Crystal structure study of selected xanthine derivatives

2010 ◽  
Vol 43 (1) ◽  
pp. 163-167 ◽  
Author(s):  
W. Lasocha ◽  
B. Gaweł ◽  
A. Rafalska-Lasocha ◽  
M. Pawłowski ◽  
P. Talik ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Powder Diffraction ◽  
Structure Study ◽  
Asymmetric Unit ◽  
Pharmaceutical Samples ◽  
X Ray ◽  
Xanthine Derivatives ◽  
Structure Solution ◽  
Theophylline Derivatives

The crystal structures of two compounds belonging to a group of theophylline derivatives have been solved by X-ray powder diffraction methods. Despite the fact that these compounds seemed to be rather simple (23 atoms in an asymmetric unit), the preferred orientation and dominant zone problems created very serious obstacles in the investigations, even for the most modern powder diffraction methods. The crystal structure of the first compound, 8-phenylazoxanthine, C14H14N6O2, was finally solved from laboratory diffractometer data, while in the case of the second compound, 8-(3-bromobenzylidene)xanthine, C15H14N5O2Br, it was not possible to reliably index its diffraction pattern until data had been collected at the high-resolution powder diffractometer ID31 at the ESRF Grenoble. The serious problems encountered during anab initiocrystal structure solution from powder data of these pharmaceutical samples are described and discussed.

scholarly journals Crystal structure solution of an elusive polymorph of Dibenzylsquaramide

2013 ◽  
Vol 28 (S2) ◽  
pp. S470-S480 ◽  
Author(s):  
Anna Portell ◽  
Xavier Alcobé ◽  
Latévi M. Lawson Daku ◽  
Radovan Černý ◽  
Rafel Prohens
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structural Features ◽  
Powder Diffraction Data ◽  
Asymmetric Unit ◽  
X Ray ◽  
The Third ◽  
Group Assignment ◽  
Structure Solution

The crystal structure of the third polymorph of dibenzylsquaramide (Portell, A. et al., 2009), (fig. 1) has been determined from laboratory X-ray powder diffraction data by means of direct space methods using the computing program FOX. (Favre-Nicolin and Černý, 2002) The structure resolution has not been straightforward due to several difficulties on the indexing process and in the space group assignment. The asymmetric unit contains two different conformers, which has implied an additional difficulty during the Rietveld (Rietveld, 1969) refinement. All these issues together with particular structural features of disquaramides are discussed.

scholarly journals Powder study of 3-azabicyclo[3.3.1]nonane-2,4-dione form 2

2006 ◽  
Vol 62 (7) ◽  
pp. o3046-o3048 ◽  
Author(s):  
Ashley T Hulme ◽  
Philippe Fernandes ◽  
Alastair Florence ◽  
Andrea Johnston ◽  
Kenneth Shankland
Keyword(s):  
Crystal Structure ◽  
Simulated Annealing ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Title Compound ◽  
Variable Temperature ◽  
Polycrystalline Sample ◽  
Asymmetric Unit ◽  
X Ray ◽  
Compound C

A polycrystalline sample of a new polymorph of the title compound, C8H11NO2, was produced during a variable-temperature X-ray powder diffraction study. The crystal structure was solved at 1.67 Å resolution by simulated annealing from laboratory powder data collected at 250 K. Subsequent Rietveld refinement yielded an R wp of 0.070 to 1.54 Å resolution. The structure contains two molecules in the asymmetric unit, which form a C 2 2(8) chain motif via N—H...O hydrogen bonds.

Barrydawsonite-(Y), Na1.5CaY0.5Si3O9H: a new pyroxenoid of the pectolite–serandite group

2015 ◽  
Vol 79 (3) ◽  
pp. 671-686 ◽  
Author(s):  
R. H. Mitchell ◽  
M. D. Welch ◽  
A. R. Kampf ◽  
A. K. Chakhmouradian ◽  
J. Spratt
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Red Wine ◽  
Structural Formula ◽  
Potassium Feldspar ◽  
Monoclinic Space Group ◽  
Asymmetric Unit ◽  
X Ray ◽  
Final Agreement ◽  
Simplified Formula

AbstractThe new pyroxenoid barrydawsonite-(Y) occurs at the Merlot Claim, North Red Wine Pluton, Labrador, Canada (62°32'38.54'' W; 54°08'1.37'' N). The host rock is a metamorphosed eudialyte syenite consisting of eudialyte, potassic arfvedsonite, jadeitic aegirine, nepheline, albite and potassium feldspar with accessory Y-bearing pectolite, britholite and steenstrupine. Barrydawsonite-(Y) crystals commonly have discrete thin rims of Y-bearing pectolite. The average empirical formula (based on nine anions p.f.u.) is Na1.54Ca0.74Mn0.15Fe0.07Y0.38Nd0.01Sm0.01Gd0.02Tb0.01Dy0.04Ho0.01Er0.02Yb0.01Si3.00O9H. The simplified formula is Na1.5Y0.5CaSi3O9H. Barrydawsonite-(Y) is related to pectolite by the substitution ½[NaM3+Ca–2] (M3+ = Y,REE), and is exceptional in being the only member of the pectolite group that has the structure of the monoclinic M2abc polytype. The crystal structure has been determined in monoclinic space group P21/a: a = 15.5026(2), b = 7.0233(1), c = 6.9769(1) Å, β = 95.149(1)°, V = 756.58(2) Å3(Z = 4). Final agreement indices are R1 = 0.038, wR2 = 0.068, Goof = 1.136. The asymmetric unit of barrydawsonite-(Y) has three metal sites: M(1) = Ca, M(2) = Na0.5(Y,REE)0.5, M(3) = Na. M(1) and M(2) are octahedrally-coordinated sites, whereas M(3) is [8]-coordinated as in pectolite and serandite. The structural formula for the empirical composition is M(3)Na1.00M(2)(Na0.50Y0.38REE0.13)Σ=1.01M(1)(Na0.04Ca0.74Mn0.152+Fe0.072+)Σ=1.00Si3O9H. There is excellent agreement between the refined site-scattering values and those calculated based upon the structural formula.Barrydawsonite-(Y) is biaxial (+) with α = 1.612(1), β = 1.617(1), γ = 1.630(1) (white light) and 2V = 63(1)°. The five strongest peaks in the X-ray powder diffraction pattern are [dobs (Å), Iobs%, (hkl)]: [2.905, 100, (023)], [3.094, 30, (210,211,121,202)], [1.7613, 29, (127,323,040)], [3.272, 27, (202,104)], [1.7016, 27, (140,227,325)].

Disordered crystal structure of pentamethylcyclopentadienylsodium as seen by high-resolution X-ray powder diffraction

2001 ◽  
Vol 57 (5) ◽  
pp. 673-679 ◽  
Author(s):  
Consiglia Tedesco ◽  
Robert E. Dinnebier ◽  
Falk Olbrich ◽  
Sander van Smaalen
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Lattice Parameters ◽  
Space Group ◽  
X Ray ◽  
Disordered Crystal

The crystal structure of pentamethylcyclopentadienylsodium, [NaC10H15] (NaCp*), has been determined from high-resolution X-ray powder diffraction. The compound crystallizes in space group Cmcm with lattice parameters a = 4.61030 (3), b = 16.4621 (3), c = 14.6751 (2) Å, V = 1113.77 (4) Å3 (Z = 4). NaCp* forms polymeric multidecker chains along the a axis. The Rietveld refinement (Rp = 0.050 and RF = 0.163) shows that the Cp* moieties occupy, with disorder, two different orientations rotated away from the eclipsed conformation by ±13.8°.

Effect of the ligand in the crystal structure of zinc oxide: an x-ray powder diffraction, x-ray absorption near-edge structure, and an extended x-ray absorption fine structure study

2016 ◽  
Vol 6 (2) ◽  
pp. 93-97
Author(s):  
María de los A. Cepeda-Pérez ◽  
Cristina M. Reyes-Marte ◽  
Valerie Ann Carrasquillo ◽  
William A. Muñiz ◽  
Edgar J. Trujillo ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Zinc Oxide ◽  
Fine Structure ◽  
Powder Diffraction ◽  
Structure Study ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Image Position ◽  
X Ray Absorption

Abstract

Crystal structure and powder diffraction reference pattern of type I clathrate Ba8Ni4Ge42

2012 ◽  
Vol 27 (1) ◽  
pp. 25-31 ◽  
Author(s):  
W. Wong-Ng ◽  
Q. Huang ◽  
I. Levin ◽  
J. C. Woicik ◽  
X. Shi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structure Study ◽  
Unit Cell ◽  
Type I ◽  
Reference Pattern ◽  
X Ray ◽  
Transmission Electron ◽  
Different Types ◽  
X Ray Absorption

The crystal structure of type I clathrate Ba8Ni4Ge42 has been determined using neutron powder diffraction, transmission electron microscopy (TEM, for possible superlattice), and extended X-ray absorption fine structure (EXAFS) measurements. Ba8Ni4Ge42 is cubic with the space group Pmn and unit-cell parameter a = 10.6769(2) Å (Dx = 5.988 g cm−3). The structure combines two different types of polyhedra: the dodecahedron (Ge20, 20-atom cage with 12 pentagonal faces) and the tetrakaidecahedron (Ge24, 24-atom cage with 12 pentagonal and 2 hexagonal faces). Each unit cell contains two Ge20 dodecahedra and six Ge24 tetrakaidecahedra. The Ge20 dodecahedra are linked via the interstitial 6c positions. The framework structure is formed by a tetrahedrally bounded network of Ge atoms, whereas Ba atoms reside inside the Ge20 and Ge24 cavities at the 2a and 6d crystallographic positions, respectively. Ni atoms exclusively occupy the 6c positions located on the hexagonal faces of the larger tetrakaidecahedra; no Ni atoms are found in the smaller dodecahedra that consist of pentagonal faces. A local structure study using EXAFS supports the coexistence of Ge and Ni on the 6c site. Electron diffraction in TEM reveals no detectable Ge/Ni ordering.

Combined Rietveld and stereochemical restraint refinement of a protein crystal structure

1999 ◽  
Vol 32 (6) ◽  
pp. 1084-1089 ◽  
Author(s):  
R. B. Von Dreele
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Tertiary Structure ◽  
Protein Crystal ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Protein Crystal Structure

By combining high-resolution X-ray powder diffraction data and stereochemical restraints, Rietveld refinement of protein crystal structures has been shown to be feasible. A refinement of the 1261-atom protein metmyoglobin was achieved by combining 5338 stereochemical restraints with a 4648-step (dmin= 3.3 Å) powder diffraction pattern to give the residualsRwp= 2.32%,Rp= 1.66%,R(F2) = 3.10%. The resulting tertiary structure of the protein is essentially identical to that obtained from previous single-crystal studies.

Crystal structure solution for the A 6 B 2O17 (A = Zr, Hf; B = Nb, Ta) superstructure

2019 ◽  
Vol 75 (2) ◽  
pp. 227-234 ◽  
Author(s):  
Scott J. McCormack ◽  
Waltraud M. Kriven
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
X Ray ◽  
Order And Disorder ◽  
Solid Solution Range ◽  
Structure Solution ◽  
Compositional Variations ◽  
Structural Mechanisms

Zr6Ta2O17, Hf6Nb2O17 and Hf6Ta2O17 crystal structure solutions have been solved using synchrotron X-ray powder diffraction and neutron powder diffraction in conjunction with simulated annealing, charge flipping and Rietveld refinement. These structures have been shown to be isomorphous with the Zr6Nb2O17 superstructure, leading to the classification of the A 6 B 2O17 (A = Zr, Hf; B = Nb, Ta) orthorhombic compound family with symmetry Ima2 (No. 46). The asymmetrical structural units of cation-centred oxygen polyhedra used to build the structure are as follows: (i) one set of symmetry-equivalent six-coordinated polyhedra, (ii) three sets of symmetry-equivalent seven-coordinated polyhedra and (iii) one set of symmetry-equivalent eight-coordinated polyhedra. The potential for cation order and disorder was discussed in terms of cation atomic number contrast in X-ray and neutron powder diffraction as well as the bond valence method. In addition, the structural mechanisms for experimentally observed compositional variations within the solid solution range can be attributed to the addition or removal of a set of symmetry-equivalent seven-coordinated polyhedra accompanied by corresponding oxygen tilts within the A 6 B 2O17 structure.

Crystal structure of brigatinib Form A (Alunbrig®), C29H39ClN7O2P

2021 ◽  
pp. 1-8
Author(s):  
Ryan L. Hodge ◽  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Density Functional ◽  
Phosphoryl Group ◽  
Powder Diffraction Data ◽  
Factor Solution ◽  
Powder Diffraction File ◽  
Functional Theory ◽  
X Ray ◽  
Structure Solution

The crystal structure of brigatinib Form A has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Brigatinib Form A crystallizes in space group P-1 (#2) with a = 9.59616(20), b = 10.9351(3), c = 14.9913(6) Å, α = 76.1210(13), β = 79.9082(11), γ = 74.0802(6)°, V = 1458.497(15) Å3, and Z = 2. Structure solution was complicated by the lowest cost factor solution having an unreasonable conformation of the dimethylphosphoryl group. The second-best structure yielded a better refinement. The crystal structure is characterized by alternating layers of aliphatic and aromatic portions of the molecules along the b-axis. Strong N–H⋯N hydrogen bonds link the molecules into pairs, with a graph set R2,2(8). There is a strong intramolecular N–H⋯O hydrogen bond to the phosphoryl group, which determines the orientation of this group. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

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