The hydrothermal synthesis and structure of a one-dimensional Fe(II)molybdophosphate

A new one-dimensional Fe(II)molybdophosphate of the formula, [(C₁₀H₈N₂)H₂]₂[Fe₄^(II)Mo₁₂^(V)(HPO₄)₆(PO₄)₂(H₂O)₈(OH)₆O₂₄]·8H₂O, (1), has been synthesized by employing hydrothermal methods and characterized by single crystal X-ray diffraction. The structure consists of a network of MO₆ (M = Fe, Mo) octahedra and (H)PO₄ tetrahedra linked through their vertices. The connectivity between the polyhedral units gives rise to one-dimensional chains with eight-membered apertures. The hydrogen bonded interactions between the chains form pseudo two-dimensional layers. Extensive hydrogen bonding also exists between the amine molecule, 4,4^′-bipyridine, water molecule and framework oxygen atoms. Crystal data for 1: monoclinic, space group = P2₁ (no. 4), a=12.549(3) (Å), b=23.496(5) (Å), c=14.551(3) (Å), β=114.87(3)°, , and Z=2.     

Solid solutions of mixed metal Mn3−xMgxFe4(PO4)6 orthophosphates: Colouring performance within a double-firing ceramic glaze

Solid solutions of mixed metal Mn_3−xMg_xFe₄(PO₄)₆ orthophosphates (x = 0, 0.5, 1, 1.5, 2, 2.5, and 3) were prepared for the first time (from coprecipitate powders calcined up to 1000 °C) and characterized by thermal analysis, XRD, SEM/EDX, UV-vis-NIR spectroscopy and colour measurements (CIE-L*a*b*). Orthophosphate (Mn,Mg)_3−yFe_4+z(PO₄)₆ solid solutions isotypic to Fe₇(PO₄)₆ structure (triclinic P-1(2) spatial group) formed successfully as the major crystalline phase within the studied range of compositions, accompanied only by variable quantities of α- and/or β-Mg₂P₂O₇ diphosphates as secondary phases. Noteworthy, the obtained solid solutions were tested as potential ceramic dyes and exhibited an interesting interaction upon enamelling within a double-firing ceramic glaze: considerable amounts of Fe segregated from the solid solutions to be stabilized as hematite particles (α-Fe₂O₃) in the ceramic glaze and conferring the glaze an intense dark-brown colouration, which was almost independent of the amount of Mg doping. Thus, the obtained solid solutions with a minimized Mn content (especially Mg₃Fe₄(PO₄)₆ composition, without Mn) could serve as low-toxicity Fe reservoirs to stabilize hematite in double-firing glazes and produce an interesting dark-brown colouration, being an alternative to other brown ceramic pigments containing hazardous metals (i.e. Cr, Ni, Zn, or Sb).     

The synthesis and crystal structure of [M{H2B(tz*)2}2(H2O)] (M=Cu,Zn and tz*=3,5-dimethyl-1,2,4-triazole)

New ligand [KH₂B(tz^*)₂] (tz*=3,5-dimethyl-1,2,4-triazolyl) has been synthesized and the reactions of two different metal salts (copper and zinc) with the new ligand in agar gave two similar crystalline polymorphic forms: [Cu{H₂B(tz^*)₂}₂(H₂O)] (1) and [Zn{H₂B(tz^*)₂}₂(H₂O)] (2). A single crystal X-ray study revealed that the compound 1 was the monoclinic system with space group C2/c and a=8.462(3) Å, b=14.039(6) Å, c=19.991(8) Å, β=94.622(7)°, Z=4, R₁=0.0451, wR₂=0.1110. And the compound 2 was the monoclinic system with space group C2/c and a=8.4214(4) Å, b=13.8765(7) Å, c=20.2969(6) Å, β=95.615(2)°, Z=4, R₁=0.0667, wR₂=0.1375. The metal(II) ion in the complex is five-coordinated with four nitrogen atoms which come from triazolyl and one oxygen atom which come from water molecular. In both compounds, the hydrogen atoms of water molecule are connected by hydrogen bonding with N atoms of two adjacent complex molecules to form 2-D planes. The spectroscopic results are consistent with the crystallographic study.     

A novel lead borate of NaPb4(H2O)(B5O9)2·BO3 with nonlinear optical property

A new mixed metal borate, NaPb₄(H₂O)(B₅O₉)₂·BO₃, with an acentric structure has been successfully made under hydrothermal conditions and structurally characterized by IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and single-crystal X-ray diffraction, respectively. The structural analysis shows that 1 crystallizes in the orthorhombic space group Pnn2 (No. 34) with a = 11.3724(5) Å, b = 11.4455(4) Å, c = 6.5578(2) Å and Z = 2. In the structure 1, the structural building unit, B₅O₁₂ cluster, connects adjacent six same ones to form a 3-D oxoboron framework with 8-membered ring (MR) and 10-MR channels along the c-axis. The Pb atoms and coordinated water molecules are located in the 8-MR channels, while the 10-MR channels were occupied by the chains built by Na atoms and the BO₃ groups. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 2 times that of KH₂PO₄ (KDP). Also it has a UV cutoff edge below 220 nm.     

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.     

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,crystal structure,photoluminescence of Ba3Y2(BO3)4:Er3+ and thermal expansion of Ba3Y2(BO3)4

The Ba₃Y_2–xEr_x(BO₃)₄ (х = 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) phosphors were obtained by crystallization from a melt. The Ba₃Y₂(BO₃)₄ crystal structure was refined from single crystal X-ray diffraction data to R = 0.037. Its anisotropic atomic displacement parameters for all atoms were refined for the first time. The borate crystallizes in the orthorhombic crystal system, space group Pnma with unit cell parameters a = 7.673(1), b = 16.44(1), c = 8.977(2) Å, V = 1132.3(3) ų, Z = 4. These phosphors are isotypical to those of the A₃M₂(BO₃)₄ (A = Ca, Sr, Ba, M = Ln, Y, Bi) family. The crystal structure contains the isolated BO₃ triangles, two general and a special one independent crystallographic sites for large cations, which are disordered over sites. Thermal behavior of Ba₃Y₂(BO₃)₄ was investigated by high-temperature X-ray powder diffraction and thermal expansion coefficients are calculated in a wide temperature range. An inflections of temperature dependencies of the unit cell parameters is observed in a range 600–740 °C. Luminescence spectra, excitation and kinetic curves of the Ba₃Y₂(BO₃)₄:Er³⁺ series are reported. A maximum luminescence intensity is observed for the x = 0.1 sample. According to vibrational spectroscopy data no structural changes upon activation of the Ba₃Y₂(BO₃)₄ matrix with the Er ions are observed.     

Formation of extended 1D coordination polymers in tetrathioether complexes of mercury(II): Effect of the organic substituents on the crystal structures of {Si(CH2SR)4}HgBr2 (R = Me,Ph)

Two novel one-dimensional (1D) coordination polymers of stoichiometry [{Si(CH₂SR)₄}HgBr₂]_n (R = Me, 2a; R = Ph, 2b) have been prepared by treatment of HgBr₂ with the functionalized silanes Si(CH₂SR)₄ (R = Me, 1a; R = Ph, 1b) acting as tetradentate thioether ligands. The extended structures result from intermolecular Hg–S interactions linking the monomeric {Si(CH₂SR)₄}HgBr₂ units, as established for 2a, b using single-crystal X-ray diffraction. The effective coordination around the Hg atoms in both compounds is best described as distorted octahedral.     

A new binuclear Cr(III) citrate anion: Synthesis,characterization and crystal structure of [Cr(CO(NH2)2)6]2[Cr2(CO(NH2)2)2(C6H4O7)2]3

The new anion [Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]^2 − has been isolated in the complex [Cr(CO(NH₂)₂)₆]₂[Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]₃. The crystals of this complex were obtained by a one-pot synthetic method using 1:1 molar ratio of hexaureachromium(III) chloride and trisodium citrate in aqueous medium. It was characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction analysis. The compound crystallizes in space group R‾3 of the trigonal system with three formula units in a cell of dimensions a = b = 24.7461(4) Å, c = 13.7204(3) Å and γ = 120°. The crystal structure comprises the columns consisting of [Cr(CO(NH₂)₂)₆]^3 + cations surrounded by a cylinder of complex anions, [Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]^2 − which are packed in a honeycomb-like manner. This supramolecular architecture is formed and stabilized by inter- and intramolecular NH⋯O hydrogen bonds.     

A Novel Mixed-Valence Tetranuclear Iron-Oxygen Clusters in the Organically Templated Iron Phosphate [H3N(CH2)2NH3]2 Fe4O(PO4)4 ċH2O

A novel iron phosphate templated with ethylenediammonium cation, [H₃N(CH₂)₂NH₃]₂ Fe₄ O(PO₄)₄H₂O, has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction, thermo-gravimetric analysis, magnetic susceptibility and Mossbauer spectroscopy. The compound crystallizes in the mono-clinic space group C2 with a= 30.3801(5),b= 10.1204(5),c= 10.0977(5) Å, = 107.712(1)°, V = 2957.5(4) ų and Z = 6. The structure contains 5 and 6-coordinated Fe atoms bridged by ₄-oxygen and PO₄ groups to form two types of mixed-valence Fe₄P₄ cubane-like clusters, which are connected via Fe- O- P bonds to give rise to intersecting channels that house the ethylenediammonium cations and water molecules. Room-temperature Mossbauer data confirm the presence of Fe^II and Fe^III.     

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.     

Samarium Coordinated Polymer: Structural, Vibrational and Thermal Studies of [Sm2(C3H2O4)3(H2O)6]n

The title compound, [Sm₂(C₃H₂O₄)₃(H₂O)₆]_, was investigated by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with cell parameters a = 17.1650(8) ?, b = 12.3010(5) ?, c = 11.1420(4) ?, β = 127.5161(10)°, Z = 4 and V = 1866.04(14) ?³. The Sm atom lies on a two-fold axis and has nine-coordination with six oxygen atoms from carboxylate groups and three water molecules. The compound forms a layer-type polymeric structure. The layers are formed by samarium and one independent malonate group to give a three-dimensional framework. The extensive network of hydrogen bonds and bridge bonds observed in this structure enhances the structural stability. The thermal dehydration of the compound was investigated by thermogravimetric analysis.     

Structural,morphological, optical,cation distribution and Mössbauer analysis of Bi3+ substituted strontium hexaferrite

Single-phase M-type hexagonal ferrites, SrBi_xFe_12−xO₁₉ (0.0≤x≤1.0), were prepared by a co-precipitation assisted ceramic route. The influence of the Bi³⁺ substitution on the crystallization of ferrite phase has been examined using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Mössbauer spectroscopy. The XRD data show that the nanoparticles crystallize in the single hexagonal magnetoplumbite phase with the crystallite size varying between 65 and 82 nm. A systematic change in the lattice constants, a=b and c, was observed because of the ionic radius of Bi³⁺ (1.17 Å) being larger than that of Fe³⁺ ion (0.64 Å). SEM analysis indicated the hexagonal shape morphology of products. From ⁵⁷Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi substitutions have been determined.     

Interaction of nitrogen with iron surfaces: II. Fe(110)

Previous work on the interaction of N₂ with Fe(100) and (111) single-crystal planes was extended to the most densely packed (110) face. The dissociative chemisorption proceeds even slower than with the two other planes and is associated with an activation energy of about 7 kcal/mole at low coverages. At 683 K the initial rates of adsorption have a ratio of about 60:3:1 for Fe(111):(100):(110). The activation energy for desorption is estimated to be about 50 kcal/mole and is thus slightly smaller than on Fe(100)(58 kcal/mole), but higher than on Fe(111) (51 kcal/mole). The formation of two ordered surface structures (I and II) was observed. Their unit cell vectors b₁, b₂ are related with the (unreconstructed) substrate lattice vectors a₁, a₂ through: b₁ = 3a₁, b₁ = 2a₁ (I) (which may also be designated as 2 × 3 structure), and b₁ = 4a₁, b₁ = a₁ + 3a₂ (II). Both phases appear with two equivalent domain orientations with the mirror plane along the [001] direction. Structure I appears at lower surface concentrations than structure II; however their kinetics of formation is also influenced by the concentration of dissolved nitrogen. It is most probably that these large unit cells reflect the reconstruction of the topmost layer of Fe atoms [as in the case of the (111) plane]. For both surface structures quasihexagonal arrangements of Fe atoms may be constructed the nearest-neighbor distances for which agree to within ±3% with those in the (111) plane of fcc Fe₄N. Thus the concept of the formation of “surface nitrides” is further supported. Dissolution of nitrogen atoms in the bulk again interferes with the surface processes.     

Synthesis,structure and characterization of a new nonlinear optical calcium borate [Ca2B5O9]·[H(OH)2]

A new nonlinear optical crystal [Ca₂B₅O₉]·[H(OH)₂] (1) has been synthesized under hydrothermal condition. Compound 1 crystallizes in the monoclinic space group C2 with lattice constants a = 10.111(2) Å, b = 7.754(11) Å, c = 6.198(14) Å, β = 127.04(3)° and Z = 2. The fundamental building block (FBB) of 1 is a [B₅O₁₂] unit with two BO₃ triangles and three BO₄ tetrahedra. 1 was characterized by single-crystal X-ray diffraction, IR and UV–Vis spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) respectively. Also, powder second harmonic generation (SHG) measurements indicate that 1 is phase matchable and displays a SHG response of about 3.5 times that of KDP (KH₂PO₄).     

Phase formation and magnetic properties of M-type lanthanum substituted strontium ferrites

Rare earth ion substitution is one of the most important methods for adjusting the magnetic properties of M-type hexagonal ferrites; however, the regularity of these phase formations has rarely been studied. In this work, La substituted Sr hexaferrite La_xSr_1-xO·nFe₂O₃ (La-SrM, 4.9 ≤ n ≤ 6.0, 0 ≤ x ≤ 0.6) was prepared using the traditional ceramic method. The effects of the Fe/Sr molar ratio (n), calcining temperature, and La³⁺ substitution (x) on SrM phase formation, the crystalline structure, and magnetic properties were investigated. With an increase of x up to a maximum value of 0.5–0.6, a higher calcining temperature is required to form the single M-phase of La-SrM samples. However, the optimal n values of single-phase La-SrM samples differ as the La substitution varies: when x = 0.1, n = 5.5–6.0; x = 0.2, n = 5.5–5.9; x = 0.3, 0.4 and 0.5, n = 5.7–5.8. The magnetic measurements show that La_0.2Sr_0.8O·5.8Fe₂O₃ has the highest specific saturation magnetization (σ_s), which is 2.2% higher than that of unsubstituted SrM (SrO·6Fe₂O₃), while the anisotropic field (H_A), the anisotropic constant (K₁), and Neel point (T_N) of La³⁺ substituted SrM decreased. Detailed structure analyses were conducted to explain the changes in magnetic properties. Fe³⁺ in the spin-up 2a sublattice of La_xSr_1-xO·5.8Fe₂O₃ decreased by approximately 5% from 98.5% (x = 0) to 93.85% (x = 0.4) with an increase in x. Additionally, a small amount of Fe³⁺ was reduced to Fe²⁺ in the spin-down 4f₂ sublattice with the maximum reduction amount of 4.13% reached at x = 0.2, thereby improving σ_s. The decrease in the bond angle of (4f₁) Fe3–O2–Fe5 (12k), (2a) Fe1–O4–Fe3 (4f₁), and (4f₁) Fe3–O4–Fe5 (12k) lead to the weakening of Fe–O–Fe superexchange of La-SrM so that H_A, K_1, and T_n decreased with increasing values of x. This work lays a solid foundation for the study of process regulation and ion substitution of permanent magnet ferrite.     

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.     

Structural,dielectric, vibrational and magnetic properties of Sm doped BiFeO3 multiferroic ceramics prepared by a rapid liquid phase sintering method

Rare earth Sm substituted Bi_1−xSm_xFeO₃ with x=0, 0.025, 0.05, 0.075 and 0.10 polycrystalline ceramics were synthesized by a rapid liquid phase sintering method. The effect of varying composition of Sm substitution on the structural, dielectric, vibrational, optical and magnetic properties of doped BiFeO₃ (BFO) ceramics have been investigated. X-ray diffraction patterns of the synthesized rare earth substituted multiferroic ceramics showed the pure phase formation with distorted rhombohedral structure with space group R3c. Good agreement between the observed and calculated diffraction patterns of Sm doped BFO ceramics in Rietveld refinement analysis of the X-ray diffraction patterns and Raman spectroscopy also confirmed the distorted rhombohedral perovskite structure with R3c symmetry. Dielectric measurements showed improved dielectric properties and magnetoelectric coupling around Néel temperature in all the doped samples. FTIR analysis establishes O–Fe–O and Fe–O stretching vibrations in BiFeO₃ and Sm-doped BiFeO₃. Photoluminescence (PL) spectra showed visible range emissions in modified BiFeO₃ ceramics. The magnetic hysteresis measurements at room temperature and 5 K showed the increase in the magnetization with the increase in doping concentration of Sm which is due to the structural distortion and partial destruction of spin cycloid caused by Sm doping in BFO ceramics.     

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.