Synthesis of Hydrotalcite using Magnesium from Seawater and Dolomite

Abstract

Three methods of synthesizing hydrotalcite(HT) have been developed using magnesium from seawater and dolomite(MgCa(CO₃)₂). In the first process, 1.0M Na₂CO₃solution was added to calcium ion free artificial seawater containing AlCl₃ with an initial Mg/Al molar ratio of 2.0～3.7 until a pH of 10 was obtained. The solution was then continuously stirred for Ih at 60°C. CO₃ ^2--HT was precipitated as a single phase, and the initial Mg/Al molar ratio, which each recovery of Mg²⁺and Al³⁺ from the solution was above 98%, was 2.0–2.3. In the second process, a Ca(OH)₂ slurry was added to artificial seawater containing AlCl₃ with an initial Mg/Al molar ratio of 1.0～5.0 until a pH of 10.5 was obtained, and then was stirred for Ih at 60°C. HT was also precipitated as a single phase with initial Mg/Al molar ratio 2.0～4.0. The initial Mg/Al molar ratio, which each recovery of Mg²⁺ and Al³⁺ from the solution was above 98%, was 2.2～3.3, but SO₄ ^2- and Cl^? were contained in the precipitated HT. When HT was produced using initial Mg/Al molar ratio of 3.0 at 25°C, SO₄ ^2- and Cl^?in the HT were ion-exchanged with CO₃ ^2- in a 0.05M Na₂CO₃solution for 24h at 25°C, and SO₄ ^2- and Cl^? content of the HT were decreased to 0.5 and 0.05wt%, respectively. In the third process, dolomite calcined at 1000°C was added to an AlCl₃ solution with an initial Mg/Al molar ratio of 1.0～2.0, and the solution was stirred for 1～4h at 25～90°C. HT was precipitated with the smallest amount of MgO and Mg(OH)₂ when the initial Mg/Al molar ratio was 1.5 and the solution was stirred for 4h at 90°C.     

Spin-Spin Relaxation Process of 23Na-NMR in Na-Loaded NaY

Abstract

Spin-spin relaxation of ²³Na-NMR is observed by the spin echo method at room temperature for Y-type zeolite loaded with Na metal without hydration. For saturated and no levels of loading, the echo decay is well fitted by single exponential function. T ₂ decreases to be 0.25 times smaller by loading. This decrease of T ₂ is explained semiquantitatively with assuming nuclear dipole-dipole interaction between neighboring Na.     

Enhanced persistent photoconduction in CuInS2–ZnIn2S4 alloys single crystals and processes of its relaxation

ABSTRACT

Photoelectrical response in CuInS₂–ZnIn₂S₄ alloys single crystals was analysed in the low temperature region from 30 K up to 100 K. The molar ratio of ZnIn₂S₄ in the alloys was varied in the range 0 mol%?16 mol%. The crystals with up to 12 mol% were the single-crystalline, meanwhile those with 16 mol% were the two phase ones. We have analysed spectral distribution of their photocurrent at different temperatures and the following relaxation towards the stationary values. The photo-induced photoconductivity phenomena were identified. Moreover the long-lasting relaxations with characteristic times exceeding 1.5×10³ sec were observed at lowest temperatures. They used to shorten exponentially with increasing temperature showing thermally activated behaviour. The main parameters of the photoconductivity kinetics and their temperature dependencies were determined. The observed behaviour was explained by the slow multicenter recombination due to the combined effect of different trapping and recombination centers. The effects of both – “fast” and “slow” recombination centers were taken into account.     

Distorted square-based pyramidal and trigonal bipyramidal geometries in a mercury (II) coordination compound containing 2-(aminomethyl)pyridine ligand

The new complex of [Hg(2-AMPy)₂Cl]₂.HgCl₄ (1) was synthesized from the reaction of HgCl₂ with 2-(aminomethyl)pyridine (2-AMPy) in methanolic solution. Suitable crystal of compound 1 for diffraction experiment was obtained by slow evaporation from dimethyl sulfoxide. Resulted complex was characterized by infrared, elemental analysis, thermal analysis, and single crystal X-ray diffraction. In the cationic part of this compound, two five-coordinated mercury centers have two different geometries, including distorted square-based pyramidal geometry by the trigonality index, τ₅, of 0.23 and trigonal bipyramidal geometries by the trigonality index, τ₅, of 0.57.     

Superconductivity in the Organic Charge Transfer Salts: (TMTSF)2X and (TMTTF)2X

Abstract

We report pressure dependent studies of the a-axis resistivity as a function of temperature for several members of the isostructural families of organic charge transfer salts, (TMTSF)₂X and (TMTTF) ₂X. For a typical (TMTSF)₂X material the low temperature metal-insulator transition seen at 1 bar is suppressed above some critical pressure, P_c, where a superconducting transition is observed near 1 K. We find a correlation between P_c and the ambient pressure c lattice parameter which reflects the anion size. The (TMTTF) _cX salts exhibit very different ambient pressure behaviour but we find that with the application of sufficiently high pressures (～30 kbar) their behaviour resembles that seen in the (TMTSF)₂X family but at lower pressures. In particular we find evidence of a possible superconducting transition near 4 K in (TMTTF)₂Br at 25 kbar. At this pressure the conductivity near 4 K is extremely high with a value approaching 10⁶ (Ωcm)^?1 and the resistivity ratio is about 400.     

Synthesis and crystal structure of charge-transfer salt (BEDT-TTF) [Pt(mnt)2]

The synthesis and crystal structure of the title organic charge-transfer salt (BEDT-TTF)[Pt(mnt)₂] (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene; mnt = cis-3,4-dimercapto-2-butenedinitrile) is described. The salt crystallizes in the P1 space group with a = 6.728(2) Å, b = 7.371(2) Å, c = 13.596(4) Å, = 97.904(5)°, = 90.114(5)°, and =108.147(5)°. The stoichiometry between BEDT-TTF and [Pt(mnt)₂] is 1:1. The bond length of the central C=C bond in a BEDT-TTF ion is 1.398 (16) Å, indicating an oxidation state of +1 in BEDT-TTF ion. The structure consists of layers of BEDT-TTF and Pt(mnt)₂ along the c axis. Within each layer, both BEDT-TTF and Pt(mnt)₂ ions form segregated stacks. The stacking is not in a face-to-face manner, but instead, is through a side-by-side arrangement along the a axis, with closest SS contacts of 3.461(3) Å between neighboring BEDT-TTF ions. The structure is consistent with the semiconducting behavior found in the solid.     

Transport and Electrochemical Properties of Bi2Sr2CaCu2O8 Superconductors

Abstract

Electrical conductivity and thermoelectric power measurements (77–300K) of both the pure and electrochemically doped with lithium Bi₂Sr₂CaCu₂O₈ system, are presented. Clear correlation between transport and electrochemical properties of Li_xBi₂Sr₂CaCu₂O₈ was shown.     

Principal Electrical Conductivities in the Organic Conductors TEA.(TCNQ)2 and TTF.TCNQ: The Microwave Approach

Abstract

We describe a microwave technique to measure the directions and magnitude of the principal electrical conductivities and permittivities of organic conductors. The method is applied to single crystals of triethylammonium-bis 7,7,8,8-tetracyano-p-quinodimethane (TEA.(TCNQ)₂) and of tetrathiafulvalenium-7,7,8,8-tetracyano-p-quinodimethane (TTF.TCNQ). For the former, the apriori set of principal axes (a*, (a*∧c), c) is confirmed with principal conductivities of 430, 5.3 and 0.41–0.77 Ω^?1m^?1 respectively. The room temperature permittivities have been measured for the first time (ε*_α ～ 5.4–5.5, ε*_α∧c ～ 7.5). For the latter it is clearly shown that the principal electrical axes are (a, b, c*) and, in contrary to earlier d.c data, we observe σ_c· < σ<a which is more consistent with the anisotropy of interchain interactions in this compound. The observed transverse and longitudinal anisotropies (～3.3 10² and 2.8 10⁴ respectively) are larger than believed up to now.     

Synthesis and crystal structure of anhydrous copper suberate: [Cu<Subscript>2</Subscript>(OOC-(CH<Subscript>2</Subscript>)<Subscript>6</Subscript> -COO)<Subscript>2</Subscript>]

The title compound [Cu₂(OOC-(CH₂)₆-COO)₂] was synthesized and its crystal structure has been determined by single crystal X-ray diffraction methods. The complex crystallizes in the triclinic space group P-1 with a=5.1077(5) ?, b=8.362(2) ?, c=11.378(2) ?, α=93.773(6)°, β=97.587(9)°, γ=90.493(’9)° and D _cal=1.629 mg/m³ for Z=1.  The structure is polymeric and consists of discrete anhydrous centrosymmetric binuclear units [Cu₂(OOC-(CH₂)₆-COO)₂]. The two copper(II) centres bridged by the suberate groups in a syn-syn conformation, are in pentacoordinated distorted square-pyramidal coordination environment, with an intramolecular Cu–Cu distance of 2.5793(10) ?. Each binuclear unit, related to the next through μ_oxo bridges with a Cuμ_oxo–Cuμ_oxo separation of 3.2326(10)?, defines infinite chains of one-edge sharing CuO₅ square pyramid.     

Fabrication of two-dimensional MoS2 thin-film transistors using a reactive thermal evaporation method combined with an annealing step

ABSTRACT

Two-dimensional (2-D) MoS₂ films were fabricated by reactive thermal evaporation combined with thermal annealing. The 2-D nature of the MoS₂ films is demonstrated by observation of direct transition and a Van Hove singularity in the absorbance curve. The 1T phase MoS₂ is confirmed by X-ray photoelectron spectroscopy. MoS₂ thin-film transistors (TFTs) are fabricated using the MoS₂ active layer transferred onto an oxidized Si wafer from a sapphire wafer. The MoS₂ TFT demonstrates a threshold voltage of 37.6 V, a field-effect mobility of 6.94 cm²V^?1s^?1 a sub-threshold swing of 29.2 V/dec and a switching ratio of 10³.     

Preparation and Characterization of [Zn(H2O)6][Zn2V10O28(H2O)10]?·?6H2O Single Crystals with a Novel Metallic Heteropolyoxoanion

Abstract  The compound investigated in this study contains a novel centrosymmetric heteroanion [Zn₂V₁₀O₂₈(H₂O)₁₀]²⁻. This cluster results from the connection between a V₁₀O₂₈ group and two Zn(2)O(OH₂)₅ octahedra. The Zn(1)O₆ octahedron and three water molecules associated with it are located between the different layers. The [Zn(H₂O)₆][Zn₂V₁₀O₂₈(H₂O)₁₀] · 6H₂O compound belongs to P-1 space group, with a = 8.967(2) ?, b = 10.390(4) ?, c = 12.338(13) ?, α = 108.31(7)°, β = 100.68(7)°, γ = 103.00(3)°, V = 1022(1) ?³ and Z = 1. Refinement gave R = 0.035 and wR(F²) = 0.098 for 3837 unique observed reflexions [I > 2σ(I)]. Index Abstract  The compound investigated in this study contains a novel centrosymmetric heteroanion [Zn₂V₁₀O₂₈(H₂O)₁₀]²⁻. This cluster results from the connection between a V₁₀O₂₈ group and two Zn(2)O(OH₂)₅ octahedra.      

Synthesis and crystal structure of (+)-(2R,3R)-N, N′-bis-trityl-2,3-bis-aziridine

A new C₂ symmetric bis-aziridine derivative was synthesized starting from L-(+)-tartaric acid. The molecular structure of (+)-(2R, 3R)-N, N-bis-trityl-2,3-bis-aziridine 4, was determined by ¹H, ¹³C NMR and elemental analysis and was confirmed by single-crystal X-ray diffraction. Crystal data for 4: C₄₂H₃₆N₂, orthorhombic, space group: P2₁2₁2₁, a = 12.7633(14), b = 14.5661(6), c = 17.4184(14) Å, and Z = 4.     

Overhauser Shift of the Conduction Electron Spin Resonance in (FA)2PF6 Single Crystals

The shift ΔB _ov of the ESR line due to saturation of the NMR of the hyperfine coupled nuclei (Overhauser shift) was measured for single crystals of the organic conductor (FA)₂PF₆. ΔB_ov , is proportional to [Abar] _tt , being the average hyperfine interaction between the conduction electrons and the protons in resonance, and the dynamic nuclear spin polarization (DNP), respectively. The DNP enhancement factor V was determined for the two orientations of the static magnetic field B _o , perpendicular (V _∥ = 525 ± 40) and parallel (V _∥ = 280 ± 25) to the needle axis a, respectively. The absolute value of the average hyperfine coupling is [Abar]^zz = –(1.16 ± 0.05) Gauss · g_e μ _B . Both, the temperature dependence and the anisotropy of the proton spin relaxation times T ₁ ^p and T ₁ ^p were measured from the time dependence of the Overhauser shift, ΔB_ov (t) after rf-pulses or after switching “on” and “off” the ESR saturation. Within the metallic phase of the crystal the proton relaxation is governed by a Korringa law. The experiments definitely show, that the electron spins, showing up in the ESR are those of the conduction electrons.     

Synthesis of Layered-Structure LiFeO2

Abstract

LiFeO₂, with a layered rocksalt structure of α-NaFeO₂-type was prepared by ion exchange reaction from Na⁺ ion to Li⁺ ion using α-NaFeO₂. α-NaFeO₂-type LiFeO₂ was synthesized by using the mixture of LiI and KI in the temperature range 220 to 480 °C. The heat treatment temperature of 600 °C gave α-LiFeO₂-type LiFeO₂ as a main product. As a result of Rietveld analysis, the structure of LiFeO₂ which assigned to α-NaFeO₂-type by an XRD measurement, was the mixture of α-NaFeO₂-type and Li-intercalated spinel-type structures.     

Crystal Structure and Vibrational Spectra of Erbium Trisodium Bis(Cyclotriphosphate) Nonahydrate,ErNa<Subscript>3</Subscript>(P<Subscript>3</Subscript>O<Subscript>9</Subscript>)<Subscript>2</Subscript> · 9H<Subscript>2</Subscript>O

Abstract The cyclotriphosphate salt, ErNa₃(P₃O₉)₂ · 9H₂O, has been characterized by single-crystal X-ray diffraction [hexagonal, space group , with unit cell parameters of a = b = 30.8451(14), c = 12.8063(8) ?; Z = 18]. The structure consists of alternating layers of [P₃O₉]³⁻ groups, ErO₈ dodecahedra, Na(1)O₆ and Na(2)O₇ polyhedra linked together by water molecules. The P₃O₉ rings are grouped along the c-axis in a P₃O₉–ErO₈ arrangement thereby producing broad, hexagonal channels of diameter of 6.65 ? with a side dimension of 3.907 ?. The absence of coincidences for the majority of the IR and Raman bands observed for the cyclotriphosphate salt is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted on the basis of factor group effects. Graphical abstract We report the crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate)nanohydrate salt ErNa ₃ (P ₃ O ₉ ) ₂ · 9H ₂ O H. Assaaoudi, M. Ijjaali, A. Ennaciri, I. S. Butler* and J. A. Kozinski Crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate) nonahydrate,ErNa₃(P₃O₉)₂ · 9H₂O. Projection of the coordination polyhedra of ErNa₃(P₃O₉)₂ · 9H₂O down the c axis     

Syntheses,Structural, and Biological Studies of Two New Peptide Compounds, 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl Acetate Hemihydrate and 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl Acetic Acid

Abstract  Two new peptide compounds, 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetate hemihydrate (1:1/2H ₂ O) and 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetic acid (2), have been synthesized and characterized by elemental analysis, IR, ¹H- and ¹³C NMR spectroscopy. Two new compounds were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of compounds 1:1/2H ₂ O and 2 were studied by DSC-TGA techniques. The result of the biological test showed that the compounds 1:1/2H ₂ O and 2 have certain antitumor activities. Index Abstract  Two new peptide compounds, 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetate hemihydrate (1:1/2H2O) and 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetic acid (2), have been synthesized and characterized by elemental analysis, IR, 1H-, and 13C NMR spectroscopy. Two new compounds were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of compounds 1:1/2H2O and 2 were studied by DSC-TGA techniques. The result of the biological test showed that the compounds 1:1/2H2O and 2 have certain antitumor activities.      

Synthesis,crystal and molecular structure and vibrational characterization of N,N-dimethyl-oxathioamidate monohydrate

The title compound (SO₂NC₄H₆) has been prepared and characterized by X-ray diffraction and infra-red and Raman spectra. The structure has been refined using single-crystal X-ray diffraction data measured at 295K [MoK-radiation with =0.71073 Å]. The crystals are monoclinic, space groupP2₁/n,Z=4,a=6.240(2),b=6.786(2),c=19.988(1)Å, =108.47(2)°,V=802.8(7)ų.D _calc.=1.566 Mg m^–3,F(000)=392, =8.582 cm^–1. The final agreement factors for 1906 observed refections [I>3(I)] were:R=0.030 andR _w=0.043. The dihedral angle between de C–C–S–N plane and the C–C–O–O plane is 88.31(4). The potassium atom within the title compound structure has a slightly distorted trigonal bipyramidal coordination. Infrared and Raman spectra of the normal CH₃/CD₃ and H₂O/D₂O isotopes and the waterfree compounds at different temperatures made it possible to perform isotopes complete vibrational analysis and clearly shows the very special hydrogen bonded water molecule in the crystal.     

Redetermination of the crystal structure of [Na4(H2O)14]SnS4: a compound containing a novel chain of aquated sodium ions

[Na₄(H₂O)₁₄]SnS₄ is obtained by the reaction of Na₂S·9H₂O with SnCl₄·5H₂O in aqueous solution at 21°C. It crystallizes in the space group Cc with a = 8.621(2) Å, b = 23.543(5) Å, c = 11.358(2) Å, = 110.58(3)° and V = 2158.2 ų with Z = 2. Refinement of 3826 unique reflections from a racemically twinned crystal yielded a final value of R₁ = 0.0464 (|F| > 4) and wR₂ = 0.104 and a goodness of fit of 1.125. The structure consists of a Na⁺/H₂O network supporting the tetrahedral SnS₄ ^4– anions. Water molecules or sulfide ions octahedrally coordinate each of the four crystallographically independent Na⁺ ions. The dominant feature of the structure is the existence of zigzag chains of edgeshared Na octahedra. These chains are tied together into a three-dimensional network by bridging Na(H₂O)₆ octahedra and individual H₂O molecules.     

A new assembly containing [Fe(dien)2]2+ and [Ni(CN)4]2− ions

A tetracyanometallate with complex dien cation [Fe(dien)₂][Ni(CN)₄] (1) (dien = diethylenetriamine), has been prepared and characterized by IR, UV-Vis and ESR spectroscopies. Single crystal X-ray analysis reveals that the compound assumes a ‘zero-dimensional’ structure in which one iron(II) ion is coordinated by six nitrogen atoms of the two dien ligands and the [Ni(CN)₄]²⁻ anion remains outside the coordination sphere. The six-coordinate iron(II) centres display a distorted octahedral arrangement.     

Anion Symmetry and the Separability of Structural Parameters for Tetramethyltetraselenafulvalenium Salts, (TMTSF)2X

Empirical correlations of various structural parameters for a series of (TMTSF)₂X salts have been explored utilizing a van der Waals-like estimate for the radius of the counterion X. Included amongst the parameters studied are: (a) the lengths of the transverse cell constants c and b; (b) the interdonor Se .. Se contact distances; (c) the alternate separation between molecular centers of mass along the columnar stack of donors (a); and (d) the symmetry and strength of the anion coupling to its donor-dominated structural cavity. The notable result is that independent correlations are found for salts containing centrosymmetric and non-centrosymmetric anions.