The (E)-1-(2-oxo-2-(2-(quinolin-2-ylmethylene)hydrazinyl)ethyl)pyridin-1-ium chloride ligand, HLCl , was obtained from the condensation reaction of 2-quinolinecarboxaldehyde and Girard’s P reagent in ethanol. Reaction of the ligand HLCl with Zn(BF₄)₂·6H₂O and NH₄SCN in molar ratio 1 : 1 : 2 in methanol/acetonitrile/water mixture resulted in formation of the mononuclear thiocyanato Zn(II) complex with composition [ZnL(NCS)₂].

The [ZnL(NCS)₂] complex has distorted trigonal bipyramidal geometry, according to the X-ray, elemental analysis, NMR and IR spectroscopy. The tridentate hydrazone ligand is coordinated in deprotonated form to the Zn(II) with a NNO set of donor atoms, while the other two coordination sites are occupied by thiocyanate ligands.

The cytotoxic effects of the complex and its precusor ligand were examined against five human malignant cell lines: cervical adenocarcinoma HeLa, melanoma A375, breast adenocarcinoma MCF7, prostate adenocarcinoma PC-3, and lung carcinoma A549, as well as against normal human keratinocyte cell line HaCaT. Zn(II) complex showed moderate cytotoxic activity against HeLa, A375, and A549 malignant cells. This complex showed lower cytotoxicity against normal keratinocytes HaCaT when comparing its activity against these three malignant cell lines. The complex exerted lower cytotoxic effect on PC-3 cells, while the lowest cytotoxicity was observed against MCF7 cells. The complex exhibited higher cytotoxic effects on examined cell lines in comparison with its ligand HLCl, with the exception of the effect on MCF7 cells. Treatment of HeLa cells with 2IC₅₀ concentration of the complex induced increase in the percentage of cells within G2/M cell cycle phase when compared with control cells.