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<p>Three new mononuclear Co(II), Ni(II), and Cu(II) complexes of nicotinamide (NA) and 2,2′-bipyridine (bipy) with the general formula [M(NA)(bipy)(H<sub>2</sub>O)<sub>3</sub>]Cl<sub>2</sub>·nH<sub>2</sub>O were synthesized in a 1:1:1 molar ratio (M: NA: bipy). Chelates were completely studied utilizing UV-Vis, <sup>1</sup>H NMR, FT-IR, TGA, conductivity and magnetic studies. The results of experiments indicate the whole complexes were mononuclear. The divalent metals chelated through one nicotinamide ligand nitrogen atom, two 2,2’-bipyridine nitrogen atoms and three water molecular oxygen atoms. The results of magnetic moment and ultraviolet-visible measurements indicated octahedral architecture in all chelates. Thermogravimetric studies showed high thermal stability with activation energies of 105.15–234.54&#xa0;kJ mol⁻¹ (Coats–Redfern method). DFT calculations at the B3LYP/CEP-31G level revealed octahedral coordination involving N1 and N4 of bipy and N5 of NA, with HOMO–LUMO energy gaps ranging from 0.066 to 0.186&#xa0;eV. The Ni(II) complex exhibited the highest dipole moment (8.254 D), indicating strong charge delocalization. Antimicrobial assays showed significant improvement compared to free ligands. The Ni(II) complex displayed inhibition zones up to 22&#xa0;mm against <i>Bacillus subtilis</i> and 13&#xa0;mm against <i>Candida albicans</i>, with activity indices exceeding 130%. Molecular docking studies against β-lactamase (PDB ID: 6NVU) confirmed strong binding affinities, particularly for Ni(II)-NA-bipy (binding energy = − 6.46&#xa0;kcal mol⁻¹, RMSD = 1.35 Å), supporting the enhanced biological activity observed experimentally. These findings suggest that Ni(II)-NA-bipy is a promising candidate for antimicrobial drug development.</p>

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Synthesis, Spectroscopic Characterization, DFT Analysis, and Molecular Docking Studies of Co(II), Ni(II), and Cu(II) Nicotinamide–Bipyridine Complexes with Antimicrobial Activity

  • 期刊论文

  • 发表日期：

    2026年3月21日

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  • Walaa H. El-Shwiniy,
  • Reham M. Saeed,
  • Wael A. Zordok,
  • M. G. Abd Elwahed,
  • Leila M. Abbass

摘要

Three new mononuclear Co(II), Ni(II), and Cu(II) complexes of nicotinamide (NA) and 2,2′-bipyridine (bipy) with the general formula [M(NA)(bipy)(H2O)3]Cl2·nH2O were synthesized in a 1:1:1 molar ratio (M: NA: bipy). Chelates were completely studied utilizing UV-Vis, 1H NMR, FT-IR, TGA, conductivity and magnetic studies. The results of experiments indicate the whole complexes were mononuclear. The divalent metals chelated through one nicotinamide ligand nitrogen atom, two 2,2’-bipyridine nitrogen atoms and three water molecular oxygen atoms. The results of magnetic moment and ultraviolet-visible measurements indicated octahedral architecture in all chelates. Thermogravimetric studies showed high thermal stability with activation energies of 105.15–234.54 kJ mol⁻¹ (Coats–Redfern method). DFT calculations at the B3LYP/CEP-31G level revealed octahedral coordination involving N1 and N4 of bipy and N5 of NA, with HOMO–LUMO energy gaps ranging from 0.066 to 0.186 eV. The Ni(II) complex exhibited the highest dipole moment (8.254 D), indicating strong charge delocalization. Antimicrobial assays showed significant improvement compared to free ligands. The Ni(II) complex displayed inhibition zones up to 22 mm against Bacillus subtilis and 13 mm against Candida albicans, with activity indices exceeding 130%. Molecular docking studies against β-lactamase (PDB ID: 6NVU) confirmed strong binding affinities, particularly for Ni(II)-NA-bipy (binding energy = − 6.46 kcal mol⁻¹, RMSD = 1.35 Å), supporting the enhanced biological activity observed experimentally. These findings suggest that Ni(II)-NA-bipy is a promising candidate for antimicrobial drug development.