•Preparation of Mn(II), Co(II), Pd(II) Zn(II) and Cd(II) complexes of salen ligand.•Theoretical studies for the isolated compounds were computed using DFT technique.•Fluorescence studies of Co(II) and Zn(II) complexes have been measured.•Cyclic voltammetric study of Cd(II)-complex has been estimated.•Biological activities of the compounds have been determined. 2,2′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidiene))bis(methanylylidene))diphenol (H2L) ligand and its Mn(II), Co(II), Pd(II) Zn(II) and Cd(II) chelates have been isolated and characterized by conventional and spectroscopic techniques including FTIR spectrum, 1HNMR , 13CNMR , powder X-ray diffraction PXRD, UV–visible, mass spectroscopy besides elemental analyses, and magnetic susceptibility measurements. The DMOL3 tool in the material studio package was also used to optimize the structures. The ligand behaves as binegative N2O2 tetradentate in Pd(II) and Zn(II) complex, neutral N2 bidentate in Mn(II), Co(II) and Cd(II)-complexes. Horowitz–Metzger and Coats–Redfern approaches were used to estimate the various kinetic and thermodynamic parameters. Zeta Potentials for the H2L ligand and its Pd(II), Cd(II) and Co(II) complexes in ethanol as a dispersive medium were measured. Ligand and its complexes were tested for their biological potency as anti-bacterial activity against gram (-) E. coli, P. aeruginosa, and gram (+) B. subtilis, S. aureus bacteria as well as antifungal activity against C. albicans. The antioxidant potentials of the isolated compounds were also screened by using DPPH scavenging methods. The isolated compounds were examined for cytotoxic activity using the MTT assay on MDA-MB-231 and HepG2 cell lines, and the results were verified using molecular docking simulations.