Study of Synthesis, Characterization, DFT, and In Vitro Biological Activity of Cu(II), Co(II), and Fe(II) Metal Complexes Based on Heterocyclic Azo Pyrazole Dye Ligand

A new azo dye ligand was synthesized by coupling 5-amino-3-methyl-1-phenylpyrazole with a diazonium ion of 2-amino-1-naphthalene sulfonic acid. Its Co(II), Fe(II), and Cu(II) complexes were also synthesized. This ligand and its complexes were characterized based on elemental analysis, IR, 1H NMR, UV-vis spectra, and thermogravimetric analysis. The data showed that the proposed complexes have an octahedral geometry around the central metal ion. The nonelectrolytic nature of the complexes was confirmed by molar conductance measurement. X-ray powder diffraction indicates that Co(II) and Fe(II) complexes are amorphous in nature, whereas the Cu(II) complex has crystalline and amorphous phases. The bond strength and molecular stability between the interaction of metal ions and the ligand were investigated by density functional theory (DFT). The in vitro antibacterial activity of the ligand and complexes was tested against two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Neisseria gonorrhoeae) and a fungus (Candida albicans). The Cu(II) complex exhibited a high antimicrobial effect against all tested microorganisms. The DNA fragmentation percentage and cytotoxic activity against human liver cancer cells (HepG2) were evaluated. All tested compounds showed potential anticancer activity, and the Co(II) complex showed better activity results than the other tested compounds, with IC50 = 19.55 μg/mL.