Nickel(II) complexes of thiosemicarbazones: synthesis,characterization, X-ray crystallographic studies and in vitro antitubercular and antimicrobial studies

Three nickel(II) thiosemicarbazone complexes have been synthesized and characterized by spectroscopic and physicochemical techniques. The molecular structures of two of the complexes have been determined by single-crystal X-ray diffraction studies. In both of these complexes, the nickel center is coordinated by two tridentate ligands in a meridional fashion using C=S, C=N and neutral hydroxyl OH donors. The ligand is bound to nickel in its thione form in all three complexes. The synthesized compounds were tested for antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi. Additionally, all the compounds were screened for antituberculosis activity. Several complex/organism combinations returned an MIC value of 0.8 μg/mL or better, which is almost 8 times more active than the standard (streptomycin, 6.25 μg/mL).