The X-ray crystal structures, molecular docking and biological activities of two novel Cu(II) and Zn(II) complexes with a ligand having a potentially N4O2 donor set and two nitro phenyl rings as pendant arms.

A new ligand (L) containing two nitro phenyl rings as side chains was synthesized. The reaction of this ligand with copper(II) and zinc(II) metal ions gave complexes with different coordination environments. The free ligand and the metal complexes were characterized using a number of spectroscopic methods. The crystal structure of [ZnLBr]ClO4 showed that the Zn(II) ion was in a distorted square pyramidal environment. The crystal structure of [CuL](ClO4)2 showed that the Cu(II) ion is in a tetragonally distorted octahedral environment. Molecular docking studies with DNA indicated that the binding of L, [ZnLBr]ClO4 and [CuL](ClO4)2 involved the major groove of DNA, H-bonds and Vander Waals interactions. In contrast, the molecular docking of L, [ZnLBr]ClO4 and [CuL](ClO4)2 with human glutathione reductase (GR) showed that the dominant interactions of these compounds with GR were H-bonding, vander Waals and hydrophobic interactions. The antioxidant activity of the synthesized complexes was analyzed by the free radical scavenging activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay with [CuL](ClO4)2 showing maximum activity. In addition, in vitro anticancer activity of the complexes against human breast MCF-7 cancer cell line was confirmed through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. All compounds showed a dose-dependent inhibitory effect on the growth of breast cancer cells with the inhibition activity of [CuL](ClO4)2 being more active than the other synthesized compounds. Furthermore, results from the antibacterial activity screening of the compounds against two Gram-positive and Gram-negative pathogenic bacteria by the micro-broth dilution and disk diffusion methods indicated that [CuL](ClO4)2 complex had the strongest antibacterial potential.