A binuclear zinc(II) Schiff base complex: Crystal structure characterization, antitumor activity and cell apoptosis induction in BEL-7404 tumor cells

The Schiff base ligand, 4-chloro-2-(quinolin-8-yliminomethyl)-phenol (HClQP), reacts with ZnCl2.4H2O to afford a binuclear zinc(II) complex (1), which has been synthesized and characterized by IR, ESI-MS, elemental analysis and single crystal X-ray diffraction analysis. In complex (1), the two zinc atoms are in a five-coordinated tetragonal pyramidal geometry and a four-coordinated tetrahedral geometry, respectively. The in vitro cytotoxicities of complex (1) against four human tumor cell lines and the HL-7702 normal liver cell line have been screened and evaluated by MTT assay, in comparison with HClQP and cisplatin. The IC50 values of complex (1) is in the range of 7.51–15.66 μM against these tumor cell lines, in which the MCF-7 and BEL-7404 cells showed the highest sensitivity to complex (1). The HL-7702 cell line was neither sensitive to complex (1) nor to HClQP and cisplatin. This suggests the potent cytotoxic selectivity of complex (1) on the tumor cell lines. The cell apoptosis induction of complex (1) visualized by fluorescence microscopy shows evident apoptosis in BEL-7404 tumor cells induced by complex (1). In view of these results, the central zinc(II) of complex (1) is expected to play a key role to exert the cell apoptosis induction in BEL-7404 cells, which may explain the significant antitumor activity of complex (1).