Synthesis, crystal and magnetic structure of a novel brownmillerite-type compound Ca2Co1.6Ga0.4O5

The novel compound Ca₂Co_1.6Ga_0.4O₅ with brownmillerite (BM) structure has been prepared from citrates at 950 °C. The crystal structure of Ca₂Co_1.6Ga_0.4O₅ was refined, from neutron powder diffraction (NPD) data, in space group Pnma, , , , χ²=1.798, , R_wp=0.0378 and R_p=0.0292. On the basis of the NPD refinement the compound was found to be a G-type antiferromagnet (space group Pn^′m^′a) at room temperature, with the magnetic moments of cobalt atoms directed along chains of tetrahedra in the BM structure. Electron diffraction and electron microscopy studies revealed disorder in the crystallites, which can be interpreted as the presence of slabs with BM-type structure of Pnma and I2mb symmetry.     

Sr4PbPt4O11, the first platinum oxide containing Pt2 ions

We report the synthesis and crystal structure of the new compound Sr₄PbPt₄O₁₁, containing platinum in highly unusual square pyramidal coordination. The crystals were obtained in molten lead oxide. The structure was solved by X-ray single crystal diffraction techniques on a twinned sample, the final R factors are R=0.0260 and wR=0.0262. The symmetry is triclinic, space group P1¯, with , , , α=90.421(3)°, β=89.773(8)°, γ=90.140(9)° and Z=2. The structure is built from dumbell-shaped Pt₂O₉ entities formed by a dinuclear metal-metal bonded Pt₂⁶⁺ ion with asymmetric environments of the two Pt atoms, classical PtO₄ square plane and unusual PtO₅ square pyramid. Successive Pt₂O₉ entities deduced from 90° rotations are connected through the oxygens of the PtO₄ basal squares to form [Pt₄O₁₀⁸⁻]_∞ columns further connected through Pb²⁺ and Sr²⁺ ions. Raman spectroscopy confirmed the peculiar platinum coordination environment.     

The synthesis and crystal structure of vanadium complexes: [VO2(phen)2]·6H2O and [2,2′-(bipy)2VO2](H2BO3)·3H2O

The organic-inorganic hybrid materials vanadium oxide [V^IVO₂(phen)₂]·6H₂O (1) and [(2,2′-bipy)₂V^VO₂](H₂BO₃)·3H₂O (2) have been conventional and hydrothermal synthesized and characterized by single crystal X-ray diffraction, elemental analyses, respectively. Although the method and the ligand had been used in the syntheses of the compounds (1) and (2) are different, they almost possess similar structure. They all exhibit the distorted octahedral [VO₂N₄] unit with organonitrogen donors of the phen and 2,2′-bipy ligands, respectively, which coordinated directly to the vanadium oxide framework. And they are both non-mixed-valence complexes. But the compound (1) is isolated, and the compound (2) consists of a cation of [(2,2′-bipy)₂V^VO₂]⁺ and an anion of (H₂BO₃)⁻. So the valence of vanadium of (1) and (2) are tetravalence and pentavalence, respectively. Meanwhile it is noteworthy that π-π stacking interaction between adjacent phen and 2,2′-bipy groups in compounds 1 and 2 also play a significant role in stabilization of the structure. Thus, the structure of [V^IVO₂(phen)₂]·6H₂O and [(2,2′-bipy)₂V^VO₂](H₂BO₃)·3H₂O are both further extended into interesting three-dimensional supramolecular. Crystal data: (1) Triclinic, a=8.481(4), b=12.097(5), and α=66.32(2), β=82.97(3), and γ=82.59(4)°, Z=2, R₁=0.0685, wR₂=0.1522. (2) Triclinic, a=6.643(13), b=11.794(2), and α=101.39(3), β=101.59(3), and γ=97.15(3)°, Z=2, R₁=0.0736, wR₂=0.1998.     

Hydrothermal synthesis and crystal structure of a new inorganic/organic hybrid of scandium sulfate: (H2en)Sc2(SO4)4·(H2O)0.72

The first organically templated layered structure of scandium sulfate, (H₂en)Sc₂(SO₄)₄·(H₂O)_0.72, (en=ethylenediamine) was synthesized by a hydrothermal method and characterized by single crystal X-ray diffraction. In the title compound, scandium ions are bridged by sulfate groups with a ratio of 1:2 into a 4₃⁶ layer structure. These layers are parallel packed and separated from each other by ethylenediammonium dications and water molecules. The title compound crystallizes in the monoclinic space group P2/c, with cell parameters , , , β=91.210(3)°, and Z=2. Refinement gave R₁[I>2σ(I)]=0.0354 and wR₂[I>2σ(I)]=0.0878. Thermogravimetric analysis indicates that this material is thermally stable to above 400 °C.     

Three-dimensional framework of uranium-centered polyhedra with non-intersecting channels in the uranyl oxy-vanadates A2(UO2)3(VO4)2O (A=Li, Na)

The uranyl vanadates A₂(UO₂)₃(VO₄)₂O (A=Li, Na) have been synthesized by solid-state reaction and the structure of the Li compound was solved from single-crystal X-ray diffraction. The crystal structure is built from chains of edge-shared U(2)O₇ pentagonal bipyramids alternatively parallel to - and -axis and further connected together to form a three-dimensional (3-D) arrangement. The perpendicular chains are hung on both sides of a sheet parallel to (001), formed by U(1)O₆ square bipyramids connected by VO₄ tetrahedra, and derived from the autunite-type sheet. The resulting 3-D framework creates non-intersecting channels running down the - and -axis formed by empty face-shared oxygen octahedra, the Li⁺ ions are displaced from the center of the channels and occupy the middle of one edge of the common face. The peculiar position of the Li⁺ ion together with the full occupancy explain the low conductivity of Li₂(UO₂)₃(VO₄)₂O compared with that of Na(UO₂)₄(VO₄)₃ containing the same type of channels half occupied by Na⁺ ions in the octahedral sites.Crystallographic data for Li₂(UO₂)₃(VO₄)₂O: tetragonal, space group I41/amd, , , , Z=4, ρ_mes=5.32(2) g/cm³, ρ_cal=5.36(3) g/cm³, full-matrix least-squares refinement basis on F² yielded, R₁=0.032, wR₂=0.085 for 37 refined parameters with 364 independent reflections with I?2σ(I).     

New alkaline earth-zirconium oxalates M2Zr(C2O4)4·nH2O (M=Ba, Sr, Ca) synthesis, crystal structure and thermal behavior

Three new alkaline earth-zirconium oxalates M₂Zr(C₂O₄)₄·nH₂O have been synthesized by precipitation methods for M=Ba, Sr, Ca. For each compound the crystal structure was determined from single crystals obtained by controlled diffusion of M²⁺ and Zr⁴⁺ ions through silica gel containing oxalic acid. Ba₂Zr(C₂O₄)₄·7H₂O, monoclinic, space group C2/c, a=9.830(2), b=29.019(6), , , , Z=4, R=0.0427; Sr₂Zr(C₂O₄)₄·11H₂O, tetragonal, space group I4₁/acd, a=16.139(4), , ,Z=8, R=0.0403; Ca₂Zr(C₂O₄)₄·5H₂O, orthorhombic, space group Pna2₁, a=8.4181(5), b=15.8885(8), , , Z=4, R=0.0622. The structures of the three compounds consist of chains of edge-shared MO₆(H₂O)_x (x=2 or 3) polyhedra connected to ZrO₈ polyhedra through oxalate groups. Depending on the arrangement of chains, the ZrO₈ polyhedron geometry (dodecahedron or square antiprism) and the connectivity, two types of three-dimensional frameworks are obtained. For the smallest M²⁺ cations (Sr²⁺, Ca²⁺), large tunnels are obtained, running down the c direction of the unit cell, which can accommodate zeolitic water molecules. For the largest Ba²⁺ cation, the second framework is formed and is closely related to that of Pb₂Zr(C₂O₄)₄·nH₂O. The decomposition at 800°C into strontium carbonate, barium carbonate or calcium oxide and MZrO₃ (M=Sr, Ba, Ca) perovskite is reported from thermal analyses studies and high temperature X-ray powder diffraction.     

Hydrothermal synthesis and characterization of two new bicapped Keggin heteropoly tungstovanadated derivatives

Two new heteropoly tungstovanadate derivatives, [Fe(phen)₃]₂[W_10.5V_4.5O₄₂]·3H₂O (1) and [Fe(phen)₃]₂[W₁₀V₅O₄₂].6H₂O (2) (phen=1,10′-phenanthroline), have been synthesized under hydrothermal conditions by using different starting materials, and characterized by elemental analysis, IR, ESR, XPS, TGA and single-crystal X-ray diffraction analysis. Crystal data for compound 1: C₇₂H₅₄Fe₂N₁₂O₄₅V_4.5W_10.5, monoclinic, space group C2/c, , , , β=99.882(8)°, V=10002(5) ų, Z=4; for compound 2, C₇₂H₆₀Fe₂N₁₂O₄₈V₅W₁₀, monoclinic, space group C2/c, a=30.246(6) Å, , c=25.329(5) Å, β=100.34(3)°, V=10483(4) ų, Z=4. The crystal structure analysis reveals that both polyoxoanions are decorated with the [Fe(phen)₃]²⁺ cations_, and that they have analogous structure to each other with slightly different packing modes of the polyoxoanions, [Fe(phen)₃]²⁺ cations and water molecules. They are further linked to form two-dimensional (2D) supramolecular networks through extensive hydrogen bonding.     

A novel inorganic-organic compound: Synthesis and structural characterization of tin(II) phenylbis(phosphonate), Sn2(PO3C6H4PO3)

A novel tin(II) phenylbis(phosphonate) compound has been synthesized hydrothermally and its structure has been determined by single crystal X-ray diffraction. The structure is monoclinic, space group P2₁/c (no. 14), a=4.8094(4), b=16.2871(13), ; β=106.292(6)°, , Z=2. The three-dimensional structure consists of 3-coordinated tin and 4-coordinated phosphorus double layers separated (pillared) by phenyl rings. These phenyl rings are placed 4.8 Å apart along the a-axis in the structure resulting in lower surface area (∼14 m²/g). The porosity has been increased by replacing phenyl groups by methyl groups (∼31 m²/g).     

The crystal structure of CuSb2O3Br: Slabs from cubic Sb2O3 interspersed between puckered hexagonal CuBr-type layers

The new compound CuSb₂O₃Br crystallize in the monoclinic space group Cc. The unit cell parameters are , , , β=90°, Z=16. The crystal structure is solved from single crystal data, R=0.0490. The compound show a layered structure with slabs from cubic Sb₂O₃ interspersed in between puckered layers of CuBr. The Sb(III) atoms have tetrahedral [SbO₃E] coordination where E is the 5s² lone pair, these units build up Sb₄O₄E₆ cages. The CuBr layers resemble those in hexagonal CuBr but the Cu(I) ions have actually tetrahedral [CuBr₃O] coordination. The Cu-O bonds link the Sb₄O₆ cages with the CuBr layers.     

[Cu(dca)2(en)]n: a two-dimensional copper(II) coordination polymer with both μ1,5-dca and pseudo-μ1,3-dca bridges

A copper(II)-dicyanamide (dca=dicyanamide anion, [N(CN)₂]⁻) compound, [Cu(dca)₂(en)]_n (1) (en=ethylene diamine), has been synthesized and its structure has been determined by single X-ray diffraction analysis. It crystallizes in the monoclinic space group C2/c with unit cell dimensions: β=99.499°, Z=8, and 1 is the first coordination polymer containing both μ_1,5-dca and pseudo-μ_1,3-bridging dca. The adjacent copper atoms are connected by dca with μ_1,5-bridging mode to form a chain structure. Furthermore, the chains are cross linked via the pseudo-μ_1,3-bridging dca into a 2D layer structure. Magnetic characterization of 1 suggests that the complex exhibits a weak antiferromagnetic interaction between the copper(II) ions.     

Solvothermal synthesis of new metal organic framework structures in the zinc-terephthalic acid-dimethyl formamide system

Two new metal organic framework (MOF) structures have been obtained from the Zn-terephthalic acid (H₂BDC)-dimethyl formamide (DMF) system and examined by single-crystal X-ray diffraction: Zn(C₈H₄O₄)(C₃H₇NO), 1, monoclinic C2/m, a=11.1369(5), b=14.0217(7), , β=106.316(1)°, , , Z=4, R₁=0.060, wR₂=0.169, S=1.27; Zn(HCO₂)₃(C₂H₈N), 2, trigonal , a=8.1818(1), , , , Z=6, R₁=0.014, wR₂=0.039, S=1.11. Contrary to previously published structures in the same system, the crystals were obtained by solvothermal synthesis at 381 K. Structure 1 consists of 2-D layers stacked in an offset manner to accommodate DMF moieties coordinated to Zn²⁺ within voids in adjacent layers. Structure 2 consists of a 3-D network constructed from Zn²⁺ ions bridged by deprotonated formic acid moieties. Over time, the structure of 1 rearranges to Zn(C₈H₄O₄)(C₃H₇NO)(H₂O) [monoclinic P2₁/n, a=6.6456(2), b=15.2232(5), , β=104.110(2)°, , , Z=4, R₁=0.048, wR₂=0.100, S=1.07], which is identical to the known MOF-2 structure, obtained by crystallization at ambient conditions. The three structures were determined from crystals with similar crystal habits picked from a single solvothermal synthesis batch. The study demonstrates that MOF syntheses can give not only multiple crystal structures under different conditions, but also that numerous different structures, including some that are metastable, can be formed under identical conditions.     

A new layered cobaltite (Ga1/3Co2/3)2Sr2CoO6+δ with high spin Co: modulated structure and physical properties

Investigations in the Sr-Co-Ga-O system by means of transmission electron microscopy techniques have allowed the detection of a new layered cobaltite. Its structure has been obtained by combining high-resolution images and powder X-ray diffraction. The modulated structure of this novel oxide, (Ga_1/3Co_2/3)₂Sr₂CoO_6+δ is derived from the perovskite with a=a_p√2, b=a_p√2, and a modulation vector q^*=q₁a^*+q₂c^*. For the as-prepared samples, the δ value is close to 0.4 and the modulated structure (q₁≈1/3 and q₂=1) can be described in an ideal orthorhombic 3D supercell Bb2b with the unit cell parameters , and . The layer stacking consists in an intergrowth between a [SrCoO₃] perovskite-type block and a block of triple layers, [(SrO)(Co_2/3Ga_1/3O_1+δ/2)(Co_2/3Ga_1/3O_1+δ/2)] derived from [AO] rock-salt type layers. The magnetic study shows that the Co³⁺ cations exhibit a high spin state in this structure. The θ_p value, −570 K, suggests that antiferromagnetic interactions dominate in this compound as in the brownmillerite cobaltites. Nonetheless, its resistivity is lower than that of the brownmillerite compounds. Since the positive Seebeck coefficient indicates the presence of holes (Co⁴⁺) in the CoO₂ conducting layers, the existence of weak ferromagnetic Co³⁺-O-Co⁴⁺ interactions developing below ≈150 K is proposed to explain the electronic properties of this new oxide.     

Syntheses and crystal structures of two new pentaborates

Two new pentaborates, [Zn(DIEN)₂][B₅O₆(OH)₄]₂ (DIEN=diethylenetriamine) (I) and [B₅O₇(OH)₃Zn(TREN)] (TREN=tris(2-aminoethyl)amine) (II), have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, FTIR, elemental analysis and thermogravimetric analysis. Compound I crystallizes in the monoclinic system, space group P2₁/c (No. 14), , , , β=91.259(2)°, , Z=2. The structure consists of isolated borate polyanion [B₅O₆(OH)₄]⁻ and zinc complex cation [Zn(DIEN)₂]²⁺. The anionic units, [B₅O₆(OH)₄]⁻, are linked by hydrogen bonds to form a 3D supramolecular network containing large channels, in which the templating [Zn(DIEN)₂]²⁺ cation are located. II is monoclinic, P2₁/c (No. 14), , , , β=99.635(2)°, , Z=4. The structure of II is constructed from two distinct motifs, a usual [B₅O₇(OH)₃]²⁻ cluster and a supporting zinc complex [Zn(TREN)]²⁺, which are integrated through Zn-O-B linkage. This compound represents the first example of the combination of B-O cluster with transition-metal complex.     

The first organically templated linear metal selenate

An organically templated cadmium selenate of the formula [enH₂][Cd(H₂O)₂(SeO₄)₂], , has been synthesized by carrying out the reaction between CdO and H₂SeO₄ in the presence of the amine in aqueous medium at 80°C. The structure of involves isolated infinite [Cd(H₂O)₂(SeO₄)₂]²⁻ chains running along the c-axis, with the protonated ethylenediamine molecules between them. Crystal data for are as follows: Monoclinic, space group=C2/c, a=10.5059(7), b=10.3605(7), , β=94.666(2)°, , z=8, R₁=0.0237, wR₂=0.0500 (for all data).     

Synthesis, crystal structure and magnetic properties of an Os-containing pillared perovskite La5Os3MnO16

A new Os-containing, pillared perovskite, La₅Os₃MnO₁₆, has been synthesized by solid state reaction in sealed quartz tubes. This extends the crystal chemistry of these materials which had been known only for Mo and Re, previously. The crystal structure has been characterized by X-ray and neutron powder diffraction and is described in space group C-1 with parameters a=7.9648(9) Å; b=8.062(1) Å; c=10.156(2) Å, α=90.25(1)°, β=95.5(1)°; γ=89.95(2)°, for La₅Os₃MnO₁₆. The compound is isostructural with the corresponding La₅Re₃MnO₁₆ phase. A very short Os-Os distance of 2.50(1) Å was found in the dimeric pillaring unit, Os₂O₁₀, suggestive of a triple bond as demanded by electron counting. Nearly spin only values for the effective moment for Os⁵⁺ () and Mn²⁺ () were derived from magnetic susceptibility data. Evidence for magnetic transitions was seen near ∼180 and 80 K. Neutron diffraction data indicate that T_c is 170(5) K. The magnetic structure of La₅Os₃MnO₁₆ at 7 K was solved revealing that Os⁵⁺ and Mn²⁺ form ferrimagnetically coupled layers with antiferromagnetic interlayer ordering. The ordered moments are for Mn²⁺ and for Os⁵⁺, which are reduced from the respective spin only values of 5.0 and . The observation of net ferrimagnetic (antiparallel) intraplanar coupling between Os⁵⁺(t_2g³) and Mn²⁺(t_2g³e_g²) is interesting as it appears to contradict the Goodenough-Kanamori rules for 180° superexchange.     

Structural and magnetic properties of perovskite Ca3Fe2WO9

A complex perovskite with composition Ca₃Fe₂WO₉ has been synthesised, and the temperature evolution of nuclear and magnetic structures investigated by neutron powder diffraction. It was shown that at room temperature this compound adopts a monoclinic perovskite structure belonging to space group P12₁/n1 (, , ), β=90.04(2)°). The partial B-site ordering, of the Fe⁺³ and W⁺⁶ cations, at (2c) and (2d) sites was determined. At low temperatures the magnetic diffraction peaks were registered and a possible model for the magnetic structure was proposed in accordance with the ferrimagnetic properties of the title compound. The magnetic structure is defined by a propagation vector k=(1/2,1/2,0) and can be described as an array of ferromagnetic (20−1) layers, which couple antiferromagnetically to each other. All the Fe moments within a layer are aligned parallel (or anti-parallel) to the c-axis. The structural and magnetic features of this compound are discussed and compared with those of some other quaternary oxides A₃Fe₂WO₉ (A=Ba, Sr, Pb).     

Crystal structure and conformational analysis of 1-[N-(2-bromophenyl)]naphthaldimine

1-[N-(2-bromophenyl)]naphthaldimine (C₁₇H₁₂NOBr) (1) was synthesised and its crystal structure was determined. The compound 1 is orthorhombic, space group P2₁2₁2₁ with a=12.653(2), b=13.7311(14), Z=4, R=0.032 for 499 reflections I>2σ(I)]. There is an intramolecular hydrogen bond of distance 2.473(3) Å between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the oxygen atom. Minimum energy conformation was calculated as a function of torsion angle θ (C10-C11-N1-C12) varied every 5 degrees. The optimized geometry of the crystal structure corresponding to the non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by hydrogen-hydrogen repulsions between the ortho-hydrogen atoms on the aldehyde rings. Complementary IR, ¹H NMR and UV measurements in solution and in the solid state were carried out.