Novel transition metal complexes of hydrazone with isonicotinoyl N-oxide and ortho vanillin moieties: Spectroscopic analysis, in vitro biological activity and in silico docking studies

The synthesized novel hydrazone consisting of isonicotinoyl and ortho-vanillin moieties is characterized and its interaction with metal ions is explored by equilibrium studies in 40 % dimethyl formamide-water medium. The properties of frontier molecular orbitals of title compound were evaluated through HyerChem7.5 software. These studies are informative in understanding chelation properties of title hydrazone and its modes of bonding with metal ions. Metal complexes of title hydrazone with cobalt, nickel, copper and zinc were synthesized and characterized by various spectro analytical tools, and further investigated for their biological activities. The infrared data provided evidential information to understand chelating properties of ligand and coordination sites in metal complexes. The electronic spectra of complexes indicated the symmetry-based spin allowed d-d transitions and charge transfer transitions. Mass spectral studies, elemental analyses and thermal studies enabled to establish the composition of the metal complexes. Scanning electron microscopy images and powder X-ray diffraction results specified distinct surface morphology and nanocrystalline nature of particles in each of the title compounds. Thermal studies in all metal complexes are informative to monitor loss of water molecules and decomposition of ligand moiety in distinct steps. The electron spin resonance studies are informative in ascertaining axial symmetry and covalency in the copper complex of present investigation. Based on the aforementioned studies and through evaluation of the results obtained, the complexes are assigned octahedral geometry with O − , O − and N donor sites of coordinated ligand and with three coordinated water molecules. The synthesized compounds were investigated for binding with calf-thymus deoxy ribonucleic acidby absorption and fluorescence emission titration procedure to envisage the binding interactions. The screening for antioxidant activity of all the systems was assessed with radical scavenging assay. Antibacterial and antifungal studies conducted with all title compounds were helpful to evaluate their relative potential activities. Further, the cytotoxic activity of synthesized compounds was done by using 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromideassay againsthumanbreast adenocarcinoma cancer cell lines and found that complexes acted as good anticancer agents. The molecular docking of title molecules carried out at the active site of cyclin-dependent kinase 2, applying Autodock software signified their potential binding. • The 3d series coordinated tridentate ligand shows strong chelation properties with O-, O-, and N donor sites, inferring tridentate dibasic nature interaction with metal ions. • Prepared Co(II), Ni(II), Cu(II) and Zn(II) complexes with O-, O-, and N donor ligand and characterized were found to exhibit octahedral geometry. • The outcome in ligation properties explored through HyperChem computational and equilibrium studies were fruitful for further biological applications. • Relative binding affinity of compounds with biomolecules and at the active site was examined to assess their potential for future applications. • pH metric titration results are helpful for studying interactions between metal ions and ligands in biological systems.