Effects of changing ions on the crystal design, non-covalent interactions, antimicrobial activity, and molecular docking of Cu(II) complexes with a pyridoxal-hydrazone ligand.

The present work reports the influence of the presence of different ions (Cl - , Br - , NO 3 - , or SO 4 2- ) on the formation and proprieties of Cu(II) complexes with pyridoxal-benzoylhydrazone (PLBHZ). Four new complexes were successfully synthesized, [CuCl 2 (PLBHZ)] (1), [CuBr 2 (PLBHZ)] (2), [CuCl(PLBHZ)H 2 O]⋅NO 3 ⋅H 2 O (3), and [CuSO 4 (PLBHZ)H 2 O]⋅3H 2 O (4), and characterized by spectroscopic and physicochemical methods. A single-crystal X-ray study reveals the Schiff base coordinated to the metal center tridentate by the ONS -donor system, resulting in distorted square pyramidal coordination geometries. Noncovalent interactions were investigated by 3D Hirshfeld surface analysis by the d norm function, 2D fingerprint plots, and full interaction maps. The ion exchange is important in forming three-dimensional networks with π⋅⋅⋅π stacking interactions and intermolecular hydrogen bonds. The in vitro biological activity of the free ligand and metal complexes was evaluated against Gram-positive and Gram-negative bacterial strains and the free pyridoxal-hydrazone ligand showed higher activity than their Cu(II) complexes. Molecular docking was used to predict the inhibitory activity of the ligand and complexes against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria.