Syntheses,characterization, and luminescence of two lanthanide complexes [Ln2（acetate）6（HeO）4]·4H2O （Ln=Tb（1）, Sm（2））

Two dinuclear compounds [Ln2（acetate）6（H2O）4]-4H2O （Ln=Tb（1）, Sm（2）） were obtained by the hydrothermal reaction of Ln2O3 with malonic acid at 150 ℃. Both compounds were characterized by elemental analyses, infrared spectra, and single crystal X-ray diffraction. The results showed that complexes 1 and 2 were isomorphous and crystallize in triclinic space group P 1. The coordination geometry around Ln（Ⅲ） ions in the complexes 1 and 2 was a distorted tricapped trigonal prism with a nine coordination. In the crystal, the molecular organization was further stabilized by well-defined weak hydrogen bonding interactions between the neutral dinuclear molecular units that led to the formation of a three-dimensional network. The fluorescence properties of the two complexes 1 and 2 in organic solvents were also studied. The results show that the ligand acetate favored energy transfer to the emitting energy level of Tb（Ⅲ） in complex 1. Some factors that influence the fluorescent intensity were also discussed in the article.     

Leaching of a sphalerite concentrate with H2SO4–HNO3 solutions in the presence of C2Cl4

The enhanced leaching of sphalerite concentrates in H₂SO₄–HNO₃ solutions and the extraction of sulfur with tetrachloroethylene were studied. Variables of the process were investigated including leaching temperature, reaction time, liquid / solid ratio, and tetrachloroethylene concentration. The number of cycles that tetrachloroethylene could be recycled did not have a significant effect on zinc extraction. The results indicated that 99.6% zinc extraction was obtained after three hours of leaching at 85 °C and 0.1 MPa O₂, when 20 g of sphalerite concentrate were leached in a 200 ml solution containing 2.0 mol/L H₂SO₄ and 0.2 mol/L HNO₃, in the presence of 10 ml C₂Cl₄. Leaching rates were significantly improved under these conditions.     

Morphology of dispersed nickel electrochemically deposited in solutions of the system NiSO4(NiCl2)-(NH4)2SO4-NH3·H2O

Morphology of dispersed nickel obtained by electrolysis in electrolytes (0.1–0.5 M) NiSO₄(NiCl₂)-0.5 M (NH₄)₂SO₄-NH₃·H₂O (to pH 8.0–8.5), which model the leaching solutions of secondary metal, is investigated. It is noted that the sediment of three structural levels is formed on the cathode at the current density 20–100 A/dm². These are (i) spherical particles, (ii) spherical agglomerates, and (iii) conglomerates of the particles of the second structural level. The shape of first-level elemental particles is governed by adsorption of the surface-active NH₃ molecules on the surface of crystalline nuclei. The second and the third levels of structuring emerge due to high surface energies of elemental particles. Spherical agglomerates are mechanically stable and determine the main characteristics of the nickel powder. The sizes of these agglomerates decrease as the cathode current density increases and the nickel concentration in electrolytes decreases, and lie in the limits 2–10 μm. Original Russian Text ? O.I. Kuntyi, 2007, published in Izvestiya VUZ. Tsvetnaya Metallurgiya, 2007, No. 1, pp. 20–23.     

Hydrothermal synthesis and crystal structure study of two novel 3-D mellitates {Nd2[C6（COO）6] （H2O）6} and {Ho2[C6（COO）6]（H2O）6}

Two novel 3-D coordination compounds, Nd2[C6（COO）6]（H2O）6 （1）and Ho2[C6（COO）6]（H2O）6 （2）, were hydrothermaily synthesized from mellitic acid and neodymium perchlorate （or holmium perchlorate） in the alkaline aqueous solution and characterized with elemental analysis, TG, IR spectrum, and single crystal X-ray diffraction. The two compounds were isostructural and crystallized in the orthorhombic system, space group Pnnm, with a=1.3531 （4） nm, b=0.6687 （2） nm, c=1.0224（3） nm, V=0.92523（5） nm^3, Z=4, D=2.630 g/cm^3, F（000）=696.0, Goof=1.052. Final R indices [1 〉2∑（Ⅰ）]： R1=0.0195, wR2=0.0382 for 1; a=1.3411 （2） nm, b=0.6586（1） nm, c=1.0116（2） nm, V=0.8935（3） nm^3, Z=4, D=2.877 g/cm^3, F（000）=724.0, Goof=1.061. Final R indices [1 〉2∑（Ⅰ）]： R1=0.0200, wR2=0.0479 for 2. In the two compounds 1 and 2, the mellitic acid ligand, in which all the carboxylate groups were deprotonated, had only one kind of coordination mode to bridge metal ions to form four-connected three-dimensional diamondiod networks.     

Thermochemical Properties of the Complexes RE(HSal)3·2H2O(RE = La, Ce, Pr, Nd, Sm)

Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(HSal)₃·2H₂O(RE = La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE³⁺ ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, Δ_cU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, Δ_cH_m^θ, and standard molar enthalpies of formation, Δ_fH_m^θ, were calculated.