An Isoperibolic Reaction Twin Calorimeter for Investigating Precipitation

An isoperibolic reaction twin calorimeter is described and its application to studying precipitation is shown. This technique is suitable for determining both the total reaction enthalpy and also, in specific ranges of supersaturation, kinetics of the process. The total enthalpy of BaSO₄ and CaC₂O₄ · H₂O precipitation at 25 °C was determined as −16.2 and −18.1 kJ mol⁻¹, respectively. The spontneous precipitation of these compounds affected by mixing reactant solutions together proceeds through initial surge of nucleation and fast crystal growth that steeply diminishes. No major wave of secondary nucleation during precipitation was observed.     

A Novel Three Dimensional Organic–Inorganic Hybrid Based Porous Phase: Synthesis and Characterization of Reduced Oxovanadium pyromellitate, [VIV2O2(H2O)2(C6H2(COO)4)]

The hydrothermal reaction of a mixture of VOSO₄ · xH₂O, 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) and 0.1 M H₂SO₄ for 72 h at 160 °C gives blue needle like crystals of [V^IV ₂O₂(H₂O)₂(C₆H₂(COO)₄)] in 30% yield. The compound has a porous 3-D extended network structure having a rigid architecture which is held together by the multidentate functionalities of 1,2,4,5-benzenetetracarboxylate ligand. Crystal data for the compound: monoclinic space group C 2/c (No:15), a = 11.756(5) ?, b = 9.645(3) ?, c = 11.822(7) ?, β = 107.10(4)°, Z = 8. The compound constitutes the first example of a fully reduced oxovanadium based solid incorporating the organic ligand. This article consists of synthesis, crystal structure and characterization of [V^IV ₂O₂(H₂O)₂(C₆H₂(COO)₄)].     

Crystal structure, vibrational spectra, and thermal decomposition and nitrogen adsorption behaviour of a new tetramanganese(II) dipyrophosphate decahydrate, Mn4(P2O7)2·10H2O

A new manganese(II) pyrophosphate, Mn₄(P₂O₇)₂·10H₂O, has been synthesized and characterized by single-crystal X-ray diffraction [orthorhombic space group Pnma, with unit cell parameters of a=9.3288(3) ?, b=25.9532(9) ?, c=8.4783(3) ?; Z=4]. All the pyrophosphate anions show non-linear P–O–P bonds with an average angle of 128.60°. The framework of this new pyrophosphate is made up of packed layers of MnO₆ octahedra connected by double-tetrahedra P₂O₇ groups and a layer of Mn(H₂O)₆ units. The [P₂O₇]⁴⁻ anions adopt a bent, near-staggered conformation. The absence of coincidences for the majority of the IR and Raman bands is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted in part on the basis of factor group effects. The structural changes occurring during heating have been investigated by TG-ATD. When Mn₄(P₂O₇)₂ ^.10H₂O is gradually heated, it decomposes into an intermediate hydrated salt at 96°C and then to anhydrous Mn₂P₂O₇ at 325°C. This thermal behaviour is different from that of Zn₄(P₂O₇)₂·10H₂O. The crystal structure of the new managenese(II) pyrophosphate is compared with the known structures of Zn₄(P₂O₇)₂·10H₂O, Mn₂P₂O₇·2H₂O and anhydrous Mn₂P₂O₇. The adsorption and desorption isotherms of Mn₄(P₂O₇)₂·10H₂O, Zn₄(P₂O₇)₂·10H₂O and MnKHP₂O₇·2H₂O have been investigated by BET measurements and the results show that the capacity for N₂ sorption of the Mn(II) salt is two times lower than is that of the Zn(II) isotype and two or three times higher than is that of MnKHP₂O₇·2H₂O.     

Effect of CuCl2 · 2 H2O additive in ethanol on dissolution and selective etching behaviour of CsI crystals

{100} faces of Kyropoulos grown CsI crystals had undergone a selective etching, and CsI spheres of ∼ 10 mm in diameter were subjected to dissolution at room temperature for 10 hrs. The results are: pure ethanol does not bring about any anisotropy in dissolution, addition of CuCl₂ · 2 H₂O leads to an anisotropy in dissolution of CsI, change in CuCl₂ · 2 H₂O concentration changes etch pit morphology, whereas the dissolution form does not depend on additive concentration. With increasing CuCl₂ · 2 H₂O etching rates at first increase, later decrease, dissolution rates linearly increase.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

Kinetics and thermodynamics of ferrous-ferric equilibrium in sodium aluminoborate glasses

The oxidation-reduction equilibrium between ferrous and ferric iron in sodium aluminoborate glass melts having molar composition 15Na₂O·10Al₂O₃·75B₂O₃ has been studied as a function of temperature. The reaction was observed to follow first order kinetics. The energy of activation for the above reaction was calculated. Equations previously suggested to represent the Fe²⁺–Fe³⁺ equilibrium were discussed and a new equation is proposed. The enthalpy of the reaction was ?8.80 kcal mol^?1.     

Structural Characterization of Heterodinuclear ZnII-LnIII Complexes (Ln = Pr,Nd) with a Ring-Contracted H2valdien-Derived Schiff Base Ligand

Synthesis and structural characterization of two heterodinuclear Zn^II-Ln^III complexes with the formula [ZnLn(HL)(µ-OAc)(NO₃)₂(H₂O)_x(MeOH)_1-x]NO₃ · n H₂O · n MeOH [Ln?=?Pr (1), Nd (2)] and the crystal and molecular structure of [ZnNd(HL)(µ-OAc)(NO₃)₂(H₂O)] [ZnNd(HL)(OAc)(NO₃)₂(H₂O)](NO₃)₂ · n H₂O · n MeOH (3) are reported. The asymmetrical compartmental ligand (E)-2-(1-(2-((2-hydroxy-3-methoxybenzylidene)amino)-ethyl)imidazolidin-2-yl)-6-methoxyphenol (H₂L) is formed from N¹,N³-bis(3-methoxysalicylidene)diethylenetriamine (H₂valdien) through intramolecular aminal formation, resulting in a peripheral imidazoline ring. The structures of 1–3 were revealed by X-ray crystallography. The smaller Zn^II ion occupies the inner N₂O₂ compartment of the ligand, whereas the larger and more oxophilic Ln^III ions are found in the outer O₂O₂’ site.

Graphic Abstract

Synthesis and structural characterization of two heterodinuclear Zn^II-Ln^III complexes (Ln?=?Pr, Nd) bearing an asymmetrical compartmental ligand formed in situ from N¹,N³-bis(3-methoxysalicylidene)diethylenetriamine (H₂valdien) through intramolecular aminal formation are reported.

     

Structural analysis of Na2OGa2O3SiO2 glasses by the X-ray diffraction method

The structure of Na₂OGa₂O₃SiO₂ glasses of four different compositions containing up to 45 mol. % Ga₂O₃ has been determined by the X-ray diffraction method. The radial distribution function D(r) obtained indicates that Ga³⁺ ions are in fourfold coordination and GaO₄ tetrahedra are formed in these glasses. The reduced intensity function S·i(S) and radial distribution function D(r) which were calculated based on a structural model for A-25, 0.25(Ga₂O₃)·0.75(Na₂O·2SiO₂)/3 glass agreed well with the observed ones.     

Crystal Structure Determination of Nickel (2,2-Dipyridyl) Sulphate Hexahydrate [Ni(C10H8N2) · 4 H2O]SO4 · 2H2O

[Ni(C₁₀H₈N₂) · 4 H₂O]SO₄ · 2 H₂O, Mr = 418.7, monoclinic, P1 , a = 7.781(3), b = 9.421(3), c = 11.457(4) Å, α = 87.54(2)º, β = 96.40(2)º, γ = 102.58(2)º, ν = 814.5 Å, D_x = 1.26 g/cm³, Z = 2, (MoKx) = 0.71073 Å, μ = 7.0 cm⁻¹: T = 23 °C, R = 0.047 for 2139 reflections having intensities greater than 36. The structure was solved using the Patterson heavy-atom method and the remaining atoms were located in succeeding difference Fourier syntheses. The structure was then refined by full matrix least-squares using anisotropic temperature factors. Hydrogen atoms were located and their positions and isotropic parameters were refined.     

Crystal structure of 4,5-dihydro-6-(2-thienyl)-3(2H) pyridazinone azine, (C16H16N16S2)

M_r = 484, monoclinic, P 2₁/c, a = 5.567(1), b = 7.857(2), c = 19.194(10) Å, β = 99.97(3)°, V = 826.9 ų, Z′ = 2, D_x = 1.43 g · cm⁻³, F(000) = 372, MoKα, λ = 0.71069 Å, μ = 0.328 mm⁻¹, final R = 0.055 for 889 observed reflections, T = 293 K. The compound was prepared from a direct unusual reaction of 6-(2-thienyl)-2,3,4,5-tetrahydropyridazine-3-one with hydrazine hydrate. The structure was solved by direct methods and refined by full-matrix least squares. The molecule in the solid state consists of a dimer with its two equivalent halves related by a center of symmetry at the middle of the N N bond. Each molecular fragment is nearly planar and the N N bond between the two halves is 1.296(5) Å indicating that it is a partial double bond.     

Crystal chemistry of the salts Me+Cl · Me2+Cl2 · 2 H2O

The crystal chemistry of the double salts Me⁺Cl · Me²⁺Cl₂ · 2 H₂O (where (Me⁺ = K, Rb, Cs; Me²⁺ = Mn, Fe, Co, Ni) is considered. It is concluded that these salts crystallize in three types of structures, the Me⁺ ion size being decisive for the structure type. Salts containing the large Cs⁺ ions crystallize in an orthorhombic structure in which [Me²⁺ (H₂O)₂Cl₄] octahedra form chains having common Cl⁻ corners. Salts with the smaller K⁺ ions crystallize in a tricline system, the [Me²⁺ (H₂O)₂Cl₄] octahedra being connected by a common Cl–Cl edge and forming dimers. When the intermediate in size Rb⁺ ions are present in the salts, either of the above structures is possible as well as a monoclinic structure which is intermediate in symmetry. The expected isostructure of the cesium salts was checked by studing the CsCl · NiCl₂ · 2 H₂O–CsCl · MnCl₂ · 2H₂O–H₂O system. A continuous series of mixed crystals is found.     

Crystal Structure,Infrared Spectra and DFT Study of Benzyl 2,3-Anhydro-β-<Emphasis Type="SmallCaps">d</Emphasis>-Ribopyranoside

Abstract  

The crystal structure of benzyl 2,3-anhydro-β-d-ribopyranoside is orthorhombic, P2₁2₁2₁, Z = 4. The pyranose ring adopts the E _O conformation distorted considerably to the ⁵ H _O direction. The molecules of the title compound are linked into infinite chains running along the a-axis by bifurcated O–H···O hydrogen bonds. Interaction energies of these hydrogen bonds are significantly different, ~−5.4 for the bond with the smaller and ~−1.1 kcal/mol for the bond with the larger O···O separation. The hydrogen-bond pattern is completed by the two weaker C–H···O intermolecular hydrogen bonds, aiming at the epoxy oxygen atom. IR vibrational spectrum was interpreted by means of comparison with the full list of vibrational modes predicted using DFT method in the solid state. While till 1495 cm⁻¹ the individual bands can be reconciled with single calculated modes, the region below this limit is populated by heavily overlapped HCH, HCO, HOC, COC and HCC bending modes merged with few ν(CC) and ν(CO) modes. The respective “red” shifts of the positions of the ν(OH) bands correlate well with the size of the O···O separation.     

Square-wave voltammetry and impedance spectroscopy in iron-doped melts of the system Li2O/Al2O3/SiO2

Glass melts with the basic compositions xLi₂O · 15Al₂O₃ · (85 − x)SiO₂ (x = 8.5, 11, 13.5, 16 and 18.5) doped with 0.25 mol% Fe₂O₃ were studied by square-wave voltammetry and impedance spectroscopy at temperatures in the range from 1100 to 1600 °C. The square-wave voltammograms show a pronounced peak attributed to the reduction of Fe³⁺ to Fe²⁺. The attributed peak potentials which are equal to the standard potentials of the redox pair decrease linearly with the temperature. Impedance spectra measured could be simulated using an equivalent circuit attributed to a simple electron transfer reaction controlled by diffusion.     

Composition and morphology control of Fex(PO4)y(OH)z·nH2O microcrystals

A series of Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals were prepared by the hydrothermal reaction at 150 °C. The ratio of Fe²⁺/Fe³⁺ in Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals can be adjusted by using Na₂S₂O₃·5H₂O as a reducing agent. The morphology control of Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals was realized through regulating the molar ratio of LiAc·2H₂O/FeCl₃. Further, the morphology, structure and composition of Fe_x(PO₄)_y(OH)_z·nH₂O microcrystals were also investigated by x‐ray diffraction (XRD), x‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) techniques. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrothermal synthesis and characterization of (N(C2H5)4)4[VMo12V2O44]

The hydrothermal reaction of a mixture of Na₂MoO₄·2H₂O, V₂O₅, pyromellitic acid (1,2,4,5‐C₆H₂(COOH)₄), (C₂H₅)₄NCl and 0,1 M H₂SO₄ for 88 h at 180°C gives blue needle‐like crystals of [V^IV₂O₂(H₂O)₂ (C₆H₂(COO)₄)] in 20% yield (based on V) and dark blue prismatic crystals of the title compound, mixed‐valance (N(C₂H₅)₄)₄[VMo₁₂V₂O₄₄], 1, in 12% yield (based on Mo). 1 was investigated by means of elemental analysis, thermogravimetry, Fourier Transform Infrared Spectroscopy and Single Crystal X‐ray Diffraction Methods. Crystal data for the compound: monoclinic space group P2₁/c (No:14), a=13.7815(12) b=13.0271(9) c= 21.189(2) Å, β= 113.909(7)°, Z=2. Although [XM₁₄O₄₂]^‐n (X=P, Si, Ge, V and M=Mo and/or V) cores have been previously determined, this is the first time that [VMo₁₂V₂O₄₄]^‐4 core is synthesized and characterized. The structural difference between 1 and these HPOMs is the coordinational geometry of the central metal atoms. The central vanadium in 1 has an octahedral coordination geometry, whereas in literature, the central V, P, Si and Ge atoms in [V₁₅O₄₂]^‐9 / [SiM₈V₆O₄₂]^‐4 / [PM₈V₆O₄₂]^‐5 / [GeM₈V₆O₄₂]^‐4 have tetrahedral coordinational geometry. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of [CuCl(phen)2]3H3V10O28 · 7 H2O

The new compound, [CuCl(phen)₂]₃H₃V₁₀O₂₈ · 7 H₂O, was prepared by reaction of an aqueous KVO₃ solution (pH 3) with an aqueous solution of CuSO₄ · 5 H₂O in which 1,10‐phenanthroline (phen) and KCl were added. The crystal structure of the compound was determined, and the proton position in H₃V₁₀O₂₈^3– were calculated by the bond length/bond number method and also determined from difference electron density map. The protons are bound to colinearly arranged μ–OV₂ and μ–OV₃ groups which is the common protonation type in trihydrogen decavanadates. The structure crystallizes in P1 space group symmetry. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Untersuchung epitaktischer Molybdänkarbidschichten an Molybdän-(110)-Oberflächen

The initial phases of high temperature (1700 K) carburization of (110) molybdenum surfaces by C₆H₆ at low pressure are examined with low energy electron diffraction (LEED) and emission electron microscopy. After an exposition of about 8 · 10⁻⁵ Torr · sec a (4 × 4) superstructure was observed by means of LEED, interpreted as coincidence lattices with the Mo₂C (10.0) plane parallel to the Mo (110) surface. Heating a sample without further exposition resulted in the appearance of a complex and of a (2 × 2) superstructures. After an exposition of about 2 … 9 · 10⁻³ Torr · sec needle shaped molybdenum carbide crystallites grew on the surface into the [111] and [111] directions. The orientation Mo₂C (10.1) parallel to Mo (110) was concluded from the LEED patterns.     

The investigation of the magnetic interaction between Cu2+ and V4+ ions in x(CuO·2V2O5)(1 − x)[2B2O3·K2O] glasses

EPR and magnetic susceptibility measurements have been performed on (CuO·2V₂O₅)(1?x)[2B₂O₃·K_2O] glasses with 0 ? x ? 40 mol. %.For x < 10 mol.%, both Cu²⁺ and V⁴⁺ ions are present mostly as the isolated species. The values of MO coefficients indicate a high covalent degree of the transition metal (TM)-oxygen bonds. Also, the EPR parameters suggest the presence of strong (TM)-oxygen bonds along the 0_z axis, which lead to an octahedral (Oh) symmetry component at TM ions sites.In the case of 10 ? x ? 40 mol.%, the dipole-dipole and superexchange interactions occur between transition metal ions, which determine a broad resonance line at $\text{g ? 2}$. The strong interactions between Cu²⁺ and V⁴⁺ ions give rise to the exchange coupled Cu²⁺ V⁴⁺ pairs in the studied glasses with x > 10 mol.% (y > 3.9 mol.%).     

Synthesis and Crystal Structure of 2-Amino-4-(4-hydroxyphenyl)-5-propylthiazole Ethanol Solvate 0.25 Hydrate

Abstract  

2-Amino-4-(4-hydroxyphenyl)-5-propylthiazole was synthesized by the reaction of α-bromo-1-(4-hydroxyphenyl)-1-pentone with thiourea. The crystal structure of its ethanol solvate 0.25 hydrate, C₁₂H₁₄N₂OS···C₂H₅OH···0.25·H₂O, was determined by X-ray diffraction analysis. The crystal belongs to monoclinic system, space group C2/c with a = 20.9046(10), b = 10.1057(5), c = 30.0017(15) ?, β = 105.5850(10)°, Z = 8, M _r = 569.77, V = 6105.0(5) ?³, D _c = 1.240 g/cm³, μ = 0.214 mm⁻¹, F(000) = 2440, the final R = 0.0598 and wR = 0.1825 for 5,911 observed reflections [I > 2σ(I)]. Compound (1) is composed by two non-coplanar ring systems of phenol and thiazole. The structure displays extensive O–H···N, N–H···O and O–H···O intermolecular hydrogen bonds.     

The effect of fluoride on the Fe2+/Fe3+-redox equilibrium in glass melts in the system Na2O/NaF/CaO/Al2O3/SiO2

Liquids with the base compositions (16 − x/2)Na₂O · xNaF · 10CaO · 74SiO₂ (x = 0, 1, 3, and 4) and (10 − x/2) · Na₂O · xNaF · 10CaO · yAl₂O₃ · (80 − y)SiO₂ (x = 0, 1, 3, 5 and y = 5 and 15) doped with 0.25 mol% Fe₂O₃ were studied by means of square-wave voltammetry in the temperature range from 1000 to 1500 °C. With increasing temperature, the redox equilibria were shifted to the reduced state. Also while increasing the alumina concentration, the Fe²⁺/Fe³⁺-redox equilibrium is shifted to the reduced state. In the soda-lime–silica melt the addition of fluoride shifts the equilibrium to the oxidized state, while in the aluminosilicate melts with 15 mol% Al₂O₃, the equilibrium is shifted to the reduced state. In the aluminosilicate melts with 5 mol% Al₂O₃, the equilibrium was not affected by the fluoride concentration. This is explained by the structure of the respective glass compositions.