Space Group P2 Research Articles

Synthesis and crystal structure of silicon pernitride SiN2 at 140 GPa.

Silicon pernitride, SiN2, was synthesized from the elements at 140 GPa in a laser-heated diamond anvil cell. Its crystal structure was solved and refined by means of synchrotron-based single-crystal X-ray diffraction data. The title compound crystallizes in the pyrite structure type (space group Pa , No. 205). The Si atom occupies a site with multiplicity 4 (Wyckoff letter b, site symmetry ..), while the N atom is located on a site with multiplicity 8 (Wyckoff letter c, site symmetry .3.). The crystal structure of SiN2 is comprised of slightly distorted [SiN6] octa-hedra inter-connected with each other by sharing vertices. Crystal chemical analysis of bond lengths suggests that Si has a formal oxidation state of +IV, while nitro-gen forms pernitride anions (N-N)4-.

BaCu2SiS4: A New Member of the AIIBI2MIVQ4 Chalcogenide Family with a Chiral Crystal Structure

AbstractNoncentrosymmetric ternary and quaternary chalcogenides are studied as promising nonlinear optical (NLO) materials in the mid‐infrared region. Here, we report the synthesis of a new material BaCu2SiS4 in the AIIBI2MIVQ4 family (A=divalent metal; B=monovalent metal; M=tetrel, Q=chalcogen), and discuss its crystal structure, thermal stability, optical behavior, and electronic structure. BaCu2SiS4 crystallizes in the noncentrosymmetric chiral space group P3221 with lattice parameters a=6.1440(3) Å, c=15.3542(8) Å, V=501.95(6) Å3, Z=3. The structure features helical channels formed by corner‐sharing [CuS4] and [SiS4] tetrahedral units. Synthesis was carried out in a molten salt flux, as opposed to a traditional solid‐state route from elements, to minimize the formation of a competing ternary phase, Ba2SiS4. BaCu2SiS4 is a semiconductor with an experimentally‐determined direct bandgap of ~2.2 eV. The material exhibits second harmonic generation (SHG) activity, confirming the noncentrosymmetric nature of the structure. Analysis of reported AIIBI2MIVQ4 crystal structures pointed out a correlation among potential structure types and the radii of the constituent elements. Total energy calculations were carried out to explore the relative stability of several reported crystal structures in this family of compounds.

Ca2 Ln(BS3 )(SiS4 ) (Ln = La, Ce, and Gd): Mixed Metal Thioborate-Thiosilicates as Well-Performed Infrared Nonlinear Optical Materials.

The first examples of thioborate-thiosilicates, namely Ca2 Ln(BS3 )(SiS4 ) (Ln = La, Ce, and Gd), are synthesized by rationally designed high-temperature solid-state reactions. They crystalize in the polar space group P63 mc and feature a novel three-dimensionalcrystal structure in which the discrete [BS3 ]3- and [SiS4 ]4- anionic groups are linked by Ca2+ and Ln3+ cations occupying the same atomic site. Remarkably, all three compounds show comprehensive properties required as promising infrared nonlinear optical materials, including phase-matchable strong second harmonic generation (SHG) responses at 2.05µm (1.1-1.2 times that of AgGaS2 ), high laser-induced damage thresholds (7-10 times that of AgGaS2 ), wide light transmission range (0.45-11µm), high thermal stabilities (>800 °C), and large calculated birefringence (0.126-0.149 @1064nm), which justify the material design strategy of combining [BS3 ]3- and [SiS4 ]4- active units. Theoretical calculations suggest that their large SHG effects originate mainly from the synergy effects of the LnS6 , BS3 , and SiS4 groups. This work not only broadens the scope of research on metal chalcogenides but also provides a new synthetic route for mixed anionic thioborates.

Mallestigite, Pb3Sb(SO4)(AsO4)(OH)6·3H2O, from the type locality – new data, crystal structure, and structural relationships

A report of the supergene mineral mallestigite, Pb3Sb5+(SO4)(AsO4)(OH)6·3H2O, from the type locality Neufinkenstein-Grabanz district, Mallestiger Mittagskogel, Carinthia, Austria, is given in order to close gaps that have been left open since its first description. At the type locality, the dump of an abandoned small copper-lead-zinc mine, the mineral occurs frequently in up to ⁓2 mm long clear colourless idiomorphic hexagonal prisms {100} terminated by the bipyramid {101}. Details of the occurrence, paragenesis, physical properties, a FTIR spectrum and X-ray powder diffraction data are reported. Chemical analysis in a scanning electron microscope in conjunction with a crystal structure analysis gave the empirical formula Pb3.02Sb1.06(SO4)0.96(AsO4)0.97(OH)6·3H2O. An ab-initio crystal structure determination with CCD diffractometer data, MoKα radiation, and a nearly untwinned crystal proved that mallestigite is hexagonal, space group P63, a = 8.9326(4), c = 11.1044(5) Å, V = 767.33(8) Å3, Z = 2, and gave a final R1 = 0.0184 for 1632 independent reflections with I > 2σ(I). Mallestigite belongs to the fleischerite group. The structure is built up from [Sb5+(OH)6]1– octahedra which are linked by triplets of edge-sharing Pb2+ into chains [Pb3Sb(OH)6]5+ extending along a 63 axis. Each three of such chains are bridged by triplets of H2O and by rows of SO42– and AsO43– tetrahedra alternating along a 3-fold axis and showing very different links to the Pb atom. Pb2+ is in a strongly distorted one-sided [9]-coordination by O atoms that makes the structure clearly hemimorphic. Structural relationships to the fleischerite group minerals schaurteite, genplesite, despujolsite and fleischerite as well as to synthetic Ba3Sn4+(SeO4)2(OH)6·3H2O are outlined and changes in the space group symmetry of despujolsite (P6¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline6$$\\end{document}2c → P63/mmc) and fleischerite (P6¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline6$$\\end{document}2c → P63) are proposed.

Strategy for a Rational Design of Deep-Ultraviolet Nonlinear Optical Materials from Zeolites.

Deep-ultraviolet (DUV) nonlinear optical (NLO) materials play a crucial role in cutting-edge laser technology. In order to solve the serious layered growth tendency of the sole commercial DUV NLO crystal KBe2BO3F2 (KBBF), developing alternative systems of compounds with bulk crystal habits has become an urgent task for practical applications. Herein, a novel strategy was developed by applying non-centrosymmetric (NCS) cancrinite (CAN)-type zincophosphates {Na6(OH)2(H2O)2}Cs2[ZnPO4]6 with bulk-crystal habits as the prototype to design new DUV NLO crystals. Two new anhydrous alkali zincophosphates, namely, {(Li6-xNaxO)A2}[(ZnPO4)6] (A = Cs, Rb; x = 2-3) crystallizing in the NCS hexagonal space group P63 (no. 173) with a CAN-type framework, were successfully synthesized via a modified fluoro-solvo-hydrothermal method by applying triethylamine (TEA) and concentrated NaF solution as a co-solvent. Interestingly, the rigidity of the NCS CAN-type framework acting as the host ensures the non-centrosymmetry of the resulting new compounds. Meanwhile, the replacement of water molecules by guest cationic species in the channels or cages can greatly improve the thermal stability of the resultant crystal and tune its NLO properties. The synergetic effect of the host framework and the guest species makes the two compounds transparent down to the DUV region (<200 nm) and exhibit SHG effects. Therefore, the proposed rational design strategy of applying the known zeotype NCS frameworks as prototypes together with the modified fluoro-solvo-hydrothermal method opens a great avenue for highly effectively exploring new DUV NLO materials.

Thermal stability of the CuZrSe2

The CuZrSe2 compound was synthesized for the first time by intercalation of Cu into the ZrSe2 lattice at room temperature. Experimental study of the thermal stability of CuZrSe2 has been performed by in-situ temperature-dependent synchrotron radiation X-ray diffraction (SR-XRPD). CuZrSe2 has a layered structure with space group P3‾m1. The copper atoms at room temperature in the interlayer space are octa- and tetrahedrally coordinated by selenium. Heating leads the decomposition of the main layered phase into binary copper chalcogenides and zirconium trichalcogenide as previously shown for CuxZrTe2. With the increase in temperature the octahedral sites in main layered phase become empty, copper atoms occupy the tetrahedral sites only. Thus, the high-temperature form of CuZrSe2 has a delafossite-like structure.

Crystal structure of Methionyl-tRNA Synthetase from Rickettsia typhi in complex with its cognate amino acid

Rickettsia typhi is the causative agent of murine typhus (endemic typhus), a febrile illness that can be self-contained, though in some cases it can progress to death. The three dimensional structure of Methionyl-tRNA Synthetase from R. typhi (RtMetRS) in complex with its substrate l-methionine was solved by molecular replacement and refined at 2.30 Å resolution in space group P1 from one X-ray diffraction dataset. Processing and refinement trials were decisive to establish the lower symmetry space group and indicated the presence of twinning with four domains. RtMetRS belongs to the MetRS1 family and was crystallized with the CP domain in an open conformation, what is distinctive from other MetRS1 enzymes whose structures were solved with a bound L-methionine (therefore, in a closed conformation). This conformation resembles the ones observed in the MetRS2 family.

Study of optical, thermal, mechanical, dielectric and nonlinear optical study on nonlinear optical material Bis-(L-Tyrosinato) Cupric acetate single crystals for optoelectronics application

The semi-organic nonlinear optical single crystal Bis (L-Tyrosinato) Cupric acetate (BLTC) was synthesized through a slow evaporation process in atmospheric conditions. A single crystal X-ray diffraction analysis of the formed crystal revealed that it is an orthorhombic crystal system with the space group P212121. Additionally, the powder X-ray diffraction patterns and diffracting planes of the BLTC crystal were recorded and identified. Fourier Transform Infrared (FTIR) spectroscopy analysis was used to characterize the formed crystals in order to identify the various vibrational modes caused by the different functional groups present in BLTC. The 1H and 13C NMR spectra were used to examine the crystal’s hydrogen and carbon environments. The UV-visible, near-infrared, and photoluminescence (PL) analyses have been used to do optical studies. According to our findings, the material has a decreased cut-off wavelength and a high transparency window, making it suitable for nonlinear optical (NLO) and optoelectronic applications. The BLTC crystal’s predicted band gap was found to be 4.1 eV. Thermo gravimetric (TG) and differential thermal analysis (DTA) techniques were used to determine the thermal properties of BLTC. With three different frequencies, the dielectric measurement of the crystal was observed with respect to temperature. An analysis has been done on the harvested crystals mechanical characteristics. In the developed BLTC crystal, morphological changes on the surface are seen. The material’s second harmonic generation (SHG) was tested using the Kurtz and Perry powder method, and it was found to be higher than the KDP.

Crystal structure of calcium L-5-methyltetrahydrofolate trihydrate type I, C20H23N7O6Ca(H2O)3

The crystal structure of L-5-methyltetrahydrofolate calcium trihydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Calcium levomefolate trihydrate crystallizes in space group P212121 (#19) with a = 7.1706(6), b = 6.5371(5), c = 53.8357(41) Å, V = 2523.58(26) Å3, and Z = 4. The structure is characterized by alternating hydrophobic and hydrophilic layers along the c-axis. The Ca cations are 7-coordinate, and share edges to form chains along the b-axis. Each of the water molecules acts as a donor in two hydrogen bonds. The coordinated water molecule makes two strong intermolecular O–H⋯O hydrogen bonds to carboxyl and carbonyl groups. The two zeolitic water molecules form weaker hydrogen bonds, to carbonyl O atoms, ring N atoms, and aromatic C atoms. Several N–H⋯O/N hydrogen bonds, as well as C–H⋯O hydrogen bonds, also contribute to the lattice energy.

Discreditation of Platarsite: A S-Rich Variety of Sperrylite

Abstract Platarsite is a relatively uncommon platinum-group mineral, reported from several world-wide localities, that has been defined as both Pt(As,S)2 and PtAsS in the literature. It was first described using material from the Onverwacht mine, eastern Bushveld Complex, Republic of South Africa, where it occurs with genkinite, geversite, and Pt-Fe alloy. Data from chemical analyses indicate (1) Pt is the dominant PGE, but with significant enrichments of both Rh and Ru; (2) ΣAs+S ∼ 2; (3) ΣPGE:ΣAs+S ∼ 1:2; and (4) As:S ratios of ∼1 (but with most data showing As &amp;gt; S), all of which suggest either PtAsS or Pt(As,S)2 as ideal compositions. Results from crystal-structure analyses conducted on both platarsite and sperrylite (Szymański 1979) demonstrate that the two are isostructural, both crystallizing in the cubic space group Pa3, with refined unit-cell edges of 5.788(1) and 5.9681(1) Å, respectively. They possess a pyrite-like crystal structure that includes a single metal site and a single anion site. The latter indicates that As and S, even if present in ratios of ∼1, must be disordered over a single site, rather than occupying two separate crystallographic sites. A re-evaluation of the available chemical data, along with the results from crystal-structure analyses, indicate that platarsite is a S-enriched variety of sperrylite and, as such, it has been discredited as a valid mineral species.

Investigation of structural, mechanical, dielectric, and thermal behaviour of pure and L-H doped LSMH single crystals

Lithium Sulphate Monohydrate (LSMH) and L-histidine amino acid doped Lithium Sulphate Monohydrate single crystals in a conjugate solution were grown using a slow evaporation process. The mechanical properties, thermal stability, and dielectric properties have all been confirmed by using various characterization techniques. Powder X-Ray diffraction studies were used to examine the space group and its lattice parameters, and the results showed that both crystals were arranged in a monoclinic system that was non-Centro symmetric and had the space group P21. Functional groups that were present in the grown samples were explained in great detail by Fourier Transform Infrared Spectroscopy. EDAX analysis was used to identify the measurements of the various elements that were present in the crystal sample of Lithium Sulphate Monohydrate doped with L-histidine amino acid. A Vickers micro hardness analyzer was used to determine the crystals' hardness characteristics. In-depth explanations were provided for the thermal stability of the samples, which was determined by TG/DTA analysis. The electrical behaviour of the pure LSMH and L-Histidine-doped LSMH crystal was observed using the LCRZ metre.

A novel energetic cocrystal of DATNBI/TNT with low sensitivity and an unexpected polymorphic transition

A novel type of 4,4′,5,5′-tetranitro-1H,1′H-(2,2′-biimidazole)-1,1′-diamine (DATNBI)/TNT energetic cocrystal (cocrystal-1) was prepared by the solvent evaporation method. The molar ratio of the cocrystal is 1:2 and the crystal density is 1.784 g cm−3 at 23°C. It belongs to the triclinic system with space group P 1. The thermal stability, mechanical sensitivity and detonation performance of cocrystal-1 were studied. Compared with DATNBI, the mechanical sensitivity (H 50 and FS, friction sensitivity) and thermal stability (T d, detonation temperature) of cocrystal-1 were significantly improved (H 50, FS and T d of DATNBI and cocrystal-1 are, respectively, 27.8 cm, 160 N, 240°C and 65.6 cm, &gt;360 N, 253°C). Combining these results with other characterizations, it was found that cocrystal-1 exhibited a polymorphic transformation, phase separation and melting of the two single components in succession. The ability to control the properties and understand the structural stability of this explosive cocrystal is of great value.

Nanoscale Study of the Polar and Electronic Properties of a Molecular Erbium(III) Complex Observed via Scanning Probe Microscopy

We successfully synthesized millimeter-sized single crystals of the molecular erbium(III) complex Er(acac)3(cphen), where acac = acetylacetonate and cphen = 5-chloro-1,10-phenanthroline. The novelty of this work stems from the exhaustive examination of the polar and electronic properties of the obtained samples at the macro-, micro-, and nanoscale levels. The single crystal X-ray diffraction method demonstrates the monoclinic (noncentrosymmetric space group P21) crystallographic structure of the synthesized samples and scanning electron microscopy exhibits the terrace–ledge morphology of the surface in erbium(III) crystals. By using the piezoelectric force microscopy mode, the origin of the polar properties and the hyperpolarizability in the synthesized samples were assigned to the internal domain structure framed by the characteristic terrace–ledge topography. The direct piezoelectric coefficient (~d33) was found to be intensely dependent on the local area and was measured in the range of 4–8 pm/V. A nanoscale study using the kelvin probe force and capacitance force (dC/dz) microscopy modes exposed the effect of the Er ions clustering in the erbium(III) complex. The PFM method applied solely to the Er ion revealed the corresponding direct piezoelectric coefficient (~d33) of about 4 pm/V. Given the maximum piezoelectric coefficient in the erbium(III) complex at 8 pm/V, we highlight the significant importance of the spatial coordination between the lanthanide ion and the ligands. The polar coordination between the lanthanide ion and the nitrogen and oxygen atoms was also corroborated by Raman spectroscopy supported by the density functional theory calculations. The obtained results can be of paramount importance for the application of molecular erbium(III) complex crystals in low-magnitude magnetic or electric field devices, which would reduce the energy consumption and speed up the processing switching in nonvolatile memory devices.

Batoniite, [Al8(OH)14(H2O)18](SO4)5 ⋅ 5H2O, a new mineral with the [Al8(OH)14(H2O)18]10+ polyoxocation from the Cetine di Cotorniano Mine, Tuscany, Italy

Abstract. The new mineral batoniite, [Al8(OH)14(H2O)18](SO4)5 ⋅ 5H2O, was discovered in the Cetine di Cotorniano Mine, Chiusdino, Siena, Tuscany, Italy. It occurs as hemispherical aggregates composed of brittle tabular crystals, up to 1 mm in size, white to colorless in color, with a white streak and a vitreous to greasy luster. Batoniite is biaxial negative, with α= 1.4833(6), β= 1.4948(6), γ= 1.5019(5) (589 nm), and 2V(meas.)= 71(1)∘. Electron microprobe analysis, affected by the dehydration of batoniite under the chamber vacuum, gave (in wt %) the following: Al2O3 33.48, Fe2O3 0.05, SO3 33.00, and H2Ocalc 44.41, total 110.94. It corresponds to the chemical formula (Al7.98Fe0.013+)Σ7.99(SO4)5.01(OH)13.95(H2O)18 ⋅ 5H2O. Batoniite is triclinic, belonging to space group P1‾, with a= 9.1757(6), b= 12.0886(9), c= 20.9218(15) Å, α= 82.901(3), β= 87.334(3), γ= 86.999(2)∘, V= 2297.8(3) Å3, and Z= 2. The crystal structure was refined to R1= 0.0916 for 8118 unique reflections with Fo&gt;4σ(Fo) and 811 refined parameters and 60 restraints. Batoniite is characterized by isolated [Al8(OH)14(H2O)18]10+ polyoxocations, H-bonded to five interstitial (SO4)2− and five H2O groups. In type material, it is associated with gypsum and a poorly crystallized Al–Fe sulfate. The crystallization of batoniite is probably due to the action of H2SO4 on Al-bearing rocks of Paleozoic age cropping out in the Garibaldi Tunnel, the lowest mining level of the Cetine di Cotorniano Mine.

Red and Blue-Black Tin Monoxide, SnO: Pitfalls, Challenges, and Helpful Tools in Crystal Structure Determination of Low-Intensity Datasets from Microcrystals

The crystal structures of red and blue-black tin(II) oxide, SnO, have been determined for the first time by single-crystal X-ray diffraction. Blue-black SnO crystallizes in the tetragonal space group P4/nmm, representing a layer structure consisting of the square–pyramidally coordinated tin and slightly distorted tetrahedrally coordinated oxygen atoms, in accordance with previous results. In contrast, red SnO crystallizes in the orthorhombic centrosymmetric space group Pbca rather than in the non-centrosymmetric space group Cmc21, as assumed for a long time. Its layer structure consists of very regular, trigonal–pyramidally coordinated tin atoms as well as trigonal–planar coordinated oxygen atoms. Special care was taken on space group determination, including lattice centering. C-centering could be excluded because of systematic absence violations detected when collecting and processing a primitive triclinic dataset and by generating precession images. In the absence of meaningful extinction conditions resulting from the very small crystal under examination, the structure was initially solved and refined in the triclinic space group P1. Subsequently, the observed atom coordinates were used to reconstruct the actual symmetry skeleton. The various possibilities to identify the correct space group starting from the triclinic solution are demonstrated, and the unique structural features of the crystal structure are visualized.

Methanol‐Induced Crystallization of Chiral Hybrid Manganese (II) Chloride Single Crystals for Achieving Circularly Polarized Luminescence and Second Harmonic Generation

AbstractChiral hybrid Mn (II)‐based halides have attracted great interest in the optoelectronic field due to their low cost, non‐toxicity, abundant structural diversity, and excellent photoluminescence, chiroptical, and nonlinear optical characteristics. Here, chiral hybrids (R/S‐MBA)MnCl3·CH3OH (MBA = C6H5CH(CH3)NH3+) and (R/S‐NPA)Cl·H2O and (R, S‐NPA)Cl (NPA = C10H7CH(CH3)NH3+) single crystals are successfully obtained using methanol (CH3OH) as an induced‐crystallization reagent by slow evaporation method. Interestingly, (R/S‐MBA)MnCl3·CH3OH single crystals with obvious circular dichroism (CD) characteristics exhibit the strong red emission characteristics originating from the d‐d transition of Mn2+ cation, while (R/S‐NPA) Cl·H2O and (R, S‐NPA)Cl exhibit blue emission originating from the organic NPA group. Based on their chiral space group P21 (no.4), (R/S‐MBA)MnCl3·CH3OH single crystals show excellent circularly polarized luminescence (CPL) with a relatively high luminescence dissymmetry factor (glum) value, which is equivalent to that of reported Mn (II)‐based metal halides. Also, (R/S‐NPA)Cl·H2O and (R/S‐MBA)MnCl3·CH3OH exhibit the obvious second harmonic generation (SHG) response. This work not only deepens the understanding of the role of methanol‐induced crystallization in improving the quality and growth habits of Mn (II)‐based halide hybrid single crystals, but also provides guidance for further structural design, crystal growth, and optoelectronic applications of multi‐functional chiral hybrid Mn (II)‐based halide materials.

Structure of the imine reductase from Ajellomyces dermatitidis in three crystal forms.

The NADPH-dependent imine reductase from Ajellomyces dermatitidis (AdRedAm) catalyzes the reductive amination of certain ketones with amine donors supplied in an equimolar ratio. The structure of AdRedAm has been determined in three forms. The first form, which belongs to space group P3121 and was refined to 2.01 Å resolution, features two molecules (one dimer) in the asymmetric unit in complex with the redox-inactive cofactor NADPH4. The second form, which belongs to space group C21 and was refined to 1.73 Å resolution, has nine molecules (four and a half dimers) in the asymmetric unit, each complexed with NADP+. The third form, which belongs to space group P3121 and was refined to 1.52 Å resolution, has one molecule (one half-dimer) in the asymmetric unit. This structure was again complexed with NADP+ and also with the substrate 2,2-difluoroacetophenone. The different data sets permit the analysis of AdRedAm in different conformational states and also reveal the molecular basis of stereoselectivity in the transformation of fluorinated acetophenone substrates by the enzyme.

Structural Investigation of Tetra-n-Butylammonium Perchlorate

The crystal structure of tetra-n-butylammonium perchlorate has been successfully elucidated using single-crystal X-ray diffraction. The compound crystallizes in the triclinic space group P1¯ with unit cell of dimensions a = 14.2706(7) Å, b = 20.6904(9) Å, c = 39.970(2) Å, α = 89.316(4)°, β = 88.638(4)°, and γ = 87.801(4)°. Although complicated by partial disorder, the structure has remarkable features where columns of some of the perchlorate anions running down [100] lie within what can be regarded as nanotubular entities formed by some of the tetrabutylammonium cations, while the remaining tetrabutylammonium cations lie in parallel columns surrounded by the remaining perchlorate anions, one entity being essentially the inverse of the other. Interactions within the structure have been characterized using Hirshfeld surface analysis and comparisons drawn with other unsolvated salts of the cation.

Crystal structure of danofloxacin mesylate (C19H21FN3O3)(CH3O3S)

The crystal structure of danofloxacin mesylate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Danofloxacin mesylate crystallizes in space groupP1(#1) witha= 6.77474(8),b= 12.4973(4),c= 12.82826(28) Å,α= 84.8709(29),β= 87.7501(10),γ= 74.9916(4)°,V= 1044.723(11) Å3, andZ= 2. The protonation of the danofloxacin cations was established by the analysis of potential intermolecular interactions and differs from that expected from isolated-cation calculations. The crystal structure consists of alternating layers of cations and anions parallel to theac-plane. There is parallel stacking of the oxoquinoline rings along thea-axis. The expected N–H⋯O hydrogen bonds between the cations and anions are not present. Each cation makes an N–H⋯O hydrogen bond with the other cation, resulting in zig-zag chains along thea-axis. Both cations have strong intramolecular O–H⋯O hydrogen bonds. There are several C–H⋯O hydrogen bonds between the danofloxacin cations and mesylate anions. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Structural and computational studies on a quenchable high-temperature polymorph of magnesium tungstate (MgWO4-II)

Single-crystals of a quenchable high-temperature polymorph of magnesium tungstate (MgWO4-II) have been grown using the flux method. Polycrystalline material of the same compound could be obtained from solid-state reactions performed at 1200 °C. Basic crystallographic data of the previously unknown modification are as follows: space group P1‾, a = 6.5525(6) Å, b = 7.5883(7) Å, c = 7.6976(6) Å, α = 119.064(9)°, β = 95.545(7)°, γ = 107.645(8)°, V = 304.84(5)3 Å and Z = 4. The crystal structure was solved from single-crystal diffraction using direct methods and refined to a residual value of R1 = 2.16%. Both cation species exhibit an octahedral oxygen coordination environment. By sharing common edges and corners, the octahedra form a three-dimensional network, which can be built from infinite rod-like elements running along [010] having a 2 × 2 octahedra wide cross section. MgWO4-II is topologically equivalent to the VO2(HT) structure-type. A detailed analysis of the relationships with other ABO4-compounds is presented. Solid-state characterization has been supplemented by micro-Raman spectroscopy. Interpretation of the spectroscopic data, including the allocation of the bands to certain vibrational species, has been aided by DFT-calculations. The thermal expansion tensor between ambient temperature and about 700 °C has been determined. The calculations indicate quasi-two-dimensional expansion behavior.