Unusual 2 k   CDW state with enhanced charge ordering in P-(BEDT-TTF) AsF  and PF6

2002 ◽  
Vol 12 (9) ◽  
pp. 233-234
Author(s):  
Y. Nogami ◽  
T. Mori
Keyword(s):  
Organic Compounds ◽  
Coulomb Repulsion ◽  
Molecular Shape ◽  
Internal Degree ◽  
Charge Ordering ◽  
Two Dimensional ◽  
X Ray ◽  
Bond Lengths ◽  
Charge Modulation ◽  
Conformational Ordering

X-ray superstructure analyses of the $2k_{\rm F}$ CDW states for two-dimensional organic compounds β-(BEDT-TTF)2PF6 and AsF6 were presented Molecular ionicity of BEDT-TTF was evaluated with both intramolecular bond lengths and molecular shape. Strong bending of quasi-neutd BEDT-TTF molecules coupled with the enhanced amplitude of charge modulation was observed Conformational ordering of the terminal ethylenes of BEDT-TTF molecules anddmeriiation between quasi-ionic BEJYI-TTF molecules were also observed These characteristic indicates this CDW is not Peierls-Frohlich type but mupled with the internal degree of the molecular shape and possibly the intersite Coulomb repulsion.

A twofold interwoven two-dimensional→two-dimensional (2-D→2-D) cluster–organic network based on the [Cu2I2] cluster and the 4,4′-(diazenediyl)dipyridine ligand: poly[[μ2-4,4′-(diazenediyl)dipyridine]-μ2-iodido-copper(I)]

2013 ◽  
Vol 69 (2) ◽  
pp. 123-126 ◽  
Author(s):  
Wenjiang Huang ◽  
Jinfang Zhang ◽  
Jianghua Li ◽  
Chi Zhang
Keyword(s):  
Organic Compounds ◽  
Title Compound ◽  
Two Dimensional ◽  
Tetrahedral Geometry ◽  
Bridging Ligands ◽  
Bond Lengths ◽  
First Time

In the polymeric title compound, [CuI(C10H8N4)]n, the CuIatom is in a four-coordinated tetrahedral geometry, formed by two I atoms and two pyridine N atoms from two different 4,4′-(diazenediyl)dipyridine (4,4′-azpy) ligands. Two μ2-I atoms link two CuIatoms to form a planar rhomboid [Cu2I2] cluster located on an inversion centre, where the distance between two CuIatoms is 2.7781 (15) Å and the Cu—I bond lengths are 2.6290 (13) and 2.7495 (15) Å. The bridging 4,4′-azpy ligands connect the [Cu2I2] clusters into a two-dimensional (2-D) double-layered grid-like network [parallel to the (10\overline{2}) plane], with a (4,4)-connected topology. Two 2-D grid-like networks interweave each other by long 4,4′-azpy bridging ligands to form a dense 2-D double-layered network. To the best of our knowledge, this interwoven 2-D→2-D network is observed for the first time in [Cu2I2]–organic compounds.

Tables of bond lengths determined by X-ray and neutron diffraction. Part 1. Bond lengths in organic compounds

1987 ◽  
pp. S1 ◽  
Author(s):  
Frank H. Allen ◽  
Olga Kennard ◽  
David G. Watson ◽  
Lee Brammer ◽  
A. Guy Orpen ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Organic Compounds ◽  
X Ray ◽  
Bond Lengths

The crystallography of the biscyclic dibenzacridines I. The electron distribution in 1.2:8.9-dibenzacridine

1960 ◽  
Vol 258 (1294) ◽  
pp. 302-318 ◽  
Keyword(s):  
Electron Distribution ◽  
Crystal And Molecular Structure ◽  
Molecular Orbital Theory ◽  
Two Dimensional ◽  
Orbital Theory ◽  
X Ray ◽  
Bond Lengths ◽  
Molecular Arrangement ◽  
Difference Density ◽  
The Mean

The crystal and molecular structure of 1.2:8.9-dibenzacridine has been determined by a least-squares refinement of the complete two-dimensional X-ray data. The average estimated standard deviations of the carbon-carbon and carbon-hydrogen bond lengths are 0·009 and 0·08Å respectively, the mean C—H bond length in the molecule being 1·08Å. The observed ‘difference’ density and bond lengths are compared with predictions based on molecular-orbital theory. The molecular arrangement in the crystal is discussed in relation to the calculated charge distribution in the molecule.

3-D reconstruction of molecular shape from microcrystal thin sections

1983 ◽  
Vol 41 ◽  
pp. 748-749
Author(s):  
S. Cusack ◽  
J.-C. Jésior
Keyword(s):  
Three Dimensional ◽  
Molecular Shape ◽  
Biological Molecules ◽  
Fourier Space ◽  
Single Particles ◽  
Thin Sections ◽  
Standard Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

Two dimensional Sr silicate grown on Si(001) studied using X-ray Photoelectron Spectroscopy

2006 ◽  
Vol 132 ◽  
pp. 87-90
Author(s):  
M. El Kazzi ◽  
G. Delhaye ◽  
S. Gaillard ◽  
E. Bergignat ◽  
G. Hollinger
Keyword(s):  
Photoelectron Spectroscopy ◽  
Two Dimensional ◽  
X Ray

Synthesis and Structure of a Clathrated Two-Dimensional Metal-Organic Framework: [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2·H2O (L = Bis(1-pyrazinylethylidene)hydrazine)

2008 ◽  
Vol 73 (1) ◽  
pp. 24-31
Author(s):  
Dayu Wu ◽  
Genhua Wu ◽  
Wei Huang ◽  
Zhuqing Wang
Keyword(s):  
Metal Organic Framework ◽  
Channel Structure ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Square Planar ◽  
Metal Organic ◽  
Aqueous Meoh ◽  
Organic Framework

The compound [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2 was obtained by the reaction of Cd(ClO4)2, bis(1-pyrazinylethylidene)hydrazine (L) and 4,4'-bipyridine in aqueous MeOH. Single-crystal X-ray diffraction has revealed its two-dimensional metal-organic framework. The 2-D layers superpose on each other, giving a channel structure. The square planar grids consist of two pairs of shared edges with Cd(II) ion and a 4,4'-bipyridine molecule each vertex and side, respectively. The square cavity has a dimension of 11.817 × 11.781 Å. Two guest molecules of bis(1-pyrazinylethylidene)hydrazine are clathrated in every hydrophobic host cavity, being further stabilized by π-π stacking and hydrogen bonding. The results suggest that the hydrazine molecules present in the network serve as structure-directing templates in the formation of crystal structures.

Use of TALP with laboratory powder diffraction data from 2D detectors

2013 ◽  
Vol 28 (S2) ◽  
pp. S481-S490
Author(s):  
Oriol Vallcorba ◽  
Anna Crespi ◽  
Jordi Rius ◽  
Carles Miravitlles
Keyword(s):  
Organic Compounds ◽  
Structural Study ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Pattern ◽  
Experimental Setup ◽  
Intensity Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Molecular Compounds

The viability of the direct-space strategy TALP (Vallcorba et al., 2012b) to solve crystal structures of molecular compounds from laboratory powder diffraction data is shown. The procedure exploits the accurate metric refined from a ‘Bragg-Brentano’ powder pattern to extract later the intensity data from a second ‘texture-free’ powder pattern with the DAJUST software (Vallcorba et al., 2012a). The experimental setup for collecting this second pattern consists of a circularly collimated X-ray beam and a 2D detector. The sample is placed between two thin Mylar® foils, which reduces or even eliminates preferred orientation. With the combination of the DAJUST and TALP software a preliminary but rigorous structural study of organic compounds can be carried out at the laboratory level. In addition, the time-consuming filling of capillaries with diameters thinner than 0.3mm is avoided.

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