Structural studies in the lepidopterene system

1984 ◽  
Vol 37 (6) ◽  
pp. 1313 ◽  
Author(s):  
H Becker ◽  
SR Hall ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Methylene Chloride ◽  
Metastable Phase ◽  
Stable Form ◽  
X Ray Diffraction ◽  
X Ray ◽  
Methylene Chloride Solution ◽  
Diffraction Determination ◽  
Exciplex Luminescence ◽  
Crystalline Forms

.A new, metastable phase of lepidopterene, (5,6,11,12-tetrahydro-4b,12[1',2']:6,10b[1",2"]-dibenzenochrysene) (1), has been obtained from methylene chloride solution, exhibiting a luminescence which differs from that of the stable form, having an absorption maximum at 580 nm rather than 560 nm. Single crystal X-ray diffraction determination of the structure of the new phase shows it to be orthorhombic, Pbcn, a 36.75(3), b 7.229(7), c 44.85(3) Ǻ, Z 24, the structure being refined to a residual of 0.065 for 2413 independent 'observed' reflections. Despite the relatively low precision of the determination, it is evident that in the metastable form, the gross molecular disposition is severely distorted. The crystal structure of dimethyllepidopterene (2) has also been determined, and refined by least squares to a residual of 0.041 for 632 'observed' reflections. Crystals are mono- clinic, P21/c, with a 9.607(4), b 11.564(7), c 10.576(6) Ǻ, β 107.72(4), Z 2; the molecules are centrosymmetric. Tetrachlorolepidopterene (31, formed by the dimerization of 1,5-dichloro-9-anthrylmethyl, yields two crystalline forms from xylene and methylene chloride solutions which differ in their crystal exciplex luminescence, showing emission maxima at 590 and 575 nrn respectively. Single- crystal X-ray structure determination confirms that the two crystalline forms, α- and β-, are polymorphs of the same centrosymmetric molecular species. For the α-form, crystals are triclinic, P1 , a 15.374(6), b 9.858(4), c 8.000(4) Ǻ, α 83.98(4), β 83.73(3), γ 71.53(3)°, Z 2, 2138 independent 'observed' reflections being refined to a residual of 0.037; the unit cell contains two independent centrosymmetric molecules. For the β-form, crystals are monoclinic, C2/c, a 11.03(2), b 13.67(2), c 16.32(3) Ǻ, β 1 1 1.13(12)°, Z 4; the residual for 1554 independent reflections was 0.053.

Size distribution of single-crystal nanoparticles by Monte Carlo fitting of wide-angle X-ray scattering peak shape

1999 ◽  
Vol 32 (3) ◽  
pp. 546-548 ◽  
Author(s):  
P. E. Di Nunzio ◽  
S. Martelli
Keyword(s):  
Monte Carlo ◽  
Single Crystal ◽  
Size Distribution ◽  
Peak Shape ◽  
X Ray Diffraction ◽  
Acta Cryst ◽  
X Ray ◽  
Transmission Electron ◽  
Diffraction Determination ◽  
Fitting Algorithm

According to Bertaut's theorem [Acta Cryst.(1950),3, 14–18], the size distribution of a powder sample constituted by perfect single-crystal particles can be easily determined from the peak shape analysis. The comparison between particle size distributions determined by a Monte Carlo fitting algorithm and those determined by direct observation using transmission electron microscopy shows that, as expected, the X-ray diffraction determination cannot be confidently used for particles with maximum dimensions above about 60 nm.

scholarly journals Understanding complex phase transition mechanism by crystal structure analysis

2014 ◽  
Vol 70 (a1) ◽  
pp. C1704-C1704
Author(s):  
Kristīne Krūkle-Bērziņa ◽  
Andris Actiņš
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Crystal Structure Analysis ◽  
Stable Form ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transition Mechanism

Xylazine hydrochloride (2-(2,6-xylidino)-5,6-dihydro-4H-1,3-thiazine hydrochloride) is an adrenergic α-agonist used as a sedative, analgesic, and muscle relaxant in veterinary medicine. It has four polymorphous forms (A, Z, M and X), monohydrate (H), hemihydrate and solvates with dichloromethane and 2-propanol. It has been reported that the polymorph X is thermodynamically the least stable of these polymorphs, while the A is the most stable form at temperatures above 500C. The X forms only in H dehydration process, and at elevated temperature X transforms to polymorph A [1]. The crystal structures of the polymorphs A and X as well as hydrate H have been reported. Crystal structure of A and X have been determined from the powder X-ray diffraction data (PXRD), whereas that of hydrate have been determined from single crystal X-ray diffraction data [2-3]. In this study structure of A have been determined from single crystal data and compared to that determined by PXRD data. Crystal structures of A, X and H have been compared and analysed. Molecule conformation in crystal structure of all three forms is the same and molecular packing is similar. However, that in monohydrate H and polymorph X is basically the same and the only difference is the inclusion of the water molecules next to the chlorine anions, whereas relative xylazine moiety orientation and arrangement of the chlorine anions is different in the structure of polymorph A. The structural similarity or differences between all three forms noted above were also approved by the 2D-fingerprint plots of the Hirshfeld surfaces. Analysis of all three form crystal structures allowed to better understand complex solid-state phase transition from xylazine hydrochloride polymorph X to polymorph A during and after the dehydration of it monohydrate H.

Electron Microscopy of Shock Loaded Polycrystalline Beryllium

1974 ◽  
Vol 32 ◽  
pp. 506-507 ◽  
Author(s):  
J. M. Galbraith ◽  
L. E. Murr ◽  
A. L. Stevens
Keyword(s):  
Electron Microscopy ◽  
Wave Propagation ◽  
Structural Change ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Shock Loading ◽  
Slip Systems ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
X Ray

Uniaxial compression tests and hydrostatic tests at pressures up to 27 kbars have been performed to determine operating slip systems in single crystal and polycrystal1ine beryllium. A recent study has been made of wave propagation in single crystal beryllium by shock loading to selectively activate various slip systems, and this has been followed by a study of wave propagation and spallation in textured, polycrystal1ine beryllium. An alteration in the X-ray diffraction pattern has been noted after shock loading, but this alteration has not yet been correlated with any structural change occurring during shock loading of polycrystal1ine beryllium.This study is being conducted in an effort to characterize the effects of shock loading on textured, polycrystal1ine beryllium. Samples were fabricated from a billet of Kawecki-Berylco hot pressed HP-10 beryllium.

Crystal structure of an inclusion complex between chiral monoaza-15-crown-5 and S(–)-1-phenyl-ethyl ammonium percholorate

2003 ◽  
Vol 218 (5) ◽  
Author(s):  
Süheyla Özbey ◽  
F. B. Kaynak ◽  
M. Toğrul ◽  
N. Demirel ◽  
H. Hoşgören
Keyword(s):  
Crystal Structure ◽  
Inclusion Complex ◽  
Single Crystal ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
New Type

AbstractA new type of inclusion complex, S(–)-1 phenyl ethyl ammonium percholorate complex of R-(–)-2-ethyl - N - benzyl - 4, 7, 10, 13 - tetraoxa -1- azacyclopentadecane, has been prepared and studied by NMR, IR and single crystal X-ray diffraction techniques. The compound crystallizes in space group

Unusual Rearrangement of Naphthalene in the Synthesis of a Novel B8-B8-Bridged Derivative in the [(1,2-C2B9H11)2-3-Co]- Series. X-Ray Structure and 11B NMR Spectra of [8,8'-μ-(CH2-C9H6)-(1,2-C2B9H10)2-3-Co]- (CH3)4N+

1997 ◽  
Vol 62 (5) ◽  
pp. 746-751 ◽  
Author(s):  
Andreas Franken ◽  
Jaromír Plešek ◽  
Christiane Nachtigal
Keyword(s):  
Nmr Spectroscopy ◽  
Single Crystal ◽  
Nucleophilic Substitution ◽  
Nmr Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Unusual Rearrangement ◽  
Multinuclear Nmr Spectroscopy ◽  
11B Nmr ◽  
Isolated Compound

On treatment of the [(1,2-C2B9H11)2Co]- ion with naphthalene in presence of AlCl3 a remarkably bridged [8,8'-μ-(CH2-C9H6)-(1,2-C2B9H10)2-3-Co]- ion is obtained as a single isolated compound. The triatomic -CH2-C9H6- bridge is derived from the rearranged naphthalene nucleus. The mechanism of this reaction is obscure but it does resemble the "Electrophile-Induced Nucleophilic Substitution" reported earlier. The structure of the compound was established by multinuclear NMR spectroscopy and by single crystal X-ray diffraction.

scholarly journals An investigation of polyhedral deformation in two mixed-metal diarsenates: SrZnAs2O7and BaCuAs2O7

2015 ◽  
Vol 71 (4) ◽  
pp. 330-337 ◽  
Author(s):  
Sabina Kovač ◽  
Ljiljana Karanović ◽  
Tamara Đorđević
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
General Formula ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Open Framework ◽  
Geometrical Characteristics ◽  
Barium Copper

Two isostructural diarsenates, SrZnAs2O7(strontium zinc diarsenate), (I), and BaCuAs2O7[barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. The three-dimensional open-framework crystal structure consists of corner-sharingM2O5(M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7group shares its five corners with five differentM2O5square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine-coordinatedM1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of theM1O9,M2O5and As2O7groups of known isostructural diarsenates, adopting the general formulaM1IIM2IIAs2O7(M1II= Sr, Ba, Pb;M2II= Mg, Co, Cu, Zn) and crystallizing in the space groupP21/n, are presented and discussed.

Sign in / Sign up

Export Citation Format

Share Document