Laboratory X-ray Powder Diffraction Data Research Articles

Synthesis, Structure and Properties of Related Microporous N,N‘-Piperazinebismethylenephosphonates of Aluminum and Titanium

A porous framework titanium(IV) N,N‘-piperazinebis(methylenephosphonate) (MIL-91(Ti)) and its aluminum analogue have been prepared under hydrothermal conditions (MIL = Material Institut Lavoisier). The structure of the aluminum analogue, AlOH(H2L)·nH2O (n ∼ 3, L = O3P−CH2−NC4H8N−CH2−PO3) was solved from a small single crystal and refined against laboratory powder X-ray diffraction data. The structure of the titanium form (TiO(H2L)·nH2O (n ∼ 4.5)) was determined using the structure of the aluminum form as a starting model and refining it against laboratory X-ray data. Their structures are built up from trans corner-sharing chains of TiO6 or AlO6 octahedra linked together in two directions via the diphosphonate groups. In each case this gives rise to a three-dimensional hybrid network with small channels along the b axis, filled with free water molecules. Thermogravimetric analysis and X-ray thermodiffractometry of the samples reveal that water is lost reversibly below 423 K and that both structures are stable up to 463 K. Dehydration gives porous solids (pore size ∼ 3.5 × 4.0 Å2) which adsorb nitrogen at 77 K to give Langmuir surface areas close to 500 m2·g-1. Crystal data for MIL-91(Ti) are as follows: space group C2/m (No. 12) with a = 19.415(2) Å, b = 7.071(1) Å, c = 11.483(1) Å, β = 92.78(1)°, V = 1574.70(1) Å3, and Z = 2. Crystal Data for MIL-91(Al) are as follows: space group C2/m (No. 12) with a = 18.947(2) Å, b = 6.915(1) Å, c = 11.295(1) Å, β = 90.45(1)°, and V = 1479.90(1)Å3.

A Novel Three-Dimensional Network Containing Pr(III) Ions and Tartrate: Synthesis, Spectroscopic, Thermal, Ab Initio X-ray Powder Structure Analyses, and Photoluminescence Properties

A new praseodymium tartrate [Pr(C4H4O6)(C4H5O6)(H2O)] has been synthesized under hydrothermal conditions and investigated by UV−Vis, FTIR, X-ray powder diffraction, thermal and photoluminescence analyses. The compound crystallizes in the orthorhombic system with a = 21.973(4), b = 7.587(1), c = 5.958(1) Å, space group P212121, and Z = 4. The crystal structure has been solved from laboratory X-ray powder diffraction data using a direct space global optimization technique and refined by the Rietveld method. The Pr atoms in the complex have 9-fold coordination with respect to the oxygens, with the metal center in a distorted monocapped square antiprism coordination. The molecular structure of the complex reveals 22-membered (Pr4C10O8) nanosized rectangular motifs assembled into helical chains, which are further linked via carboxylate groups of the tartrate ligands forming a novel three-dimensional polymeric framework. A X-ray powder pattern of the anhydrous praseodymium tartrate obtained by heating the title compound at 230 °C revealed a monoclinic unit cell with a = 10.964(3), b = 11.612(2), c = 10.456(4) Å, β = 108.96(2)°. The luminescence spectra of the hydrated Pr complex exhibit a signal at 645 nm due to a 3P0 → 3F2 transition.

Layered and pillared metal carboxyethylphosphonate hybrid compounds

A series of carboxyethylphosphonate hybrid materials has been prepared: Mn(II)(O3PCH2CH2COOH) *H2O (1), Mn(III)(OH)(O3PCH2CH2COOH)*H2O (2), Al3(III)(OH)3(O3PCH2CH2CO2)2 *3H2O (3) and Cr2(III)(OH)3(O3PCH2CH2CO2) *3H2O (4). Compounds 1 and 2 were synthesized from Mn(III)(CH3COO)3 *2H2O under hydrothermal, or refluxing treatments, respectively. The crystal structures of the manganese-bearing solids have been solved ab initio from laboratory X-ray powder diffraction data and refined by the Rietveld method. 1 crystallises in a orthorhombic cell and 2 in monoclinic symmetry. Both solids have inorganic 2D layered structures with the acid carboxylic groups pointing towards the interlayer space, and the layers linked only through hydrogen bonds. The inorganic layers of these compounds are formed by manganese atoms in distorted octahedral environments linked together by the phosphonate groups. The crystal structure of 3 has been solved ab initio from synchrotron X-ray powder diffraction data. This solid shows a pillared structure with the phosphonate and carboxylate groups cross-linking the inorganic layers. These layers contain chains of aluminium octahedra running parallel to each other. 4 is amorphous and the IR-UV-VIS spectra suggest a framework with Cr(III) cations in octahedral environments. Thermal, spectroscopic and magnetic data for manganese and chromium compounds as well as the structural details of these solids are discussed.

High-Pressure Synthesis, Crystal Structures, and Properties of Perovskite-like BiAlO3 and Pyroxene-like BiGaO3

New oxides, BiAlO3 and BiGaO3, were prepared using a high-pressure high-temperature technique at 6 GPa and 1273−1473 K. BiAlO3 is isotypic with multiferroic perovskite-like BiFeO3 and has octahedrally coordinated Al3+ ions. Structure parameters of BiAlO3 were refined from laboratory X-ray powder diffraction data (space group R3c; Z = 6; a = 5.37546(5) Å and c = 13.3933(1) Å). BiGaO3 has the structure closely related to pyroxene-like KVO3. Structure parameters of BiGaO3 were refined from time-of-flight neutron powder diffraction data (space group Pcca; Z = 4; a = 5.4162(2) Å, b = 5.1335(3) Å, and c = 9.9369(5) Å). The GaO4 tetrahedra in BiGaO3 are joined by corners forming infinite (GaO3)3- chains along the a axis. Bi3+ ions in BiGaO3 have 6-fold coordination. Both BiAlO3 and BiGaO3 decompose at ambient pressure on heating above 820 K to give Bi2M4O9 and Bi25MO39 (M = Al and Ga). Vibrational properties of BiAlO3 and BiGaO3 were studied by Raman spectroscopy. In solid solutions of BiAl1-xGaxO3, a C-centered monoclinic phase structurally related to PbTiO3 with lattice parameters of a = 5.1917(4) Å, b = 5.1783(4) Å, c = 4.4937(3) Å, and β = 91.853(3)° was found.

Crystal structure determination of 1-pentanol from low-temperature powder diffraction data by Patterson search methods

In the course of our research on normal alkanols, the crystal structure of 1-pentanol has been solved by applying Patterson-search methods to laboratory powder X-ray diffraction data recorded on a curved position-sensitive detector (CPS120) at 183 K. The crystal structure was refined with the rigid-body Rietveld least-squares method. The cell is monoclinic, space group P21∕c, Z=4, and the cell parameters are a=15.592(9) Å, b=4.349(1) Å, c=9.157(1) Å, β=104.7(7)°, V=600.6(3) Å3. There is one molecule in the asymmetric unit with the O–H bond in gauche conformation with respect to the alkyl skeleton. Packing is defined by the hydrogen bonds linking the 1-pentanol molecules along zigzag chains parallel to b.

Structural properties of methoxy derivatives of benzyl bromide, determined from powder X-ray diffraction data

Structure determination of 3,5-dimethoxybenzyl bromide and 3,4,5-trimethoxybenzyl bromide has been carried out from laboratory powder X-ray diffraction data using the direct-space Genetic Algorithm technique for structure solution followed by Rietveld refinement. These two compounds are of interest for their potential use as building blocks for the synthesis of dendritic materials. Although the two molecules differ only in the presence/absence of the methoxy group at the 4-position of the aromatic ring, the structural properties of the two materials are significantly different.

Characterization and ab Initio XRPD Structure Determination of a Novel Silicate withViererSingle Chains: The Crystal Structure of NaYSi2O6

The crystal structure of a sodium yttrium silicate with composition NaYSi2O6 has been determined from laboratory X-ray powder diffraction data by simulated annealing, and has been subsequently refined with the Rietveld technique. The compound is monoclinic with space group P2(1)/c and unit cell parameters of a=5.40787(2) A, b=13.69784(5) A, c=7.58431(3) A, and beta=109.9140(3) degrees at 23.5 degrees C (Z=4). The structure was found to be a single-chain silicate with a chain periodicity of four. The two symmetry dependent [Si4O12] chains in the unit cell are parallel to c. A prominent feature is the strong folding of the crankshaft-like chains within the b,c-plane resulting in intrachain Si-Si-Si angles close to 90 degrees. The coordination of the Y3+ ions by O2- is 7-fold in the form of slightly irregular pentagonal bipyramids, with oxygen atoms from four different chains contributing to the coordination polyhedron. Na+ ions are irregularly coordinated by 10 oxygens from two neighboring chains. No disorder of Na+ and Y3+ between the two nontetrahedral cation sites could be observed. Furthermore, micro-Raman spectra have been obtained from the polycrystalline material.

Rietveld Analysis of a High Pressure Modification of Monocalcium Oxogallate (CaGa2O4).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Structural and Electrical Investigation of Oxide Ion and Proton Conducting Titanium Cuspidines

The La4(Ga2-xTixO7+x/2□1-x/2)O2 (x = 0−2) cuspidine series has been prepared as single phases in the full compositional range. The evolution of the cell parameters is smooth along the series although the symmetry changes from monoclinic P21/c for La4(Ga2O7□1)O2 to orthorhombic Pnam for La4(Ti2O8)O2. The crystal structure of La4(Ga1Ti1O7.5□0.5)O2 has been determined from a refinement of neutron and laboratory X-ray powder diffraction data at room and high temperatures. This compound crystallizes in the P21/c space group, Z = 4, with a = 7.9629(2) A, b = 11.1000(2) A, c = 11.8294(4) A, β = 109.689(4)°, and V = 984.44(4) A3. The neutron Rietveld disagreement factors at room temperature were RWP = 3.10% and RF = 3.36%. The Ga3+/Ti4+ aliovalent substitution is accompanied by extra oxygen needed for the charge compensation. This oxygen transforms the isolated ditetrahedral groups in La4(Ga2O7□1)O2 into infinite trigonal bipyramid chains with interruptions due to the oxygen vacancies in La4(Ga1.0Ti1.0O7.5□0.5)O2...

Powder study of hydrochlorothiazide–methyl acetate (1/1)

A polycrystalline sample of the title compound, C7H8ClN3O4S2·C3H6O2, was produced during an automated parallel crystallization search on hydro­chloro­thia­zide (HCT). The crystal structure was solved by simulated annealing from laboratory X-ray powder diffraction data collected at room temperature to 1.75 Å resolution. Subsequent Rietveld refinement yielded an Rwp value of 0.0182 to 1.54 Å resolution. The compound crystallizes with one mol­ecule of HCT and one of methyl acetate in the asymmetric unit and displays an extensive hydrogen-bonding network.

Powder study of hydrochlorothiazide form II

The crystal structure of hydro­chloro­thia­zide form II, C7H8ClN3O4S2, was solved by simulated annealing from laboratory X-ray powder diffraction data collected at room temperature to 1.76 A resolution. Subsequent Rietveld refinement yielded an Rwp of 0.0376 to 1.49 A resolution. The molecules crystallize in the space group P21/c with one molecule in the asymmetric unit. The structure is stabilized by three N—H⋯N and one N—H⋯O hydrogen-bonded intermolecular interaction.

Barite-type Ba(BeF4)x(SO4)1−x (x = 1 and ≈0.5)

Barite-type α-BaBeF4 (a = 8.8594(3), b =5.3265(2), c = 7.0493(2) A, Pnma (No. 62)) and Ba(BeF4)0.535(7)(SO4)0.465(7) (a = 8.8657(2), b = 5.3902(2), c = 7.1007(2) A, Pnma (No. 62)) were prepared by precipitation from aqueous solutions and their structures refined from laboratory X-ray powder diffraction data. In the case of α-BaBeF4 it was possible to identify the light atom Be on a difference Fourier map and to refine its positional parameters in the presence of a heavy atom (Ba). Both phases contain almost ideal isolated BX42− tetrahedra (B = Be, Be/S and X = F, F/O) together with Ba, that is 12-fold coordinated by X. The plausibility of the resulting structures was proved with the help of the bond valence model. For both compounds no phase transitions were found up to 550∘C.

Single Crystal and Powder Diffraction Characterization of Three Polymorphic Forms of Acitretin

Acitretin [all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetraenoic acid or 3-methoxy-2-methyl-17-nor-1,2,3,4-tetradehydroretinoic acid], a widely marketed oral synthetic retinoid, introduced for clinical use as effective therapy against psoriasis, was found to crystallize in three polymorphic modifications (hereafter, I, II, and III), the crystal structures of which have been determined by single-crystal diffractometry (form I) or X-ray powder diffraction methods (form II and III) from conventional laboratory data only. In these latter cases, real space techniques (simulated annealing and whole-profile pattern matching) have been employed. Polymorph I crystallizes in space group P21, Z=8, with unit cell parameters a=7.894(1), b=58.454(6), c=8.161(1) Å, β=102.04(1)°, and V=3682.9(8) Å3. Polymorph II crystallizes in space group P21/n, Z=4, with unit cell parameters a=13.999(2), b=10.714(1), c=12.465(2) Å, β=98.76(5)°, and V=1847.9(3) Å3. Polymorph III crystallizes in space group P21/c, Z=4, with unit cell parameters a=3.0751(4), b=4.0487(4), c=14.956(2) Å, β=100.41(7)°, and V=1831.3(4) Å3. Polymorph I, found to be identical with that deposited in the European Pharmacopeia, shows four crystallographically independent Acitretin molecules, arranged in pairs through conventional hydrogen-bonded carboxylic dimers; also in form II, carboxylic dimers are observed, located on crystallographic inversion centres, while in form III, a catameric arrangement of the carboxylic residues, winding up about the rather short monoclinic axis, generates one-dimensional chains of hydrogen-bonded Acitretin molecules. Thermal analysis showed that form I can be quantitatively transformed into form II by moderate heating near 200°C, under vacuum. These results show that ab initio structural studies from conventional laboratory X-ray powder diffraction (XRPD) data are fully providing the opportunity to investigate the structural aspects of moderately complex substances also in the absence of single crystals, disclosing the crystal chemistry of a few polymorphs of pharmaceutically relevant species. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association

Powder diffraction study of 1,2:3,4-dibenzanthracene

The crystal structure of 1,2:3,4-dibenzanthracene, C22H14, was solved by simulated annealing from laboratory X-ray powder diffraction data collected at room temperature to 1.8 Å resolution. Subsequent Rietveld refinement yielded an Rwp value of 0.036. The molecules crystallize in space group P21 with two independent molecules in the asymmetric unit which pack in a stacked arrangement along the b axis.

Solving molecular crystal structures from laboratory X-ray powder diffraction data withDASH: the state of the art and challenges

The crystal structures of 35 molecular compounds have been redetermined from laboratory monochromatic capillary transmission X-ray powder diffraction data using the simulated-annealing approach embodied within theDASHstructure solution package. The compounds represent industrially relevant areas (pharmaceuticals; metal coordination compounds; nonlinear optical materials; dyes) in which the research groups in this multi-centre study are active. The molecules were specifically selected to form a series within which the degree of structural complexity (i.e. degrees of freedom in the global optimization) increased systematically, the degrees of freedom increasing with increasing number of optimizable torsion angles in the structural model and with the inclusion of positional disorder or multiple fragments (counterions; crystallization solvent;Z′ > 1). At the lower end of the complexity scale, the structure was solved with excellent reproducibility and high accuracy. At the opposite end of the scale, the more complex search space offered a significant challenge to the global optimization procedure and it was demonstrated that the inclusion of modal torsional constraints, derived from the Cambridge Structural Database, offered significant benefits in terms of increasing the frequency of successful structure solution by restricting the magnitude of the search space in the global optimization.

Structural, Magnetic, and Electrical Characterization of New Polycrystalline Phases of Nickel- and Platinum-Doped [(DT-TTF)n][Au(mnt)2] (n = 1, 2)

Doping of spin-ladder systems by isostructural paramagnetic complexes was attempted. Despite the close isostructural nature of the pure (DT-TTF)2[M(mnt)2] (M = Au, Ni, Pt) end-members, which present a ladder structure, doping of the spin-ladder (DT-TTF)2[Au(mnt)2] with either 5% or 25% [M(mnt)2]- (M = Ni, Pt) generates two (metrically) new phases. Their markedly different crystal structures have been determined using laboratory X-ray powder diffraction data. (DT-TTF)2[Au0.75Ni0.25(mnt)2] consists of a mixed-valence compound (of triclinic symmetry), which was only detected, pure or in a mixture of phases, when [Ni(mnt)2]- was used as a dopant. Differently, the stoichiometric 1:1 [DT-TTF][Au0.75Pt0.25(mnt)2] monoclinic phase was found when [Pt(mnt)2]- (in 5% and 25%) was employed as the doping agent. Remarkably, only in the 5% Pt doping experiment, the major component of the mixture was the ladder structure compound (DT-TTF)2[Au(mnt)2] doped with minor amounts of Pt. This 5% Pt-doped specimen shows an EPR signal (g = 2.0115, DeltaHpp = 114 G at 300 K) wider than the pure compound (DT-TTF)2[Au(mnt)2], denoting exchange between the donor spins and Pt(mnt)2- centers. The electrical transport properties of the 5% Pt-doped composition at high temperatures are comparable to those of (DT-TTF)2[Au(mnt)2] with room-temperature conductivity sigma300K = 13 S/cm and thermopower S300K = 46 microV/K, with a sharp transition at 223 K similar to that previously observed in the Cu analogue at 235 K.

Enhancement of Oxide Ion Conductivity in Cuspidine‐Type Materials.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Interstitial oxygen in oxygen-stoichiometric apatites

Several oxy-apatite materials La10−xSrx(TO4)6O3−0.5x (T = Ge, Si; 10−x = 9.00, 8.80, 8.65 and 8.00) and La9.33(Si1−xGexO4)6O2 (x = 0, 0.5, 0.67) have been prepared as highly crystalline phases. The impedance study showed that all samples are oxide ion conductors. However, bulk conductivities changed by more than 2 orders of magnitude at a given temperature for some compositions. A thorough study on the oxygen sublattices for oxygen-stoichiometric oxy-apatites has been carried out. Constant-wavelength neutron powder diffraction data have been collected for La9.33(SiO4)6O2. Time-of-flight neutron data have been collected for La9.33(Si0.5Ge0.5O4)6O2, La8Sr2(SiO4)6O2 and La8Sr2(GeO4)6O2. The room-temperature structures have been derived from joint Rietveld refinements of neutron and laboratory X-ray powder diffraction data. High temperature structures have been obtained only from Rietveld refinements of neutron powder diffraction data. The refinements show that La9.33(SiO4)6O2 and La9.33(Si0.5Ge0.5O4)6O2 contain interstitial oxygen, associated to vacancies at the oxygen channels. The amount of interstitial oxygen is negligible in La8Sr2(SiO4)6O2 and La8Sr2(GeO4)6O2. Hence, the novelty of this work is to explain the high oxide conductivity of the lanthanum-deficient samples which it is due to the presence of interstitial oxygens. Lanthanum stoichiometric samples do not have interstitial oxygens and, so, their conductivities are much lower.

Crystal structure of Cu doped La0.67Ca0.33MnO3 by Rietveld refinement

The crystal structure of La0.67Ca0.33Mn0.80Cu0.20O3 (LCMCO) compound was determined from laboratory X-ray powder diffraction data and refined by the Rietveld method. LCMCO is isostructural with La0.67Ca0.33MnO3 (LCMO). The crystal data are: La0.64Ca0.36Mn0.82Cu0.18O3.01, Mr=843.80, orthorhombic system, space group Pnma, a=5.4364(1) Å, b=7.6725(2) Å, c=5.4452(1) Å, V=227.124(8)Å3, Z=4, Dx=6.168 g∕cm3. In comparing with the Cu-free compound, subtle structural changes such as bond lengths and bond angles found in the Cu-doped compound may be responsible for the larger effects on the transport and magnetic properties when Cu partially substitutes for Mn in CMCO.

Enhancement of Oxide Ion Conductivity in Cuspidine-Type Materials

Two oxy-cuspidine series, RE4(Ga2O7)O2 (RE = La, Nd, Sm) and La4(Ga2-xGexO7+x/2)O2 (x = 0.2, 0.4, 0.6), have been prepared as single phases. The room-temperature crystal structures have been determined from joint Rietveld refinements of neutron and laboratory X-ray powder diffraction data for La4(Ga2O7)O2 and La4(Ga1.4Ge0.6O7.3)O2. La4(Ga2O7)O2 is monoclinic (space group P21/c) with a = 7.9791(1) A, b = 11.2054(2) A, c = 11.6276(2) A, β = 109.468(1)°, and V = 980.18(3) A3; and the Rietveld refinement converged to RFNPD = 0.8% and RFLXRPD = 2.1%. La4(Ga1.4Ge0.6O7.3)O2 is also monoclinic with a = 8.0097(1) A, b = 11.1601(2) A, c = 11.6426(4) A, β = 110.107(4)°, and V = 977.29(5) A3; and the Rietveld refinement converged to RFNPD = 1.9% and RFLXRPD = 3.3%. The main structural result is the location of the extra-oxygen between the tetrahedral digallate/germanate groups. The insertion of this oxygen transforms the isolated pyrogroups to infinite distorted trigonal bipyramid chains with some interruptions due t...