Electrical conductivity of Cs<Subscript>2</Subscript>CuCl<Subscript>4</Subscript> crystals

The electrical conductivity of Cs₂CuCl₄ single crystals, synthesized by crystallization from aqueous solutions in the CsCl–CuCl₂–H₂O system, has been investigated. The temperature dependence of the electrical conductivity of crystals in a temperature range of 338–584 K exhibits no anomalies. The electrical transfer activation enthalpy is ΔH_σ = 0.72 ± 0.05 eV and the conductivity is σ = 3 × 10^–4 S/cm at 584 K. The most likely carriers in Cs₂CuCl₄ are Cs⁺ cations, which transfer electric charge according to the vacancy mechanism.     

Spectroscopic and Transport Properties of (NH4)2CuCl4 · 2 H2O Single Crystal

Electron paramagnetic resonance (EPR), Optical absorption and Transport properties of (NH₄)₂CuCl₄ 2 H₂O single crystals have been studied. An anisotropic g tensor was observed with gl = 2.241 and g∥ = 2.081 by EPR method. The spin orbit coupling constant is found to be 540 cm⁻¹. The optical absorption in UV region are characterized by charge transfer band, in the visible and near infrared region at 13,333, 4,480, 4,336, and 3,998 cm⁻¹ attributed to the transitions between the (d-d) stark energy levels of the copper (II) ion in an extended octahedral crystal field. Dc electrical conductivity measurements with temperature reveal an anisotropic characteristic of a two-dimensional layered structure, and exhibits two first order structural phase transitions at about 383 K and 413 K. These transitions are attributed to loss of the two water inolecules of hydration and free rotation of NH⁺₄ ion from a state of torsional oscillation.     

Structural and Spectral Studies of ZnKPO4 · 6H2O Crystals

Zinc Potassium Phosphate Hexahydrate (ZPPH) is analogous to naturally occurring struvite. ZPPH crystals are grown by slow evaporation technique. These crystals are characterised by x‐ray and infrared studies. Powder x‐ray pattern indicates the orthorhombic crystal structure analogous to struvite with unit cell parameters a = 5.964, b = 5.808 and c = 12.495 Å. Infrared spectrum is characteristic of H₂O and PO₄^3‐ radicals.     

Synthesis and characterization of (NH4)2CuBr2Cl2·2H2O crystals

Single crystals of a new compound, (NH₄)₂CuBr₂Cl₂.2H₂O, were grown from saturated aqueous solution at room temperature by slow evaporation method. The grown crystals were characterized through elemental, powder XRD, thermal and DSC analyses and FTIR and far IR spectra. The elemental analysis and the decomposition pattern formulated using the TG‐DTG studies confirm the stoichiometry of the compound. The crystallinity of the compound is confirmed from the powder XRD pattern. A preliminary single crystal X‐ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with a = 7.7466 Å, b = 7.783 Å and c = 8.1211 Å. The low temperature DSC shows thermal anomalies at –161.1, –156.5, –152.4, –145.2, –134, –18.5, and 1.4°C during the heating run and at –4.3, –54.8, –66.1, –90.6, –109.7 and –147.2 °C during the cooling run. The thermal hysterses indicate first order phase transitions in the title compound at these temperatures. The FTIR spectra were used to assign the characteristic vibrational frequencies due to NH₄⁺, CuX₄^2– ions and other chemical bonds. The effect of substitution of two bromine atoms on the phase transitions of a closely related crystal, diammonium tetrachloro cuprate dihydrate is also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of a new inorganic – organic complex: (4‐ClC7H6NH3)9[Nd(P6O18)2]·9H2O

Single crystals of (4‐ClC₇H₆NH₃)₉[Nd(P₆O₁₈)₂]·9H₂O were synthesized in aqueous solution. This compound crystallizes in a triclinic P1 unit‐cell, with a = 14.898(6), b = 18.049(7), c = 20.695(6)Å, α = 102.04(3), β = 100.49(3), γ = 98.82(3)°, V = 5245(4) ų and Z = 2. The crystal structure has been solved and refined to R = 0.043 (Rw = 0.061) for 20420 observed reflections. The atomic arrangement of the title compound can be described as infinite layers built by complex of Neodyme [Nd(P₆O₁₈)₂] and nine water molecules. The organic cations are located in the space delimited by the successive inorganic layers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,growth and characterization of a new nonlinear optical crystal: l‐arginine maleate dihydrate

A new nonlinear optical material L‐arginine maleate dihydrate, C₆H₁₄N₄O₂,C₄H₄O₄,2H₂O (LAMD) was synthesized and single crystals were grown by slow cooling and also by slow evaporation method at constant temperature from its aqueous solution. Quality and size of the crystals are found to be dependent on pH of the solution and best crystals were obtained at pH = 4. Single crystal X‐ray diffraction analysis reveal that the crystal lattice of LAMD is triclinic with unit cell parameters a = 5.264(3)Å, b = 8.039(3)Å, c = 9.784(3)Å, α = 106.19(3)°, β = 97.24(3)°, γ = 101.66(2)°. Second harmonic generation efficiency is found to be about 6.8 times that of quartz. It is optically transparent down to 300 nm and possesses a large optical window between 300–2000 nm. The compound is thermally stable up to 93.4 °C. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of single crystals of the layered copper hydroxide acetate Cu2(OH)3(CH3COO)·H2O

Single‐crystals of the layered copper hydroxide acetate Cu₂(OH)₃(CH₃COO)·H₂O were synthesized by heating copper acetate solution at 60 °C. The standard synthesis of the title compound based on slow titration of copper acetate solution with NaOH yielded materials with worse morphology and an additional phase present. The obtained products were characterized with powder X‐ray diffraction, high temperature powder X‐ray diffraction, scanning electron microscopy and infrared spectroscopy. The crystal structure was determined from single‐crystal X‐ray diffraction data, collected both at 120 K and at 293 K. The title compound crystallizes in the monoclinic botallackite‐type layered structure, space group P 2₁, with the lattice parameters a = 5.5776(3) Å, b = 6.0733(2) Å, c = 18.5134(8) Å, β = 91.802(4)° and a = 5.5875(4)Å, b = 6.0987(4) Å, c = 18.6801(10)Å, β = 91.934(5)° for 120 K and for 293 K, respectively. Acetate groups and water molecules are interlayered between corrugated sheets of edge‐sharing CuO6 octahedra exhibiting strong distortion resulted from the Jahn‐Teller effect. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and characterization of PbI2‐AgI binary system

The crystals of the binary system PbI₂‐AgI (PIAI) were obtained by heating the mixture of individual PbI₂ (PI) and AgI (AI) placed at 30° angle in the horizontal tubular furnace of variable temperature zone. The crystals were characterized by powder XRD, TG/DTA, FT‐IR and SEM. The 3.37% weight loss in the sample after heating at 853 K is due to the presence of water molecules absorbed (3446 cm^–1) by the crystals during sintering and cooling process. The cell parameters of the crystal were determined using the powder X‐ray data. The PbI₂‐AgI crystallizes in monoclinic system a = 10.799 (±0.009), b = 7.492 (±0.004), c = 6.929(±0.004) Å and α = 90°, β = 108.04(±0.073) γ = 90°, V = 533.18 ų. The electrical conductivity measurements of the crystals showed a sudden change in the current value at the temperature range 385–393 K. The activation energy before and after the drift was found to be 0.49 and 0.35 eV respectively. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of optical and transport properties of K2CuCl4 · 2H2O single crystal

Optical absorption, transport properties and EPR of K₂CuCl₄ · 2H₂O single crystals have been studied. The optical absorption in UV, and visible region are characterized by a charge transfer band, and in the near infrared region at 3998, 4336, and 4480 cm⁻¹ are attributed to transitions between the stark levels of copper(II) ion in an extended octahedral crystal field. An anisotrophic ‘g’ value was observed with g_∥ = 2.12 and g_∥ = 2.24 by EPR method. The spin orbit coupling constant is found to be 500 cm₋₁. D.C. electrical conductivity measurements with temperature reveal an anisotropy characteristic of a two-dimensional layered structure and exhibit a first order irreversible structural phase-transition at 377 K, i.e. from tetragonal to monoclinic crystal system. X-ray diffraction studies and density calculations from the crystal structure data in both the phases suggest that the first order irreversible transition occurs following the loss of the two water molecules of hydration.     

Synthesis,characterization and impedance spectroscopy of the new material [(CH3) (C6H5) 3P] 2CoBr4: a member of the A2BX4 family

The crystal structure of bis‐(methyltriphenylphosphonium) tetrabromocobaltate (II), [(C₁₉H₁₈P)₂ CoBr₄] is determined: M_r = 933.203, monoclinic, P2₁, a = 9. 6977 (3) Å, b = 12.5547 (4)Å, c = 16.4503 (6)Å, β = 105.603 (2)°, V = 1929.04 (11)ų, Z = 2, D_x = 1.607 Mg m^‐3, T = 298 K. Differential thermal analysis at high temperatures shows three endothermic peaks characterizing four phases, with onset temperatures at T₁= 313±2 K, T₂ = 320±4 K and T₃= 360±1 K. The structural instability detected via the temperature dependence of permittivity at T₁ is ascribed to order‐disorder transition associated with cation dipole reorientation. Permittivity and ac conductivity studies as a function of temperature (295 K‐375 K) and frequency (0.11 kHz < f <100 kHz) are presented. The results indicate the importance of the cation size and shape on the phase transitions in the system. Bulk conductivity behavior is thermally activated. The associated activation energies are in the range 2.9 to 1.0 eV depending on the temperature regime. Two contributions to the ac conductivity, one dominating at low temperatures and high frequencies which are characterized by superlinear frequency exponent and the second dominates at high temperatures characterized by a sublinear frequency exponent. The behavior is interpreted in terms of the jump relaxation model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase transitions in Cs5(HSO4)2(H2PO4)3 crystal

The symmetry (sp. gr.I $\bar 4$ 3d) and lattice parameters have been determined for the first time for Cs₅(H₂SO₄)₂(H₂PO₄)₃ crystals in the temperature range from 172 to 390 K. The thermal and optical properties of crystals, as well as their conductivity, have been investigated at elevated temperatures. It is shown that a crystal heated to T = 365 K undergoes a phase transition with symmetry lowering to the tetragonal phase (with the parameters a = 4.965(1) Å and c = 5.016(1) Å), while at T ≈ 390 K a phase transition to the cubic phase is presumably observed. With a decrease in temperature, a phase transition without a change in symmetry occurs at T = 240 K.     

Growth,structure, and superconducting properties of Bi2Sr2Ca2Cu3O10 and (Bi,Pb)2Sr2Ca2Cu3O10‐y crystals

Large and high‐quality single crystals of both Pb‐free and Pb‐doped high temperature superconducting compounds (Bi_1‐xPb_x)₂Sr₂Ca₂Cu₃O_10‐y (x = 0 and 0.3) were grown by means of a newly developed “Vapour‐Assisted Travelling Floating Zone” technique (VA‐TSFZ). This modified zone‐melting technique was realised in an image furnace and allowed for the first time to grow Pb‐doped crystals by compensating for the Pb losses occurring at high temperature. Crystals up to 3×2×0.1 mm³ were successfully grown. Post‐annealing under high pressure of O₂ (up to 10 MPa at T = 500°C) was undertaken to enhance T_c and improve the homogeneity of the crystals. Structural characterisation was performed by single‐crystal X‐ray diffraction (XRD) and the structure of the 3‐layer Bi‐based superconducting compound was refined for the first time. Structure refinement showed an incommensurate superlattice in the Pb‐free crystals. The space group is orthorhombic, A2aa, with cell parameters a = 27.105(4) Å, b = 5.4133(6) Å and c = 37.009(7) Å. Superconducting studies were carried out by A.C. and D.C. magnetic measurements. Very sharp superconducting transitions were obtained in both kinds of crystals (ΔT_c ≤ 1 K). In optimally doped Pb‐free crystals, critical temperatures up to 111 K were measured. Magnetic critical current densities of 2�10⁵ A/cm² were measured at T = 30 K and μ₀H = 0 T. A weak second peak in the magnetisation loops was observed in the temperature range 40‐50 K above which the vortex lattice becomes entangled. We have measured a portion of the irreversibility line (0.1‐5 Tesla) and fitted the expression for the melting of a vortex glass in a 2D fluctuation regime to the experimental data. Measurements of the lower critical field allowed to obtain the dependence of the penetration depth on temperature: the linear dependence of λ(T) for T < 30 K is consistent with d‐wave superconductivity in Bi‐2223. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and electrochemical property of one‐dimensional complex: [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]2[Cu(mnt)2]

One metalorganic complex [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]₂[Cu(mnt)₂] (mnt = maleonitriledithiolate) has been obtained by the reaction of dicyclohexyl‐18‐crown‐6 with K₂mnt and CuCl₂·2H₂O. The title complex has been characterized by elementary analysis, FT‐IR, UV‐Vis spectroscopy and x‐ray single crystal diffraction. The title complex crystallizes in the triclinic space group P1 with crystallographic data: a = 10.870(6) Å, b = 11.536(6) Å, c = 12.904(7) Å, α = 101.541(10)°, β = 110.573(9)°, γ = 99.441(9)°, V = 1435.2(13) ų, Z = 1, D_calcd = 1.350 g/cm³, F(000) = 615, R₁ = 0.0641, wR₂ = 0.1475. It displays one‐dimensional chain‐like structure formed by [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]⁺ complex cations and [Cu(mnt)₂]^2‐ complex anions through N‐K‐N interactions. Its electrochemical behavior has also been studied by the cyclic voltammetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and molecular stereochemistry of polymeric Cu2(DMP)4(DMSO) as a platform for phosphate diester binding

Treatment of a solution of CuCl₂ in dimethyl phosphate (DMP) in an inert solvent under nitrogen atmosphere resulted in a light blue fluorescence powder. Slow evaporation of H₂O‐DMSO solution of this powder led to the formation of blue‐sky crystals of a new polymeric Cu(II) complex, with a unit cell composed of Cu₂(DMP)₄(DMSO), (1). The crystal and molecular structure of the complex was established crystallographically. Compound (1) crystallizes in the monoclinic space group P2₁/n with a = 12.8920(11)Å, b = 13.1966(11)Å, c = 14.7926(13)Å, α = 90°, β = 98.943(2)°, γ = 90° and Z = 4. A square pyramidal environment for the metal center is established by coordination of oxygen atoms of four bridging DMP ligands in the basal positions and a tri‐centered oxygen atom of DMSO in the apical disposition. The sixth position is also affected by a weak interaction with the sulfur atom of DMSO. The phosphorous atom in the bridging DMP is arranged in a deformed tetrahedron with gg conformation for methyl esters with C_2v symmetry. Accordingly, the angles of methoxy substituents are unexpectedly smaller than the bridging oxygens, and synchronous z‐in and z‐out distortions are suggested for DMP anion. The oxygen atom of SOCuCu’ fragment derived from DMSO, functions as a tri‐centered nuclei lie almost in a trigonal triangle environment. This study helps provide further insights into the binding nature of phosphate esters to the active sites of enzymes, which catalyze phosphoryl transfer reactions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural study of [(CH3)2NH2]2CoCl4 single crystals at room temperature

The structure of the crystals grown from a solution of dimethylammonium and cobalt chlorides is determined. It is found that the crystals have the composition [(CH₃)₂NH₂]₂CoCl₄. At room temperature, the crystals are monoclinic (space group P2₁/c, Z = 4) and the unit cell parameters are as follows: a = 8.545(2) Å, b = 11.447(2) Å, c = 13.313(3) Å, and β = 90.10°. Cations and anions form simple and bifurcated hydrogen bonds N-H?Cl.     

DC conductivity studies in K3Na(SeO4)2 single crystals

DC electrical conductivity studies were carried out along the three crystallographic axes for Tripotassium sodium diselenate (K₃Na(SeO₄)₂ or KNSe). Earlier studies of phase transition in this crystal show successive phase transitions at 334 K, 346 K, 730 K, and 758 K. In this paper we report the dc electrical conductivity measurements in the temperature region 303 K – 430 K along a, b and c – axes. An anomaly in conductivity was obtained around 341 K and another one around 333 K. These can be attributed as due to phase transitions in this crystal. A strong anomaly also has been observed along the c‐axis and comparatively week one along a and b axes around 395 K for the first time. This can be due to newly observed phase transition in the crystal. DSC taken for the sample also shows endothermic peak supporting the occurrence of newly observed phase transition. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Crystal and Molecular Structure of 2‐[(3,4‐dimethoxybenzylidene)amino]adamantane

The crystal structure of the title compound, C₁₉H₂₅NO₂ was determined by single crystal X‐ray diffraction technique. The crystal data are Orthorombic, space group Pbca, with a = 9.2119(4), b = 9.5555(4), c = 37.6049(5) Å, Z = 8, T = 293(2) K, MoKα radiation, λ = 0.71073 Å, Mr = 299.40, R = 0.0839 for 1945 reflections with I > 2σ(I). The title compound shows intermolecular C‐H…O type interactions.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural,optical and dielectric studies on K1‐x(NH4)xH2PO4 mixed crystals grown from z‐cut seeds

Mixed crystals of K_1‐x(NH₄)_xH₂PO₄(KADP) were grown from KDP (KH₂PO₄) dominated mixed solutions with varying molar proportion of ADP (NH₄H₂PO₄) addition. It was found that, as the increase of ADP molar concentration, the growth rate along z‐axis of KADP crystal decreased rapidly. The structure of KADP crystals was investigated by powder XRD and the lattice parameter was calculated. The results showed that the lattice parameter c of KADP crystal increased with the molar concentration of ADP. The optical homogeneity of grown KADP crystals was determined with a differential phase‐shifting interferometry. Frequency dependences of the dielectric constant and dielectric loss of KADP crystals were measured at room temperature (290 K). The dielectric constants of KADP crystals were almost invariant with the increase of frequency. In the region of 10²∼10⁴Hz, the values of the dielectric loss reduced with the increase of frequency. The piezo‐resonance coupling effect still exists in KADP crystals at room temperature, but shifted to low frequency band. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of pyridinium isopolymolybdate (C5H6N)2n[Mo4O13]n

Synthesis and crystal structure are described for pyridinium isopolymolybdate of chemical composition (C₅H₆N)_2n[Mo₄O₁₃]_n. The crystals are triclinic, space group P1, with the following unit‐cell parameters: a =8.2695(11) Å, b =10.544(4) Å, c =11.177(4) Å, α = 71.76(5)°, β = 89.68(3)°, γ = 78.79(3)°, V =906.4(4) ų, Z = 2 (chemical formula (C₅H₆N)₂[Mo₄O₁₃]), D _calcd = 2.755 g·cm^–3. Crystal structure was solved by Patterson methods and refined to a final R value 0.085 for 4045 independent reflections. The studied compound, considered in analogy to triclinic (NH₄)₂Mo₄O₁₃ as pyridinium polyoctamolybdate, is proposed to be better described as pyridinium isopolytetramolybdate (C₅H₆N)_2n[Mo₄O₁₃]_n. It seems that the proper coordination number of molybdenum (VI) ions is five, resulting in pyramidal coordination polyhedra [MoO₅]. Coordination polyhedra joined by common edges form tetramolybdate monomeric unit [Mo₄O₁₃]. The mers are connected by oxygen bridges Mo ‐ O ‐ Mo into infinite ribbon chains. Each two infinite chains are hold together by weaker intermolecular interactions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)