Synthesis, structural characterization, DFT calculations, biological investigation, molecular docking and DNA binding of Co(II), Ni(II) and Cu(II) nanosized Schiff base complexes bearing pyrimidine moiety

Abstract

Three new NNO tridentate Schiff bases derived from 5-bromosalicylaldehyde with 2-amino-4,6-dimethylpyrimidine, 2-amino-4-methoxy-6-methylpyrimidine and 2-amino-4-chloro-6-methylpyrimidine (HL1, HL2 and HL3, respectively) and their complexes with Co(II), Ni(II) and Cu(II) have been prepared. These complexes were characterized by elemental analysis, 1H NMR, IR and electronic spectra, and with the aid of magnetic moment, molar conductivity and mass spectrometry. We further determined some of their size on the nanoscale. The results indicated that Schiff bases behaved as a tridentate NNO chelator that coordinates to the metal ions by azomethine nitrogen, pyrimidine nitrogen and phenolic oxygen, demonstrating 1 to 1 (metal to ligand) ratio. The measurements of conductivity revealed a nonelectrolytic nature of the complexes. Electronic absorption and viscosity were used to explore the ability of investigated complexes to bind to DNA, and the results indicated that binding occurred through intercalation. The antimicrobial activities of the considered complexes were evaluated against some types of fungi and bacteria. Metal complexes exhibited more antimicrobial activity as compared to their ligands. Interestingly, the CuL3 showed the highest antimicrobial activity. The anticancer activity of the chelators and their metal complexes were investigated on hepatic cellular and human colon carcinoma cells (HepG-2 cell line) and (HCT-116 cell line), respectively. The metal complexes have shown promising results in preclinical testing and they have enhanced anti-proliferative activity against growth of cancer cells compared to their ligand. Moreover, the docking study of the HL1, HL2, HL3 and their Co(II), Ni(II) and Cu(II) was reported. The theoretical DFT calculations were applied to verify the molecular geometry of chelators and their complexes. The geometry optimization results are in agreement with experimental observations.