Pyrido[1,2-a]quinoxalines: synthesis, crystal structure determination and pH-dependent fluorescenceElectronic supplementary information (ESI) available: NMR data of compounds 3a–k and views of the crystal structures of 3g, 3i and 3k. See http://www.rsc.org/suppdata/p2/b1/b102755g/

2001 ◽  
pp. 181-185 ◽  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Supplementary Information ◽  
Nmr Data ◽  
Ph Dependent

scholarly journals Automated Crystal Structure Determination has its Pitfalls: Correction to the Crystal Structures of Iodine Azide

2021 ◽  
Author(s):  
Ulrich Müller ◽  
Sergei Ivlev ◽  
Stephan Schulz ◽  
Christoph Wölper
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Determination ◽  
Crystal Structure Determination

scholarly journals Crystal structures of two furazidin polymorphs revealed by a joint effort of crystal structure prediction and NMR crystallography

2020 ◽  
Vol 76 (3) ◽  
pp. 322-335 ◽  
Author(s):  
Marta K. Dudek ◽  
Piotr Paluch ◽  
Edyta Pindelska
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Determination ◽  
Structure Prediction ◽  
Structural Features ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
Crystal Forms ◽  
Space Groups ◽  
Nmr Crystallography

This work presents the crystal structure determination of two elusive polymorphs of furazidin, an antibacterial agent, employing a combination of crystal structure prediction (CSP) calculations and an NMR crystallography approach. Two previously uncharacterized neat crystal forms, one of which has two symmetry-independent molecules (form I), whereas the other one is a Z′ = 1 polymorph (form II), crystallize in P21/c and P 1 space groups, respectively, and both are built by different conformers, displaying different intermolecular interactions. It is demonstrated that the usage of either CSP or NMR crystallography alone is insufficient to successfully elucidate the above-mentioned crystal structures, especially in the case of the Z′ = 2 polymorph. In addition, cases of serendipitous agreement in terms of 1H or 13C NMR data obtained for the CSP-generated crystal structures different from the ones observed in the laboratory (false-positive matches) are analyzed and described. While for the majority of analyzed crystal structures the obtained agreement with the NMR experiment is indicative of some structural features in common with the experimental structure, the mentioned serendipity observed in exceptional cases points to the necessity of caution when using an NMR crystallography approach in crystal structure determination.

Crystal structure determination from powder diffraction data by the application of a genetic algorithm

1997 ◽  
Vol 212 (8) ◽  
Author(s):  
K. Shankland ◽  
W. I. F. David ◽  
T. Csoka
Keyword(s):  
Crystal Structure ◽  
Genetic Algorithm ◽  
Full Advantage ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Powder Diffraction Data ◽  
Flexible Molecules

AbstractA genetic algorithm (GA) based method for solving crystal structures directly from powder diffraction data has been developed. The method is based around fitting the diffraction data generated from trial structures against the measured diffraction data and has the ability to handle flexible molecules and multiple fragments. It is computationally highly efficient and takes full advantage of the implicit parallelism of the GA. The method is illustrated with the solutions of three crystal structures of varying complexity.

The Anion [Co(C8H12)2]–. A Comparative Study of the Crystal Structures of [{K(18-crown-6)}2(C5H5)][Co(C8H12)2] and Co(C8H12)(C8H13)

2009 ◽  
Vol 64 (8) ◽  
pp. 985-988 ◽  
Author(s):  
Jian-Qiang Wang ◽  
Thomas F. Fässler
Keyword(s):  
Crystal Structure ◽  
Crown Ether ◽  
Comparative Study ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Determination ◽  
Cobalt Complex ◽  
Crystal Structure Determination ◽  
X Ray ◽  
Cyclopentadienyl Anion

The cobalt complex [{K(18-crown-6)}2(C5H5)]- [Co(C8H12)2]・(THF)2 (3) has been synthesized and characterized by X-ray single-crystal structure determination. The crystal structure of Co(C8H12)(C8H13) (2) has been reinvestigated and compared with the structure of 3. The 1,5-cyclooctadiene (C8H12) and C8H13 ligands are coordinated in an η4 and η3 fashion, respectively. The cyclopentadienyl anion in [{K(18-crown-6)}2(C5H5)]+ in 3 is η5-coordinated to the two crown ether-encapsulated potassium cations

Chemistry and Crystal Structures of Some Constituents of Zingiber cassumunar

1979 ◽  
Vol 32 (1) ◽  
pp. 71 ◽  
Author(s):  
T Amatayakul ◽  
J Cannon ◽  
P Dampawan ◽  
T Dechatiwongse ◽  
RF Giles ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Crystal Structures ◽  
Structure Determination ◽  
Aromatic Compounds ◽  
Crystal Structure Determination ◽  
The Novel ◽  
X Ray ◽  
Zingiber Cassumunar ◽  
Block Diagonal

The novel aromatic compounds cis-3-(2',4',5'-trimethoxyphenyl)-4-[(E)-2''',4''',5'''-trimethoxy-styryl]cyclohex-1-ene(1), cis-3-(3',4'-dimethoxyphenyl)-4-[(E)-3''',4'''-dimethoxystyryl]cyclohex-1-ene (2), a substance assigned the tentative structure cis-3-(3',4'-dimethoxyphenyl)-4-[(E)-2''',4''',5'''- trimethoxystyryl]cyclohex-1-ene (3),(E)-4-(3',4'-dimethoxypheny1)but-3-en-1-ol (5), (E)-4-(3',4'-dimethoxypheny1)but-3-en-1-yl acetate (6), and 8-(3',4'-dimethoxyphenyl)-2-methoxynaphtho-1,4- quinone (7) have been isolated from the rhizomes of Zingiber cassurnunav Roxb. (Zingiberaceae). The crystal structures of the cyclohexene derivative (1) and the quinone (7) have been determined from X-ray diffractometer data at 295 K and refined by block diagonal least squares to residuals of 0.046 (2099 'observed' reflections) and 0.093 (1246), respectively. Crystals of compound (1) are triclinic, P1, a 18.027(12), b 10.037(9), c 6.530(5) α, 84.22 (7), β 81.87 (6), γ 85.72 (6)�, Z 2. Crystals of the quinone (7) are monoclinic, P21/a, a 22.89 (1), b 8.022 (5), c 8.458 (5) �, β 91.98 (5)�, Z 4. Although the latter crystal structure determination is imprecise, due largely to the very small size of the crystal available, the solution is unambiguous. A simple two-step synthesis of the quinone (7) has been achieved.

Kristallographische Konsequenzen von Pseudosymmetrie in Kristallstrukturen

2000 ◽  
Vol 215 (3) ◽  
Author(s):  
M. Ruck
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Crystal Structures ◽  
Structure Determination ◽  
Stacking Faults ◽  
Spatial Arrangement ◽  
Crystal Structure Determination ◽  
Small Deviations ◽  
New Class

The term pseudo-symmetry means a spatial arrangement that feigns a symmetry without fulfilling it. In crystal structures pseudo-symmetry is a more common feature than often recognized. In case of small deviations a variety of phenomena results: polytypism and stacking faults, disorder and twinning, commensurate and incommensurate super-structures, phase transitions and unusual reflection conditions. Most of these effects complicate crystal structure determination considerably. A series of examples with focus on the new class of ternary bismuth subhalides illustrates the different crystallographic consequences of pseudo-symmetry in crystal structures.

scholarly journals The Consistent Hexameric Paddle-Wheel Crystallisation Motif of a Family of 2,4-Bis(n-Alkylamino)Nitrobenzenes: Alkyl = Pentyl, Hexyl, Heptyl and Octyl

2017 ◽  
Vol 41 (4) ◽  
pp. 235-238 ◽  
Author(s):  
M. John Plater ◽  
William T.A. Harrison ◽  
Laura M. Machado de los Toyos ◽  
Lewis Hendry
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Paddle Wheel ◽  
Alkyl Chains ◽  
Single Crystal Structures ◽  
Hydrogen Bonded

Three examples of 2,4-bis(n-alkylamino)nitrobenzenes have been crystallised (alkyl = pentyl, hexyl and heptyl) and the single crystal structures were determined. The three structures are similar and adopt a cyclic hydrogen bonded hexameric motif. n-Octyl alkyl chains prevented a crystal structure determination owing to disorder.

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