scholarly journals Absolute structure and absolute configuration

1999 ◽  
Vol 55 (5) ◽  
pp. 908-915 ◽  
Author(s):  
H. D. Flack ◽  
G. Bernardinelli
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Structure Determination ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Absolute Structure

Fundamental notions concerning absolute structure and absolute configuration, and their determination from single-crystal diffraction measurements, are presented and reviewed. A glossary of terms with definitions useful in this field is provided. For absolute structure and its determination, the separate but interacting influences of the structure and the inversion-distinguishing power of an X-ray diffraction experiment with dispersive scatterers are examined. Important experimental and algorithmic details of the current methods used for absolute-structure determination are provided. Characterization of crystals for absolute-structure determination and of molecules for absolute-configuration determination are treated. Attention is given to the analysis of absolute structure and absolute configuration in twinned crystals.

scholarly journals STRUCTURAL CHARACTERIZATION OF 2-AMINO-2-OXOACETIC ACID BY X-RAY POWDER DIFFRACTION AND QUANTUM CHEMISTRY

2019 ◽  
Vol 16 (33) ◽  
pp. 516-523
Author(s):  
G. E. DELGADO ◽  
L. M. BELANDRIA ◽  
M. GUILLEN ◽  
A.. J. MORA ◽  
L. E. SEIJAS
Keyword(s):  
Hydrogen Bonds ◽  
Single Crystal ◽  
Structural Study ◽  
Powder Diffraction ◽  
Structural Characterization ◽  
Structure Determination ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray

2-amino-2-oxoacetic acid, carbamoyl formic acid, or oxamic acid is an active pharmaceutical ingredient (API) of great importance mainly because is an inhibitor of lactic dehydrogenase (LDH). It acts as an inhibitor to the metabolic pathways of the tumor cells and exhibited significant anticancer activity against nasopharyngeal carcinoma (NPC) cells in vitro and can be considered as a potential drug for the treatment of type 2 diabetes. Also, this compound could be used as a building block in the design of supramolecular architectures based on hydrogen bonds through the complimentary hydrogen-bond functionalities of the carbonyl and amide functional groups present. Single-crystal X-ray diffraction is the most powerful technique for crystal structure determination of small molecules. However, for several materials, including oxamic acid, it could be complicated to grow single crystals of suitable size and quality that make them appropriated to structure analysis. For this reason, the structural study was conducted with powder X-ray diffraction which is a process significantly more challenging than structure determination from single-crystal data. Oxamic acid has been characterized by FT-IR and NMR spectroscopic techniques, thermal TGA-DSC analysis, semi-empirical PM7 calculations, and X-ray powder diffraction. The title compound crystallizes in the monoclinic system with space group Cc, Z=4, and unit cell parameters a= 9.4994(4) Å, b= 5.4380(2) Å, c= 6.8636(3) Å, b= 107.149(2)°, V= 338.79(2) Å3. The molecule has a trans conformation. The molecular structure and crystal packing are stabilized mainly by intra- and intermolecular O--H···O and N--H···O hydrogen bonds. The structural characterization of this type of API compound is important to understand its mechanisms of action due to its considerable biological effects. In particular, for oxamic acid, this structural study would allow subsequent examination of its medicinal properties as an antitumor and antidiabetic agent.

Neutron and X-ray single-crystal diffraction from protein microcrystalsviamagnetically oriented microcrystal arrays in gels

2016 ◽  
Vol 72 (7) ◽  
pp. 823-829 ◽  
Author(s):  
Shu Tsukui ◽  
Fumiko Kimura ◽  
Katsuhiro Kusaka ◽  
Seiki Baba ◽  
Nobuhiro Mizuno ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Structure Determination ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Diffraction Structure ◽  
First Time ◽  
Magnetically Aligned

Protein microcrystals magnetically aligned in D2O hydrogels were subjected to neutron diffraction measurements, and reflections were observed for the first time to a resolution of 3.4 Å from lysozyme microcrystals (∼10 × 10 × 50 µm). This result demonstrated the possibility that magnetically oriented microcrystals consolidated in D2O gels may provide a promising means to obtain single-crystal neutron diffraction from proteins that do not crystallize at the sizes required for neutron diffraction structure determination. In addition, lysozyme microcrystals aligned in H2O hydrogels allowed structure determination at a resolution of 1.76 Å at room temperature by X-ray diffraction. The use of gels has advantages since the microcrystals are measured under hydrated conditions.

scholarly journals Memorial Issue Dedicated to Dr. Howard D. Flack: The Man behind the Flack Parameter

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 818-820
Author(s):  
Catherine E. Housecroft ◽  
Katharina M. Fromm
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Molecular Species ◽  
Crystalline Material ◽  
Special Issue ◽  
X Ray Diffraction ◽  
X Ray ◽  
Memorial Issue ◽  
The Absolute ◽  
Absolute Structure

This Special Issue of Chemistry is dedicated to Dr. Howard D. Flack (1943–2017), a renowned crystallographer who transformed the way in which, by using single crystal X-ray diffraction, we are able to determine the absolute structure of a crystalline material, and thereby determine the absolute configuration of molecular species within the material [...]

Structural characterization of RE10W22O81 rare-earth tungstates (RE = Ce, Nd)

2008 ◽  
Vol 64 (6) ◽  
pp. 708-712 ◽  
Author(s):  
Rosemary S. Barker ◽  
Ivana Radosavljevic Evans
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Diffraction Study ◽  
General Formula ◽  
Structural Characterization ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Space Groups

The single-crystal diffraction study of Ce10W22O81 and powder X-ray diffraction (XRD) experiments on Ce10W22O81 and Nd10W22O81 show that the true space group of these phases is Pbnm, contrary to the previous literature reports of the space groups Pbcn and Pbcm for the rare-earth tungstates (RE = La, Ce, Pr, Nd) with this general formula. The structure contains rare-earth cations in seven-, eight- and ninefold coordination. W atoms are found in corner-sharing WO5 groups, and also in WO6 and WO7 polyhedra which share edges and corners to form W6O17 units. The new model obtained from our single-crystal work gives better agreement with powder XRD data on both Ce10W22O81 and Nd10W22O81, and gives more plausible coordination environments and bond-valence sums.

Crystal structures of (S)- and (R,S)-2,2′-bipyridine-3,3′-dicarboxylic acid 1,1′-dioxides and of their barium salts: absolute configuration and molecular distortion enforced by supramolecular self-assembly

1997 ◽  
Vol 212 (3) ◽  
Author(s):  
P. Vojtíšek ◽  
I. Císařová ◽  
J. Podlaha ◽  
Z. Žák ◽  
S. Böhm ◽  
...  
Keyword(s):  
Single Crystal ◽  
Dicarboxylic Acid ◽  
Crystal Structures ◽  
Absolute Configuration ◽  
Self Assembly ◽  
Barium Salt ◽  
X Ray Diffraction ◽  
X Ray

AbstractCrystal structures of the title compounds were determined by single crystal X-ray diffraction. Absolute configuration of the barium salt of (+)-(

scholarly journals Some experimental aspects of absolute configuration determination using single crystal X-ray diffraction

2017 ◽  
Vol 28 (10) ◽  
pp. 1330-1336 ◽  
Author(s):  
Amber L. Thompson ◽  
Sarah F. Jenkinson ◽  
George W.J. Fleet
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals After 200 Years: The Structure of Bleach and Characterization of Hypohalite Ions by Single‐Crystal X‐Ray Diffraction

2021 ◽  
Author(s):  
Filip Topić ◽  
Joseph M. Marrett ◽  
Tristan H. Borchers ◽  
Hatem M. Titi ◽  
Christopher J. Barrett ◽  
...  
Keyword(s):  
Single Crystal ◽  
X Ray Diffraction ◽  
X Ray

Synthesis and Characterization of Tetraphenylphosphonium Tetraazidoborate

2002 ◽  
Vol 57 (6) ◽  
pp. 621-624 ◽  
Author(s):  
Wolfgang Fraenk ◽  
Heinrich Nöth ◽  
Thomas M. Klapötke ◽  
Max Suter
Keyword(s):  
Single Crystal ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray

AbstractTetraphenylphosphonium tetraazidoborate, [P(C6H5)4][B(N3)4], was obtained from B(N3)3 - in situ prepared from BH3 · O(C2H5)2 and HN3 - and [P(C6H5)4][N3]. Recrystallization from an acetonitrile / hexane mixture yielded colorless crystals in 60% yield. The molecular structurewas determined by single crystal X-ray diffraction and the [B(N3)4]- anionwas shown to possess S4 symmetry.

scholarly journals Serendipitous formation and characterization of K2[Pd(NO3)4]·2HNO3

2019 ◽  
Vol 74 (4) ◽  
pp. 381-387
Author(s):  
Michael Zoller ◽  
Jörn Bruns ◽  
Gunter Heymann ◽  
Klaus Wurst ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Monoclinic Space Group ◽  
Solvothermal Process ◽  
X Ray Diffraction ◽  
Glass Ampoule ◽  
Space Group ◽  
X Ray ◽  
Complex Anions

AbstractA potassium tetranitratopalladate(II) with the composition K2[Pd(NO3)4] · 2HNO3 was synthesized by a simple solvothermal process in a glass ampoule. The new compound crystallizes in the monoclinic space group P21/c (no. 14) with the lattice parameters a = 1017.15(4), b = 892.94(3), c = 880.55(3) Å, and β = 98.13(1)° (Z = 2). The crystal structure of K2[Pd(NO3)4] · 2HNO3 reveals isolated complex [Pd(NO3)4]2− anions, which are surrounded by eight potassium cations and four HNO3 molecules. The complex anions and the cations are associated in layers which are separated by HNO3 molecules. K2[Pd(NO3)4] · 2HNO3 can thus be regarded as a HNO3 intercalation variant of β-K2[Pd(NO3)4]. The characterization is based on single-crystal X-ray and powder X-ray diffraction.

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