Synthesis, crystal structures, and anticancer studies of Ni(II), Co(III), and Zn(II) complexes derived from chlorinated-2-(2-aminophenyl)-1H-benzimidazole Schiff base

Three chlorinated metal complexes [Ni2(HL)2(C2H5OH)2Cl2]·2C2H5OH (complex 1), [Co(HL)(L)] (complex 2), and [Zn2(HL)2(CH3COO)2] (complex 3) derived from 5-chlorosalicylaldehyde and 2-(2-aminophenyl)-1H-benzimidazole Schiff base ligand (H2L). The crystal structures of the three complexes were characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, X-ray single-crystal diffraction, and UV-visible absorption spectrum. The in vitro cytotoxicity of chlorinated ligand and its metal complexes were evaluated on four different tumor cell lines (A-549 lung cancer, SMMC-7721 liver cancer, MDA-MB-231 breast cancer, and CNE-2Z nasopharyngeal carcinoma), and normal ovarian epithelial cell (IOSE 80) was determined by MTT assay. The results indicated that chloro-benzimidazole Schiff base Co (III) complex (complex 2) displayed higher cytotoxicity against MDA-MB-231 cell line than cisplatin, while the cytotoxicity on IOSE 80 was lower than that of cisplatin. The results of further study of MDA-MB-231 cells by complex 2 showed that complex 2 could inhibit MDA-MB-231 cells in the G0/G1 phase, inhibit cell proliferation and migration, promote cell apoptosis, and increase intracellular ROS level. The Western blot analysis demonstrated that complex 2 could increase Bax protein expression and decrease Bcl-2 protein expression in MDA-MB-231 cells.