Four transition metal complexes with a semicarbazone ligand bearing pyrazine unit

Abstract Four new complexes based on L (where L = 3-ethyl-2-acetylpyrazine semicarbazone), namely [CoL 2 ]Cl 2 ·0.5H 2 O ( 1 ), [CoL 2 ](NO 3 ) 2 ( 2 ), [CdL(H 2 O) 2 (NO 3 )](NO 3 )·H 2 O ( 3 ) and [CuL(CH 3 OH)Cl 2 ]·[CuLCl 2 ] ( 4 ) have been synthesized and characterized by X-ray diffraction analyses. The results show that the semicarbazone acts as a tridentate neutral ligand in all complexes. Each of complex 1 and 2 reveals a distorted octahedral geometry around the metal ion provided by two units of the ligand, while the ratio of the ligand and metal is 1:1 in complexes 3 and 4 . The effect of complexes 1 – 4 on cell proliferation, apoptosis of human pancreatic cancer (Patu8988), human gastric cancer (SGC7901) and human hepatic cancer (SMMC7721) cell lines have been detected by MTT assay, Annexin V/PI double staining flow cytometry and TUNEL assay. The results show that complexes 1 – 4 can inhibit cell proliferation of Patu8988, SGC7901 and SMMC7721 cells, significantly higher than the effect of the ligand. However, the complex 4 reveals higher apoptosis rate, and displays up-regulated expression level of caspase 3, detected by western blotting, which also indicates the complex 4 can induce caspase-dependent cell apoptosis in SMMC7721.