Experimental and theoretical analysis of molecular structure, vibrational spectra and biological properties of the new Co(II), Ni(II) and Cu(II) Schiff base metal complexes

•Metal complexes have been synthesized and characterized.•Electronic analysis of the molecule was performed with the help of DFT calculations.•The biological activity of the synthesized compounds has been evaluated.•The molecular docking studies of synthesized complexes have been conducted. A new novel Cobalt, Nickel and Copper metal complexes were synthesized from Schiff base ligand of 2,2′-((1E,1′E)-((4-nitro-1,2-phenylene) bis(azanylylidene)) bis(methanylylidene)) diphenol. The structures of all the synthesised compounds have been analysed using Fourier-Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR) spectroscopy, Ultraviolet-Visible (UV-Vis) spectrum, elemental analysis and Powder X-ray diffraction (PXRD). The experimental spectral frequencies of ligand and metal complexes are correlated with theoretically computed vibrational frequencies. The molecular structure of the ligand and its metal complexes has been optimized using B3LYP-6-311G(d,p)/LANL2DZ basis set and their parameters have been discussed. Natural bond orbital and Frontier Molecular Orbital analysis have assessed the presence of a metal-ligand bond in complexes. Further, biological activity studies such as antioxidant, anti-inflammatory, antidiabetic have also been analyzed using various methods. In addition, molecular docking studies have also been performed on all complexes using the α-amylase enzyme structure to calculate the possible binding energy of inhibitors. [Display omitted]