Nickel(II) and copper(II) complexes of 2,2'-bibenzo[d]thiazole: Synthesis, characterisation and biological studies

Benzothiazole moiety has gained a lot of attention because of its importance as essential pharmacophore in the development of metal based drugs. Nickel(II) and copper(II) complexes of a benzothiazole based ligand, 2,2'-bibenzo[d]thiazole (L-1), synthesized by the reaction of benzothiazole-2-carbonylchloride and o-aminothiophenol, is reported. The compounds were characterised by elemental and percentage metal analyses, spectroscopic (FTIR and UV-vis), H-1 and C-13 NMR, Mass spectra, thermal, magnetic moment and molar conductance analyses. The mass spectra, elemental and percentage metal composition of the metal complexes gave a 2:1 ligand to metal stoichiometric mole ratio. The spectral data showed that the ligand was coordinated to the metal ions through the nitrogen atoms of the benzothiazole moiety. The electronic spectra and magnetic susceptibility measurements showed that the nickel and copper complexes adopted square planar geometries. The ligand and its metal(II) complexes were screened against some drug resistant microbes and were found to exhibit varied degree of antimicrobial activities. The nickel complex was more active compared to ciprofloxacin against Staphylococcus aureus and Bacillus cereus. Similarly, the antioxidant potential of the ligand was evaluated. The ligand is a better ferrous ion chelating agent compared to 1,10-phenanthroline and 2,2-bipyridine. The ligand and its complexes exhibited good antimicrobial and Fe2+ chelating properties making them probable compounds of interest in antibiotic and antioxidant drug researches.