Structure of BaGd2（MoO4）4 Crystal

The title compound belongs to monoclinic,space group C2/c with a=5.2694(1),b=12.6659(4),c=19.4108(2) ,β=91.504(2)°,V=1295.06(5) 3,Z=4 and Dc=5.599 g/cm3. The structure of BaGd2(MoO4)4 contains a MoO4 tetrahedron,a distorted GdO8 polyhedron,and Ba2+ ions in a tenfold coordination. The GdO8 polyhedra are linked together through edge-sharing to give a two-dimensional Gd layer. The MoO4 tetrahedra connected to the Gd atoms are capped up and down the Gd layer through common oxygen apices,thus forming a new Gd-Mo layer. Finally,the Gd-Mo layers are held together through bridging BaO10 polyhedra to form a three-dimensional framework. Since the Ba-μ3-O bond has a large average distance of 2.888 ,this structural characteristic will result in a cleavage along the (001) plane.     

An Efficient Preparation of 4, 4′-Dicarboxy-2, 2′-Bipyridine

A convenient and high yield preparation of 4, 4′-dicarboxy-2, 2′-bipyridine from the oxidation 4, 4′-dimethyl-2, 2′-bipyridine with potassium dichromate in sulfuric acid is reported.     

Structure of Barium Tetrafluorborate Ba2（BF4）4

The title compound Ba2 (BF4)4 crystallizes in the monoclinic spacegroup P21/n with crystallographic parameters: a = 8. 339 (3), b = 16. 530 (7), c =10. 212(4) A, V=1348. 7 A3, β= 106. 64(3)°, Z=4, Dc=3. 06 g/cm3, F(000)=1104, μ=5. 98 mm-1, (MoKa) =0. 71069, M= 621. 90. Least-squares refinementaffords the final residuals R=0. 0639 and Rw=0. 0676 for 2841 observed reflections (I>3(I)). The structure consists of columns of BF4 groups, which parallel to the b direction. All columns are linked together through Ba…F bonds, Both the two crystallographically different barium atoms are nine-coordinated by a distorted tri-capped prismof fluorine atoms from the nearest six BF4 tetrahedrons. There are two types of fluorineatoms, one connecting one barium atom and the other connecting two barium atoms.Each BF4 tetrahedron is connected to three barium atoms, so it (tetrahedron) can beviewed as unidentate ligand and bidentate ligand at the same time.     

Non-isothermal Kinetics of the Dehydration Process of Na_2MoO_4·2H_2O

Introduction In the field of thermal analysis kinetics, there have been many kinetic models and methods of processing the corresponding data, which can depict the most probable kinetic mechanism of solid state reactions, such as the method combining differential and integral methods,1-6 the method combining isothermal and non-isothermal processes7,8 and method of TA curve shape,9,10 and so on. Recently, based on the predeces-sor抯 work, a more complete kinetic method of process-ing thermal ana…     

Thermal Transformations of CuNH4PO4⋅H2O

The isothermal and non-isothermal transformations of polycrystalline CuNH₄PO₄⋅H₂O in vacuum and in various gas atmospheres (in open air and in gaseous ammonia atmosphere) were studied at 20–800°C by means of differential thermal analysis, thermogravimetry, X-ray diffraction, paper chromatography, optical microscopy and chemical analyses. The effects of the gas phase composition on the kinetic peculiarities of total gas evolution and on the partial processes of dehydration, ammonia removal and rearrangement of the anionic sub-lattice were considered. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electronic Energy Structure of a Series of Chalcopyrite-Like Compounds AgGaS2–CdGa2S4–InPS4

The effect of pseudovacancies on the density of electronic states of valence electrons in AgGaS₂, CdGa₂S₄, and InPS₄ is studied both experimentally, by means of X-ray spectroscopy, and theoretically, by calculating the partial densities of electronic states using the local coherent potential. The compounds under study are the derivatives of the sphalerite structural type (doubled cell) with gradually increasing deficiency of metals from to and further to , where is a vacancy. The environment of the metal atoms remains tetrahedral, while that of the sulfur atoms changes with increasing number of vacancies from four (AgGaS₂) to three (CdGa₂S₄) and two (InPS₄). For the compounds under study, SK and PK X-ray emission and absorption spectra were recorded at a resolution of about 0.2 eV, and the local partial densities of states were calculated for all components of the compounds. The theoretical curves practically coincide in shape and energy position of fine structure elements with the corresponding experimental curves. This allowed reliable conclusions about the energy positions of electronic states at the top of the valence band and about the dependence of the SK emission and absorption spectra in the series of compounds under study on variation of the crystal structure and on the chemical composition of the nearest surroundings of sulfur atoms.     

One-pot Synthesis of 4-Trifluoromethyl-l,2-dihydropyrimidines

4-Trifluoromethyl-1,2-dihydropyrimidines were synthesized in moderate yields by the one-pot reaction of 4-ethoxy-1,1,1-trifluoro-3-buten-2-one, aldehydes and ammonia catalyzed by zinc chloride under mild conditions.     

An investigation of the polythermal diagram of the H2ONa2HPO4Na2SO4 system

The polythermal diagram of the ternary system H₂ONa₂HPO₄Na₂SO₄ has been established, setting up nine isotherms obtained between 0 and 25°C by conductimetric analysis. The solubility domains of the various solid phases have been determined. One eutectic, three stable and one metastable transitional transformations have been observed. Temperature and composition of the eutectic point have been obtained by thermal analysis at constant flow.     

Crystal structure of K3SbS4·4 1/2 H2O

Summary The crystal structure of K₃SbS₄·4 1/2 H₂O, monoclinic, P2₁/c-C ₅ ^2h ,a=12.732(3),b=7.720(2),c=13.928(4) Å, =90.19(1)°,V=1369.0(5) ų,Z=4, has been determined from X-ray single crystal data and refined by least-squares methods toR=0.031 for 3 024 reflections. The structure is built up from KS_{4 – 5}(H₂O)_{3 – 5} polyhedra and SbS₄ tetrahedra (Sb-S=2.327 Å) which are three-dimensionally linked. The water molecules are bonded to two or three K⁺ ions and form exclusively O-H ... S-type hydrogen bonds. One of the five crystallographically different water molecule sites is due to space limitations only half occupied.

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Die Kristallstruktur von K₃SbS₄·4 1/2 H₂O

Zusammenfassung Die Kristallstruktur von K₃SbS₄·4 1/2 H₂O, monoklin, P2₁/c-C ₅ ^2h ,a=12.732(3),b=7.720(2),c=13.928(4) Å, =90.19(1)°,V=1369.0(5) ų,Z=4, wurde mit Röntgen-Einkristalldaten bestimmt und für 3 024 Reflexe aufR=0.031 verfeinert. Die Kristallstruktur ist aus dreidimensional verknüpften KS_{4 – 5}(H₂O)_{3 – 5}-Polyedern und SbS₄-Tetraedern (Sb-S=2.327 Å) aufgebaut. Die Wassermoleküle sind an zwei bis drei Kaliumionen gebunden und bilden ausschließlich Wasserstoffbrücken des Typs O-H...S aus. Eine der fünf kristallographisch verschiedenen H₂O-Lagen ist aus Platzmangel nur zur Hälfte besetzt.

     

Synthesis,crystal structure of Gd(H2O)(C2O4)2 · NH4 and of La(C2O4)2 · NH4. Characterization of the Ln(H2O)(C2O4)2 · NH4 with Ln=Eu…Yb

Single crystals of two lanthanide complexes, presenting similar formula Ln(H₂O)_x(C₂O₄)₂ · NH₄ with Ln=La, x=0 and Ln=Gd, x=1, have been prepared, in closed system at 200 °C. The gadolinium complex is bi-dimensional. A layer is built by the packing of the basic unit, [Gd(C₂O₄)]₄. The gadolinium atoms are related only by bischelating oxalate ligands, the ammonium ion and the water molecule (bound to the gadolinium atom) are localized into the interlayer space. The lanthanum complex is tri-dimensional. The basic building unit remains approximately the same and the packing of these units form a layer. However, within these units, the lanthanum atoms are related by either an oxalate ligand or an edge. Moreover, an oxalate ligand assumes the connection between the layers. The ammonium ion is localized into two sets of intersecting channels. Pure phase of the gadolinium complex has been prepared at 100 °C and extended to some lanthanide elements, Eu…Yb. As the size of the lanthanide ionic radius is decreasing, it is noticeable that the a unit–cell constant follows an expansion pattern while the others two follow an usual contraction one. The thermal behavior of this family shows that the anhydrous compounds are obtained and that some water molecule is sorbed during the cooling. Thus, the anhydrous compounds present a relatively open-framework with some small micropores.     

Excitation and luminescence spectra of UO2F2−4

The luminescence and excitation spectra of [(CH₃)₄]₂UO₂F₄, M₃UO₂F₅ (M = K and Rb) and Cs₂SnCl₆:UO₂Cl²⁻₄ have been recorded at temperatures down to 10 K. The excitation spectrum of [(CH₃)₄]₂UO₂F₄ is unique because the electronic origin is located at the lowest energy reported for any uranyl compound. The analysis of the excitation spectrum is consistent with a D_4h, but not a D_5h coordinated uranyl chromophore. A detailed interpretation of the vibronic structure of the spectrum enables the lower excited states of the uranyl ion to be located, and the symmetries of these are consistent with the model of Denning. A comparison with the excitation spectra of salts of the UO₂F³⁻₅ anion is made.     

Neutron diffraction study of UO2SeO4 · 2D2O

A powdered sample of deuterated uranyl selenate dihydrate UO₂SeO₄ · 2D₂O is studied by neutron diffraction. This compound crystallizes in monoclinic space group P2₁/c; a = 6.974(1) Å, b= 8.289(2) Å, c = 11.664(2) Å, β=92.319(6)°, Z = 4, R _f = 3.14, R _I = 5.53, gC² = 2.82. The main structural units of the compound are [UO₂SeO₄(D₂O)₂] chains propagating along [100]. These chains are linked into a framework group (A = UO ₂ ²⁺ , T³ = SeO ₄ ^2? , and M¹ = D₂O) of uranyl complexes. These chains are linked into a framework by a system of hydrogen bonds formed by water hydrogen atoms of one chain and uranyl oxygen atoms of another.     

Solubility and stability of (NH4)2SO4 · H2O2 in aqueous solutions and change in some crystallographic parameters of (NH4)2SO4 precipitates

Stability of (NH₄)₂SO₄ · H₂O₂ aqueous solutions and some structural changes in ammonium sulfate in the course of its solvation and subsequent desolvation were studied.     

FTIR spectra of the 2ν4, ν4 + ν6 and 2ν6 bands of formaldehyde

High resolution IR spectra of the overtones and the combination band of the ν₄ and ν₆ modes of formaldehyde (2ν₄, ν₄ + ν₆ and 2ν₆) were measured in the region of 2200–2650 cm⁻¹ using FTIR. The combination band ν₄ + ν₆, whose dipole transition is forbidden from molecular symmetry, was observed due to the intensity borrowed from the other bands. The observed frequencies were analysed by a Hamiltonian in which A-type Coriolis interactions and Darling—Dennison interaction were taken into account. The ratio and the relative signs of the transition dipole moments of the overtone bands, μ_2ν4 and μ_2ν6, have been determined by analysing the intensity distribution of the vibration—rotation lines.     

Synthesis of 1-Benzoyl-3-aryl-4-hydroxy-4-phenylimidazolidin-2-thiones

l-Benzoyl-3-aryl-4-hydroxy-4-phenylimidazolidin-2-thiones can be synthesized readily from the cyclization of 1-benzoyl-3-arylthioureas with bromine-acetophenone in the presence of excess triethylamiqe.     

Formation of Pyrrolidin-1-ylcyclopentadienes via Cyclization of Alkyl 2-Dimethoxyacetyl-and 2-Ethoxalyl-4-oxopentanoates

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Crystal Structure and Properties of Rb4H2I2O10 · 4H2O

Single crystals of the Rb₄H₂I₂O₁₀· 4H₂O were synthesized for the first time and studied by X-ray diffraction analysis. The crystals are monoclinic, a = 7.321(6) Å, b = 12.599(8) Å, c = 8.198(8) Å, = 96.30(7)°, Z = 2, space group P2₁/c. The H₂I₂O₁₀ ^4– anion is formed by the edge-sharing IO₆ octahedra. The anions are united by hydrogen bonds into a chain running along the x axis. The chains are combined by water molecules into a three-dimensional structure through hydrogen bonds. The compound is a proton conductor. The conductivity values measured at 20–60°C vary within 10^–6 to 10^–4 ohm^–1 cm^–1.