Two new cobalt (II) and copper (II) complexes with Azo-azomethine ligand: Synthesis, antioxidant and antibacterial activities, thermal investigations, DFT calculations, and molecular docking studies

Abstract

Two new cobalt (II) and copper (II) complexes were synthesized by the condensation of azo-Schiff base ligand derived from (E)-5-((2, 4-dichlorophenyl) diazenyl)-2-hydroxybenzaldehyde and p-toluidine with metal ions (Cu (II) and Co (II)). The complexes CuL and CoL were characterized by UV–Vis, infrared, elemental analysis, fluorescence, mass spectra and thermal analysis (TGA). In the electronic absorption spectra of the cobalt (II) complex, the absorption bands appeared at 470 and 540 nm assignable to d→d transitions. Moreover, the copper (II) complex has two bands at 370, and 400 nm assigned to LMCT transitions.The cobalt and copper complexes showed an emission band at 360 nm upon excited with 258 nm radiation at ambient temperature. The ESI-mass spectra ofthe investigated complexes confirmed the stoichiometric ratio of 2: 1 (L: M) type.Antioxidant activity studies of the investigated compounds showed a remarkable biological activity against DPPH.The ligand and its cobalt and copper complexes were screened against the Staphylococcus aureus (gram-positive bacteria) and Escherichia coli (gram-negative bacteria), by disc diffusion method. Besides the experimental investigations, DFT calculations were accomplished to achieve the optimized three-dimensional structures and energies of frontier molecular orbitals. Also, the details of binding information of the synthesized metal complexes to the active site of HAS was extracted using molecular docking calculations, and showed these complexes are embedded into the IIA subdomain of the HSA protein.