The mechanism of Pu<Superscript>VI</Superscript> oxidation with ozone and other reagents in alkaline solutions

The analysis of reported data on the interaction of ozone with alkaline solutions of Pu^VI leads to the conclusion that the process of ozonation involves reactions O₃ + OH^– → HO ₂ ^- + O₂, O₃ + + HO ₂ ^- + OH^– → O ₃ ^- + O ₂ ^- + H₂O and O₃ + O ₂ ^- → O ₃ ^- + O₂. The O ₃ ^- radical ion oxidizes Pu^VI, the HO ₂ ^- and O ₂ ^- anions reduce Pu^VII and Pu^VI and react with O ₃ ^- . Using persulfate instead of O₃ in aerated solution at 80—95 °C results in thermal decomposition of the S₂O ₈ ^2- anion into radical ions of SO ₄ ^- , oxidizing OH^– to the O^– ion, which in reaction with O₂ forms O ₃ ^- . The oxidation of PuVI proceeds via the formation of an activated complex with O ₃ ^- . where charge transfer occurs with the simultaneous elimination of two H⁺ ions. A similar mechanism is operating in reactions of Pu^VI with BrO^–, Fe(CN) ₆ ^3– , Am^VI, and Am^VII. Upon the γ-radiolysis of alkaline solutions of Pu^VI saturated with N₂O or containing S₂O ₈ ^2– , e _aq ^– is converted into O^– and then into O ₃ ^- ; F₂ and XeF₂ in alkaline solutions are decomposed with the formation of H₂O₂, which prevents producing Pu^VII.     

Structure and Magnetic Properties of a New Lattice System of the Heterometallic Decanuclear Ce<Subscript>6</Subscript>Mn<Subscript>4</Subscript> Aggregate

In this paper, we present a mixed valence f–d Ce₆Mn ₄ ^III compound having formula [Ce ₆ ^IV Mn ₄ ^III (μ₄-O)₄ (μ₃-O)₄(O₂C^tBu)₁₂(ea)₄(OAc)₄]·H₂O (1), which is obtained by the reaction of hydrated lanthanide nitrate, pivalic acid, and ethanolamine in MeCN as a solvent. The single crystal X-ray diffraction analysis demonstrates that the central core consists of an octahedron with four triangular pyramids added to four related faces or as an octahedron encapsulated in a tetragon. The fitting of magnetization data using the anisotropic model gives D = 2.13 cm^–1 and g = 1.97 (D is the axial zero-field splitting parameter).     

Thermal properties,phase transitions,vibrational and reorientational dynamics of [Mn(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

[Mn(NH₃)₆](NO₃)₂ crystallizes in the cubic, fluorite (C1) type crystal lattice structure (Fm \( \overline{3} \) m) with a = 11.0056 Å and Z = 4. Two phase transitions of the first-order type were detected. The first registered on DSC curves as a large anomaly at T _C1 ^h  = 207.8 K and T _C1 ^c  = 207.2 K, and the second registered as a smaller anomaly at T _C2 ^h  = 184.4 K and T _C2 ^c  = 160.8 K (where the upper indexes h and c denote heating and cooling of the sample, respectively). The temperature dependence of the full width at half maximum of the band associated with the δ_s(HNH)F_1u mode suggests that the NH₃ ligands in the high temperature and intermediate phase reorientate quickly with correlation times in the order of several picoseconds and with activation energy of 9.9 kJ mol^?1. In the phase transition at T _C2 ^c probably only a some of the NH₃ ligands stop their reorientation, while the remainders continue to reorientate quickly with activation energy of 7.7 kJ mol^?1. Thermal decomposition of the investigated compound starts at 305 K and continues up to 525 K in four main stages (I–IV). In stage I, ²/₆ of all NH₃ ligands were seceded. Stages II and III are connected with an abruption of the next ²/₆ and ¹/₆ of total NH₃, respectively, and [Mn(NH₃)](NO₃)₂ is formed. The last molecule of NH₃ per formula unit is freed at stage IV together with the simultaneous thermal decomposition of the resulting Mn(NO₃)₂ leading to the formation of gaseous products (O₂, H₂O, N₂ and nitrogen oxides) and solid MnO₂.     

Ion state of atoms and the properties of perovskite-like compound CaCu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

The binding energies and valence state of atoms in the perovskite-like compound CaCu₃V₄O₁₂ have been determined using XPS spectroscopy. The stoichiometry of this phase is formulated as Ca²⁺Cu²⁺Cu ₂ ⁺ (V ₂ ⁵⁺ V ₂ ⁴⁺ O₁₂). Under an air atmosphere, the phase interacts with water vapor and oxygen. As a result, Ca(OH)₂ is formed on its surface, the Cu⁺ and V⁴⁺ ion concentrations decrease, and the Cu²⁺ and V⁵⁺ concentrations increase in association. Raman spectra show shortened cation-anion bond lengths and cation-anion-cation bond angles in CaCu₃V₄O₁₂ compared to perovskite CuVO₃; the two structures are alike. The electrical conductivity, magnetic susceptibility, thermal and sensor properties of CaCu₃V₄O₁₂ in aqueous salt solutions have been studied.     

Geometric and spectral characteristic of the tetrahalocuprate(II) complexes (HL)<Subscript>2</Subscript>CuX<Subscript>4</Subscript> (X = Cl,Br). Crystal and molecular structures of bis(2-methylimidazolium) tetrabromocuprate(II)

The crystal and molecular structures of bis(2-methylimidazolium) tetrabromocuprate(II) are determined. The linear dependences of the degree of distortion of the CuBr ₄ ^2? coordination polyhedron on the protonation constant of the organic cation are revealed for the structures with θ < 140°. The dependence of the hydrogen bond parameters (distances H…Br and N…Br, angle NHBr) on the degree of distortion of CuBr ₄ ^2? is shown. The degree of distortion of CuX ₄ ^2? (X = Cl, Br) is determined by the type of the organic cation and is almost the same for the CuBr ₄ ^2? and CuCl ₄ ^2? polyhedra. The empirical equations relating the degree of distortion of CuX ₄ ^2? (X = Cl, Br) and the position of the Cu ← X ligand-to-metal charge-transfer band (νLMCT) are obtained.     

The thermodynamic characteristics of vaporization in the NaI-PrI<Subscript>3</Subscript> system

The vaporization of the NaI-PrI₃ quasi-binary system was studied by high-temperature mass spectrometry over the whole concentration range. At 623–994 K, saturated vapor contained not only (NaI) _n and (PrI₃) _n molecules (n = 1, 2) and Na⁺(NaI) _n (n = 0–4) and I^?(PrI₃) _n (n = 1–2) ions but also mixed molecular and ionic associates recorded for the first time (NaPrI₄, Na₂PrI₅, NaPrI ₃ ⁺ , Na₂PrI ₄ ⁺ , Na₃PrI ₅ ⁺ , Na₄PrI ₆ ⁺ , NaPrI ₅ ^? , and NaPr₂I ₈ ^? ). The partial vapor pressures of molecules were calculated, and the equilibrium constants of the dissociation of neutral and charged associates were measured. The enthalpies of molecular and ion-molecular reactions were determined, and the enthalpies of formation of gaseous molecules and ions were obtained.     

Synthesis,structure, physicochemical properties,and solid-phase thermolysis of Co<Subscript>2</Subscript>Sm(Piv)<Subscript>7</Subscript>(2,4-Lut)<Subscript>2</Subscript>

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 (C _p , H _T ⁰ - H ₁₈₀ ⁰ , and S _T ⁰ ), and parameters were determined for solid-phase thermolysis where samarium cobaltate SmCoO₃ is the only product.     

Synthesis of dugganite Pb<Subscript>3</Subscript>TeZn<Subscript>3</Subscript>As<Subscript>2</Subscript>O<Subscript>14</Subscript> and its analogues

A ₃ ²⁺ Te⁶⁺M ₃ ²⁺ X ₂ ⁵⁺ O₁₄ (A = Pb, Ba, Sr; M = Zn, Mg, Co, Mn, Cu, Cd; X = P, As, V) compounds and Pb₃WZn₃P₂O₁₄, all with Ca₃Ga₂Ge₄O₁₄ structure (space group P321), were prepared by solid-phase synthesis in air at 600–1000°C. Most compounds melt incongruently or experience solid-phase decomposition.     

Interactions in the Al<Subscript>2</Subscript>TiO<Subscript>5</Subscript>-Ti<Subscript>2</Subscript>O<Subscript>3</Subscript> System

Interactions in the Al₂TiO₅-Ti₂O₃ system were studied and the regions of existence of Al_2?2xTi _2x ³⁺ Ti⁴⁺O₅ solid solutions with a pseudobrookite structure were determined.     

Structure and some properties of [UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(C<Subscript>5</Subscript>H<Subscript>12</Subscript>N<Subscript>2</Subscript>O)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]

The complex [UO₂(SeO₄)(C₅H₁₂N₂O)₂(H₂O)] (I) was synthesized and studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are orthorhombic: a = 13.1661(3) Å, b = 16.4420(5) Å, c = 17.4548(6) Å, Pbca, Z = 8, R = 0.0423. The structural units of crystal I are chains with the composition coinciding with that of the compounds of the AB₂M ₃ ¹ crystal chemical group of the uranyl complexes (A = UO ₂ ²⁺ , B² = SeO ₄ ^2? , M¹ = C₅H₁₂N₂O and H₂O).     

Phase transitions in double molybdates K<Subscript>2</Subscript>M<Stack><Subscript>2</Subscript><Superscript>II</Superscript></Stack>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> with M = Mg or Co

Phase transitions and cation mobility in double molybdates K₂M ₂ ^II (MoO₄)₃ with M = Mg or Co and the products of their heterovalent doping with scandium(III) and vanadium(V) have been studied. The transition from low to high conductivity in K₂M ₂ ^II (MoO₄)₃ is the result of a two-stage phase transition, whose occurrence is significantly extended in time. Heterovalent substitutions noticeably decrease the heat of the phase transition. The transition to the low-temperature phase is not achieved even after long-term exposure.     

Radiation-chemical yield of excited neodymium(III) in laser liquids POCl<Subscript>3</Subscript>-MCl<Subscript>n</Subscript>-<Superscript>235</Superscript>UO<Subscript>2</Subscript><Superscript>2+</Superscript>-Nd<Superscript>3+</Superscript> (M = Ti,Zr, Sn,or Sb)

Results of measurements of the yield of Nd³⁺ radioluminescence photons in inorganic laser liquids POCl₃-MCl_n-²³⁵UO ₂ ²⁺ -Nd³⁺ (M = Ti, Zr, Sn, or Sb) during homogeneous excitation by uranium α-particles are presented. It was found that the intensity of radioluminescence corresponding to the ⁴ F _3/2 → ⁴ I _11/2 transition in neodymium ions depends on the solvent composition. Data on the radiation-chemical yield, G, of excited neodymium ions in the POCl₃-MCl_n-²³⁵UO ₂ ²⁺ -Nd³⁺ (M = Ti, Zr, Sn, or Sb) system were obtained. At a neodymium concentration of 0.25 mol/l, the values of G for the excited ions were 0.60 ± 0.10, 0.84 ± 0.10, 1.20 ± 0.10, and 1.64 ± 0.16 ion/100 eV in solutions with TiCl₄, ZrCl₄, SnCl₄, and SbCl₅, respectively. The maximum yields of excited ions estimated at G = 1.68 ± 0.10 and 2.20 ± 0.24 ion/100 eV were obtained for the solutions with SnCl₄ and SbCl₅, respectively, at neodymium ion concentrations above 0.4 mol/l.     

La<Subscript>2</Subscript>M<Stack><Subscript>3</Subscript><Superscript>II</Superscript></Stack>Mn<Subscript>4</Subscript>O<Subscript>12</Subscript> (M = Mg,Ca, Sr,or Ba) manganites: Synthesis and X-ray diffraction study

La₂M ₃ ^II Mn₄O₁₂ (M = Mg, Ca, Sr, or Ba) manganites have been synthesized by ceramic technology from lanthanum oxide, manganese(III) oxide, and magnesium, calcium, strontium, or barium carbonate. X-ray powder diffraction shows that these compounds crystallize in cubic perovskite space group Pm3m.     

Phase equilibria in the Tl-TlCl-Te system and thermodynamic properties of the compound Tl<Subscript>5</Subscript>Te<Subscript>2</Subscript>Cl

The Tl-Te-Cl system was studied in the Tl-TlCl-Te composition region by differential thermal analysis, X-ray powder diffraction, and emf and microhardness measurements. A series of polythermal sections, an isothermal section at 400 K, and a projection of the liquidus surface of the phase diagram were constructed. The ternary compound Tl₅Te₂Cl characterized by a wide homogeneity region and incongruent melting by a syntectic reaction at 708 K was shown to exist. This compound was found to crystallize in tetragonal lattice (space group I4/mcm) with the parameters a = 8.921 Å, c = 12.692 Å, Z = 4. Wide phase separation regions were also found in the system, including a three-phase separation region in the Tl-TlCl-Tl₂Te subsystem. Regions of primary crystallization of phases, and the types and coordinates of in- and monovariant equilibria in the T-x-y diagram were determined. From emf measurement data, the standard thermodynamic functions of formation and the standard entropy were calculated for the compound Tl₅Te₂Cl, as follows: ?ΔG ₂₉₈ ⁰ = 355.9 ± 1.1 kJ/mol, ?ΔH ₂₉₈ ⁰ = 377.1 ± 5.0 kJ/mol, and S ₂₉₈ ⁰ = 474.1 ± 6.8 J/(mol K).     

The oxidation of chlorine ions under the joint action of ozone and permanganate ions

The oxidation of chlorine ions in the system O₃ + MnO ₄ ^? + H⁺ + Cl^? with the formation of Cl₂ in the gas phase was studied. The phenomenon of transfer catalysis of the reaction between O₃ and Cl^? by the MnO ₄ ^? ion was observed (the products of the reduction of MnO ₄ ^? by the chlorine ion are oxidized by ozone to recover MnO ₄ ^? ). The rate of the formation of Cl₂ in the O₃ + MnO ₄ ^? + H⁺ + Cl^? system was higher than the sum of the corresponding rates in the oxidation of Cl^? by O₃ and MnO ₄ ^? separately. A scheme explaining the trends observed experimentally for the formation of Cl₂ and changes in MnO ₄ ^? concentration was suggested. The formation of MnO ₄ ^? in the oxidation of Mn³⁺ with ozone in acid media was studied.     

Synthesis and structure of [UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>){CONH<Subscript>2</Subscript>N(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

The single crystals of [UO₂(C₂O₄){CONH₂N(CH₃)₂}₂] were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 7.461(2) Å, b = 8.828(2) Å, c = 11.756(2) Å, β = 107.21(3)°, space group Pc, Z = 2, R = 2.94%. The structure comprises infinite chains [UO₂(C₂O₄){CONH₂N(CH₃)₂}₂] extended along [001] and corresponding to the AT¹¹M ₂ ¹ crystallochemical group (A = UO ₂ ²⁺ , T¹¹ = C₂O ₄ ^2? , M¹ = N,N-CONH₂N(CH₃)₂) of uranyl complexes. The chains are connected into a three-dimensional framework by hydrogen bonds involving the oxygen atoms of oxalate and uranyl ions and the N,N-dimethylcarbamide methyl groups.     

MALDI-TOF Mass Spectrometry of Nanosized MoO<Subscript>2</Subscript>. Structure and Relative Stability of Isomers of Lower Molybdenum Oxide Cations

MALDI-TOF was used to study molybdenum dioxide (MoO₂) containing a nanosized fraction. The composition of cationic clusters of nonstoichiometric lower molybdenum oxides in the gas phase was determined, and the thermodynamic stabilities and configurations of isomers were calculated for selected symmetric molecular structures and for cations MoSO ₈ ⁺ and Mo₅O ₉ ⁺ . Molecular orbital analysis was performed for two trigonal-bipyramidal clusters Mo₅O₈ and Mo₅O₉. Changes in molybdenum–molybdenum interatomic distances in going from MoO ₈ ⁺ and Mo₅O ₉ ⁺ cations to neutral clusters are discussed.     

Crystal Structure of [UO<Subscript>2</Subscript>SO<Subscript>4</Subscript>{(CH<Subscript>3</Subscript>)HNCONH(CH<Subscript>3</Subscript>)}<Subscript>2</Subscript>]

The single crystals of [UO₂SO₄{(CH₃)HNCONH(CH₃)}₂] (I) were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 6.847(1) Å, b = 14.259(3) Å, c = 14.297(3) Å, β = 93.451(4)°, space group P2₁/n, Z = 4. The main structural units of crystals I are ribbons whose composition coincides with the composition of the compound. The crystal chemical formula of the complex is AT³M ₂ ¹ (A = UO ₂ ²⁺ ).     

Synthesis,Structure, and Magnetic Properties of a Twist Linear Tetranuclear Co<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack>Ln<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack> Complexes

A series of twist linear tetranuclear 3d–4f Co ₂ ^III Ln ₂ ^III [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)] complexes have been prepared under solvothermal conditions and structurally characterized with Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H₄L). The two central Co ions are linked by two alkoxyl oxygen atoms, and one Ln ion lying above and the other below the Co–Co dimer, form a twist linear array. The magnetic susceptibility studies reveal antiferromagnetic or ferromagnetic behaviour, whilst dynamic magnetic studies indicate no slow magnetic relaxation for these complexes.     

Catalytic Mo<Subscript>2</Subscript>C coatings for the water gas shift reaction: Electrosynthesis in molten salts

Electrosynthesis methods using molten salts are suggested for obtaining a new catalytic system based on the Mo₂C/Mo composition for the water gas shift reaction. The coatings obtained by the discharge of the carbonate ion on a molybdenum substrate and by the simultaneous reduction of the electroactive species MoO ₄ ^2? and CO ₃ ^2? are catalytically more active than bulk Mo₂C or the commercial catalyst Cu-ZnO-Al₂O₃ by one and three orders of magnitude, respectively.