New data on sodium salts of Np(VII) and Pu(VII)

A new Pu(VII) compound, Na₃[PuO₄(OH)₂]·2H₂O, was prepared by X-ray diffraction analysis, and its structure was studied. To reveal the character of actinide contraction in going from Np(VII) to Pu(VII), the geometric parameters of the tetragonal-bipyramidal surrounding of Pu(VII) in the [PuO₄(OH)₂]³⁻ anion were compared with those of Np(VII) in the previously studied isostructural compound Na₃[NpO₄(OH)₂]·2H₂O. To reveal the specific feature of hydrogen bonding in crystals of the general composition Na₃[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4), the structure of the compound Na₃[NpO₄(OH)₂]·4H₂O studied previously by the photographic method was refined. The effect of hydrogen bonds on the geometric characteristics of the coordination polyhedra of the Np and Na atoms was considered.     

Unusual route for preparation of manganese(II), cobalt(II), zinc(II) and cadmium(II) carbonate compounds: synthesis and spectroscopic characterizations

The manganese(II) carbonate, MnCO₃·H₂O, cobalt(II) carbonate, CoCO₃·4H₂O, zinc(II) carbonate, ZnCO₃ and cadmium(II) carbonate, CdCO₃, respectively, were synthesis by a new simple unusual route during the reaction of aqueous solutions of MnX₂, CoX₂, ZnX₂ and CdX₂, where (X = Br⁻ and ClO₄⁻) with urea at high temperature within ∼ 90°C for 6 h. The infrared spectra of the reaction products clearly indicate the absence of the bands of urea, but show the characteristic bands of ionic carbonate, CO₃²⁻. A general mechanism describing the preparation of manganese(II), cobalt(II), zinc(II) and cadmium(II) carbonate compounds are discussed.     

Preparation, characterization and conductivity studies of Li3?2xAl2?xSbx(PO4)3

New NASICON type materials of composition, Li_3−2x Al_2−x Sb _x (PO₄)₃ (x = 0·6 to 1·4), have been prepared and characterized by powder XRD and IR. D.C. conductivities were measured in the temperature range 300–573 K by a two-probe method. Impedance studies were carried out in the frequency region 10²−10⁶ Hz as a function of temperature (300–573 K). An Arrhenius behaviour is observed for all compositions by d.c. conductivity and the Cole-Cole plots obtained from impedance data do not show any spikes on the lower frequency side indicating negligible electrode effects. A maximum conductivity of 4·5 × 10⁻⁶ S cm⁻¹ at 573 K was obtained for x = 0·8 of the Li_3−2x Al_2−x Sb _x (PO₄)₃ system.     

Spectroscopic characterization of tungstated zirconia prepared by equilibrium adsorption from hydrogen peroxide solutions of tungsten(VI) precursors

Two series of WO _x /ZrO₂ samples are prepared by equilibrium adsorption from H₂O₂ solutions at pH 1.8 containing two different precursor anions, [W₂O₃(O₂)₄(H₂O)₂]²⁻ and [H₂W₁₂O₄₀]⁶⁻. The starting material is amorphous zirconium oxyhydroxide. The maximum W densities obtained are larger than that reported in the literature for systems synthesized by the same method using aqueous non-peroxide solutions. In the case of the metatungstate precursor, this increase is attributed to the generation of additional anchoring sites by interaction between the amorphous support and H₂O₂. The high uptake achieved when the peroxo complex is used as a precursor is a result of both the ZrO _x (OH)_4-2x –H₂O₂ interaction and low nuclearity of the adsorbing anion. The materials are characterized by XRD, DR–UV–vis, Micro-Raman and FT-IR spectroscopy. The surface acidities of samples with identical W loading prepared by equilibrium adsorption from the [H₂W₁₂O₄₀]⁶⁻–H₂O₂ system and by impregnation with aqueous solution of ammonium metatungstate are investigated by FT-IR spectroscopy of CO adsorbed at 80 K.     

Synthesis and Spectral Study of New Complexes of Eu3+, Am3+, and Cm3+ with GaMo6O18(OH)

Complexing of Am(III) with GaMo₆O₁₈(OH) ₆ ³⁻ polyanion in an aqueous solution was studied. The stability constant β of the resulting complex was estimated at 100–150 l mol⁻¹ at pH 4.0. Crystalline complexes of Eu(III) and Gd(III) [doped with 0.5–1.5% Cm(III) ion] with GaMo₆O₁₈(OH) ₆ ³⁻ polyanion were synthesized from H₂O and D₂O solutions. The luminescence spectra and lifetime were measured for the compounds at T = 295 and 77 K. The luminescence characteristics of the Eu(III) complex proved to be virtually identical to those of the previously synthesized compound EuAlMo₆O₁₈(OH)₆·xH₂O. This also concerns the luminescence of Cm³⁺-doped GdGaMo₆O₁₈(OH)₆·xH₂O complex. The results suggest identical structures of the new compounds and complexes of lanthanides with the AlMo₆O₁₈(OH) ₆ ³⁻ anion. __________ Translated from Radiokhimiya, Vol. 47, No. 6, 2005, pp. 507–511. Original Russian Text Copyright ? 2005 by Yusov, Fedoseev.     

Synthesis and crystal structure of new U(VI) and Np(VI) benzoates, K11(AnO2)23(OOCC6H5)57(H2O)18+x

The structure of new double benzoates of hexavalent actinides, K₁₁(AnO₂)₂₃(O₂C₇H₅)₅₇(H₂O)_18+x (An = U, Np), was studied. There are five crystallographically independent actinide atoms in the crystals. The coordination polyhedra of An(1), An(3), An(4), and An(5) are distorted hexagonal bipyramids, and that of An(2) is a distorted pentagonal bipyramid. Ten crystallographically independent benzoate ions have been found in the crystals. All but one anions are bidentate chelating and form with AnO₂²⁺ cations either electrically neutral [AnO₂(O₂C₇H₅)₂(H₂O)₂][An(1)O₂²⁺ cations] or negatively charged [AnO₂(O₂C₇H₅)₃]⁻[An(3)O₂²⁺, An(4)O₂²⁺, An(5)O₂²⁺ cations] complexes. The bidentate bridging benzoate ion links two adjacent An(2)O₂²⁺ cations with the formation of peculiar electrically neutral cyclic fragments [AnO₂(O₂C₇H₅)₂(H₂O)]₆ arranged perpendicular to the c-axis. There are three independent K⁺ cations in the structure. The coordination surrounding of K(1)⁺ (coordination number CN 6) is formed by oxygen atoms of two electrically neutral [AnO₂(O₂C₇H₅)₂(H₂O)₂] fragments and of the complex anion [AnO₂(O₂C₇H₅)₃]⁻. The coordination surrounding of K(2)⁺ (CN 6) consists of oxygen atoms of three complex anions [AnO₂(O₂C₇H₅)₃]⁻. The disordered K(3)⁺ cation is arranged near the sixfold axis between the cyclic fragments [AnO₂(O₂C₇H₅)₂(H₂O)]₆. An important structure-forming factor in the crystals is hydrogen bonding involving coordinated water molecules. In the coordination polyhedra of actinides, the An-O bond lengths regularly decrease in going from U to Np owing to actinide contraction.     

Effect of praseodymium substitution on the growth and properties of Y1−x Pr x Ba2Cu3O7−δ (o <x < 0·4) single crystals

In the present paper, a modified self-flux technique has been successfully employed for the growth of pure and praseodymium substituted (partially) large single crystals of high temperature superconducting Y_1−x Pr _x Ba₂Cu₃O_7−δ (x = 0·0,0·2,0·4). Typical sizes of the platy and bulky crystals of pure YBCO(123) material are ≈ 2 × 2 × 0·1 mm³ and 4 × 1 × 1 mm³, respectively. In case of Pr-substitution, the typical sizes of platy and bulky crystals of Y_0·8Pr_0·2Ba₂Cu₃O_7−δ and Y_0·6Pr_0·4Ba₂Cu₃O_7−δ materials are ≈ 2 × 3 × 0·1 mm³ and 5 × 1 × 1 mm³ and ≈ 1 × 1·5 × 0·1 mm³ and 7 × 0·2 × 0·1 mm³, respectively. The morphology and growth habit of the as-grown single crystals and the critical transition temperature (T _c) of the oxygenated crystals were found to depend on the Pr-content. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Synthesis,structure and IR absorption studies of LnBaCuCoO5 (Ln=rare earth) oxides

A series of oxides LnBaCuCoO₅ (Ln=Pr, Nd, Sm, Dy, Gd, Ho and Er) have been synthesized by ceramic method. The oxides crystallize in a tetragonal structure, isostructural to YBaCuCoO₅. All the oxides in the series are semiconducting. IR spectra of these oxides show distinct absorption bands at 630 cm⁻¹, 550 cm⁻¹ and 330 cm⁻¹ which are assigned toE,A ₂ andA ₁ modes respectively. Doping of holes in these oxides, by calcium substitution in Er_1−x Ca _x BaCuCoO_5−x (up tox ⋍ 0·3) was done but, these oxides did not show metallic behaviour. Contribution no 1175 from Solid State and Structural Chemistry Unit.     

Reduction of Np(V) with Fe(II) in weakly acidic solutions containing H<Subscript>2</Subscript>C<Subscript>2</Subscript>O<Subscript>4</Subscript>

The kinetics of the reaction of Np(V) with Fe(II) in dilute perchloric and nitric acid solutions containing H₂C₂O₄ was studied by spectrophotometry. In the range pH 1–2, the reaction rate is described by the equation d[Np(V)]/dt = k[Np(V)][Fe(II)][H₂C₂O₄]²[H⁺]^−1.6, k = 182 mol^−1.4 l^1.4 s⁻¹. The activation energy in the range 25–45°C is 26 kJ mol⁻¹. The reaction mechanism involves formation of Fe(II) and Np(V) oxalate complexes, followed by their reaction with the participation of the H⁺ ion.     

Crystal Structure of (H3O)6[(UO2)5(SeO4)8(H2O)5](H2O)5

Crystals of (H₃O)₆[(UO₂)₅(SeO₄)₈(H₂O)₅](H₂O)₅ were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 13.835(2), b = 13.4374(16), c = 14.310(3) Å, β = 108.004(14)°, V = 2530.1(7) Å ³] was solved by the direct method and refined to R ₁ = 0.090 for 4409 reflections with |F _hkl ≥ 4σ|F _hkl |. The structure is based on [(UO₂)₅(SeO₄)₈(H₂O)₅]⁶⁻ layers arranged parallel to the (101) plane; these layers have a unique topological structure. The U(1)O₆(H₂O) and U(3)O₆(H₂O) linked through selenate groups form chains running along [ [`1]\bar 1 01] direction. The chains are combined in layers by U(2)O₆(H₂O) bipyramids. The layers are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups located between the layers.     

An X-ray spectral study of the influence on the electronic structure of highT c superconductors of the parameters determining the superconducting transition temperature

CuL _α and OK _α X-ray fluorescence spectra, corresponding to the Cd3d-Cu2p and O2p-O1s transitions, and XANES and EXAFS spectra (CuK, YK, BiL, PbL) have been obtained for the following series of samples: (i) YBa₂Cu₃O_7−δ (0<δ<0·8), (ii) La_2−x Sr _x CuO₄ (0<x<0·3) and (iii) Bi₂(Sr, Ca) _n+1 Cu _n O_2n+4 (n=1,2,3), Bi_1·8Pb_0·3Sr_1·9Ca₂Cu₃O _y . A correlation has been found between the decrease in the superconducting transition temperature (T _c ) with variation in the stoichiometric parametersδ andx in series (i) and (ii), and the shift of the maximum in their CuL _α spectra and the relative increase in the number of occupied states Cu3d in the upper part of the valence band. The changes in the distribution of the Cu3d and O2 _p densities and in the spectral parameters of the samples are discussed.     

Synthesis of hexagonal Al2−x Cr x O3 nanodisks by a thermal decomposition of mesoporous Cr4+:Al2O3 powders

Monodispersed hexagonal Al_2−x Cr _x O₃ nanodisks are synthesized through a reactive doping of Cr⁶⁺ cations in a hydrogenated mesoporous AlO(OH)·αH₂O powder followed by annealing at 1,200 °C in air. The reaction was carried out by a drop wise addition of an aqueous Cr⁶⁺ solution (0.5–1.0 M) to AlO(OH)·αH₂O, at room temperature. Al_2−x Cr _x O₃ nanostructure formation was controlled by the nucleation and growth from the intermediate amorphous mesoporous Cr⁴⁺:Al₂O₃ composites in the temperature range 400–1,000 °C. The nanodisks of ∼50 nm diameter and thickness of ∼16 nm is observed in the sample with x of 0.2 and similar nanodisks with a low dimension is observed at a higher value of x of 1.6 (after 2 h of heating at 1,200 °C). The Cr³⁺ ↔ Al³⁺ substitution, x ≤ 1.2, inhibits grain growth in small crystallites. The crystallites in x = 0.2 composition have 43 nm diameter while it is 15 nm in those with x = 1.2 composition.     

Thermogravimetric method for determination of oxygen stoichiometry in superconducting 1:2:3 and metal-substituted 1:2:3 compounds

The paper presents a modified thermogravimetric method for determination of oxygen stoichiometry of the oxide superconductors YBa₂Cu₃O_7−δ and metal-substituted compounds of the type YBa_2−x La _x Cu₃O_7+δ and YBa₂(Cu_1−x M _x )₃O_7−δ (M=Mg/Zn) between 25° and 930°C.     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: V. Crystal Structure of [Co(NH3)6][PuO2(C2O4)2] · 3H2O

The compound [Co(NH₃)₆][PuO₂(C₂O₄)₂] · 3H₂O was studied by single crystal X-ray diffraction. The structure contains dimeric complex anions [PuO₂(C₂O₄)₂] ₂ ⁶⁻ in which the coordination polyhedra of the Pu atoms are distorted pentagonal bipyramids sharing a common equatorial edge. In going from [Co(NH₃)₆] · [NpO₂(C₂O₄)₂] · 3H₂O to [Co(NH₃)₆][PuO₂(C₂O₄)₂] · 3H₂O, the An-O distances, both axial (in the actinyl group) and equatorial, decrease virtually isotropically. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 419–422. Original Russian Text Copyright ? 2005 by Grigor'ev, Antipin, Krot, Bessonov.     

Two Electrically Different Molecular Conductors Based on Unsymmetrical Au(III)-Dithiolene Complexes with Similar Crystal Structures

We report the first molecular charge transfer salt containing layers of Na⁺ within its lattice. From the crystal structure and from C=C and C-S bond lengths and Raman stretching frequencies we obtain a formula a′"-(BEDT-TTF)₉[Fe(C₂O₄)₃]₈Na₁₈(H₂O)₂₄. The structure consists of alternating layers of BEDT-TTF, and layers comprising [Fe(C₂O₄)₃]³⁻, Na⁺ and H₂O. The packing of the layers follows the sequence ABCDABCDA as previously seen in the compound β″-(BEDT-TTF)₄[Fe(C₂O₄)₃]_2.C₁₂O₆H₂₄.9H_xO¹.     

Characterizations of trimetallic heteronuclear Bi1−x La x [Fe(CN)6]·n(H2O) complexes and their thermal decomposition products

Heteronuclear Bi_1−x La _x [Fe(CN)₆]·nH₂O complexes were synthesized, and their crystal structures and thermal decomposition process were investigated by X-ray diffraction (XRD), thermogravimetry analysis (TGA), Auger electron spectroscopy (AES) with scanning electron microscope (SEM), and transmission electron microscopy (TEM). The crystal system of the complexes was orthorhombic having n = 4 for x = 0–0.7 and was hexagonal having n = 5 for x = 1.0. Their mixture was confirmed for x = 0.8 and 0.9. The lattice parameters for the orthorhombic increased with increasing the x value for the complexes. The single phase of trimetallic perovskite-type Bi_1−x La _x FeO₃ was obtained by its thermal decomposition at low temperature. The crystal system was hexagonal for BiFeO₃ (x = 0) and orthorhombic for x = 0.1–1.0. In the case of the decomposed perovskite sample, the lattice parameters decreased with increasing x values for Bi_1−x La _x FeO₃. The particle size was ca. 30 nm for Bi_0.2La_0.8FeO₃ obtained by thermal decomposition at 500 °C and it grew with an increase in decomposition temperature. For the Bi_0.5La_0.5FeO₃, AES showed that the elemental distributions of Bi, La, and Fe on the surface were very homogeneous for the sample decomposed at 700 °C.     

Self-propagating high-temperature synthesis of Y2O3 powders from Y(NO3)3x(CH3COO)3(1 ? x) · nH2O

We have studied the self-propagating high-temperature synthesis (SHS) of yttrium oxide from Y(NO₃)_3x (CH₃COO)_{3(1 − x)} · nH₂O (0.3 ≤ x ≤ 0.7) acetate nitrates, calculated their standard enthalpies of formation using the method of valence states of atoms in a chemical compound, and compared calculated and experimentally determined yttrium oxide SHS temperatures. Using thermogravimetry and differential scanning calorimetry data and thermodynamic analysis, we have determined the optimal range of yttrium acetate nitrate compositions for the SHS of Y₂O₃ powder.     

Crystal growth of YBaCuO and BaKBiO systems from half-melt flux

Single crystals of YBa₂Cu₃O_7−δ and Ba_0.88K_0.12BiO₃ have been grown from the half-melt flux. Largest crystals with size up to 12×7×0.5 mm³ have been obtained from previously synthesized powders of YBa₂Cu₃O_7−δ, BaCuO₂ and copper oxide on MgO single crystal plates. The 3.5BaO-B₂O₃-BaF₂-(1−x)CuO·xCu₂O solvents is a promising system for controlled growth of YBa₂Cu₃O_7−δ single crystals on seeds.     

X-ray photoelectron spectroscopy of lead fluorosilicate glasses

X-ray photoelectron spectra were measured of F 1s, O 1s, Pb 4f, and Si 2p core levels for lead fluorosilicate glasses of analysed compositionsxPbF₂·(69−x)PbO·(27–29)SiO₂ (x<18 mol%). The observed binding energies were discussed in terms of atomic charges and repulsion with taking the binding energy data of relevant compounds in the literature as the reference. The 688 eV component of an F 1s doublet was attributed to fluorines of [O_4−α SiF_α] units and the 684 eV component to free fluoride ions under ionic interaction with lead ions. The fraction of the fluoride ions increased withx up to 51 %. The Si-F bonds were confirmed in the glasses with 3<x<18 mol%.     

Structural and Magnetic Properties of Copper(II) Coordination Polymers Containing Fluoride-Based Anions and Ancillary Organic Ligands

The fluoride (F⁻) and bifluoride (HF₂⁻) anions have been little used in the self-assembly of molecular and polymeric magnets. We have recently synthesized several new compounds, namely CuF₂(3-OHpy)₄ (OHpy = hydroxypyridine) (1), Cu(SiF₆)(2,6-me₂pyz)₄ (me₂pyz = dimethylpyrazine) (2), CuF₂(H₂O)₂(pyz) (pyz = pyrazine) (3) and [Cu(HF₂)(pyz)₂]BF₄ (4). Compound 1 contains coordinate covalent and hydrogen bonding interactions that link the Cu(II) ions into 3D networks while 2 features square-pyramidal Cu(II) ions that are weakly bridged by SiF₆²⁻ anions into 1D chains. Preliminary structural data indicate that compound 3 contains 1D Cu-pyz-Cu chains while 4 contains two dimensional [Cu(pyz)₂]²⁺ layers, which held together via HF₂⁻ anions so as to form an unprecedented 3D network. The magnetic properties of each are briefly described herein.