Ya-Xi Huang

Shape development and structure of a complex (otoconia-like?) calcite-gelatine composite

A large number of recent publications deal with control of the size and shape of calcium carbonate in its calcite modification by organic additives acting as growth modifiers or templates. Other reports focus not only on shape control but also on the control of the calcium carbonate modification formed. Only a few publications concentrate on calcite specimens showing a habit that is more or less close to the shape of biogenic (calcite) otoconia (see Figure 1), charac-

Strong spin frustration from isolated triangular Cu(II) trimers in SrCu(OH)3Cl with a novel cuprate layer

Strontium oxocuprates such as Sr2CuO2Cl2 have been extensively investigated for their two-dimensional (2D) planar CuO2 square layers that are typical of high-temperature cuprate superconductors. A new synthetic strontium cuprate SrCu(OH)3Cl features a novel cuprate layer with isolated triangular Cu(II) trimers. The crystal structure of the title compound can be derived from breaking the cuprate planar layer to form isolated, nonplanar triangular copper trimers ({[Cu3(μ3-Cl)(OH)3](OH)6Cl2}6−), which are connected by strontium coordination spheres to form a novel framework structure. The copper trimers exhibit an unprecedented array that has triangular Cu3-planes perpendicular not only to their own layer but also to their counterparts in the next layers, which is thus different from the parallel array in the Kagome layer of ZnCu3(OH)6Cl2. This cross-orientation arrangement of the triangular Cu(II) trimers is proposed to be responsible for a strong antiferromagnetic exchange (J = −233(2) cm−1) in the triangles characterized by a Weiss temperature θcw = −135 K but virtually zero (or negligible) magnetic coupling between the triangles. Such remarkable magnetic properties make the title compound a Mott insulator – an ordered inorganic solid with Cu spin-1/2 spins forming an intrinsic “molecular magnet”.

Crystal structure of sodium gallium [monohydrogenmonophosphate-dihydrogenmonoborate-monophosphate],NaGa[BP2O7(OH)3]

BGaH3NaO10P2, monoclinic, C12/c1 (No. 15), a = 10.408(3) A, b = 8.094(2) A, c = 9.099(2) A, = 116.64(2)°, V = 685.2 A, Z = 4, Rgt(F) = 0.025, wRref(F ) = 0.068, T = 293 K. Source of material NaGa[BP2O7(OH)3] was synthesized under mild hydrothermal conditions. The reaction was carried out with mixtures of Ga metal (0.139 g) dissolved in 1ml of HCl (18%) with Na2HPO4·12H2O (1.075 g) and Na2B4O7·10H2O (0.4767 g) (molar ratio of Ga:P:B = 2:3:6) in aqueous solution. The mixture was sealed in glass tubes (after adding 1 ml H2O to achieve a degree of filling of 30%) with subsequent heating at 408 K for 60 days. The starting materials are all of analytical grade. Discussion With the increasing interest in microporous materials, synthesis of compounds like borophosphates with open framework structure have drawn much attention during the past few years and show a rich crystal chemistry [1]. Systems including a p-block metal have not been widely explored up to now besides one Al compound [2] reported only recently. The structure of the title compound is isotypic to the Fe [3] and Al analogues [2] and is characterized by isolated GaO4(OH)2 octahedra sharing common O-corners with phosphate and common O(OH)-corners with hydrogenborate groups from the ol igomeric uni ts [B2P2O7(OH)3]. The condensation of the borophosphate oligomers with Ga-coordination octahedra via common corners results in an overall three-dimensional framework which contains elliptical channels running along the [001] direction. The cross section of the channels is defined by eight-membered octahedral/tetrahedral rings (four Ga coordination octahedra, two phosphateand two borate-groups). Sodium ions are distributed within the open channels. The Ga—O bond distances are 1.925 and 1.965 A, while the Ga—OH value is increased to 1.995 A. The bond distances P—O and B—O in the oligomeric borophosphate groups correspond to respective values in the Feand Al-analogues [2,3]. Z. Kristallogr. NCS 216 (2001) 15–16 15

Perfect Kagomé lattices in YCu3(OH)6Cl3: a new candidate for the quantum spin liquid state

Polymorphs of ZnCu3(OH)6Cl2 (herbertsmithite and kapellasite) and related cuprates MCu3(OH)6Cl2 (M = Mg2+, Ca2+, Cd2+, Co2+, Fe2+, Mn2+ and Ni2+) with antiferromagnetic Kagome lattices have attracted attention for intensively investigating the quantum spin liquid (QSL) materials. However, mixing between magnetic (Cu2+) and diamagnetic divalent ions (Zn2+, Mg2+, etc.) is commonly significant in MCu3(OH)6Cl2 and therefore disturbs the perfect Kagome lattices consequently adversely affecting the magnetic performance. Herein we report on the synthesis and characterization of YCu3(OH)6Cl3, the first-ever cuprate of the kapellasite-type structure with a trivalent cation. Single-crystal X-ray structure refinements show that the diamagnetic Y3+ cations in the title compound are located at the Zn positions and are charge balanced by additional Cl− anions between the Kagome layers. 65Cu and 35Cl MAS NMR analyses confirm single-crystal X-ray diffraction data that there is no detectable mixing between Y3+ and Cu2+ in the title compound, resulting in a more idealized Kagome lattice than those in herbertsmithite and kapellasite. Magnetic analyses demonstrate that the title compound is a geometrically frustrated S = 1/2 antiferromagnet with a Curie–Weiss temperature θ of −99 K and does not show any magnetic transition down to 2 K (i.e., the frustration parameter f > 49), suggesting a possible QSL candidate.

Two Isotypic Transition Metal Germanophosphates MII4(H2O)4[Ge(OH)2(HPO4)2(PO4)2] (MII = Fe, Co): Synthesis, Structure, Mössbauer Spectroscopy, and Magnetic Properties

Synthetic, structural, thermogravimetric, Mössbauer spectroscopic, and magnetic studies were performed on two new isotypic germanophosphates, M(II)(4)(H(2)O)(4)[Ge(OH)(2)(HPO(4))(2)(PO(4))(2)] (M(II) = Fe, Co), which have been prepared under hydro-/solvo-thermal conditions. Their crystal structures, determined from single crystal data, are built from zigzag chains of M(II)O(6)-octahedra sharing either trans or skew edges interconnected by [GeP(4)O(14)(OH)(4)](8-) germanophosphate pentamers to form three-dimensional neutral framework structure. The edge-sharing M(II)O(6)-octahedral chains lead to interesting magnetic properties. These two germanophosphates exhibit a paramagnetic to antiferromagnetic transition at low temperatures. Additionally, two antiferromagnetic ordering transitions at around 8 and 6 K were observed for cobalt compound while only one at 19 K for the iron compound. Low-dimensional magnetic correlations within the octahedral chains are also observed. The divalent state of Fe in the iron compound determined from the Mössbauer study and the isothermal magnetization as well as thermal analyses are discussed.

Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder

Structural assembly from phosphate to germanophosphate by applying germanate as a binder has been achieved. Two isotypic porous compounds, K3[M(II)4(HPO4)2][Ge2O(OH)(PO4)4]·xH2O (M(II) = Fe, Cd; x = 2 for Fe and 3 for Cd, denoted as KFeGePO-1 and KCdGePO-1, respectively), contain a known transition-metal phosphate (TMPO) layer, (∞)(2){[M2(HPO4)3]2–}, which is built from chains of trans-edge-sharing MO6 octahedra bridged by MO5 trigonal bipyramids that were further linked and decorated by phosphate tetrahedra. The layers are bound by infinite chains of GeO5(OH) octahedra, resulting in a 3D open-framework structure with 1D 12-ring channels that are occupied by K+ ions and water molecules. The curvature of the TMPO layers and shape of the 12-ring windows can be tuned by the transition metals because of their Jahn–Teller effect.

Crystal structure of sodium indium (monohydrogenmonophosphate- dihydrogenmonoborate-monophosphate), NaIn(BP2O7(OH)3)

B4H12In4Na4O40P8, monoclinic, C12/c1 (No. 15), a = 10.368(2) A, b = 8.520(1) A, c = 9.415(2) A, = 115.951(5)°, V = 747.8 A, Z = 1, Rgt(F) = 0.076, wRref(F) = 0.202, T = 293 K. Source of material NaIn[BP2O7(OH)3] was synthesized under mild hydrothermal conditions. The reactions were carried out with mixtures of In metal (0.230 g) dissolved in 1 ml of HCl (18%), Na2HPO4 · 12H2O (1.074 g) and Na2B4O7 · 10H2O (1.525 g) (molar ratio of In:P:B = 2:3:16) in aqueous solution. The mixtures were sealed in glass tubes (after adding 1 ml H2O to achieve a degree of filling of 30%) with subsequent heating at 408 K for 90 days. The starting materials were all of analytical purity grade. Experimental details The quality of the crystal studied was not good enough, which is reflected in the resulting high R-values. Discussion The synthesis of compounds like borophosphates with open framework structures has drawn much attention during the past few years due to their potential applications as microporous materials. The variety of crystal structures known up to now already shows a rich crystal chemistry [1]. Systems including a p-block metal have not been widely explored besides one Al [2] and one Ga [3] compound reported only recently. Two In containing phases are published in this issue [4,5]. The structure of the title compound is isotypic to the Fe [6], Al and Ga analogues [2,3] and is characterized by isolated InO4(OH)2 octahedra sharing common O-corners with hydrogen phosphate and common O(OH)-corners with hydrogenborate groups from the oligomeric units [BP2O7(OH)3]. The condensation of the borophosphate oligomers with In-coordination octahedra via common corners results in a three-dimensional framework which contains elliptical channels running along the [001] direction. The cross section of the channels is defined by eight-membered octahedral/tetrahedral rings (four In coordination octahedra, two hydrogen phosphateand two hydrogen borate-groups). Sodium ions are distributed within the open channels. The In—O bond distances 2.082 A and 2.110 A are shorter than the In—OH value (2.189 A). The bond distances P—O and B—O in the oligomeric borophosphate groups correspond to respective values in the Gaand Al-analogues [2,3] and other In compounds [4,5]. Z. Kristallogr. NCS 217 (2002) 7–8 7

Single-crystal microtubes of a novel apatite-type compound, (Na2.5Bi2.5)(PO4)3(F,OH), with well-faceted hexagonal cross sections

A novel apatite-type compound, (Na2.5Bi2.5)(PO4)3(F,OH), NBPF, in the form of single-crystal microtubes with well-faceted, hexagonal morphologies in both exterior and interior surfaces, has been synthesized under hydrothermal conditions without addition of any template, surfactant or metal catalyst. Single crystal X-ray diffraction analysis confirms that Na+ and Bi3+ ions completely replace the Ca2+ ions in the apatite-like structure and jointly occupy three crystallographic sites with significantly different site preferences [Bi0.61Na0.39 at the 6c site, and Bi0.45Na0.55 and Bi0.23Na0.77 at the 2b sites, space groupP63 (No. 173)]. Time-dependent experiments show that these NBPF microtubes form via a fluoride-induced, in situ chemical reaction nucleation–dissolution–recrystallization growth mechanism.

Simultaneously enhancing the flame retardancy and toughness of epoxy by lamellar dodecyl-ammonium dihydrogen phosphate

Organic/inorganic intercalated dodecyl-ammonium dihydrogen-phosphate (C12ADP) has been prepared by a simple one-pot method. The incorporation of C12ADP into epoxy could improve the flame retardancy and toughness of the obtained C12ADP/EP composites, simultaneously, i.e. improved formed char quality, significantly reduced heat release rate and decreased total heat release, and enhanced impact toughness of EP composites as well.

Lithium diaqua­magnesium catena-borodiphosphate(V) monohydrate, LiMg(H2O)2[BP2O8]·H2O, at 173 K

The crystal structure of LiMg(H2O)2[BP2O8]·H2O consists of tubular structural units, built from tetrahedral ∞ 1{[BP2O8]3−} borophosphate ribbons and (LiO4)n helices running along [001], which are interconnected by MgO4(H2O)2 octahedra, forming a three-dimensional network structure with one-dimensional channels along [001] in which the water molecules are located. The water molecule in the channel is significantly displaced by up to 0.3 Å from the special position 6b (..2) to a half-occupied general position. Mg, B and one Li atom all lie on twofold axes. Of the two Li positions, one is at a special position 6b (..2), while the other is at a general position; both are only half-occupied.