Mixed ligand Ni(II) complexes containing 2-chloroquinoline-3-carboxaldehyde-4(N)-substituted thiosemicarbazones and 2,2′-bipyridine: Synthesis, spectral characterization and in-vitro cytotoxicity

Ni(II) complexes (NiL1-NiL4) of 2-chloroquinoline-3-carboxaldehyde-4(N)-substituted thiosemicarbazones and 2,2′-bipyridine ligands were prepared and characterized by various spectroscopic techniques such as Fourier Transform Infrared (FT-IR), Ultraviolet–visible (UV–vis), ¹H NMR and mass spectroscopy. The binding of the ligands to the nickel ion was through their azomethine nitrogen and thiolate sulfur atoms. The redox properties of the complexes were analyzed by cyclic voltammetry. The binding affinity of the complexes with CT-DNA (Calf Thymus DNA) and BSA (Bovine Serum Albumin) was studied using absorption and emission methods. The complex NiL3 exhibited better binding activity with high binding constant value with both DNA and BSA. Antiproliferative ability of the Ni(II) complexes (NiL1-NiL4) was explored against human cervical cancer cells HeLa and human normal embryonic kidney cells HEK. The morphological changes induced by the Ni(II) complexes on HeLa cells were analyzed by AO-EB and DAPI staining assays. The results obtained from the cytotoxicity studies showed the better cytotoxicity of the complex NiL3 towards inhibiting the growth of HeLa cells, whereas non toxic nature of the complexes was proved with HEK cells.