Structural study of the cesium oxypentafluorouranate (VI) CsUOF5

1978 ◽  
Vol 56 (19) ◽  
pp. 2546-2549 ◽  
Author(s):  
Philippe Joubert ◽  
Jean-Marc Weulersse ◽  
Roland Bougon ◽  
Bernard Gaudreau
Keyword(s):  
Neutron Diffraction ◽  
Structural Study ◽  
Characteristic Time ◽  
The Other ◽  
Point Symmetry ◽  
Space Group ◽  
Dynamic Type ◽  
Nmr Study ◽  
Powder Samples ◽  
Occupation Rate

Powder samples of cesium oxypentafluorouranate(VI) were studied by both neutron diffraction and 19F broad Une nuclear magnetic resonance.CsUOF5 crystallises with the [Formula: see text] space group, with the parameters a = 5.41 ± 0.01 Ǻ; α = 95°34′ ± 5′. The structure, which was found to be unchanged at temperatures as low as 4.2 K, was interpreted by a statistical occupation of six-fold equivalents sites, the occupation rate being 1/6 and 5/6 for oxygen and fluorine, respectively. The nmr study showed that the disorder corresponding to this structure was of dynamic type, and that the UOF5− ions were in isotropical rotation. The motion is observable at temperatures as low as 223 K with a characteristic time τ equal to3 × 10-5 s at 266 K. On the other hand, it was also shown through this nmr study that the point symmetry of the UOF5− ion corresponds to the C4v group, with the axial fluorine being more covalent than the equatorial ones. Consistency of the diffraction and nmr results is discussed.

scholarly journals Über die Strukturen der CuZrF6-Modifikationen - Neutronenbeugungsuntersuchungen an den Kristallpulvern / A Neutron Diffraction Study on the Modifications of CuZrF6

1978 ◽  
Vol 33 (3) ◽  
pp. 268-274 ◽  
Author(s):  
V. Propach ◽  
F. Steffens
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Neutron Diffraction ◽  
Experimental Evidence ◽  
Neutron Diffraction Study ◽  
Three Dimensions ◽  
Space Group ◽  
Powder Samples ◽  
Jahn Teller ◽  
Jahn Teller Effect

Abstract The structures of two modifications of CuZrF6 by means of neutron diffraction on powder samples in the temperature range from 298-560 K are reported. All modifications consist of octahedra, which share corners in three dimensions and which are centered alternately by Cu2+ or Zr4+. The high temperature α-modification crystallizes in space group Fm3 (No. 202) with α = 7.939 Å. There is experimental evidence, that the CuFe-octahedra are distorted by a static Jahn-Teller-effect. The space group P1̄ (No. 2) with Z = 2 is proposed for the low-temperature γ-modification.

Neutron diffraction study of [Pt(en)2][Pt(en)2I2](ClO4)4 at 20 K: structure and evidence of a new phase transition

1996 ◽  
Vol 52 (5) ◽  
pp. 854-864 ◽  
Author(s):  
J.-F. Bardeau ◽  
A. Bulou ◽  
W. T. Klooster ◽  
T. F. Koetzle ◽  
S. Johnson ◽  
...  
Keyword(s):  
Phase Transition ◽  
Neutron Diffraction ◽  
Room Temperature ◽  
Neutron Diffraction Study ◽  
The Other ◽  
Space Group ◽  
Cell Parameters ◽  
Diffraction Peaks ◽  
Expected Values ◽  
New Phase

The structure at 20 K of fully deuterated [Pt(en)2][Pt(en)2I2](ClO4)4, where en = ethylenediamine, has been determined by neutron diffraction on a single-crystal. It is shown that the symmetry is monoclinic with cell parameters a = 16.650 (7), b = 5.760 (2), c = 14.751 (2) Å and β = 99.19 (1)°, that is, with respect to the previously reported room-temperature structures, a doubling of the c parameter is observed. The space group is C2/c and the refinements lead to an R value of 0.0374. All the bond lengths (C—C, C—N, C—D, N—D and Cl—O) and angles are consistent with the expected values and the main difference with respect to the previously reported room-temperature structures results in an ordering of the stacking of the ethylenediamines. The iodines are distributed over two sites, which gives two Pt—I distances, 2.712 (3) Å, attributed to the PtIV—I bond, and 3.048 (3) Å, attributed to PtII—I. Actually, very weak diffraction peaks that provide evidence for an additional doubling of the a and b parameters are also observed and a space group C2 is therefore proposed. This could result from a very slight ordering of the chains with respect to one another, but, due to the weakness of such signals and the large number of atoms to be considered, no reliable refinement has been obtained in C2. On the other hand, on heating the crystal the diffraction peaks with I odd greatly decrease in intensity between 150 and 160 K, which unambiguously argues for the existence of a phase transition presumably connected to an order—disorder of the ethylenediamines.

A study of oxygen and vacancy ordering in YBa2Cu3O7−x

1989 ◽  
Vol 47 ◽  
pp. 164-165
Author(s):  
Y. P. Lin ◽  
A. H. O’Reilly ◽  
J. E. Greedan ◽  
M. Post
Keyword(s):  
Electron Microscopy ◽  
Neutron Diffraction ◽  
Oxygen Content ◽  
Carbon Film ◽  
Nitrogen Atmosphere ◽  
Vacancy Ordering ◽  
Powder Samples ◽  
Vacancy Chains ◽  
Chain Ordering

In the basal planes of the orthorhombic YBa2Cu3O7-X compound with x=0.07, which has a Tc of around 90K, chains of copper-oxygen are formed along the [010] direction. Previous investigations on the variation of Tc with oxygen content have shown the existence of a plateau at Tc = 60K for x=0.3 to 0.4, suggesting the presence of a separate phase. This phase has also been identified to be orthorhombic, but with a 2x superlattice along [100] of the parent structure, and the superlattice has been attributed to the formation of alternating copper-oxygen and copper-vacancy chains. In our work, we have studied the chain ordering phenomenon by electron microscopy and neutron diffraction on samples with different oxygen contents. We report here some of our electron microscopy findings for samples with x=0.4.Powder samples of YBa2Cu3O7-X were prepared by controlled re-oxidation of previously reduced material. For electron microscopy, the sample was dry ground using a mortar and pestle in a dry nitrogen atmosphere without the use of any solvent and transferred dry onto holey carbon film for examination in a Philips CM12 microscope.

Structural role of copper in the minerals of the pearceite-polybasite group: the case of the new minerals cupropearceite and cupropolybasite

2007 ◽  
Vol 71 (06) ◽  
pp. 641-650 ◽  
Author(s):  
L. Bindi ◽  
M. Evain ◽  
P. G. Spry ◽  
K. T. Tait ◽  
S. Menchetti
Keyword(s):  
Chemical Characterization ◽  
Sample Space ◽  
The Other ◽  
Crystal Chemical ◽  
Structural Position ◽  
Space Group ◽  
Cu Content ◽  
Own Name

Abstract The pearceite-polybasite group of minerals, general formula [M6T2S7][Ag9CuS4] with M = Ag, Cu; and T = As, Sb, show a crystal structure which can be described as the succession, along the c axis, of two pseudo-layer modules: a [M6T2S7]2– A module layer and a [Ag9CuS4]2+ B module layer. Copper is present in one structural position of the B module layer and replaces Ag in the only fully occupied M position of the A module layer. When the Cu content is >4.00 a.p.f.u., the structural position of the A module layer becomes Cu-dominant and, consequently, the mineral deserves its own name. In this paper we report the crystal-chemical characterization of two Cu-rich members exhibiting the 111 unitcell type (corresponding to the Tac polytype). One sample (space group (P )m1, a 7.3218(8), c 11.8877(13) Å, V 551.90(10) Å3, Z = 1) having As >Sb and with the structural position of the A module layer dominated by Cu, has been named cupropearceite and the other sample (space group (P3̄)m1, a 7.3277(3), c 11.7752(6) Å, V 547.56(8) Å3, Z = 1) having Sb >As has been named cupropolybasite. Both the new minerals and mineral names have been approved by the IMA-CNMNC.

Zolmitriptan oxalate and zolmitriptan camphorsulfonate: the first structural study of salt complexes of the antimigraine drug zolmitriptan

2013 ◽  
Vol 69 (10) ◽  
pp. 1186-1191
Author(s):  
Balasubramanian Sridhar ◽  
Krishnan Ravikumar ◽  
Venkatasubramanian Hariharakrishnan
Keyword(s):  
Structural Study ◽  
Three Dimensional ◽  
Helical Chain ◽  
Side Chain ◽  
Indole Ring ◽  
Asymmetric Unit ◽  
Compound I ◽  
Space Group ◽  
Compound Ii ◽  
Ring Motif

Zolmitriptan hydrogen oxalate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium hydrogen oxalate], C16H22N3O2+·C2HO4−, (I), and zolmitriptan camphorsulfonate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium (S,R)-{2-hydroxy-7,7-dimethylbicyclo[2.2.1]heptan-1-yl}methanesulfonate], C16H22N3O2+·C10H15O4S−, (II), are the first reported salt complexes of the antimigraine drug zolmitriptan. Compound (I) crystallizes in the space groupP21with two molecules of protonated zolmitriptan and two oxalate monoanions in the asymmetric unit, while compound (II) crystallizes in the space groupP212121with one protonated zolmitriptan molecule and one camphorsulfonate anion in the asymmetric unit. The orientations of the ethylamine side chain and the oxazolidinone ring with respect to the indole ring of the zolmitriptan cation are different for (I) and (II). In (I), they are oriented in opposite directions and the molecule adopts a step-like appearance, while in (II) the corresponding side chains are folded in the same direction, giving the molecule a cup-like appearance. The zolmitriptan molecules of (I) form anR22(8) dimer, while in (II) they form a helical chain with aC(11) motif. The oxalate monoanions of (I) interact with the zolmitriptan cations and extend the dimer into a three-dimensional hydrogen-bonded network. In (II), the camphorsulfonate anion forms anR22(15) ring motif with the zolmitriptan cation.

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