Synthesis and X-ray crystal structures of two different zinc (II) complexes of N,N?-cyclohexane-1,2-diylidene-bis(4-fluorobenzoylhydrazide) based on zinc salt effect

Abstract

Reaction of zinc chloride or zinc nitrate hexahydrate with N,N?-cyclohexane-1,2-diylidene-bis(4-fluorobenzoylhydrazide) (L) in acetonitrile and under ambient conditions, produced two different zinc(II) complexes 1 and 2 respectively, with different coordination modes and geometrical shapes. A neutral four-coordinate complex with typical tetrahedral geometry was obtained for 1, in which, the zinc atom is sited outside the bis aroyl hydrazone core. While, a cationic eight-coordinate complex with distorted dodecahedral geometry was confirmed for 2, in which, the zinc atom is surrounded by four oxygen and four nitrogen donors from two N,N?-cyclohexane-1,2-diylidene-bis(4-fluorobenzoylhydrazide) molecules. The prepared compounds were identified and their chemical structures determined using various techniques: Nuclear magnetic resonance (NMR), Infrared (IR) and Ultraviolet–visible (UV–Vis) spectroscopy, in addition to single-crystal X-ray crystallography, X-ray powder diffraction (XRD), elemental analysis, atomic absorption and molar conductivity measurements. Furthermore, the in vitro biological activity of L, 1 and 2 was studied against some selected bacterial strains: Bacillus subtilis and Staphylococcus aureus as gram positive bacteria, and Escherichia coli and Salmonella typhimurium as gram negative bacteria. The study revealed that the prepared compound have shown a differentiated biological activity against these bacteria depending on their structural features and lipophilic nature. © 2020 Elsevier B.V.