Synthesis, crystal structure, redox property, and cytotoxic activity of a dinuclear cobalt(II) complex bearing a tetradentate benzimidazole ligand

A tetradentate benzimidazole ligand cis,cis,cis,cis-2,2′,2″,2‴-(cyclopentane-1,2,3,4-tetrayl)tetrakis(1H-benzo[d]imidazole) (cttb) and its dinuclear cobalt(II) complex [Co2(cttb)Cl4]·2DMF·H2O have been synthesized and characterized by X-ray single-crystal structure analysis. In the complex, each central Co2+ is chelated by two nitrogen atoms of the ligand and bound to two chloride ions, forming a distorted tetrahedron arrangement. The complex showed a quasi-reversible redox property for the Co(III)/Co(II) couple and exhibited inhibition on the growth of Eca109 cancer cell with the IC50 value of 37.28 μM, which is lower than that of cisplatin.