Thermolysis of Some Spirobenzopyran-3’,2-[1,3,4]oxadithiino- [5,6-c]benzopyran-4’-ones in the Presence of Some Homodienes and Crystallographic Studies of Some Adducts

2006 ◽  
Vol 61 (11) ◽  
pp. 1413-1420 ◽  
Author(s):  
Mohamed I. Hegab ◽  
A. M. Moustafa
Keyword(s):  
Single Crystal ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Other Hand ◽  
Good Support

The very reactive α-oxo-thioketone derivatives 2a - d, generated via thermolysis of spirobenzopyran- 3’,2-[1,3,4]oxadithiino[5,6-c]benzopyran-4’-ones 1a - d, reacted with 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene under [4+2]-cycloaddition to afford spirobenzopyran-3’,6-thiapyran-4’-one adducts 3a - d and spirobenzopyran-3’,3-thiabicyclo[2.2.2]oct-5-en-4’-one adducts 4a - d, respectively. On the other hand, the reaction of α-oxo-thioketones 2a - d with isoprene afforded regioselectively only 3-methyl-thiapyran derivatives 5a - d. Single crystal X-ray diffraction studies of 4b, 4c, and 5a give a good support for the established structure.

Molecular tapes in the structure of isoguaninium chloride

2017 ◽  
Vol 74 (1) ◽  
pp. 108-112 ◽  
Author(s):  
Urszula Anna Budniak ◽  
Paulina Maria Dominiak
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Charge Density ◽  
Interaction Energy ◽  
Electrostatic Interaction ◽  
Electrostatic Interactions ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Structure

Isoguanine, an analogue of guanine, is of intrinsic interest as a noncanonical nucleobase. The crystal structure of isoguaninium chloride (systematic name: 6-amino-2-oxo-1H,7H-purin-3-ium chloride), C5H6N5O+·Cl−, has been determined by single-crystal X-ray diffraction. Structure analysis was supported by electrostatic interaction energy (E es) calculations based on charge density reconstructed with the UBDB databank. In the structure, two kinds of molecular tapes are observed, one parallel to (010) and the other parallel to (50\overline{4}). The tapes are formed by dimers of isoguaninium cations interacting with chloride anions. E es analysis indicates that cations in one kind of tape are oriented so as to minimize repulsive electrostatic interactions.

Crystal Structure of Calcium Picrate Pentahydrate: A New Eight-Coordinate Stereochemistry for [M(bidentate)2(unidentate)4]

1979 ◽  
Vol 32 (2) ◽  
pp. 301 ◽  
Author(s):  
V Diakiw ◽  
TW Hambley ◽  
DL Kepert ◽  
CL Raston ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Single Crystal ◽  
Title Compound ◽  
Lattice Site ◽  
The Other ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Triangular Face ◽  
X Ray

The crystal structure of the title compound, Ca(C6H2N307)2,5H2O, has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.049 for 1513 'observed' reflections. Crystals are orthorhombic, Pmab, a 24.169(6), b l0.292(7), c 8.554(2) �, Z 4. The stereochemistry about the calcium has not been observed previously for the system [M(bidentate)2- (unidentate)4]; in the present structure, the calcium is coordinated by a pair of bidentate picrate ligands and the four water molecules in an array in which three of the water molecules occupy a triangular face of a square antiprism, the overall array having m symmetry. The remaining water molecule occupies a lattice site with no close interaction with the other species.

Synthesis and Structure of and Cation Distribution in the Zirconium Cluster Rb[(Zr6C)Cl15]

2008 ◽  
Vol 63 (5) ◽  
pp. 507-512 ◽  
Author(s):  
Henning W. Rohm ◽  
Martin Köckerling
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Cation Distribution ◽  
Type Structure ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coulombic Interactions ◽  
Cluster Network ◽  
Zirconium Cluster

Rb[(Zr6C)Cl15] was prepared by heating ZrCl4, Zr powder, RbCl and Al4C3 at 850 °C for 21 days. The crystal structure was determined by single crystal X-ray diffraction (space group Pmma, a = 18.484(3), b = 18.962(2), c = 9.708(1) Å, V = 2505.4(6) Å3, and Z = 4). Rb[(Zr6C)Cl15] crystallises in the Cs[Nb6Cl15]-type structure. It is built up from two interconnected types of cluster chains, one with linear Zr−Cla−a-Zr bridges, the other one with bent bridges. The rubidium cations are spread over three different sites within the cluster network which differs significantly from the cation distribution in the comparable potassium and caesium phases. The cation distribution can be rationalised considering the size of the cavities and the Coulombic interactions.

Conformational Comparisons Between Phenoxyacetic Acid Derivatives in Adducts and in the Free Form

1999 ◽  
Vol 52 (7) ◽  
pp. 695 ◽  
Author(s):  
Graham Smith ◽  
Catherine J. Cooper ◽  
Veena Chauhan ◽  
Daniel E. Lynch ◽  
Simon Parsons ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Single Crystal ◽  
Free Acid ◽  
Molecular Complexes ◽  
The Other ◽  
Free Form ◽  
Phenoxyacetic Acid ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dichlorophenoxy Acetic Acid

Six molecular complexes containing the herbicidally active (2,4-dichlorophenoxy)acetic acid (2,4-d) and (2,4,5-trichlorophenoxy)acetic acid (2,4,5-t) have been prepared and studied by using single-crystal X-ray diffraction techniques. These adduct structures are 2,4-d with 4,4′-dipyridine (2 : 1 complex), and 2,4,5-t with respectively 5-nitroquinoline (1 : 1), 4,4′-dipyridine (2 : 1), 2-amino-2-thiazoline (1 : 1), 2-aminobenzothiazole (1 : 1) and 2-amino-5-ethyl-1,3,4-thiadiazole (1 : 1). The conformations of the phenoxyacetic acid molecules were found to be either synclinal (in three cases) or antiperiplanar (in the other three cases). A general review is also made about the conformational aspects of previously reported adducts of phenoxyacetic acid derivatives and how they compare to their free acid structures.

scholarly journals Diffuse scattering from the lead-based relaxor ferroelectric PbMg1/3Ta2/3O3

2011 ◽  
Vol 44 (3) ◽  
pp. 603-609 ◽  
Author(s):  
Antonio Cervellino ◽  
S. N. Gvasaliya ◽  
O. Zaharko ◽  
B. Roessli ◽  
G. M. Rotaru ◽  
...  
Keyword(s):  
Single Crystal ◽  
Atomic Structure ◽  
Diffuse Scattering ◽  
Relaxor Ferroelectric ◽  
The Other ◽  
X Ray Diffraction ◽  
Correlation Lengths ◽  
X Ray ◽  
Displacement Vectors ◽  
Polar Nanoregions

The relaxor ferroelectric PbMg1/3Ta2/3O3was studied by single-crystal neutron and synchrotron X-ray diffraction, and its detailed atomic structure modelled in terms of static Pb displacements that lead to the formation of polar nanoregions. Similar to the other members of the Pb-based relaxor family like PbMg1/3Nb2/3O3or PbZn1/3Nb2/3O3the diffuse scattering in the [H00]/[0K0] scattering plane has a butterfly shape around theh00 Bragg reflections and is orthogonal to the scattering vector forhh0 peaks. In the [HH0]/[00L] plane the diffuse scattering is elongated along the 〈112〉 directions and is orthogonal to the scattering vector forhhhreflections. It is found that a model consisting of correlated Pb displacements along the 〈111〉 directions reproduces adequately the main features of the diffuse scattering in PbMg1/3Ta2/3O3when the correlation lengths between the Pb-ion displacement vectors are longest along the 〈111〉 and shortest along the 〈11{\overline 2}〉 and 〈1{\overline 1}0〉 directions.

X-Ray Diffraction of Iron Containing Samples: The Importance of a Suitable Configuration

2017 ◽  
Vol 262 ◽  
pp. 545-548 ◽  
Author(s):  
Yvonne M. Mos ◽  
Arnold C. Vermeulen ◽  
Cees N.J. Buisman ◽  
Jan Weijma
Keyword(s):  
Radiation Source ◽  
The Other ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
High Quality ◽  
Crystalline Phases ◽  
X Ray ◽  
Other Hand ◽  
Cobalt Radiation

X-ray diffraction (XRD) is a commonly used technology to identify crystalline phases. However, care must be taken with the combination of XRD configuration and sample. Copper (most commonly used radiation source) is a poor match with iron containing materials due to induced fluorescence. Magnetite and maghemite are analysed in different configurations using copper or cobalt radiation. Results show the effects of fluorescence repressing measures and the superiority of diffractograms obtained with cobalt radiation. Diffractograms obtained with copper radiation make incontestable phase identification often impossible. Cobalt radiation on the other hand yields high quality diffractograms, making phase identification straightforward.

Dinuclear oxofluorometallates as a new structural type of d 0 transition metal oxofluoride compound

2012 ◽  
Vol 68 (6) ◽  
pp. 602-609 ◽  
Author(s):  
Anatoly A. Udovenko ◽  
Natalia M. Laptash
Keyword(s):  
Transition Metal ◽  
Single Crystal ◽  
Structural Type ◽  
The Other ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
Orthorhombic Unit Cell ◽  
Fluoride Ions ◽  
X Ray ◽  
Irradiation Process

Five isomorphous d 0 transition metal oxofluoride compounds A 3[M 2O x F11 − x ]·(AF)0.333 (A = K, Rb, NH4; M = Nb, Mo, W; x = 2, 4) have been synthesized from acid fluoride solutions, and their crystal structures have been determined by single-crystal X-ray diffraction. The basic structural building units are dinuclear M 2 X 11 (dimers) formed from NbOF5 or Mo(W)O2F4 octahedra connected by the fluorine bridging atom. In the Nb2O2F9 dimer, the O atoms occupy apical corners. In the M 2O4F7 (M = Mo, W) dimers two O atoms are also apically placed, whereas the other two O atoms are statistically disordered in equatorial planes. The arrangement of dimers is so that the hexagonal tunnels containing `free' fluoride ions are formed. During the irradiation process the orthorhombic structure of K3Nb2O2F9·(KF)0.333 transforms into a pseudo-trigonal one with a = 23.15 Å, which is the [101] diagonal of the orthorhombic unit cell. The other four trigonal crystals are merohedral twins.

The perchlorotriphenylmethyl (PTM) radical

2013 ◽  
Vol 69 (3) ◽  
pp. 255-257 ◽  
Author(s):  
Judith Guasch ◽  
Xavier Fontrodona ◽  
Imma Ratera ◽  
Concepció Rovira ◽  
Jaume Veciana
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
The Other ◽  
X Ray Diffraction ◽  
Monoclinic Symmetry ◽  
Steric Strain ◽  
High Chemical ◽  
X Ray ◽  
Cl Atoms

In spite of the considerable understanding and development of perchlorotriphenylmethyl (PTM) radical derivatives, the preparation of crystals of the pure unsubstituted PTM radical, C19Cl15, suitable for single-crystal X-ray diffraction has remained a challenge since its discovery, and only two studies dealing with the crystal structure of the unsubstituted PTM radical have been published. In one study, the radical forms clathrates with aromatic solvents [Veciana, Carilla, Miravitlles & Molins (1987).J. Chem. Soc. Chem. Commun.pp. 812–814], and in the other the structure was determinedab initiofrom powder X-ray diffraction data [Rius, Miravitlles, Molins, Crespo & Veciana (1990).Mol. Cryst. Liq. Cryst.187, 155–163]. We report here the preparation of PTM crystals for single-crystal X-ray diffraction and their resolution. The structure, which shows monoclinic symmetry (C2/c), revealed a nonsymmetric molecular propeller conformation (D3symmetry) caused by the steric strain between theortho-Cl atoms, which protect the central C atom (sp2-hybridization and major spin density) and give high chemical and thermal persistence to the PTM. The supramolecular structure of PTM shows short Cl...Cl intermolecular interactions and can be described in terms of layers formed by rows of molecules positioned in a head-to-tail manner along thecaxis.

scholarly journals Success or Failure of Chiral Crystallization of Similar Heterocyclic Compounds

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5691
Author(s):  
Cyprian M. Chunkang ◽  
Iris E. Ikome ◽  
Emmanuel N. Nfor ◽  
Yuta Mitani ◽  
Natsuki Katsuumi ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Single Crystal ◽  
Single Crystals ◽  
Heterocyclic Compounds ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
The Other ◽  
X Ray ◽  
Other Hand

Single crystals of two achiral and planar heterocyclic compounds, C9H8H3O(CA1) and C8H5NO2 (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P212121 (# 19), whereas it was not observed for CA4 P21/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites.

scholarly journals On the interpretation of X-ray, single crystal, rotation photographs

1926 ◽  
Vol 113 (763) ◽  
pp. 117-160 ◽  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
The Other ◽  
X Rays ◽  
X Ray ◽  
Powder Method ◽  
Convenient Form ◽  
Other Hand ◽  
Rotation Method ◽  
Laue Method

In the development of the study of crystals by X-rays the methods used divide themselves naturally into four types : the Bragg Ionisation Spectrometer method, the Laue method, the Powder method of Debye and Scherrer, and the Rotating Crystal method of Rinne, Schiebold and Polyani. The techniques of the first three of these methods are fully explained in such books as ‘ X-Rays and Crystal Structure,’ by W. H. and W. L. Bragg, ‘ The Structure of Crystals,’ by Wyckoff, and ‘ Krystalle und Rontgenstrahlen,’ by Ewald, as well as in original papers. On the other hand, the rotation method is only slightly touched on in these works, the literature is scattered in a great number of papers, and the technique has not so far been described at any length in a convenient form. Particularly in English, references to it are scanty. In this paper the author has tried to give a concise account of the method, together with various types of charts and tables as it is used in the Davy Faraday Laboratory. The methods described differ in certain respects from those used on the Continent,* but they have been found to be rapid and sufficiently accurate.

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