Synthesis, crystal structures and anticancer studies of Ni (Ⅱ), Co (Ⅲ) and Zn (Ⅱ) complexes based on 5-bromosalicylaldehyde- 2-(2-aminophenyl)benzimidazole Schiff base

Three metal complexes [Ni 2 (HL) 2 (C 2 H 5 OH) 2 Cl 2 ]·2C 2 H 5 OH (complex 1), [Co (HL) (L)] (complex 2) and [Zn 2 (HL) 2 (CH 3 COO) 2 ] (complex 3) derived from 5-bromosalicylaldehyde-2-(2-aminophenyl)benzimidazole Schiff base ligand (H 2 L) were synthesized and characterized by infrared (IR) spectroscopy, thermogravimetric (TG) analysis and powder X-ray diffraction (XRD). Single crystal X-ray diffraction analysis confirmed that complex 1 crystallized in binuclear octahedral structure with space group P2 1 /C and complex 2 displayed in mononuclear octahedral structure with space group P 121/c 1. While complex 3 produced binuclear pyramid structure with space group P 121/c 1. Herein, cobalt (Ⅱ) salt was oxidized to form Schiff base cobalt (Ⅲ) complex by coordinating three deprotonated groups. The MTT method was employed to determine the three complexes in vitro cytotoxicity effects against human lung cancer cells (A-549), liver cancer cells (SMMC-7721), breast cancer cells (MDA-MB-231) and nasopharyngeal carcinoma cells (CNE-2Z). The results showed that Co (Ⅲ) complex has significant anticancer activity against human breast cancer MDA-MB-231 cells compared with cisplatin. The further study of its anticancer mechanisms exhibited that Co (Ⅲ) complex could inhibit MDA-MB-231 cells proliferation through both apoptosis and DNA replication inhibition.