Azo-imine based Nickel(II), Copper(II), and Zinc(II) complexes: Synthesis, physicochemical and spectral investigations, quantum chemical calculations, molecular docking studies, and antibacterial investigations

Abstract

Three new complexes of Nickel(II), Copper(II), and Zinc(II) derived from Azo-imine ligand, namely, 2-((E)-(2-(1H-indol-3-yl) ethylimino) methyl)-4-((E)-(2-nitrophenyl) diazenyl) phenol (L), were prepared with the stoichiometric ratio of 1: 2 as metal: ligand. These structures were examined by CHN, FT-IR, 1HNMR, and UV–Vis spectroscopy, powder XRD, thermal analysis, and molar conductivity measurement. Based on the experimental findings, complexation with ligands occurs through the N imino and O phenolic atoms. In infrared spectra of complexes, two weak and new bands were formed at 583–598 cm−1 and 449–520 cm−1, which correspond to ν (M-O) and ν (M-N), respectively. The amorphous nature of [Zn(L)2] and the nanocrystalline nature of [Ni(L)2], and [Cu(L)2] were revealed. Also, the quantum chemical calculations were accomplished via DFT approach. The nature of the metal–ligand bonds was checked by NBO and EDA analysis, and it was found that the nature of L → M bonding is mainly covalent. Molecular docking simulations predict significant antitumor properties for the three complexes. Eventually, the antibacterial activity was investigated against two Gram-positive and two Gram-negative bacteria.