Cytotoxicity of copper(II)-complexes with some S-alkyl derivatives of thiosalicylic acid. Crystal structure of the binuclear copper(II)-complex with S-ethyl derivative of thiosalicylic acid

The spectroscopically predicted structure of the obtained copper(II)-complex with S-ethyl derivative of thiosalicylic acid was confirmed by X-ray structural study and compared to previously reported crystal structure of the Cu complex with S-methyl derivative. Single crystals suitable for X-ray measurements were obtained by slow crystallization from a water solution. Cytotoxic effects of S-alkyl (R = benzyl (L1), methyl (L2), ethyl (L3), propyl (L4) and butyl (L5)) derivatives of thiosalicylic acid and the corresponding binuclear copper(II)-complexes on murine colon carcinoma cell lines, CT26 and CT26.CL25 and human colon carcinoma cell line HCT-116 were reported here. The analysis of cancer cell viability showed that all the tested complexes had low cytotoxic effect on murine colon carcinoma cell lines, but several times higher cytotoxicity on normal human colon carcinoma cells. Copper(II)-complexes were obtained by the direct reaction of copper(II)-nitrate with the S-alkyl derivatives of thiosalicylic acid (alkyl = benzyl (L1), methyl (L2), ethyl (L3), propyl (L4), butyl (L5)). The spectroscopically predicted structure of the obtained copper(II)-complex with S-ethyl derivative of thiosalicylic acid was confirmed by X-ray analysis. The crystal structure is built out of centrosymmetric, dinuclear complex molecules where the pairs of Cu(II) are bridged by four S-ethyl-thiosalicylate ligands forming the paddle-wheel type structure. In the crystal packing the molecules are connected into a chain by two pairs of the O1w−H … O1 hydrogen bonds which involve axially coordinated water molecule as a donor and two carbonyl oxygen atoms as acceptors. The analysis of cancer cell viability showed that all the tested complexes had low cytotoxic effect on murine colon carcinoma cell lines, but several times higher cytotoxicity on normal human colon carcinoma cells. [Display omitted] •Crystal structure of [Cu2(S-et-thiosal)4(H2O)2].•In vitro cytotoxic effects of copper(II)-complexes were determined by MTT test.•Apoptotic assay of cisplatin, copper(II)-complexes and ligand.