvent-driven structural topologies in phenanthroline-based co-crystals of Zn(ii) involving fascinating infinite chair-like {[(bzH)4Cl2]2−}n assemblies and unconventional layered infinite {bz-H2O-Cl}n anion-water clusters: antiproliferative evaluation and theoretical studies

Abstract

Two new co-crystals of Zn(II), viz. [Zn(phen)₃](bz)(Cl)·8H₂O (1) and [Zn(phen)₂(bz)](Cl)(2bzH) (2) (phen = 1,10-phenanthroline, bz = benzoate, bzH = benzoic acid), have been synthesized and characterized using the single crystal X-ray diffraction technique (SCXRD), elemental analysis, vibrational and electronic spectroscopy, and thermogravimetric analysis (TGA). Switching the solvent from water to methanol results in changes in the structural topologies in the compounds; compound 1 crystallizes as a co-crystal hydrate, while compound 2 as a co-crystal of Zn(II). Crystal structure analysis of compound 1 reveals the formation of fascinating infinite {bz-H₂O-Cl}_n anion-water clusters involving the lattice water molecules, bz and chloride anions. Enclathrated bz moieties in the tetrameric supramolecular host cavities of the complex cationic moieties of the co-crystal hydrate provide additional reinforcement to the crystal structure. Uncoordinated bzH and Cl anions of compound 2 are aggregated via non-covalent interactions to form fascinating infinite supramolecular chair-like architectures. Antiparallel π-stacking interactions observed in the compounds have been studied theoretically using DFT calculations and NCI plot computational tools. The compounds have been further investigated for antiproliferative activities considering cell cytotoxicity and apoptosis assays against Dalton's lymphoma (DL) cancer cell lines and the results were compared with cisplatin (reference drug) in the same experimental conditions. The compounds significantly induce cytotoxicity in DL cancer cells with nominal cytotoxicity in normal PBMC cells. To support the observed wet lab cytotoxicity in DL cancer cells, molecular docking simulations have been performed with the antiapoptotic proteins, which reveal strong binding affinities of the compounds with the active sites of the target proteins.