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 ).