Anticancer, antimicrobial and photocatalytic activities of a new pyrazole containing thiosemicarbazone ligand and its Co(III) and Ni(II) complexes: synthesis, spectroscopic characterization and X-ray crystallography

A new pyrazole based thiosemicarbazone ligand, 5-methyl-3-formylpyrazole-N(4)-isopropylthiosemicarbazone, (HMP_zNHPrⁱ) (compound I), and its cobalt(III) and nickel(II) complexes, [Co(MP_zNHPrⁱ)₂]Cl (compound II) and [Ni(HMP_zNHPrⁱ)₂]Br₂ (compound III), respectively, have been synthesized and characterized through various physico-chemical and spectroscopic studies. Both the reported Co(III) and Ni(II) complexes are cationic in nature and behave as 1:1 and 1:2 electrolytes in MeOH, respectively. Electronic spectral features of the complexes have classified them as distorted octahedral ones. IR spectral data (4000–450 cm^{− 1}) have suggested a monoprotic tridentate (NNS) function of compound I coordinating to the Co(III) ion via the pyrazolyl (tertiary)
ring nitrogen, azomethine nitrogen and thiolato sulphur atom; while for compound III, compound I has been found to act as neutral NNS tridentate one, coordinating to Ni(II) via the pyrazolyl iminic nitrogen, azomethine nitrogen and thioketo sulphur. Structural features of all the compounds are confirmed by the single crystal X-ray data. All the compounds reported here have been found to exhibit significant photocatalytic activity towards degradation of Methylene Blue (MB) under UV radiation. Anticancer activity of all the three compounds against cancer cell lines (HeLa and A549) and a normal cell line (HEK293) have been investigated. Compound II has been found to be more efficient against the human cervical cancer cell (HeLa) and the lung cancer cell (A549) than compounds I and III. The ligand and both the complexes display potential activities against both grampositive (Bacillus subtilis MTCC 7193) and gram-negative bacteria (E. coli MTCC 1610).