Syntheses, structures and cytotoxicity of cobalt(II) complexes with 4′-chloro-2,2′:6′,2″-terpyridine

•Three CoII complexes of 4′-Cltpy was synthesized and structurally characterized.•Different X-ray crystal structures were revealed for three complexes.•In vitro cytotoxicity of these complexes along a CuII analogue was studied.•Distinct cytotoxicity against two human cancer cells was observed.

Three cobalt(II) complexes based on 4′-chloro-2,2′:6′,2″-terpyridine (4′-Cltpy) have been synthesized and structurally characterized by X-ray crystallography. The reaction with a 1:1 metal-to-ligand ratio in a mixed CH2Cl2–MeOH solvent afforded the mononuclear complex Co(4′-Cltpy)Cl2 (1) that mimicks the previously reported Cu(4′-Cltpy)Cl2, while altering the metal-to-ligand ratio to 2:1 under the same reaction conditions resulted in the formation of a different complex with a component of [Co(4′-Cltpy)Cl2][Co2(4′-Cltpy)2Cl4] (2), based on single crystal X-ray structural analysis. The presence of both a mononuclear molecule Co(4′-Cltpy)Cl2 and dinuclear Cl-bridging Co2(4′-Cltpy)2Cl4 in 2 was revealed. The replacement of CoCl2 with Co(SCN)2 under the same reaction conditions as for 1 gave a similar mononuclear Co(4′-Cltpy)(SCN)2 (3). The cobalt(II) complexes along with the known copper analogue 4 were investigated for their in vitro cytotoxic activity towards two human cancer cell lines, the human breast cancer (MCF-7) and leukemia (K562) cells, and distinct cytotoxicity was observed.

Graphical abstractThree diverse cobalt(II) complexes based on 4′-chloro-2,2′:6′,2″-terpyridine have been synthesized and structurally characterized, and their in vitro cytotoxic activity against human breast cancer (MCF-7) and leukemia (K562) cells were investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide