Synthesis, Structure, and Magnetic and Biological Properties of Copper(II) Complexes with 1,3,4-Thiadiazole Derivatives.

New coordination compounds of copper(II) with 2,5-bis(ethylthio)-1,3,4-thiadiazole (L 1 ) and 2,5-bis(pyridylmethylthio)-1,3,4-thiadiazole (L 2 ) with compositions Cu(L 1 ) 2 Br 2 , Cu(L 1 )(C 2 N 3 ) 2 , Cu(L 2 )Cl 2 , and Cu(L 2 )Br 2 were prepared. The complexes were identified and studied by CHN analysis, infrared (IR) spectroscopy, powder X-Ray diffraction (XRD), and static magnetic susceptibility. The crystal structures of Cu(II) complexes with L 1 were determined. The structures of the coordination core of complexes Cu(L 2 )Cl 2 and Cu(L 2 )Br 2 were determined by Extended X-ray absorption fine structure (EXAFS) spectroscopy. Magnetization measurements have revealed various magnetic states in the studied complexes, ranging from an almost ideal paramagnet in Cu(L 1 ) 2 Br 2 to alternating-exchange antiferromagnetic chains in Cu(L 1 )(C 2 N 3 ) 2 , where double dicyanamide bridges provide an unusually strong exchange interaction (J 1 /k B ≈ -23.5 K; J 2 /k B ≈ -20.2 K) between Cu(II) ions. The cytotoxic activity of copper(II) complexes with L 2 was estimated on the human cell lines of breast adenocarcinoma ( MCF-7 ) and hepatocellular carcinoma ( HepG2 ).