Synthesis, characterization, catalytic, DNA binding and antibacterial activities of Co (II), Ni (II) and Cu (II) complexes with new Schiff base ligand

New Schiff base (E)-4-(3-cyano-4,6-dimethylpyridin-2-ylamino)-N′-(1-(2-hydroxyphenyl) ethylidene)benzohydrazide (HL) was synthesized by condensation of 2-hydroxyacetophenone with 4-(3-cyano-4,6-dimethylpyridin-2-ylamino) benzohydrazide. The ligand (HL) and its Co(II), Ni(II) and Cu(II) complexes (1–3) have been characterized by elemental analyses, 1H NMR, 13C NMR, IR, UV–Visible, magnetic measurements and X-ray diffraction analysis. The ligand (HL) acts as a monobasic tridentate ligand coordinating via the oxygen of the carbonyl group in the end form, the nitrogen atom of the azomethine (–C=N–) group and phenolic –OH group. The ligand and its complexes have been defined to have standardized bond lengths, bond angles and quantum chemical parameters. Absorption spectra and viscosity measurements have examined the calf thymus DNA binding behavior of the ligand and its complexes. The docking active site interactions were evaluated to predict the activity of HL against COVID-19 by binding with SARS-CoV-2 principal protease that recovered from the RCSB protein data bank with PDB (ID: 6Y84) and its anticancer activity with prostate cancer receptor 3qum. Evaluation results of synthesized complexes against the human cancer cell lines MCF-7 and HepG-2 were published in comparison with positive controls in the viability assay of vinblastine and colchicine. DPPH free radical-scavenging assays determine the in vitro antioxidant activity of all complexes. After that, gram-negative bacteria (Escherichia coli) and gram-positive bacteria (Staphylococcus aureus) are fungal (Candida albicans), were investigated for the anti-microbial activities of the compounds using the disc-diffusion process. Catechol oxidase and phenoxazinone synthase mimetic activity examinations displayed that the current Co(II) oxidase models efficiently catalyze the oxidative coupling of o-aminophenol (o-APH3) to the corresponding oxidation product o-amino-3H-phenoxazine-3-ones (APX).