Template Synthesis of Ni(II) and Zn(II) Complexes Derived from N2O2 Donor Symmetrical Tetradentate Ligands System: Comparative Antioxidant, Xanthine inhibitory, and Computational Studies

Ibrahim Waziri1*, Grema A. Mala1, Ibrahim M. Wakil1, Louis-Charl C. Coetzee2, Husseini Garba1

1Department of Pure and Applied Chemistry, University of Maiduguri, P,M.B. 1069, Maiduguri, Nigeria
2Department of Chemical Sciences, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa.

*Corresponding author: triumph2236@gmail.com, doi.org/10.55639/607.2737


Four mononuclear symmetric coordination compounds of Ni(II) and Zn(II) (C1–C4), obtained from N2O2 donor Schiff base ligand systems were synthesized in-situ and characterized with a variety of analytical and spectroscopic techniques such as elemental CHN-analysis, 1H-NMR, 13C{H}NMR, UV-Visible, Infrared, powder X-ray diffraction, scanning electron, and high-resolution mass spectroscopies. These analyses revealed that the ligands chelate the metal ions through the oxygen and nitrogen (N2O2) atoms of the phenolate and azomethine functional groups, resulting in distorted and perfect square planar geometry around Zn(II) and Ni(II) ions, respectively. The 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging and xanthine oxidase activity of the complexes were investigated using in vitro assay techniques. The studies revealed that the complexes possess moderate radical scavenging activity with no or very weak xanthine oxidase activity, in which the controls show better activity than the complexes in both assays. However, C3 and C1 demonstrated some level of activity at higher concentrations but not commensurate with the controls. The DFT calculation of the complexes using the M06- 2X/B3LYP-311G9d.p) level of the theory presented electronic properties that supported the experimental findings on the complexes.

Metal complexes,
Schiff bases,
In-situ synthesis,
Free radicals,
Xanthine oxidase