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 (L1) and 2,5-bis(pyridylmethylthio)-1,3,4-thiadiazole (L2) with compositions Cu(L1)2Br2, Cu(L1)(C2N3)2, Cu(L2)Cl2, and Cu(L2)Br2 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 L1 were determined. The structures of the coordination core of complexes Cu(L2)Cl2 and Cu(L2)Br2 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(L1)2Br2 to alternating-exchange antiferromagnetic chains in Cu(L1)(C2N3)2, where double dicyanamide bridges provide an unusually strong exchange interaction (J1/kB ≈ -23.5 K; J2/kB ≈ -20.2 K) between Cu(II) ions. The cytotoxic activity of copper(II) complexes with L2 was estimated on the human cell lines of breast adenocarcinoma (MCF-7) and hepatocellular carcinoma (HepG2).

Magnetic Properties of Novel Layered Disulfides CuCr0.99Ln0.01S2 (Ln = La Lu).

The comprehensive study of the lanthanide-doped solid solutions CuCr0.99Ln0.01S2 (Ln = La…Lu) magnetic properties was carried out using static magnetochemistry and differential scanning calorimetry techniques. It was shown that magnetic properties of CuCr0.99Ln0.01S2 are significantly affected by the magnetic properties of the lanthanide ion. The magnetic susceptibility and the effective magnetic moment were found to deviate from the Curie-Weiss law in the temperature 90 K below and 50 K above the order-disorder transition at 695 K. The observed behavior of the temperature dependence of the effective magnetic moment in the order-disorder transition temperature region was described as a result of copper atoms redistribution over different types of the crystallographic sites.

Crystal Structure and Predominant Defects in CdS Quantum Dots Fabricated by the Langmuir-Blodgett Method.

The crystal structure and shape of the CdS quantum dots (QDs) obtained by the Langmuir-Blodgett method were studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy (EXAFS), and ultraviolet spectroscopy. X-ray photoelectron spectroscopy (XPS) and stationary photoluminescence spectroscopy (PL) methods were used to determine the dominant surface defects. Initially synthesized QDs within the Langmuir-Blodgett film of fatty behenic acid have a cubic structure and oblate spheroid shape, while free-standing QDs obtained after the matrix evaporation have a wurtzite structure and sphere-like shape. QDs within the matrix demonstrate a wide PL band centered at 2.3 eV corresponding to defect-assisted radiative recombination; after the matrix annealing and passivation of the QD surface in an ammonia atmosphere, the PL spectrum demonstrates a high-intensity band-edge peak together with a low-intensity defect-assisted shoulder. It was established that sulfur (VS) vacancies are the dominating defects. A model of simultaneous band-edge and defect-assisted recombination through the VS level was proposed.

Insight into the thermal decomposition of ammonium hexahalogenoiridates(IV) and hexachloroiridate(III).

Thermal decomposition of (NH4)3[IrCl6]·H2O, (NH4)2[IrCl6] and (NH4)2[IrBr6] in reductive and inert atmospheres has been investigated in situ using quick-EXAFS and temperature-resolved powder X-ray diffraction. For the first time, (NH4)2[Ir(NH3)Cl5] and (NH4)2[Ir(NH3)Br5] have been proven as intermediates of thermal decomposition of (NH4)3[IrCl6]·H2O, (NH4)2[IrCl6] and (NH4)2[IrBr6]. Thermal degradation of (NH4)2[IrCl6] and (NH4)2[IrBr6] is a more complex process as suggested previously and includes simultaneous formation of (NH4)2[Ir(NH3)Cl5] and (NH4)2[Ir(NH3)Br5] intermediates mixed with metallic iridium. In the inert atmosphere, complexes (NH4)[Ir(NH3)2Cl4] and (NH4)[Ir(NH3)2Br4] as well as [Ir(NH3)3Br3] were proposed as possible intermediates before formation of metallic iridium particles.