Ab initiostructure determination of the Γ form ofD-sorbitol (D-glucitol) by powder synchrotron X-ray diffraction

2004 ◽  
Vol 37 (5) ◽  
pp. 766-772 ◽  
Author(s):  
Mwaffak Rukiah ◽  
Jacques Lefebvre ◽  
Olivier Hernandez ◽  
Wouter van Beek ◽  
Michel Serpelloni
Keyword(s):  
Monte Carlo ◽  
Simulated Annealing ◽  
Interatomic Bond ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Rietveld Refinements ◽  
X Ray ◽  
Monte Carlo Simulated Annealing ◽  
Starting Model

A high-resolution powder synchrotron X-ray diffraction pattern of the Γ form of D-sorbitol has been recorded at 293 K on the BM1B beamline at the ESRF (Grenoble). The starting model of the structure was found by Monte Carlo simulated annealing. The final structure was obtained through Rietveld refinements performed with soft restraints on interatomic bond lengths and angles. The symmetry is orthorhombic, space groupP21212, with 12 molecules within the cell [a= 24.3012 (2),b= 20.5726 (2),c= 4.8672 (1) Å,V= 2433.30 (3) Å3,Z′ = 3, 36 non-H independent atoms]. Crystalline cohesion between neighbouring molecules is achieved by three networks of O—H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of anisotropic strain effects.

Structure determination of L-arabinitol by powder X-ray diffraction

2012 ◽  
Vol 68 (4) ◽  
pp. 407-411 ◽  
Author(s):  
Patrick Derollez ◽  
Yannick Guinet ◽  
Frédéric Affouard ◽  
Florence Danède ◽  
Laurent Carpentier ◽  
...  
Keyword(s):  
Structural Model ◽  
Interatomic Bond ◽  
Hydroxyl Groups ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Monte Carlo Simulated Annealing ◽  
Diffraction Patterns ◽  
Annealing Method

Powder X-ray diffraction patterns of the commercial phase of L-arabinitol were recorded with a laboratory diffractometer. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. H atoms of hydroxyl groups were localized by minimization of the crystalline energy. The cell is triclinic with the space group P1 and contains two molecules. The crystalline cohesion is achieved by an important network of O—H...O hydrogen bonds.

Ab initio structure determination of the hygroscopic anhydrous form of α-lactose by powder X-ray diffraction

2004 ◽  
Vol 60 (4) ◽  
pp. 453-460 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Frederic Affouard ◽  
Patrick Derollez
Keyword(s):  
Structural Model ◽  
Interatomic Bond ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Ab Initio Structure ◽  
Monte Carlo Simulated Annealing ◽  
Hydroxy Groups ◽  
Annealing Method

Annealing of α-lactose monohydrate at 408 K yielded a mixture of this compound with hygroscopic anhydrous α-lactose. A powder X-ray diffraction pattern of this mixture was recorded at room temperature. The starting structural model of hygroscopic α-lactose was found by a Monte Carlo simulated-annealing method. The final structure was obtained through Rietveld refinements, with soft restraints on interatomic bond lengths and bond angles, and crystalline energy minimization to locate the H atoms of the hydroxy groups. The crystalline cohesion is achieved by networks of O—H...O hydrogen bonds that differ from those of the monohydrate phase. The width of the Bragg peaks is interpreted by a phenomenological microstructural approach in terms of isotropic size effects and anisotropic strain effects.

Structure determination of phase II of the antifungal drug griseofulvin by powder X-ray diffraction

2018 ◽  
Vol 74 (3) ◽  
pp. 321-324 ◽  
Author(s):  
Aurélien Mahieu ◽  
Jean-François Willart ◽  
Mathieu Guerain ◽  
Patrick Derollez ◽  
Florence Danéde ◽  
...  
Keyword(s):  
Phase Ii ◽  
Structural Model ◽  
Interatomic Bond ◽  
Antifungal Drug ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Pxrd Pattern ◽  
X Ray ◽  
Monte Carlo Simulated Annealing

Two new crystalline polymorphs of the widely used antifungal drug griseofulvin (phases II and III), which originate from the crystallization of the melt, have been detected recently. The crystal structure of phase II of griseofulvin {systematic name: (2S,6′R)-7-chloro-2′,4,6-trimethoxy-6′-methyl-3H,4′H-spiro[1-benzofuran-2,1′-cyclohex-2-ene]-3,4′-dione}, C17H17ClO6, has been solved by powder X-ray diffraction (PXRD). The PXRD pattern of this new phase was recorded at room temperature using synchrotron radiation. The starting structural model was generated by a Monte Carlo simulated annealing method. The final structure was obtained through Rietveld refinement with soft restraints for interatomic bond lengths and angles, except for the aromatic ring, where a rigid-body constraint was applied. The symmetry is orthorhombic (space groupP212121) and the asymmetric unit contains two molecules.

Structure determination of forms I and II of phenobarbital from X-ray powder diffraction

2005 ◽  
Vol 61 (1) ◽  
pp. 80-88 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Stephanie Hemon ◽  
Carsten Baehtz ◽  
Florence Danede ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
Space Group ◽  
X Ray ◽  
Bragg Peak Profiles ◽  
Monte Carlo Simulated Annealing ◽  
Crystal Structural ◽  
Diffraction Patterns ◽  
Annealing Method

From pure powders of forms I and II of phenobarbital, X-ray diffraction patterns were recorded at room temperature. The starting crystal structural models were found by a Monte-Carlo simulated annealing method. The structures of the two forms were obtained through Rietveld refinements. Soft restraints were applied on bond lengths and bond angles, all H-atom positions were calculated. The cell of form I is monoclinic with the space group P21/n, Z = 12, Z′ = 3. Form II has a triclinic cell, with the space group P\bar 1, Z = 6, Z′ = 3. For both forms, the crystal cohesion is achieved by networks of N—H...O hydrogen bonds along [101]. The broadening of the Bragg peak profiles is interpreted in terms of isotropic strain effects and anisotropic size effects.

Structure determination of the stable anhydrous phase of α-lactose from X-ray powder diffraction

2005 ◽  
Vol 61 (2) ◽  
pp. 185-191 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Frederic Affouard ◽  
Jean-François Willart ◽  
Patrick Derollez ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Model ◽  
Hydroxyl Groups ◽  
Rietveld Refinements ◽  
X Ray ◽  
Hydrogen Bond Networks ◽  
Monte Carlo Simulated Annealing ◽  
Annealing Method

The stable anhydrous form of α-lactose has been obtained by the dehydration of α-lactose monohydrate in methanol. An X-ray powder diffraction pattern was recorded at room temperature with a laboratory diffractometer equipped with an INEL curved sensitive detector CPS120. The starting structural model of this form was found by a Monte-Carlo simulated annealing method. The structure was obtained through Rietveld refinements and the minimization of crystalline energy for the localization of the H atoms of the hydroxyl groups. Soft restraints were applied to bond lengths and angles. Networks of O—H...O hydrogen bonds account for the crystalline cohesion. A comparison is made between the hydrogen-bond networks of this form and those of the monohydrate and hygroscopic anhydrous forms of α-lactose.

Determination of the Crystal Structure and Redefinition of Tsugaruite, Pb28As15S50Cl, the First Lead-Arsenic Chloro-Sulfosalt

2020 ◽  
Author(s):  
Cristian Biagioni ◽  
Luca Bindi ◽  
Koichi Momma ◽  
Ritsuro Miyawaki ◽  
Yoshitaka Matsushita ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Specific Position ◽  
Actual Classification ◽  
Aomori Prefecture

Abstract Tsugaruite was originally defined as a lead-arsenic sulfosalt from the Yunosawa mine, Aomori Prefecture, Japan. Until recently its crystal structure remained unsolved and its actual classification in the sulfosalt realm was unknown. Here the refinement of the crystal structure of tsugaruite using single-crystal X-ray diffraction data is reported. The mineral is orthorhombic, space group P2nn, with unit-cell parameters a = 8.0774(10), b = 15.1772(16), c = 38.129(4) Å, V = 4674.3(9) Å3, in agreement with previous studies. The solution of the crystal structure of this mineral revealed Cl occupying a specific position. Chlorine was thus sought and found using the electron microprobe; the average of six spot analyses gave (in wt.%): Pb 68.04, As 12.83, S 18.29, Cl 0.63, total 99.80. The empirical formula, calculated on the basis of Pb + As = 43 atoms per formula unit, is Pb28.26As14.74S49.08Cl1.52. Tsugaruite is an N = 4 plesiotypic derivative of the homologous series of Pb-Sb chloro-sulfosalts having the general formula Pb(2+2N)(Sb,Pb)(2+2N)S(2+2N)(S,Cl)(4+2N)ClN. It has a Cl/(Cl + S) atomic ratio close to that of other known Pb-Sb chloro-sulfosalts (pillaite, pellouxite) and slightly higher than that of dadsonite.

Ab initio structure determination of the high-temperature phase of anhydrous caffeine by X-ray powder diffraction

2005 ◽  
Vol 61 (3) ◽  
pp. 329-334 ◽  
Author(s):  
Patrick Derollez ◽  
Natália T. Correia ◽  
Florence Danède ◽  
Frédéric Capet ◽  
Frédéric Affouard ◽  
...  
Keyword(s):  
High Temperature ◽  
Phase I ◽  
Metastable State ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Ab Initio Structure

The high-temperature phase I of anhydrous caffeine was obtained by heating and annealing the purified commercial form II at 450 K. This phase I can be maintained at low temperature in a metastable state. A powder X-ray diffraction pattern was recorded at 278 K with a laboratory diffractometer equipped with an INEL curved position-sensitive detector CPS120. Phase I is dynamically orientationally disordered (the so-called plastic phase). The Rietveld refinements were achieved with rigid-body constraints. It was assumed that on each site, a molecule can adopt three preferential orientations with equal occupation probability. Under a deep undercooling of phase I, below 250 K, the metastable state enters in a glassy crystal state.

Structural Studies on Catalysts and Catalyst Precursors. II. The X-Ray Structure Determination of Chloro(Pentante-2,4-dithionato)(tributylphosphine)nickel(II), Ni(sacsac)(PBu3)Cl

1985 ◽  
Vol 38 (3) ◽  
pp. 369 ◽  
Author(s):  
KJ Cavell ◽  
DG Hay ◽  
AF Masters ◽  
GA Williams
Keyword(s):  
Structural Studies ◽  
Donor Atom ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Apical Position ◽  
X Ray ◽  
Butyl Group ◽  
Atom Bond

The preparation and characterization of Ni( sacsac )(PBu3) Cl by single crystal X-ray diffraction [refined to R 0.052, R? 0.042 with 1325 data having I ≥ 3σ(I)], are reported. The compound crystallizes as discrete molecules in the orthorhombic space group P bca, with a 15.526(4), b 15.774(4), c 18.377(8)Ǻ, U 4500.7 Ǻ3, and Z 8. The nickel-donor atom bond distances are Ni-S (trans Cl ) 2.097(3), Ni-S (trans P) 2.138(3), Ni- Cl 2.216(3) and Ni-P 2.237(3)Ǻ, with the ligands subtending angles S-Ni-S 98.6(1), S-Ni- Cl 85.4(1), S-Ni-P 89.5(1) and Cl -Ni-P 86.8(1). The coordination about the nickel(II) centre is planar; however, one butyl group of the phosphine is oriented so that a hydrogen is directed towards the apical position of the nickel. The structure is correlated with the N.M.R . spectra in both solid and solution phases and compared with the structures of related com- pounds. The Ni-S bonds are shown to be short and the Ni-P bond long relative to such dimensions in comparable compounds.

Sign in / Sign up

Export Citation Format

Share Document