Crystal growth and structure determinations of potassium hafnates: K2Hf2O5 and K4Hf5O12

Crystals of K₂Hf₂O₅ and K₄Hf₅O₁₂ were grown from molten potassium hydroxide flux. The crystal structures were determined by single-crystal X-ray diffraction. K₂Hf₂O₅ crystallizes in the space group Pnna of the orthorhombic system, with unit cell dimensions of a = 5.780(1) Å, b = 10.640(2) Å, and c = 8.666(2) Å. This compound contains infinite chains of HfO₆ octahedra that form a channel structure. K₄Hf₅O₁₂ crystallizes in the space group of the trigonal system, with unit cell dimensions of a = 5.7877(2) Å and c = 10.3693(7) Å. This compound possesses a layered structure with six-coordinate Hf in three different coordination environments (trigonal prismatic, distorted octahedral, and regular octahedral).     

The crystal structure of eulytite Pb3BiV3O12

The crystal structure of Pb₃BiV₃O₁₂ was solved using single-crystal X-ray diffraction technique. The compound crystallizes in the cubic system (No. 220) with eulytite structure with a = 10.7490(7) Å, V = 1241.95(14) Å³ and Z = 4. The final R₁ value of 0.0198 (wR₂=0.0384) was achieved for 359 independent reflections during the structure refinement. The Pb²⁺ and Bi³⁺ cations occupy the special position (16c) while the oxygen anions occupy the general position (48e) in the crystal structure. Unlike many other eulytite compounds, all the crystallographic positions are fully occupied. The structure consists of edge-shared Pb/Bi octahedra linked at the corners to independent [VO₄]³⁻ tetrahedra units, generating a eulytite-type network in the crystal lattice.     

Synthesis and characterization of a new 2,4,6-triaminopyridinium dihydrogendiphosphate dihydrate (C4H8N5)2H2P2O7·2H2O

Structural properties of the 2,4,6-triaminopyridinium dihydrogendiphosphate dihydrate are discussed on the basis of an X-ray structure investigation. (C₄H₈N₅)₂H₂P₂O₇·2H₂O is monoclinic, C2/c, with a = 10.414(1) Å, b = 13.365(1) Å, c = 13.736(2) Å, β = 98.39(4)°, and Z = 4. The structure has been solved by a direct method and refined to a reliability R factor of 0.0375 (R_w = 0.0961) using 2751 independent reflections. The structural arrangement can be described as inorganic infinite ribbons, , spreading along the c direction; the organic groups, [C₄H₈N₅]⁺, link the precedent ribbons, via their hydrogen bonds, to form a three-dimensional network. The present work, deals with crystal structure, thermal behavior and IR analysis of this new compound.     

Crystal structure of a new organic condensed phosphate (C6H9N3O)H2P2O7

Crystals of a new organic compound, the isonicotinic acid hydrazide dihydrogendiphosphate, (C₆H₉N₃O)H₂P₂O₇ (denoted INHDP) were prepared and grown at room temperature. The INHDP crystallizes in the triclinic system with the space group. Its unit cell dimensions are: a = 7.316(3) Å, b = 7.783(3) Å, c = 10.802(4) Å, α = 82.41(3)°, β = 75.19(3)°, γ = 72.57(3)°, with V = 566.3(4) Å³ and Z = 2. Crystal structure has been determined and refined to a reliability R factor of 0.0389. The atomic arrangement can be described as inorganic infinite ribbons of H₂P₂O₇²⁻ anions spreading parallel to the b-axis. These ribbons are themselves interconnected by the organic (C₆H₉N₃O)⁺ cations so as to build a three dimensional arrangement. In the present work, we describe the crystal structure, thermal behaviour and IR analysis of this new compound.     

Synthesis and characterization of a new organic dihydrogenomonophosphate [3,5-(CH3O)2C6H3NH3]2(H2PO4)2

Chemical preparation, crystal structure, calorimetric studies and spectroscopic investigation are given for a new organic cation dihydrogenomonophosphate [3,5-(CH₃O)₂C₆H₃NH₃]₂(H₂PO₄)₂. This compound is triclinic with the following unit cell parameters: a=9.030(6) Å, b=16.124(5) Å, c=8.868(3) Å, α=75.04(3)°, β=110.71(4)°, γ=104.61(1)°, Z=4, V=1148.0(1) Å³, Z=2 and ρ_cal.=1.454 g cm⁻³. Crystal structure was solved and refined to R=0.04, 2752 independent reflections. The atomic arrangement can be described as inorganic layers of H₂PO₄⁻ anions parallel to planes, between which are located the organic groups. Solid-state and MAS-NMR spectroscopies are in agreement with the X-ray structure. Ab initio calculations allow the attribution of the phosphorous and carbon signals to the independent crystallographic sites and to the various atoms of the organic groups.     

Transformation of Dion-Jacobson phase to Aurivillius phase: synthesis of (PbBiO2)MNb2O7 (M = La, Bi)

We describe transformations of the Dion-Jacobson (D-J) phases, KLaNb₂O₇ and RbBiNb₂O₇, to the Aurivillius (A) phases, (PbBiO₂)LaNb₂O₇ (1) and (PbBiO₂)BiNb₂O₇ (2), in a metathesis reaction with PbBiO₂Cl. Oxide 1 adopts centrosymmetric tetragonal structure (a = 3.905(1) Å, c = 25.66(1) Å), whereas oxide 2 crystallizes in a noncentrosymmetric orthorhombic (A2₁am) (a = 5.489(1) Å, b = 5.496(2) Å, c = 25.53(1) Å) structure. Oxide 2 shows a distinct SHG response towards 1064 nm laser radiation. The role of La³⁺ versus Bi³⁺ in the perovskite slabs for the occurrence of noncentrosymmetric structure/ferroic property in these materials is pointed out.     

Structural characterization and AC conductivity of bis tetrapropylammonium hexachlorado-dicadmate, [N(C3H7)4]2Cd2Cl6

Synthesis, crystal structure, vibrational study, ¹³C, ¹¹¹Cd CP-MAS-NMR analysis and electrical properties of the compound [N(C₃H₇)₄]₂Cd₂Cl₆, are reported. The latter crystallizes in the triclinic system (space group , Z = 2) with the following unit cell dimensions: a = 9.530(1) Å, b = 11.744(1) Å, c = 17.433(1) Å, α = 79.31(1)°, β = 84.00(1)° and γ = 80.32(1)°. Besides, its structure was solved using 6445 independent reflections down to R = 0.037. The atomic arrangement can be described by alternating organic and inorganic layers parallel to the plan, made up of tetrapropylammonium groups and Cd₂Cl₆ dimers, respectively. In crystal structure, the inorganic layer, built up by Cd₂Cl₆ dimers, is connected to the organic ones through van der Waals interaction in order to build cation-anion-cation cohesion. Impedance spectroscopy study, reported in the sample, reveals that the conduction in the material is due to a hopping process. The temperature and frequency dependence of dielectric constants of the single crystal sample has been investigated to determine some related parameters to the dielectric relaxation.     

Synthesis and crystal structure of triphosphate RbPrHP3O10

Crystals of RbPrHP₃O₁₀ have been grown by the flux technique and characterized by single-crystal X-ray diffraction. RbPrHP₃O₁₀ crystallizes in the triclinic space group with lattice parameters: a = 7.0655(5), b = 7.7791(4), c = 8.6828(6) Å, α = 74.074(3), β = 74.270(3), γ = 82.865(2)°, V = 441.09(5) ų, Z = 2. The crystal structure has been solved yielding a final R(F²) = 0.0443 and R_w(F²) = 0.1426 for 1955 independent reflections (F_o² ≥ 2σ(F_o²)). The structure of RbPrHP₃O₁₀ consists of PrO₈ polyhedra and P₃O₁₀⁵⁻ groups sharing oxygen atoms to form a two-dimensional framework; the PrO₈ polyhedra form infinite chains by edge-sharing. Each Rb⁺ ion is bonded to 10 oxygen atoms, these ions are located between chains formed of (HP₃O₁₀)⁴⁻. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared spectrum.     

GexNbSe2 and GexNbS2 intercalation compounds

The structures of two intercalation compounds, Ge_∼0.2NbSe₂ and Ge_∼0.3NbS₂ were investigated by single crystal X-ray diffraction and electron microscopy (selected area electron diffraction (SAED), high resolution electron microscopy (HRTEM) and X-ray microanalysis by energy dispersive spectroscopy (XEDS)). Crystal structure determinations of the average structure of the intercalation compounds 2H-Ge_0.217NbSe₂ and 4H-Ge_0.288NbS₂ are reported: the selenide compound crystallizes in the space group P6₃/mmc with a = 3.4560(9) Å and c = 12.966(3) Å and adopts the 2H-NbSe₂ structure-type, while the sulfide compound crystallizes in the P6₃mc space group, with a = 3.3392(9) Å and c = 25.404(7) Å with a structure-type 4H_c-NbS₂ which it is known for TaSe₂. In both structures the germanium atoms are located in the empty octahedral positions of the van der Waals gap between the NbX₂ (X = S, Se) layers. Electron diffraction patterns from several Ge_xNbSe₂ crystal flakes show different superstructures and exhibit diffracted diffuse intensity: weak satellites corresponding to and 2a₀ × 2a₀ superstructures were observed for x ∼ 0.15 (a₀ is the basal lattice parameter of the host structure). For x ∼ 0.25-0.33, the same type of satellite is observed with a stronger intensity. For x ∼ 0.5 only satellites corresponding to the superstructure were present. In the case of Ge_xNbS₂, with 0.10 < x < 0.25, the germanium atoms are ordered in domains with an superstructure. In some crystals disorder along the c-axis has been observed.     

Chemical preparation, crystal structure and characterization of the new sodium ytterbium cyclotriphosphate Na3Yb(P3O9)2·9H2O

Chemical preparation and crystal structure are reported for a new lanthanide cyclotriphosphate Na₃Yb(P₃O₉)₂·9H₂O. This salt crystallizes in the trigonal system, space group with the following parameters: a = 30.933(2), c = 12.8282(5) Å. The crystal structure was refined to R₁ = 0.0432 using 1782 reflections with I > 2 σ(I). In the Na₃Yb(P₃O₉)₂·9H₂O structure, the phosphoric ring anions, located around the axis are interconnected by YbO₈ dodecahedra and NaO₆ and NaO₇ polyhedra to build, around the threefold axis, large channels parallel to the c axis. All the nine water molecules in the present arrangement participate in the coordination spheres of the associated cations. The thermogravimetric analysis shows that the removal of these water molecules occurs in three stages between 305 and 736 K.The vibrational study by IR absorption spectroscopy of Na₃Yb(P₃O₉)₂·9H₂O is also reported.     

Preparation and crystal structure of a new bismuth vanadate, Bi3.33(VO4)2O2

Single crystals of a new bismuth vanadate, Bi_3.33(VO₄)₂O₂ was prepared by hydrothermal reaction using a hydrated sodium bismuthate, NaBiO₃·nH₂O as one of the starting compounds. The crystal structure was determined by using single crystal X-ray diffraction data. This compound crystallizes in the triclinic space group (#2) with a = 7.114(1), b = 7.844(2), c = 9.372(2) Å, α = 106.090(7), β = 94.468(7) and γ = 112.506(8)°, Z = 2 and the final R factors are R1 = 0.052 and wR2 = 0.14 for 2085 unique reflections. The crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO₄ tetrahedra, and one of four bismuth atoms is statistically distributed in the splitting sites with the distance of 0.83 Å. This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation and its activity was less than that of monoclinic BiVO₄.     

A new borophosphate chain anion in an organo-templated iron(III) borophosphate: Synthesis, crystal structure and magnetic properties of (C4H12N2)3Fe6(H2O)4[B6P12O50(OH)2]·2H2O

The organo-templated iron(III) borophosphate (C₄H₁₂N₂)₃Fe^III₆(H₂O)₄[B₆P₁₂O₅₀(OH)₂]·2H₂O was prepared under mild hydrothermal conditions (443 K). The crystal structure was determined from single-crystal X-ray data at 295 K (orthorhombic, Pbca (No. 61), Z=4, a=17.8023(7) Å, b=16.1037(5) Å, c=19.1232(6) Å, V=5482.3(3) Å³, R1=0.055, wR2=0.104, 6576 observed reflections with I>2σ(I)) and contains a new type of borophosphate anion: a mixed open- and loop-branched zehner single chain, , built from heptamers [B₂P₅O₂₁] interconnected by BO₃(OH) tetrahedra sharing their third oxygen corners with additional (terminal) PO₄ tetrahedra to form open branchings. The mixed open- and loop-branched single chains running along [0 0 1] are interconnected by three crystallographically independent iron coordination octahedra to form a 3D framework structure containing eight-membered ring channels running along [0 1 0] and cages, which are occupied by two crystallographically independent piperazine cations and H₂O molecules. The displacement parameters of C and N atoms in the piperazine cations are dramatically influenced by the strength of the hydrogen bond reflecting the shape of the cavities. The magnetic investigations indicate the existence of antiferromagnetic interactions as the major components. A narrow hysteresis at low temperatures indicates a weak ferromagnetic component, due to a non-cancellation of spins.     

The system Ag2Se-Ho2Se3 in the 0-50 mol.% Ho2Se3 range and the crystal structure of two polymorphic forms of AgHoSe2

The phase diagram of the Ag₂Se-Ho₂Se₃ system in the range of 0-50 mol.% Ho₂Se₃ was constructed with the results of XRD and differential thermal analysis. A dimorphous compound exists in the system at the equimolar ratio of the components. The investigated part of the Ag₂Se-AgHoSe₂ diagram is of the eutectic type with the eutectic coordinates 7 mol.% Ho₂Se₃ and 1125 K. The crystal structure of the high-temperature modification of AgHoSe₂ was studied by X-ray powder diffraction method. α-AgHoSe₂ is described as a NaCl structure (space group ) with the lattice parameter а = 5.7623(3) Å. Atomic parameters were calculated in the isotropic approximation (R_I = 0.0434 and R_Р = 0.0636). The crystal structure of β-AgHoSe₂ was determined by X-ray structure analysis and was refined to R = 0.0487.     

Determination of the modulated structure of the misfit layer compound (LaS)1.196VS2

Single crystal X-ray diffraction was used to determine the modulated structure of the misfit layer compound (LaS)_1.196VS₂. This compound crystallizes in the triclinic system with cell parameters: a_s = 3.410 (1) Å, b_s = 5.845(1) Å, c_s = 11.191(2) Å, α ≈ 95.15(4), β ≈ 84.79(2)°, and γ ≈ 89.98(2)°, q = 0.5978(4)a_s^* − 0.002(1)b_s^* + 0.004(2)c_s^*, and V_s = 221.2(1) Å³. A (3 + 1)D superspace group, X(α,β,γ), was used to analyze the complete structure (X is referring to a pseudo C centering). The largest modulation amplitudes are observed for La-S (between La (subsystem 2) and S (subsystem 1)), as well as V-V distances. In connection with the large V-V modulation, we observed the formation of “linear vanadium clusters” that may impact on the transport properties.     

Synthesis and crystal structure of a novel lithium bismuth phosphate, Li2Bi14.67(PO4)6O14

A lithium bismuth phosphate, Li₂Bi_14.67(PO₄)₆O₁₄, has been synthesized for the first time by the solid-state method. The crystal structure was determined by single crystal X-ray diffraction at 150 K. Li₂Bi_14.67(PO₄)₆O₁₄ crystallizes in the monoclinic system C2/c (No. 15), with a = 30.8189(4) Å, b = 5.2691(3) Å, c = 24.5302(3) Å, β = 122.84(2)°, V = 3346.81(1) Å³ and Z = 2. The structure along the b axis consists of layers of [Bi₂O₂] units as the basic building block. These are separated by isolated PO₄ and LiO₄ tetrahedra. The oxygen co-ordination around two of the phosphorus atoms is disordered. Solid-state ⁷Li NMR studies confirm the presence of lithium in the structure. The material shows ionic conductivity of the order of 10⁻⁵ S cm⁻¹ at 600 °C.     

[NH3(CH2)2NH3][Co(SO4)2(H2O)4]: Chemical preparation, crystal structure, thermal decomposition and magnetic properties

Cobalt ethylenediammonium bis(sulfate) tetrahydrate, [NH₃(CH₂)₂NH₃][Co(SO₄)₂(H₂O)₄], has been synthesised by slow evaporation at room temperature. It crystallises in the triclinic system, space group , with the unit cell parameters: a = 6.8033(2), b = 7.0705(2), c = 7.2192(3) Å, α = 74.909(2)°, β = 72.291(2)°, γ = 79.167(2)°, Z = 1 and V = 317.16(2) Å³. The Co(II) atom is octahedrally coordinated by four water molecules and two sulfate tetrahedra leading to trimeric units [Co(SO₄)₂(H₂O)₄]. These units are linked to each other and to the ethylenediammonium cations through OW-H…O and N-H…O hydrogen bonds, respectively. The zero-dimensional structure is described as an alternation between cationic and anionic layers along the crystallographic b-axis. The dehydration of the precursor proceeds through three stages leading to crystalline intermediary hydrate phases and an anhydrous compound. The magnetic measurements show that the title compound is predominantly paramagnetic with weak antiferromagnetic interactions.     

New compounds Cu2MnTi3S8 and Cu2NiTi3S8 with thiospinel structure

Cu₂MnTi₃S₈ and Cu₂NiTi₃S₈ compounds were prepared by high-temperature synthesis. The crystal structure of these quaternary phases was investigated by X-ray powder diffraction. The compounds are described in the thiospinel structure (space group ) with the lattice constants a = 1.00353(1) nm (Cu₂MnTi₃S₈) and a = 0.99716(1) nm (Cu₂NiTi₃S₈). The atomic parameters were calculated in anisotropic approximation (R_I = 0.0456 and R_I = 0.0520 for Cu₂MnTi₃S₈ and Cu₂NiTi₃S₈, respectively).     

Synthesis, structure and magnetic properties of a new iron phosphonate-oxalate with 3D framework: [Fe(O3PCH3)(C2O4)0.5(H2O)]

A new iron phosphonate-oxalate [Fe(O₃PCH₃)(C₂O₄)_0.5(H₂O)] (1), has been synthesized under hydrothermal condition. The single-crystal X-ray diffraction studies reveal that 1 consists of layers of vertex-linked FeO₆ octahedra and O₃PC tetrahedra, which are further connected by bis-chelate oxalate bridges, giving to a 3D structure with 10-membered channels. Crystal data: monoclinic, P2₁/n (no. 14), a = 4.851(2) Å, b = 16.803(7) Å, c = 7.941(4) Å, β = 107.516(6)°, V = 617.2(5) Å³, Z = 4, R₁ = 0.0337 and wR₂=0.0874 for 1251 reflections [I > 2σ(I)]. Mössbauer spectroscopy measurement confirms the existence of high-spin Fe(III) in 1. Magnetic studies show that 1 exhibits weak ferromagnetism with T_N = 30 K due to a weak spin canting.