Zh. V. Dobrokhotova

Synthesis, molecular and crystal structure, magnetic properties, luminescence, and solid-phase thermolysis of binuclear Ln(III) pivalates with 2,2′-dipyridyl and 1,10-phenanthroline molecules

Methods of synthesis of binuclear pivalate complexes L2Ln2(μ-O,η2-OOCCMe3)2(μ2-O,O′-OOCCMe3)2(η2-OOCCMe3)2, where Ln = Sm, Eu, Gd, or Er and L = 2,2′-dipyridyl (Bipy) or 1,10-phenanthroline (Phen), from the corresponding binuclear complexes Ln2(μ2-OOCCMe3)4(OOCCMe3)2(HOOCCMe3)6 · HOOCCMe3(I–IV), as well as of coordination polymers {Ln(OOCCMe3)3}n, were suggested. The compounds were characterized by X-ray crystallography and X-ray powder diffraction and their magnetic properties, solid-phase thermolysis, and the phase composition of solid decomposition products were studied. The structures of the metal carboxylate core and surrounding ligands were shown to have an effect on the thermal stability of the complexes. The luminescence properties of the Eu(III) complexes were analyzed.

Copper(II) trimethylacetate complexes with 3,5-dimethylpyrazole

Specific features of the chemical behavior and structure of copper(II) trimethylacetate complexes with 3,5-dimethylpyrazole have been considered based on X-ray crystallographic data.

Synthesis, structure, solid-state thermolysis, and catalytic properties of binuclear Ce, Nd, Eu, and Gd cymantrenecarboxylate complexes with DMSO

New rare-earth cymantrenecarboxylate complexes [Ln2(μ,η2-O2CCym)2(μ2-O2CCym)2-(η2-O2CCym)2(DMSO)4] (Cym = (η5-C5H4)Mn(CO)3, Ln = Ce (1), Nd (2), Eu (3), Gd (4)) were synthesized and characterized by X-ray diffraction. In dimeric structures 1–4, two of four bridging carboxylates are chelating-bridging, and Ln atoms have coordination number 9. The catalytic activity of complex 2 in the polymerization of 2,3-dimethyl-1,3-butadiene was investigated. The thermal decomposition of the synthesized compounds was studied by DSC and TGA. According to the X-ray powder diffraction data, the final thermal decomposition product of 1 in air consists of CeO2 and Mn3O4. Under the same conditions, complexes 2–4 afford mixtures of LnMn2O5 and Mn2O3.

Nanostructured catalysts for cathodes of oxygen-hydrogen fuel cells

Bimetallic catalysts platinum-cobalt, platinum-chromium, and platinum-tungsten, deposited onto highly dispersed carbon black from complex cluster-type compounds of corresponding metals with a 1: 1 atomic ratio of metals are developed. The catalysts are characterized by methods of x-ray diffraction analysis and energy dispersive analysis of x-rays. The procedure involving use of a thin-film rotating disk electrode is employed to probe kinetic parameters of the oxygen reduction reaction on the catalysts developed. The investigated binary catalysts exhibit specific electrochemical characteristics that are not inferior and, in some cases, are superior to the characteristics intrinsic to the commercial platinum catalyst E-TEK, when tested in the composition of a gas-diffusion electrode under conditions that are close to real conditions in which cathodes of oxygen-hydrogen fuel cells operate.

New binuclear ferrocenecarboxylates of rare-earth metals as precursors for ferrites: Syntheses, structures, and solid-phase thermolysis

New ferrocenecarboxylates of rare-earth metals, [Ln2(μ-O,η2-OOCFc)2(μ2-O,O′-OOCFc)2(η2-NO3)2(DMSO)4] (Ln = Gd (I), Tb (II), and Y (III)) and [Gd2(μ-O,η2-OOCFc)2(η2-OOCFc)4(DMSO)2(H2O)2] · 2DMSO · 2CH2Cl2 (IV), are synthesized and characterized by X-ray diffraction analysis. Unlike all earlier known ferrocenecarboxylates of rare-earth metals, in isostructural compounds I–III the Ln atoms are linked by four bridging carboxyl residues, two of which are chelate-bridging (the coordination number of Ln is 9). Binuclear structure IV is formed by two chelate-bridging carboxylate ligands (the coordination number of Gd is 9). Weak antiferromagnetic and weak ferromagnetic interactions between the Gd atoms are observed in complexes I and IV, respectively. The thermal decomposition of the synthesized compounds is studied by differential scanning calorimetry and thermogravimetry. According to the X-ray diffraction data, the final thermolysis products of the complexes in air are garnets Ln3Fe5O12.

Synthesis, structure, physicochemical properties, and solid-phase thermolysis of Co2Sm(Piv)7(2,4-Lut)2

Heterometallic pivalate Co2Sm(Piv)7(2,4-Lut)2 (1) was prepared for the first time and structurally characterized at 293 and 160 K. Antiferromagnetic exchange interactions are dominant in complex 1. This compound experiences a first-order phase transition within 210–260 K. A set of thermodynamic functions was obtained for this complex (Cp, HT0 - H1800, and ST0), and parameters were determined for solid-phase thermolysis where samarium cobaltate SmCoO3 is the only product.

Metastable states in inorganic systems

Changes in inorganic systems associated with the formation of metastable states and their relaxation are considered using supramolecular theory of eutectics. After analysis of the existing theories and concepts describing possible transition mechanisms of nonequilibrium amorphous structures to a crystalline state, the conclusion that there is poor correspondence of experimental data to those theories is made. Owing to the complexity of relaxation processes, it was proposed to divide the objects of investigation into groups considering the different interaction potentials and size parameters of substructures. Inorganic binary eutectic systems were classified as a special group. The peculiarities of the relaxation processes in quenched non-autonomous phases are shown in a few examples with consideration of characteristic temperatures and time.

Thermodynamic characteristics of europium pivalate binuclear complexes Eu2(Piv)6 and [Eu2(Piv)6 · (Phen)2]

Sublimation of europium pivalate binuclear complexes Eu2(Piv)6 and [Eu2(Piv)6 · (Phen)2] (Piv = (CH3)3CCOO, Phen = C12H8N2) in the temperature range of 383–660 K is studied by the Knudsen effusion method with mass-spectrometric analysis of the gas phase. The vaporization of Eu2(Piv)6 is shown to be accompanied by polymerization and the formation of Eu2(Piv)6 and Eu4(Piv)12 molecules. The saturated vapor over the mixed-ligand complex of europium pivalate with o-phenanthroline consists of Phen, Eu2(Piv)6, and Eu4(Piv)12 molecules. The partial pressures of the gas components, as well as the standard enthalpies of sublimation and dissociation of the reaction proceeding with removal of phenanthroline have been determined.

LiCoO2- and LiMn2O4-based composite cathode materials

We have prepared composite cathode materials based on two electrochemically active compounds, LiCoO2 and LiMn2O4, and investigated their properties. The results indicate that the discharge capacities of all the materials studied exceed the additivity rule values calculated from the discharge capacities of the starting materials. The effect of heat treatment on the physicochemical properties of the composites is analyzed.

Binuclear and Polynuclear Cymantrenecarboxylate Complexes of Heavy Lanthanides

New binuclear cymantrenecarboxylate complexes of rare-earth metals, [Ln2(μ-O,η2-O2CCym)2(μ2-O,O′-O2CCym)2(η2-O2CCym)2(DMSO)4] (Ln = Tb (I), Dy (II); Cym = (η5-C5H4)Mn(CO)3) and [Ln2(μ2-O,O′-O2CCym)4(η2-NO3)2(DMSO)4] (Ln = Tb (III), Dy (IV)), are synthesized and characterized by X-ray diffraction analysis. The carboxylate clusters containing the Mn2+ ion, which is formed due to the destruction of the cymantrenenecarboxylate anion, [Tb4(μ3-OH)4(μ2-O,O′-O2CCym)6(H2O)3(THF)4][MnCl4] · 4CH2Cl2 · 6THF (V) with the cubane-like structure, and [Er2Mn(μ2-O2CCym)6(η2-O2CCym)2((MeO)3PO)4] · 2MePh (VI) with linear structure, are also obtained. The magnetism of complexes I, II, V, and VI is studied in a direct magnetic field. The magnetic properties of complexes II and VI are studied in direct and alternating magnetic fields. Complex II exhibits the properties of a single-molecule magnet. The thermal decomposition of complexes I–IV is studied by differential scanning calorimetry and thermogravimetric analysis. According to the X-ray diffraction analysis data, the final thermolysis products of complexes III and IV in air are multiferroics LnMn2O5.