Effect of metal complex formation on the antibacterial activity of nitazoxanide: Spectroscopic and density functional theory calculations

In the present work, experimental and theoretical structural studies of two new nitazoxanide (NTZ) complexes, [Co(NTZ)(NO₃)₂(OH₂)] (1) and [Ni(NTZ)(CH₃COO)(OH₂)]·CH₃COO (2) were reported. The susceptibility of Staphylococcus aureus and Escherichia coli towards NTZ and its complexes was assessed. NTZ behaves as a monodentate ligand via the thiazole N atom forming distorted octahedral and tetrahedral complexes with Co(II) and Ni(II) ions, respectively. The d-d transitions were assigned by the aid of time-dependent density functional theory calculations. The magnetic susceptibility value of 1 remains unchanged in the temperature range of 298–77K, while that of 2 decreases linearly with the temperature to attain 2.79 μ_B at 77K. Coordination of NTZ (0.084 μmol ml⁻¹) to Co(II) (1) (0.028 μmol ml⁻¹) and Ni(II) ions (2) (0.079 μmol ml⁻¹) leads to an improvement in the toxicity against S. aureus.