Crystal and molecular structure of the superacid salt dirubidium tetrahydrogen trimalonate

The title compound, Rb₂H₄M₃, is C₉H₁₀O₁₂Rb₂, triclinic,P¯1,a=7.254(2),b=9.683(2),c=11.514(3) Å,=107.05(2),/gb=103.81(2), =93.89 (2)°. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.043 for 1649 observed reflections. Rb₂H₄M₃ occurs as three independent molecules, two HM^– and one H₂M with different conformations. Rb₂H₄M₃ has a type B₂IR spectrum and has four short, intermolecular and unsymmetrical hydrogen bonds. Rb(1)⁺ and Rb(2)⁺ ions are coordinated to nine and ten carboxylate oxygen atoms, respectively. The coordination polyhedron for each Rb⁺ ion is a distorted tricapped trigonal prism.     

The orthorhombic polymorph of diammonium trichromate(VI) decaoxide, <Emphasis Type="Italic">α</Emphasis>–(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>Cr<Subscript>3</Subscript>O<Subscript>10</Subscript>

Synthesis and crystal structure of a trichromium(VI) decaoxide compound, α–(NH₄)₂Cr₃O₁₀, is reported. The crystal structure has been determined from three dimensional X-ray data collected at low temperature, 173 K. The structure is isomorphous with its Rb and Cs trichromate analogues, orthorhombic, space group Pbca, with a = 11.2558(3), b = 9.3193(3), c = 18.9819(5) ? and Z = 8. The title compound is composed of discrete [Cr₃O₁₀]^2– chains held together by the counter ion charge and a hydrogen bonding network. The different conformations adopted by trichromate anion within its ammonium, alkali and organic salts are discussed.     

Anomalous High Pressure Properties in Fullerene Superconductors

Abstract

Correlations among lattice parameter, external pressure, and critical temperature T_c has been surveyed on fullerene superconductors with a wide range of lattice parameters and various valence states. The observed value of dT_c/dP for Na₂Rb_0.5Cs_0.5C₆₀ and Li₃CsC₆₀, having small interfullerene separations, is about a few times lager than that of K₃C₆₀. In contrast, small dT_c/dP values are found in fullerides with expanded unit cells, such as (NH₃)_xNaAA^?C₆₀ (A, A^? = K, Rb and Cs) and A₃Ba₃C₆₀. Interestingly, the chemical and physical pressure effects on T_c are considerably different in these fullerides with large interfullerene spacings. Our results suggest that the pressure dependence is scaled by an interfullerene distance when the interfullerene distances is small, but that this scaling fails when the unit cell is expanded.     

Crystal structure of caesium hydrogen (L)‐aspartate and an overview of crystalline compounds of aspartic acid with inorganic constituents

The crystal structure of the new polar compound caesium hydrogen (L)‐aspartate, Cs(C₄H₆NO₄), (abbreviated: Cs(L ‐AspH)) was determined from single crystal X‐ray diffraction data; it comprises two crystallographically different L ‐AspH anions that are connected via caesium cations to form a three dimensional framework. The Cs ions are irregularly sevenfold [Cs1O₇] respectively eightfold [Cs2O₈] coordinated to all α– and β– carboxylate oxygen atoms. Cs(L ‐AspH) represents a novel structure type of its own, as do most compounds of (L)‐aspartic acid with inorganic constituents. A brief summary of such structurally known aspartates is given. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural Influence on the Intensitiy Ratio of the T′ and T87Rb NMR Lines and the Superconductivity in Rb3C60

Abstract

The intensity ratio of the T′/T⁸⁷Rb NMR lines in Rb₃C₆₀ could be changed by different cooling rates after annealing at 380 °C. The results are discussed with respect to magnetically different surroundings of the Rb ions through the two standard orientations of the C₆₀ ^3-ions. Additionally, the superconducting volume fraction is influenced by the different cooling procedures.     

Rubidium hydrogen glutarate and ammonium hydrogen glutarate: X-ray studies of quasi-isostructural crystals involving very short hydrogen bonds

Rubidium and ammonium hydrogen glutarates (M ^{+ –}CO₂.C₃H₆.CO₂H) each crystallize with four molecules in orthorhombic unit cells of almost identical dimensions: (M = Rb)a = 18·55,b = 7·57,c = 5·29 Å; (M = NH₄)a= 18·59,b= 7·56,c= 5· 27 Å. They have very similar structures, but they are not isomorphous: space groupsCmma (Rb) andPmaa (NH₄).The crystal structures have been determined by three-dimensional X-ray analysis and refined with moderate precision. Both have infinite chains of glutarate residues, linked end-to-end by very short, symmetrical hydrogen bonds, with O···H···O = 2·40(2) (Rb) and O···H···O = 2·460(6) Å (NH₄).In the Rb salt, the glutarate residue has strict, crystallographicm symmetry. The difference in the NH₄ salt arises from small movements of the carbon and (especially) the oxygen atoms out of this symmetry plane. These are due to N-H···O bonding: two equivalent cations in the Rb salt, each making contact with eight oxygen atoms, become differentiated in the NH₄ salt by linkage to different sets of four oxygens.We wish to acknowledge financial support from the Science Research Council, and our indebtedness to Drs. J. G. Sime, K. W. Muir and others for help with KDF9 programs.     

Effect of cationic impurities on solubility and crystal growth processes of ammonium oxalate monohydrate: Role of formation of metal‐oxalate complexes

The effect of different bi‐ and trivalent cationic impurities on the solubility of ammonium oxalate and the composition and distribution of chemical complexes formed in saturated ammonium oxalate aqueous solutions as a function of impurity concentration are investigated. The knowledge of the composition and stability of complexes formed in saturated aqueous solutions is then employed to explain the appearance of dead zones of supersaturation for growth and the difference in the effective segregation coefficient of the impurities. Analysis of the experimental results revealed that: (1) at a constant temperature, the dependence of concentration of complex species formed in saturated solutions on the concentration of different impurities can be described by an equation similar to that of the concentration dependence of density of solutions, (2) the dominant metal‐containing species present in saturated solutions are negatively‐charged, most stable oxalato complexes like Cu(C₂O₄)₂²⁻, Mn(C₂O₄)₃⁴⁻, Zn(C₂O₄)₃⁴⁻, Cr(C₂O₄)₃³⁻ and Fe(C₂O₄)₃³⁻, (3) in the investigated range of impurity concentration, the solubility of ammonium oxalates increases linearly with the concentration of all impurities and the increase is associated with the stability of dominant complexes, (4) appearance of dead supersaturation zones in the presence of impurities is associated with instantaneous adsorption of all growth sites by dominant oxalato complexes in relatively short adsorption time, and (5) the segregation coefficient of an impurity cation M of charge z + increases with a decrease in the solubility product constant K_sp for the hydrolysis products of reactions of the type: M^{z +} ↔ M₁^{(z −1)+} + H⁺ (where the cation M has z + charge, and H⁺ is hydrogen ion). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vibrational spectra of polycrystallineMNCO (M = K,Rb, Cs)

IR and Raman spectra are reported for polycrystalline samples of the isomorphousMNCO (M=K,Rb,Cs). The lattice modes are generally assignable to the symmetry species of the factor groupD _4h by analogy with those ofMN₃, but the internal modes are not, in general, interpretable by any known practical analysis. These spectral features may be associated with the disorder of the NCO^– ions in the crystal structure.     

Occupied and Unoccupied Orbitals of C60 and C70

Abstract

The full spectrum of occupied and unoccupied σ and π orbitals is presented for solid C₆₀, C₇₀, and graphite, using Cls emission and absorption spectroscopy. There are significant diffcrences between C₆₀ and C₇₀, and even larger changes relative to their infinite analog graphite (C∝). A comparison is made with photocmission and inverse photoemission results, along with first principles quasiparticle calculations.     

Crystal structure,thermal and compositional deformations of β‐CsB5O8

The crystal structure of β‐CsB₅O₈ has been determined from X‐ray powder diffraction data using synchrotron radiation: Pbca, a = 7.8131(3) Å, b = 12.0652(4) Å, c = 14.9582(4) Å, Z = 8, ρ_calc = 2.967 g/cm³, R‐p = 0.076, R‐wp = 0.094. β‐CsB₅O₈ was found to be isostructural with β‐KB₅O₈ and β‐RbB₅O₈. The crystal structure consists of a double interlocking framework built up from B‐O pentaborate groups. The crystal structure exhibits a highly anisotropic thermal expansion: α_a = 53, α_b = 16, α_c = 14 · 10^‐6/K; the anisotropy may be caused by partial straightening of the screw chains of the pentaborate groups. The similarity of the thermal and compositional (Cs‐Rb‐K substitution) deformations of CsB₅O₈ is revealed: increasing the radius of the metal by 0.01 Å leads to the same deformations of the crystal structure as increasing the temperature by 35°C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

3,4,5-Triethoxybenzoic acid benzene solvate: An example of hydrogen-bonded carboxylic acid dimer

Crystals of 3,4,5-triethoxybenzoic acid benzene solvate, 3,4,5-(C₂H₅O)₃C₆H₂COOH? 0.25C₆H₆, are monoclinic, space group P2/c, with the cell dimensions at 100 K: a = 18.729(3), b = 10.6475(17), c = 14.390(2) Å, β = 98.410(2)^°, V = 2838.7(8) ų, and Z = 8, Z′ = 2. In the crystal structure two symmetrically independent molecules of 3,4,5-triethoxybenzoic acid form a planar dimer by two O–H?sO hydrogen bonds.     

Crystal growth and electric‐property change by rubidium or cesium doping on potassium‐sodium‐niobate

Alkali metals (Na, Rb or Cs) co‐doped with fiber‐ and bulk‐shaped KNbO₃ single crystals were grown using two original methods by means of doping together of small ionic Na and large ionic Rb or Cs into KNbO₃. Single‐phase crystals could be grown with an orthorhombic system at room temperature as well as pure KNbO₃. Piezoelectric and ferroelectric property changes by the co‐doping of Rb or Cs with Na were estimated using d₃₃ values and a polarization‐electric field hysteresis curve in fiber‐ and bulk‐shaped crystals. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and properties of Rb<Subscript>2</Subscript>Ni(SO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O (RNSH)

Large single crystals of rubidium nickel hexahydrate Rb₂Ni(SO₄)₂ · 6H₂O (RNSH) of optical quality were grown for the first time. The atomic structure of RNSH crystals was refined. A comparative analysis of the crystal structures of (M ¹⁺)₂Ni(SO₄)₂ · 6H₂O, where M ¹⁺ is K, Rb, or Cs, was performed. The solubility curve of RNSH in water was measured. The optical and thermogravimetric properties of RNSH were investigated. The internal defect structure of RNSH crystals was studied by X-ray topography.     

Microstructural analysis of Ga2S3–2MCl (M = K, Rb, Cs) glasses using Raman scattering

Raman scattering spectra of Ga₂S₃–2MCl (M = K, Rb, Cs) glasses have been conducted at room temperature. Based on the analysis of the local co-ordination surroundings of Cs⁺ ions, the similarities and differences of Raman spectra for the glass Ga₂S₃–2CsCl and the bridged molecular GaCl₃ were explained successfully. Through considering the effect of M⁺ ions on mixed anion units [GaS_4?xCl_x] and bridged units [Ga₂S_6?xCl_x] and the corresponding microstructural model, the Raman spectral evolution of the Ga₂S₃–2MCl (M = K, Rb, Cs) glasses was reasonably elucidated.     

Crystal and molecular structure of cesium hydrogen malonate

The title compound is C₃H₃O₄Cs, CsHM, monoclinic,P2₁/c,a=8.393 (3),b=7.960(2),c=9.023(2) Å,=92.11(2)°. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.023 for 760 observed reflections. The CsHM has no internal symmetry and one carboxy group, but not the other, is twisted almost at right angles (96°) to the plane of the three central carbon atoms. The hydrogen malonate anions are linked together by two short and symmetrical O-HO hydrogen bonds [2.468(4) and 2.482(4) Å]. The structure consists of hydrogen malonate chains cross-linked by the Cs⁺ ion. The IR spectrum of CsHM has been analyzed.     

Crystal structure and thermal behaviour of (Rb,Cs)BSi2O6 solid solutions

The crystal chemistry of Rb‐Cs boroleucites has been studied by means of X‐ray powder diffraction at room and elevated temperatures. The cubic I‐43d → cubic Ia3d phase transition was investigated using a series of samples prepared by solid‐state reaction along the pseudobinary system RbBSi₂O₆ ‐ CsBSi₂O₆. The Rietveld refinement of the structures of Rb_1‐xCs_xBSi₂O₆ solid solutions (x = 0.2, 0.4, 0.6, 0.8) demonstrates that the solutions with a high Rb content crystallise in the cubic I‐43d space group, and the boroleucites with a considerable Cs content have Ia3d symmetry. Rb can substitute Cs in a wide range of compositions. Within a narrow range of x = 0.5 ‐ 0.6 immiscibility was revealed. Under Rb‐Cs substitution the cubic lattice parameter, the (Rb,Cs)‐O distances, and the angles between tetrahedra of the I‐43d phase change clearly, while those of the Ia3d phase change slightly. The HTXRD data shows that the I‐43d phase transforms into a Ia3d phase on heating analogously to a change of the composition. As the Cs content increases the transition temperature decreases. The low temperature I‐43d phase shows a higher thermal expansion than the high temperature Ia3d phase. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Potassium 1,2,4,5-benzenetetracarboxylate,C6H2(CO2K)4·4H2O; its formation,crystal structure,and hydrogen bonding

From an aqueous mixture of 1,2,4,5-benzenetetracarboxylic acid, C₆H₂(CO₂H)₄, and KF we grew crystals first of KHF₂ then of the title compound. An X-ray crystallographic determination of this compound shows a network of C₆H₂(CO ₂ ^– )₄ units linked through hydrogen bonds to water molecules. This is the first reported structure of a benzenecarboxylate anion. Two carboxylate groups are coplanar with the benzene ring, whereas the other two are perpendicular to it.     

Synthesis and characterization of potassium, rubidium, and cesium thiogermanate glasses

Glass-forming regions were investigated for the binary xM₂S + (1 − x)GeS₂ (M=K, Rb, Cs) systems. Glasses were prepared from 0?x?0.20 mole fraction alkali sulfide using a novel preparation route involving the decomposition of the alkali hydrosulfides in situ. At higher alkali concentrations near x=0.33, the glass-forming regions are limited by the readily formed adamantane-like M₄Ge₄S₁₀ crystals. Structural characterization of the glasses and polycrystals for x?0.33 were performed using Raman scattering and IR absorption. Terminal Ge-S⁻ vibrational modes, observed between 473 and 479 cm⁻¹, increased in intensity and decreased in frequency with increasing alkali modifier content. Glass transition temperatures decreased with increasing alkali modifier, ranging from 250 to 215 °C. Corresponding crystallization onset temperatures were between 340 and 385 °C. DC conductivity values of the glasses ranged from 10⁻¹⁰ to 10⁻⁷ (Ω cm)⁻¹ with activation energies between 0.54 and 0.93 eV for the temperature range of ∼100-250 °C. Higher ionic conductivities were observed with increasing alkali concentration and decreasing alkali radii. Additionally, an increase in the activation energy was observed above the glass transition temperature.     

Crystal and Molecular Structure of N‐methyl‐N‐3‐(sulfonato)propyl‐3‐[tris(trimethylsiloxanyl)3‐silyl]pyrrolinium Sulfobetaine Hydrate at Room Temperature and 163 K

2 (C₁₇H₄₁NO₆SSi₄) . H₂O. M_r=1017.88, triclinic, space group P‐1. The molecules are arranged in bilayers. The molecules in each bilayer are held together by electrostatic forces, i.e., O‐N⁺ contacts, and hydrogen bonds. The asymmetric unit consists of two partly disordered siloxane molecules and one water molecule. The structure of the bilayers is virtually the same at 163 K and room temperature, but the stacking of the bilayers is different. The Si‐O‐Si bond angles at low temperature are significiantly smaller than at room temperature.     

Static Disorder in Hexagonal Crystal Structures of C60 at 100 K and 20 K

C₆₀ · 2C₈H₁₀ (100 K): hexagonal space group P6₃, a = 23.694(4), c = 10.046(2) Å, V = 4884(2) ų, D_x = 1.903 g cm⁻³, Z = 6, F(000) = 2856, γ(CuKa) = 1.54178 Å, μ = 0.84 mm⁻¹. C₆₀ · 2C₈H₁₀ (20 K): hexagonal space group P6₃, a = 23.67(1), c = 10.02(1) Å, V = 4862(6) ų, D_x = 1.912 g cm⁻³, Z = 6, F(000) = 2856, γ(CuKa) = 1.54178 Å, μ = 0.84 mm⁻¹. The structures were determined by Patterson syntheses and rigid-body refinements. The C₆₀ molecules show two orientations with one molecular centre in common. The solvent molecules are disordered too. Static disorder could not be overcome or influenced by cooling down. A coordination number of 10 was found for the fullerene molecules.