Cytotoxicity towards human alimentary system carcinoma cells resulting from diverse copper(II) complexes

To investigate the potential cytotoxicity of copper(II)-based complexes, three coordination compounds with heterocyclic ligands, Cu(pbmbt)Cl₂(CH₃OH) (1), Cu₂(ddbib)₂(NO₃)₄·3CH₃OH (2), and Cu₃(ttmtmb)₂Cl₆·2.5H₂O (3), which include mononuclear, dinuclear, and trinuclear structures, have been synthesized from reactions of corresponding copper(II) salts with 1-((2-pyrazinyl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole (pbmbt), 2-(2,3-dihydropyrazin-2-yl)-1-((4-((2-(2,3-dihydropyrazin-2-yl)-1H-benzod]imidazol-1-yl)methyl)phenyl)methyl)-1H-benzod]imidazole (ddbib), and 1,1′,1′′-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)tris(2-methyl-1H-benzoimidazole) (ttmtmb), respectively. IC₅₀ values revealed that 2 and 3 show strong cytotoxicity, whereas 1 is weakly cytotoxic after being tested against a panel of several human alimentary system carcinoma cell lines (SGC7901, EC109, SMMC7721, and HT29). The number of copper centers and different structures could make a tremendous difference on their cytotoxicity.