Reversible ferroelectric phase transition of 1,4-diazabicyclo [2,2,2]octane N,N′-dioxide di(perchlorate)

1,4-Diazabicyclo [2,2,2]octane N,N′-dioxide di(perchlorate), C₆H₁₄N₂O₂^2 +·2ClO₄⁻, was synthesized and separated as colorless block crystals. Differential scanning calorimetry detected that this compound underwent a reversible phase transition at ca. 216 K with a hysteresis of 5.5 K width, which was also confirmed by dielectric measurements. Single crystal X-ray diffraction data suggested that there was a transition from a room temperature phase with the space group of P2₁/c (a = 6.815(7) Å, b = 12.644(13) Å, c = 8.676(9) Å, β = 101.466(15)°, V = 732.7(13) ų, Z = 4) to a low temperature one with a space group of P2₁ (a = 9.892(8) Å, b = 12.559(10) Å, c = 17.401(13) Å, β = 92.065(8)°, V = 2160(3) ų, Z = 2). Crystallographic analysis showed that it belonged to chiral space group P2₁ with ferroelectric behaviors, and a typical ferroelectric feature of electric hysteresis loop was obtained in the low temperature phase. The disorder-order transformation of H₂-Dabcodo^2 + cation and ClO₄⁻ anion as well as the change of hydrogen bonds may drive the phase transition.     

Model bulk Mo–V–Te–O catalysts for selective oxidation of propane to acrylic acid

The crystal structures and chemical compositions of the M1 and M2 phases proposed as active and selective in propane oxidation to acrylic acid over the bulk mixed Mo–V–Te–O catalysts were investigated by the transmission electron microscopy, coupled with energy dispersive analysis of X-rays. The results revealed that the crystal structure of the M1 phase is orthorhombic with space group Pbca, lattice parameters a=21.25 Å, b=27.14 Å, c=4.03 Å and composition Mo_0.64V_0.32Te_0.1O_3.05 (Mo/V ∼2), whereas M2 is hexagonal with space group P6mm, lattice parameters a=7.10 Å, c=4.05 Å and composition Mo_1.79V_1.85Te_0.1O_11.36 (Mo/V ∼1). The M1 phase was dominant in the Mo–V–Te–O catalyst. The results obtained indicated that the bulk Mo–V–Te oxides represent a well-defined model catalytic system for the studies of the surface molecular structure-activity/selectivity relationships in propane oxidation to acrylic acid.     

Dielectric properties of M-type barium hexaferrite prepared by co-precipitation

Highly stoichiometric and phase pure barium hexaferrite has been synthesized by co-precipitation as well as a solid-state preparative method using high purity nitrates, oxides and carbonates of iron(III), barium(II) and ammonium hydroxide. The isochronal and isothermally measured complex permittivity and dielectric loss tangents over 1 MHz–1 GHz in frequency remained relatively stable until a sintering temperature between 1100 and 1300 °C. A high value of relative permittivity of 32 and low loss tangent of 0.0329 indicate suitable high frequency characteristics for barium hexaferrite. The measured apparent densities before and after each firing cycle showed a monotonic increase. The crystal structure determined from X-ray diffraction studies confirmed the presence of single phase belonging to the theoretical space group P63/mmc with calculated cell parameters of a = b = 5.895 Å and c = 23.199 Å. In addition the DTA hexaferrite formation temperature was found to be 1050 °C.     

Structural determination and microwave properties of (x)Re(Co1/2Ti1/2)O3–(1 − x)CaTiO3 (Re = La and Nd) solid solutions

Solid solutions of (x)Re(Co_1/2Ti_1/2)O₃–(1 − x)CaTiO₃ (Re = La and Nd, abbreviated to xLCT and xNCT, respectively) where x = 0, 0.25, 0.5, 0.75 and 1 have been fabricated using solid state synthesis. Samples have been examined using X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM) and their dielectric properties measured at microwave (MW) frequencies. Formation of single phase solid solutions were confirmed by XRD and the measured lattice parameters varied linearly from LCT (a = 5.66 Å, b = 7.867 Å and c = 5.494 Å) and NCT (a = 5.636 Å, b = 7.914 Å and c = 5.461 Å) to CT (a = 5.596 Å, b = 7.731 Å and c = 5.424 Å). XRD and TEM confirmed both in-phase and antiphase rotations of O-octahedra consistent with an a⁻a⁻c⁺ tilt system across the entire solid solution series. Electron diffraction revealed that LCT and NCT have reflections associated with B-site cation ordering which is absent for x ≤ 0.75. MW dielectric measurements showed that LCT and NCT were highly insulating with microwave quality factor (Qf₀) values of 39,000 and 34,000, respectively. Compositions anticipated to have a zero temperature coefficient of resonant frequency (τ_f) are 0.48LCT-CT and 0.52NCT-CT with ɛ_r = 45 and Qf₀ ∼ 5000 and ɛ_r = 43 and Qf₀ ∼ 4000, respectively.     

Synthesis,structure and fluorescence properties of a uranyl-2,5-pyridinedicarboxylic acid coordination polymer: The missing member of the UO22+-2,n-pyridinedicarboxylic series

A 3D uranium-pyridinedicarboxylate, compound (1) [UO₂(C₇H₃NO₄)], represents the final member of a series of materials incorporating a series of 2,n-pyridinedicarboxylic (pydc) acids (n = 3,4,5,6). The resulting crystal structure [FW = 419.13, monoclinic, P2₁/n, a = 9.0096(3) Å, b = 8.1371(2) Å, c = 11.6954(4) Å, V = 852.45 ų, Z = 4] was determined by single crystal X-ray diffraction and fluorescent properties were investigated. Additionally, the complete series of uranium-2,n-pydc materials was examined on a basis of fluorescent behaviors and architectural similarities.     

Single crystal X-ray structure analysis for two thiazolylazo indole dyes

To determine the tautomeric form of the hetarylazo indole dye 3-(5-methylthiazol-2-yldiazenyl)-2-phenyl-1H-indole (1), 1-methyl-3-(thiazol-2-yldiazenyl)-2-phenyl-1H-indole (2) was synthesized as a model compound and both molecules were characterized by single crystal X-ray diffraction. (1) crystallized in the monoclinic system, space group C2/c, a = 31.064(2), b = 7.4051(5), c = 27.7138(18) Å, β = 97.617(1)°, V = 6318.9(7) Å³, Z = 8, while dye 2 crystallized in the monoclinic system, space group P2₁/n, a = 11.4660(11), b = 9.8223(9), c = 14.2049(14) Å, β = 97.418(2)°, V = 1586.4(3) Å³, Z = 4. The asymmetric unit of 1 contains two crystallographically independent molecules, in which geometries and conformations differ slightly, while there is only one molecule in the asymmetric unit for 2. The intermolecular N–H?N hydrogen bonds in (1) link the molecules, via parallel, infinite sheets, along the a axis and stabilize the crystal structure; in 2, there is no classical intermolecular hydrogen bond.     

Synthesis of 1,1′-ferrocene bis(carboxypyrazole) compounds and displacement of the pyrazole ligands

The reaction of 1,1′-ferrocenedicarbonyl chloride with pyrazole or 3,5-dimethyl pyrazole generates novel 1,1′-ferrocene bis(amide) compounds 1 and 2, respectively. The crystal structure of 1 shows that the pyrazole rings are essentially co-planar with each other and with the cyclopentadienyl rings. Attempts to use the complexes as a chelating ligand were unsuccessful. Instead, treatment of 1 or 2 with Mo(CO)₄(pip)₂, pip = piperidine, led to displacement of the pyrazole ligands and formation of the known amide compound, 1,1′-ferrocene bis carbonyl piperidine. Replacement of the pyrazole is ascribed to the weakness of the amide bond caused by the aromaticity of the pyrazole ring. Crystal data for C₁₈H₁₄FeN₄O₂ (1): monoclinic P2(1)/c, a = 13.3907(18) Å, b = 10.2112(14) Å, c = 11.3082(16) Å, β = 105.209(2)°, V = 1492.1(4) Å³, Z = 4.     

Ba(dl-C4H4O5) — An alkaline earth metal-dicarboxylate hybrid crystal with the synergy of multi-bonds

The organic–inorganic hybrid crystal, Ba(dl-C₄H₄O₅), has been firstly prepared by hydrothermal method. It crystallizes in monoclinic crystal system with a centrosymmetric space group of P2₁/c with a = 8.150(2) Å, b = 10.447(3) Å, c = 6.938(2) Å, β = 95.599(3)° and Z = 4. In this compound, the coexistence of organic ligand and the alkaline earth metal cation leads to the diversity of chemical bonds. The synergy of Ba–O ionic bonds and hydrogen bonds strengthens the crystal structure. Characterization of this earth metal-dicarboxylate hybrid crystal is described by using powder X-ray diffraction, infrared spectroscopy, UV–vis–NIR diffuse reflectance spectrum and the TG curve. In addition, Ba(dl-C₄H₄O₅) possesses a short ultraviolet cutoff wavelength lower than 230 nm determined by the electronic transition of C–O group, which signifies the potential use in UV region applications. And the electronic structure and optical properties are studied by first principle calculation method, which obtains a birefringence value of 0.04.     

Synthesis,characterization, thermal study,and crystal structure of a new layered alkaline earth metal sulfonate: Sr[C2H4(SO3)2]

A rare two-dimensional layered inorganic–organic hybrid material, strontium sulfonate Sr[C₂H₄(SO₃)₂] was synthesized by hydrothermal reaction of strontium chloride hexahydrate and ethane disulfonic acid at 160 °C. Single-crystal X-ray diffraction was utilized for structural determination. Data showed that the compound, crystallized in the monoclinic system and space group of C2/c. With cell parameters a = 8.3183(7) Å, b = 5.4416(5) Å and c = 14.9784(13) Å. The new material was extensively studied by DRIFT-infrared spectroscopy, thermogravimetric analysis, SEM and powder X-ray diffraction. Results show that the compound is thermally stable.     

The first example of extended structure constructed from Knoth-type sandwich POMs and coordination fragments

A novel compound [P₂W₁₈M₃O₆₈][Cu(en)₂]₄·7H₂O·2OH^? (M = 0.5W + 0.5Cu) 1 which contains the first example of extended structure constructed from Knoth-type sandwich polyoxoanions and transition metal coordination complexes has been hydrothermally synthesized and characterized by elemental analysis, IR spectrum, UV–Vis spectrum and single-crystal X-ray diffraction analysis. Crystal data for 1: triclinic, space group, P-1, a = 13.2718(7) Å, b = 13.6432(8) Å, c = 25.7307(15) Å, α = 104.7340(10)°, β = 96.7630(10)°, γ = 90.0330(10)°, V = 4472.2(4) Å³, Z = 2. Structure solution and refinement based on 1090 parameters gave R1 (wR2) = 0.0409 (0.0993).     

LiBa1.5[B5O8(OH)3]: A new 1-D metal borate chain constructed from B5O9(OH)36 − cluster units

A new mixed metal borate LiBa_1.5[B₅O₈(OH)₃] (1) has been hydrothermally synthesized and structurally characterized by FT-IR spectroscopy, powder X-ray diffraction, single crystal X-ray diffraction, and thermogravimetric analysis, respectively. 1 crystallizes in the monoclinic system, space group C2/c, a = 11.2839(7) Å, b = 7.3974(4) Å, c = 20.7151(13) Å, β = 103.392(6)°, V = 1682.10(17) ų and Z = 8. The structure consists of infinite one-dimensional (1-D) borate chains constructed from B₅O₉(OH)₃^6 − cluster units. These BO chains are further linked by the Ba^2 + and Li⁺ cations to form a 3-D framework.     

Relaxor behavior and ferroelectric properties of a new Ba4SmFe0.5Nb9.5O30 tungsten bronze ceramic

Unfilled tungsten bronze ceramics with a composition of Ba₄SmFe_0.5Nb_9.5O₃₀ were prepared by the conventional solid-state sintering method. The phase, microstructure, dielectric and ferroelectric properties were studied. Room temperature XRD results indicated that the ceramic occurs in the tetragonal space group P4bm phase with cell parameters of a=b=12.4712(2) Å and c=3.9430(2) Å. The temperature-dependent dielectric properties, XRD data and Raman spectra data indicated that BSFN ceramics exhibit no phase changes from 35 °C to 450 °C. Fitting of a Vogel-Fulcher relationship with an activated energy E_a of 0.11 eV indicates an unambiguous dielectric relaxor state near room temperature. Furthermore, the BSFN ceramics exhibited residual polarization and coercive field of 3.45 µC/cm² and 24.65 kV/cm, respectively.     

Room temperature assembly of a uranyl carboxyphosphonate: Synthesis,characterization and UO22+ hydrolysis

A novel 1-dimensional U(VI) phosphonoacetate, UO₂(O₃PCH₂CO₂H)(H₂O)·2H₂O (1), has been synthesized from the room temperature reaction of uranium nitrate and phosphonoacetic acid (H₃PPA) in water. The compound crystallizes in a monoclinic space group (P2₁, a = 8.3517(5) Å, b = 7.0013(4) Å, c = 8.3728(5) Å, β = 107.310(1)°, Z = 2) and exhibits bonding to the UO₂²⁺ through both phosphonate and carboxylate oxygen atoms of the acid unit. The crystal structure, thermal and fluorescent behaviors, and role of UO₂²⁺ hydrolysis in the context of ambient versus hydrothermal syntheses are discussed.     

Ionothermal synthesis and crystal structure of a new layered nickel(II) diphosphate,DRM-1

A new layered ammonium nickel(II) diphosphate, (NH₄)₂[Ni₃(P₂O₇)₂(H₂O)₂], has been synthesized ionothermally in the ionic liquid 1-butyl-3-methyl imidazolium bromide and characterized by powder X-ray diffraction, elemental analysis, scaning electron microscopy, thermogravimetry etc. The results of the characterization show that the crystal adopts the monoclinic space group P2₁/a with the lattice constants a = 9.23529(2) Å, b = 7.98489(2) Å, c = 9.40772(2) Å, β = 100.2608(2)° and Z = 2. Its structure consists of chains of cis- and trans-edge-sharing [NiO₆]-octahedra linked via [P₂O₇] units to form layers of [Ni₃(P₂O₇)₂(H₂O)₂]^2? in the ab plane. Adjacent layers are separated in the c-direction by ammonium ions.     

Hydrothermal synthesis,structure and fluorescent property of a novel cuprous thiocyanate inorganic polymer directed by 1,5-bis(pyridinium) pentane cation

A novel cation-templated 3D cuprous thiocyanate polymer, {(bppt)[Cu₂(NCS)₄]}_n, bppt = 1,5-bis (pyridinium) pentane, was hydrothermally synthesized and structurally characterized. The compound crystallizes in monoclinic system, space group P2(1)/c with cell parameters of a = 10.1571(8) Å, b = 15.9785(13) Å, c = 15.3983(12) Å, V = 2407.4(3) Å³, Z = 4, D_c = 1.622 g cm^?3, F(0 0 0) = 1192, μ = 2.133 mm^?1, R₁ = 0.0551, wR₂ = 0.1246. In the polymeric architecture, Cu₂(NCS)₄ dimer is connected by NCS^? bridging ligand to constitute a infinite 3D framework with the organic cation bppt trapped in it. Photoluminescence investigation reveals that a slightly red shift of 27 nm for the complex takes place comparing with the organic cation.     

A novel cobalt(II) acylpyrazolonate complex with intermolecular hydrogen bond: Synthesis,structure and properties

A new cobalt complex, [Co(L)₂·(H₂O)₂](HL = 4-hexanoyl-3-methyl-1-phenyl-1H -pyrazol-5(4H)-one), was synthesized by us. The complex was characterized by single crystal X-ray diffraction, IR, UV, fluorescence spectra and thermogravimetric analysis. The results of characterization showed that the crystal is monoclinic system with crystal parameters: a = 15.2439(12) Å, b = 7.4101(6) Å, c = 15.7381(18) Å, and Z = 2, S = 1.074. It was found that the Co²⁺ is located in the inversion center of the complex. The Co(II) had an ideal octahedral coordination environment with four oxygen atoms of HL ligands in the equatorial plane and two water molecules in axial positions. The complex exhibits yellow emission as the result of the fluorescence from the intraligand emission excited state.     

Decomposition of allantoin in the presence of Cu(II) ions resulting in the formation of a coordination polymer containing oxalate species

A novel Cu(II) coordination polymer, [Cu(ox)(DMSO)₂]_n (1) (ox-oxalate dianion, DMSO-dimethyl sulphoxide) has been prepared in the reaction of copper nitrate dihydrate and allantoin (5-ureidohydantoin) in DMSO/water solution. Compound (1) crystallizes in the monoclinic, space group P121/c1 with a = 5.1785(7), b = 13.6311(18), c = 8.5386(12) Å, β = 107.524(12)°, V = 574,76(14) Å³, Z = 4, D_cal = 1779 mg/m³, R₁ = 0.0449. The metal ion coordinates through four oxygen atoms belonging to two bidentate bridging oxalate ligands, and two oxygen atoms from two DMSO ligands forming an elongated octahedron. The crystal structure was confirmed by FT-IR and Uv–vis spectroscopic data.     

(CH3NH3)2[Ge(B4O9)]: An organically-templated chiral borogermanate with second-order nonlinear and ferroelectric properties

An organically-templated chiral borogermanate (CH₃NH₃)₂[Ge(B₄O₉)] (1), has been solvothermally synthesized and characterized by elemental analysis, IR, PXRD, TGA, single-crystal X-ray diffraction and UV–vis spectrum. It crystallized in the monoclinic space group C2 (No. 5) with a = 10.249(1) Å, b = 9.449(1) Å, c = 6.956(2) Å, β = 131.76(2)°, V = 502.43(19) Å³, Z = 2. The structure is constructed by alternate linkage of GeO₄ tetrahedra and B₄O₉ clusters to form a zeotype framework with diamond topology. Four intersecting channels with different sizes are observed. Large circular 10-ring channels are clearly extended along the [001] direction, 9-ring channels are running along the [101], [110], and [112] directions, respectively. Additionally, two pairs of the right- and left-handed channels couple together along the [100] and [010] directions, respectively. The preliminary investigations show that compound 1 exhibits second-harmonic generation (SHG) response and ferroelectric properties.     

A novel transition-metal-linked hexaniobate cluster with photocatalytic H2 evolution activity

A novel transition-metal (TM) complex based on Lindqvist polyoxoniobate K₁₀[(Nb₆O₁₉)Cr^III(H₂O)₂]₂·28H₂O (1) has been synthesized by a new two-pot synthesis strategy and structurally characterized by single crystal X-ray diffraction analysis, IR spectrum, UV–vis spectroscopy, XRPD and TG analysis. Compound 1 crystallizes in the C2/m space group with a = 32.143(19) Å, b = 10.030(6) Å, c = 12.878(8) Å, β = 110.611(9)°, and V = 3886(4) ų. X-ray structure analysis reveals that polyanion [(Nb₆O₁₉)Cr^III(H₂O)₂]₂^10 − (1a) represents the first example of two nuclear dimeric polyoxoniobate, in which two Lindqvist anions [Nb₆O₁₉]⁸ are sandwiched by two {Cr^III(H₂O)₂} groups. Further, 1 exhibits photocatalytic H₂ evolution activity.     

Crystal and geometry-optimized structure,Hirshfeld surface analysis and spectroscopic studies of tetrachlorocuprate and nitrate salts of 1-(2-fluorophenyl)piperazine cations, (C10H15FN2)[CuCl4] (I) and (C10H14FN2)[NO3] (II)

Two new organic-inorganic hybrid materials, 1-(2-fluorophenyl)piperazine-1,4-diium tetrachlorocuprate, (C₁₀H₁₅FN₂)[CuCl₄] (I) and 1-(2-fluorophenyl)piperazin-4-ium nitrate, (C₁₀H₁₄FN₂)[NO₃] (II), have been synthesized by an acid/base reaction at room temperature in the presence of 1-(2-fluorophenyl)piperazine as an organic-structure directing agent and their structures were determined by single crystal X-ray diffraction. Compound (I), (C₁₀H₁₅FN₂)[CuCl₄], crystallizes in the monoclinic system and P2₁/c space group with a = 7.5253 (2), b = 20.6070 (7), c = 9.7281 (3) Å, β = 103.6730 (17)°, V = 1465.82 (8) Å³ with Z = 4. Full-matrix least-squares refinement converged at R = 0.037 and wR(F²) = 0.088. Compound (II), (C₁₀H₁₄FN₂)[NO₃], belongs to the monoclinic system, space group P2₁/c with the following parameters: a = 10.8034 (2), b = 7.5775 (1), c = 14.4670 (3) Å, β = 111.761 (2)°, V = 1099.91 (4) ų and Z = 4. The structure was refined to R = 0.044, wR(F²) = 0.136.In the structures of (I) and (II), the anionic and cationic entities are interconnected by means of set of hydrogen bonding contacts forming three-dimensional networks. Intermolecular interactions were investigated by Hirshfeld surfaces and the contacts of the four different chloride atoms were notably compared. The results of the optimized molecular structure are presented and compared with the experimental one. The Molecular Electrostatic Potential (MEP) maps and the HOMO and LUMO energy gap of both compounds were computed. The vibrational absorption bands were identified by infrared spectroscopy. Theory (DFT) calculations of normal mode frequencies are compared with experimental ones.