Catalytic and anticancer activity of two new Ni(II) complexes with a pyrazole based heterocyclic Schiff-base ligand: synthesis, spectroscopy and x-ray crystallography

A new pyrazole containing ‘NN’ bidentate Schiff-base ligand, N-(furan-2-ylmethyl)-1-(5-methyl-1H-pyrazol-3-yl)methanimine, (MPAFA) (compound I) and its two new Ni(II) complexes, [Ni(MPAFA)₂(H₂O)₂].2Cl.2H₂O (compound II) and [Ni(MPAFA)₃].2ClO₄ (compound III) have been synthesized and characterized by various physico-chemical and spectral parameters viz., elemental analyses, mass, IR, NMR (¹H and ¹³C, ligand only), UV-Vis spectral parameters and X-ray crystallographic studies. Both the complexes are behaving as 1:2 electrolytic species and the primary ligand, MPAFA, acts as a neutral ‘NN’ bidentate one in both the complexes. IR spectral data revealed that the coordination to each of the metal centre in both II and III, takes place through the pyrazolyl (tertiary) ring nitrogen and the azomethine nitrogen atom. X-ray data have revealed that both II and III are octahedral in nature and confirmed a NiN₄O₂ and NiN₆ octahedral coordination, respectively. Ni(II) ion has formed two sets of complexes; in II, two molecules of ligand and two water molecules are coordinated to the metal forming a mixed ligand complex (1:2 complex), while in III, three ligand molecules are coordinated to the metal (1:3 complex). The ligand and the Ni(II) complexes reported here have been tested for their catalytic and anticancer activities. II and III have been found to be efficient in reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of sodium borohydride (NaBH₄) as a reducing agent; and are more potent cytotoxic agents and stronger anti-cancer materials against the breast cancer cell lines MCF7 and MDA-MB-231 than the primary ligand system.