Pyridine-derived Schiff base copper (II), zinc (II), and cadmium (II) complexes: Synthesis, structural properties, biological evaluation, and docking studies

Herein, Cu (II), Zn (II), and Cd (II) complexes, [DEP(M)X₂], encompassing the pyridine-derived Schiff-base ligand DEP, where DEP is (E)-N,N-diethyl-2-([pyridine-2-ylmethylene]amino)ethane-1-amine, are synthesized. X-ray diffraction studies reveal distorted square pyramidal geometries for the Cd (II) and Cu (II) complexes, whereas the geometry of [DEP (Zn)Cl₂] can best be described as trigonal bipyramidal. The antibacterial potential of DEP and its [DEP(M)X₂] complexes were evaluated against four bacterial strains: Salmonella typhi, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa; five fungal strains: Candida glabrata, Candida albicans, Microsporum canis, Fusarium solani, and Aspergillus flavus; and Leishmania major protozoan. Complexes exhibited superior bactericidal, fungicidal, and leishmanicidal inhibition potential against all tested microbes compared with the free ligand. The preliminary cytotoxic activity of [DEP(M)X₂] complexes on breast and colon carcinoma cells, that is, MCF-7cell line and HCT-116 cell line, respectively, revealed that studied complexes showed high cytotoxicity compared with ligand (DEP). Among the studied complexes, [DEP (Cd)Br₂] exhibited an excellent inhibitory profile, as confirmed by the docking study. The molecular docking studies showed a good correlation between the biological activities of synthesized metal complexes and docking studies. We have confidence in the contribution of these complexes toward the design of new metal-derived candidates that can treat infectious diseases.