Sr7N2Sn3: a layered antiperovskite-type nitride stannide containing zigzag chains of Sn4 polyanions

Metallic black platelet single crystals of a new ternary compound, Sr7N2Sn3, were obtained by heating Sr and Sn in a Na flux together with NaN3 as a nitrogen source at 1073 K, followed by slow cooling. Single-crystal X-ray analysis revealed that this compound crystallizes in an orthorhombic cell with the cell parameters a = 10.4082(2), b = 18.0737(4), and c = 7.43390(10) Å (space group Pmna, Z = 2), and has a layered (modular) antiperovskite-type structure which could be related to the inverse structure of Ca2Nb2O7 ((Ca2)[Ca2Nb4O14]). Four-membered zigzag [Sn4] chains are situated between slabs comprising four antiperovskite layers cut by the (110) plane of the ideal anitiperovskite structure, and Sr7N2Sn3 can be expressed as [Sn4][Sn2N4Sr14]. Although an electron-precise valence electron distribution according to the formula (Sr2+)14(N3−)4(Sn4−)2([Sn4]8−) is proposed for this ternary compound, yet, there are certain structural peculiarities which cannot be explained by this idealized picture. Therefore, first principles-based means were employed to account for the aforementioned structural features.

Effect of Lanthanum Substitution on Structure and Modulation in Bi2Sr2-xLaxCaCu2O8+d (0≤x≤0.3) Superconducting Compound

The effect of La substitution on the structure and its modulation in samples with a nominal composition of Bi2Sr2-xLaxCaCu2O8+d where 0≤x≤0.3 superconducting phase was investigated. The X-ray powder diffraction (XRPD) results showed an almost pure Bi-2212 phase, confirmed by the estimated amount of element concentration using dispersive energy X-ray spectroscopy (EDX). Scanning electron microscopy (SEM) micrographs showed a decrease of both crystallite size and connectivity when Lanthanum concentration increases. Le Bail refinement using the Jana2006 program gives a very good value of goodness of fit (GOF) factor. Also, the refinement reveals that for x=0.3 the orthorhombic cell transforms to the tetragonal one and the modulation vector q increases when increasing La concentration.

Two new minerals, badengzhuite, TiP, and zhiqinite, TiSi₂, from the Cr-11 chromitite orebody, Luobusa ophiolite, Tibet, China: is this evidence for super-reduced mantle-derived fluids?

Titanium minerals enclosed in corundum separated from the Cr-11 orebody include native Ti, zamboite (FeTiSi2), osbornite (TiN)-khamrabaevite (TiC) solid solutions, and jingsuiite (TiB2), as well as the new minerals badengzhuite (TiP) and zhiqinite (TiSi2) and two potentially new minerals, Ti11(Si,P)10 and Ti10(Si,P,□)7, where □ indicates a vacancy. These minerals together constitute a spheroid 20 µm across inferred to have crystallized from a droplet of Ti–Si–P intermetallic melt. Energy-dispersive spectroscopy and three-dimensional electron diffraction were applied to characterize the two new minerals. Badengzhuite has a primitive hexagonal cell with a=3.49(7) Å, c=11.70(23) Å, V=124(4) Å3, and crystallizes in space group P63∕mmc (Z=4). It is isostructural with synthetic TiP. Two EDX (energy dispersive X-ray spectroscopy) analyses of badengzhuite gave 60.56 wt %Ti and 39.44 wt % P and 62.74 wt % Ti and 37.26 wt % P from which an empirical formula of Ti1.020P0.980 was calculated on the basis of two atoms (ideally TiP). Zhiqinite has a primitive orthorhombic cell with a=8.18(16) Å, b=4.85(10) Å, c=8.42(17) Å, V=334(12) Å3, and crystallizes in space group Fddd (Z=8). It is isostructural with synthetic TiSi2 (C54 type). Four EDX analyses of zhiqinite gave 39.58–44.79 wt % Ti and 55.21–60.42 wt % Si, from which an empirical formula of Ti0.905Si2.095 was calculated on the basis of three atoms (ideally TiSi2). We suggest that interaction of mantle-derived CH4 + H2 fluids with basaltic magmas in the shallow lithosphere (depths of ∼ 30–100 km) under conditions more reducing than 6 log units below the oxygen fugacities corresponding to the iron–wüstite buffer resulted in precipitation of corundum that entrapped intermetallic melts, some of which crystallized to ultra-reduced Ti–P–Si phases. Experimental work on the Ti–Si and Ti–P systems indicates that the minerals enclosed in corundum could have crystallized from the alloy melt at the lowest temperature accessible on the liquidus. It has been alleged that these ultra-reduced phases are anthropogenic contaminants inadvertently introduced with fused alumina abrasive during preparation of mineral separates. Nonetheless, we conclude that the differences between the ultra-reduced minerals in the separates and the ultra-reduced phases in fused alumina are more convincing evidence for these minerals having a natural origin than the similarities between them are evidence for an anthropogenic origin.

α-SrZn5-Type solid solution, BaZn2.6Cu2.4

Single crystals of the title compound barium zinc copper, BaCu2.6Zn2.4, were obtained from a sample prepared by heating metal chips of Ba, Cu, and Zn in an Ar atmosphere up to 973 K, followed by slow cooling. Single-crystal X-ray structure analysis revealed that BaCu2.6Zn2.4 crystallizes in an orthorhombic cell [a = 12.9858 (3), b = 5.2162 (1), and c = 6.6804 (2) Å] with an α-SrZn5-type structure (space group Pnma). The three-dimensional framework consists of Cu and Zn atoms, with Ba atoms in the tunnels extending in the b-axis direction. Although the Ba atom is larger than the Sr atom, the cell volume of BaCu2.6Zn2.4 [452.507 (19) Å3] is smaller than that of α-SrZn5 [466.08 Å3]. This decrease in volume can be attributed to the partial substitution of Cu atoms by Zn atoms in the framework because the Cu—Zn and Cu—Cu bonds are shorter than the Zn—Zn bond. The increase in Ba—Zn interatomic distances from the Sr—Zn distances is cancelled out by the partial replacement of Zn with Cu atoms, which leads to shorter average Ba—Zn/Cu distances.

4-METHYL HYPPURIC ACID: A CASE OF POLYMORPHISM AND SOLVATOMORPHISM

Polymorphism is known as the ability of a solid material to exist in more than one form or crystal structure, with important applications in the preparation of active pharmaceutical ingredients. Characterization of different polymorphs of the specific metabolite of 4-xylene can contribute to the chemical and pharmaceutical industry. Polymorphism is of particular importance in industrial processes, where different physical properties of polymorphic forms can substantially alter the viability and quality of a manufactured product. This is particularly so for the design and production of drugs in the pharmaceutical industry, as varying physical properties between different polymorphs can affect shelf life and durability, solubility, as well as bioavailability and manufacturing of the drug. The crystallization, spectroscopic and X-ray diffraction characterization of two polymorph and one solvatomorph of 4-methylhippuric acid are presented. These compounds crystallizes in different crystalline systems. Polymorph I (4mH-I) crystalize in an orthorhombic cell with space group P212121. Polymorph II (4mHII) crystallizes in a monoclinic space group P21/c. Solvatomorph (4mH-S) crystallizes in a triclinic P-1 cell. All polymorphs crystallize in neutral form. The crystal packing of the three compounds are governed by hydrogen bonds intermolecular interactions of the type N--H···O and O--H···O forming tridimensional networks.

A quarter of a century after its synthesis and with >200 papers based on its use, `Co(CO3)0.5(OH)·0.11H2O′ proves to be Co6(CO3)2(OH)8·H2O from synchrotron powder diffraction data

The successful attempt to solve the crystal structure of Co(CO3)0.5(OH)·0.11H2O (denoted CCH), based on synchrotron powder diffraction data, leads to a drastic revision of the chemical formula to Co6(CO3)2(OH)8·H2O [hexacobalt(II) bis(carbonate) octahydroxide monohydrate] and to a hexagonal cell instead of the orthorhombic cell suggested previously [Porta et al. (1992). J. Chem. Soc. Faraday Trans. 88, 311–319]. This results in a new structure-type related to malachite involving infinite chains of [CoO6] octahedra sharing edges along a short c axis, delimiting tunnels having a three-branched star section. All reports discussing cobalt hydroxycarbonates (CCH) without any structural knowledge and especially its topotactic decomposition into Co3O4 have, as a result, to be reconsidered.

Monoclinic polymorph of chlorido(dimethyl sulfoxide-κO)triphenyltin(IV)

The crystal structure of the title tin complex, [Sn(C6H5)3Cl(C2H6OS)], (I), has been reported with one molecule in the asymmetric unit in an orthorhombic cell [Kumar et al. (2009). Acta Cryst. E65, m1602–m1603]. While using SnPh3Cl as a starting material for a reaction for which the products were recrystallized over a very long time (six months) from dimethyl sulfoxide (DMSO), a new polymorph was obtained for (I), with two independent molecules in the asymmetric unit of a monoclinic cell. The coordination geometry of the Sn centres remains unchanged, with the Cl− ion and the DMSO molecule in the apical positions and the phenyl C atoms in the equatorial positions of a trigonal bipyramid. The main difference between the polymorphs is the relative orientation of the phenyl rings in the equatorial plane, reflecting a degree of free rotation of these groups about their Sn—C bonds. In the crystal, molecules are linked into [010] chains mediated by weak C—H...O interactions.

Oscarkempffite, Ag10Pb4(Sb17Bi9)∑26S48, a new Sb-Bi member of the lillianite homologous series

Oscarkempffite, ideally Ag10Pb4(Sb17Bi9)∑=26S48, is a new mineral species found in old material (1929–30) from the Colorada vein, Animas mine, Chocaya Province, Department of Potosi, Bolivia. It is associated with aramayoite, stannite, miargyrite, pyrargyrite and tetrahedrite. Oscarkempffite forms anhedral grains and grain aggregates up to 10 mm across. The mineral is opaque, greyish black with a metallic lustre; it is brittle without any discernible cleavage. In reflected light oscarkempffite is greyish white, pleochroism is distinct, white to dark grey. Internal reflections are absent. In crossed polars, anisotropism is distinct with rotation tints in shades of grey. The reflectance data (%, air) are: 39.9, 42.6 at 470 nm, 38.6, 41.7 at 546 nm, 38.1, 41.2 at 589 nm and 37.3, 40.6 at 650 nm. Mohs hardness is 3–3½, microhardness VHN50 exhibits a range 189–208, with a mean value 200 kg mm–2. The average results of four electron-microprobe analyses in a grain are: Cu 0.24(7), Ag 14.50(8), Pb 11.16(14), Sb 28.72(16), Bi 24.56(17), S 20.87(5), total 100.05(6) wt.%, corresponding to Cu0.24Ag9.92Pb4.00Sb17.36Bi8.64S47.84 (on the basis of Me + S = 88 apfu). The simplified formula, Ag10Pb4Sb17Bi9S48, is in accordance with the results of a crystal-structure determination. The density, 5.8 g cm–3, was calculated using the ideal formula. Oscarkempffite has an orthorhombic cell with a = 13.199(2), b = 19.332(3), c = 8.249(1) Å, V = 2116.3(5) Å3, space group Pnca and Z = 1. The strongest eight lines in the (calculated) powder-diffraction pattern are [d in Å(I)hkl]: 3.66(35)(122), 3.37(70)(132), 3.34(100)(250), 2.982(55)(312), 2.881(86)(322), 2.733(29)(332), 2.073(27)(004) and 2.062(31)(182). Comparison with gustavite, andorite and roshchinite confirms its independence as a mineral species.

Synthesis and crystal structure refinement of new perovskite oxides, Dy0.55Sr0.45Mn1−xFexO3 (x = 0.0 and 0.2) from X-ray powder diffraction data

Polycrystalline compounds of Dy0.55Sr0.45Mn1−xFexO3 (x = 0.0 and 0.20) were synthesized using ceramic method and characterized by X-ray powder diffraction technique using CuKα (1.5406 Å) radiation at room temperature. All the diffraction peaks were indexed to an orthorhombic cell with space group Pnma (#62). Whole powder diffraction profile refinement was performed using GSAS package.

Etude structurale et vibrationnelle d'un nouveau composé complexe de cobalt: [Co(imidazole)4Cl]Cl

In the title complex, chloridotetrakis(1H-imidazole-κN3)cobalt(II) chloride, [CoCl(C3H4N2)4]Cl, the CoIIcation has a distorted square-pyramidal coordination environment. It is coordinated by four N atoms of four imidazole (Im) groups in the basal plane, and by a Cl atom in the apical position. It is isostructural with [Cu(Im)4Cl]Cl [Morzyk-Ociepaet al.(2012).J. Mol. Struct.1028, 49–56] and [Cu(Im)4Br]Br [Hossaini Sadret al.(2004).Acta Cryst. E60, m1324–m1326]. In the crystal, the [CoCl(C3H4N2)4]+cations and Cl−anions are linkedviaN—H...Cl hydrogen bonds, forming layers parallel to (010). These layers are linkedviaC—H...Cl hydrogen bonds and C—H...π and π–π [inter-centroid distance = 3.794 (2) Å] interactions, forming a three-dimensional framework. The IR spectrum shows vibrational bands typical for imidazol groups. The monoclinic unit cell of the title compound emulates an orthorhombic cell as its β angle is close to 90°. The crystal is twinned, with the refined ratio of twin components being 0.569 (1):0.431 (1).