scholarly journals The incommensurate structure of K3In(PO4)2

2003 ◽  
Vol 59 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Alla Arakcheeva ◽  
Gervais Chapuis ◽  
Vaclav Petříček ◽  
Michal Dušek ◽  
Andreas Schönleber
Keyword(s):  
Room Temperature ◽  
Driving Forces ◽  
Three Dimensional ◽  
Close Packing ◽  
The Other ◽  
Dimensional Structure ◽  
Powder Diffraction Data ◽  
Modulated Structure ◽  
Incommensurate Structure ◽  
Modulated Phase

The incommensurately modulated structure of K3In(PO4)2 has been solved and refined. The origin of the modulation relates to the ordering of K cations within the hexagonal close packing of the PO4 anions. The driving forces for the modulation of the other cations are In—P and K—P interactions. The modulation of O atoms of rigid PO4 units follows the cations in order to stabilize the InO6 octahedron. It is shown that the previously published three-dimensional structure refined from powder diffraction data obtained at room temperature is an average structure. Therefore the incommensurately modulated phase of K3In(PO4)2 is the only one that has been unequivocally identified at room temperature. The origin of the modulation is discussed in comparison with the structures of Na3InP2, α- and β-Na3In(PO4)2, Na3Fe(PO4)2 and Rb3In(PO4)2.

scholarly journals Modulated structure of La2Co1.7 from neutron and X-ray diffraction data

2000 ◽  
Vol 56 (6) ◽  
pp. 959-971 ◽  
Author(s):  
Michal Dusek ◽  
Gervais Chapuis ◽  
Penelope Schobinger-Papamantellos ◽  
Clive Wilkinson ◽  
Vaclav Petricek ◽  
...  
Keyword(s):  
Room Temperature ◽  
Close Packing ◽  
Dimensional Structure ◽  
X Ray Diffraction ◽  
Neutron Measurement ◽  
Modulated Structure ◽  
X Ray ◽  
Cell Parameters ◽  
Position Sensitive ◽  
Space Requirements

An La2Co1.7 crystal was investigated by single-crystal neutron and X-ray diffraction. The neutron measurement was performed with a Laue white-beam technique at 15 K and room temperature, using a large position-sensitive detector. The X-ray measurements were obtained at room temperature from a CCD detector. The average structure of La2Co1.7 is hexagonal with cell parameters a = 4.885 (1), c = 4.273 (2) Å and space group P63/mmc. The satellites are located at the vertices of small hexagons perpendicular to the c axis. The modulated crystal was indexed assuming a sixfold twinned 3 + 1 dimensional structure with q = (α, 0, γ). The structure was solved in the pseudoorthorhombic cell, with a = 8.461 (1), b = 4.885 (1), c = 4.273 (2) Å, in the superspace group C2/m(α, 0, γ). Owing to space requirements, the Co atoms cannot fit precisely into the octahedral sites of the La h.c.p. (hexagonal close packing). Instead, the Co atoms adopt a different periodicity, which is not commensurate with the periodicity of the La atoms. Two structure models have been refined in order to describe this behaviour, one using the sawtooth function for the positional modulation of cobalt and the other describing the structure as a composite system. The chemical composition calculated from the composite model is La2Co1.8 (1) with the estimated standard deviation arising from the variation of q for different samples. In both models lanthanum is incommensurately modulated, while the position of cobalt seems not to be affected by any relative periodic displacement.

A new three-dimensional anionic cadmium(II) dicyanamide network

2014 ◽  
Vol 70 (11) ◽  
pp. 1054-1056 ◽  
Author(s):  
Qiang Li ◽  
Hui-Ting Wang
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Unit Cell Volume ◽  
Three Dimensional ◽  
Building Blocks ◽  
The Other ◽  
Dimensional Structure ◽  
Cadmium Nitrate ◽  
Nitrate Tetrahydrate ◽  
Anionic Framework

A new cadmium dicyanamide complex, poly[tetramethylphosphonium [μ-chlorido-di-μ-dicyanamido-κ4N1:N5-cadmium(II)]], [(CH3)4P][Cd(NCNCN)2Cl], was synthesized by the reaction of tetramethylphosphonium chloride, cadmium nitrate tetrahydrate and sodium dicyanamide in aqueous solution. In the crystal structure, each CdIIatom is octahedrally coordinated by four terminal N atoms from four anionic dicyanamide (dca) ligands and by two chloride ligands. The dicyanamide ligands play two different roles in the building up of the structure; one role results in the formation of [Cd(dca)Cl]2building blocks, while the other links the building blocks into a three-dimensional structure. The anionic framework exhibits a solvent-accessible void of 673.8 Å3, amounting to 47.44% of the total unit-cell volume. The cavities in the network are occupied by pairs of tetramethylphosphonium cations.

scholarly journals Bis(μ2-4-nitrophenolato)bis(4-nitrophenolato)di-μ3-oxido-octaphenyltetratin chloroform sesquisolvate [+ solvate]: a tetranuclear stannoxane

IUCrData ◽  
2019 ◽  
Vol 4 (8) ◽  
Author(s):  
Patrick Butler
Keyword(s):  
Hydrogen Bonds ◽  
Electron Density ◽  
Three Dimensional ◽  
The Other ◽  
Dimensional Structure ◽  
Coordination Geometry ◽  
Asymmetric Unit ◽  
Acta Cryst ◽  
Complex Molecules ◽  
Three Dimensional Structure

The title tetranuclear stannoxane, [Sn4(C6H5)8(C6H4NO3)4O2]·1.5CHCl3·solvent, crystallized with two independent complex molecules, A and B, in the asymmetric unit together with 1.5 molecules of chloroform. There is also a region of disordered electron density, which was corrected for using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18]. The oxo-tin core of each complex is in a planar `ladder' arrangement and each Sn atom is fivefold SnO3C2 coordinated, with one tin centre having an almost perfect square-pyramidal coordination geometry, while the other three Sn centres have distorted shapes. In the crystal, the complex molecules are arranged in layers, composed of A or B complexes, lying parallel to the bc plane. The complex molecules are linked by a number of C—H...O hydrogen bonds within the layers and between the layers, forming a supramolecular three-dimensional structure.

Supercoils in plant DNA: nucleoid sedimentation studies

1988 ◽  
Vol 89 (2) ◽  
pp. 243-252
Author(s):  
L.M. Stoilov ◽  
J.S. Zlatanova ◽  
A.P. Vassileva ◽  
M.G. Ivanchenko ◽  
C.P. Krachmarov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Gamma Irradiation ◽  
Protein Content ◽  
Ethidium Bromide ◽  
Three Dimensional ◽  
The Other ◽  
Dimensional Structure ◽  
Salt Treatment ◽  
Plant Dna ◽  
Ionic Detergent

Plant nuclei have been studied with respect to the three-dimensional structure of DNA. Nucleoids derived from nuclei by non-ionic detergent and high salt treatment were analysed by sedimentation in a series of sucrose gradients containing increasing amounts of the intercalating agent ethidium bromide. In addition the nucleoid sedimentation behaviour was investigated following gamma irradiation. The results show that plant DNA is supercoiled, as is the DNA from the other eukaryotes studied, and contains approximately the same concentration of superhelical turns but probably relatively fewer DNA superhelical loops. The plant nuclear populations in all cases studied give rise to two distinct nucleoid bands. These have been characterized by electron microscopy and by their DNA and protein content. The possible origin of the two bands is discussed.

Poly[deca-μ2-cyanido-dicyanidobis(μ2-ethylenediamine)bis(ethylenediamine)tricadmium(II)dicobalt(III)]: a two-dimensional coordination polymer

2009 ◽  
Vol 65 (3) ◽  
pp. m118-m120
Author(s):  
Olha Sereda ◽  
Helen Stoeckli-Evans
Keyword(s):  
Coordination Polymer ◽  
Network Structure ◽  
General Position ◽  
Rotation Axis ◽  
Three Dimensional ◽  
The Other ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Asymmetric Unit ◽  
Dimensional Network

The title coordination polymer, [Cd3Co2(CN)12(C2H8N2)4]n, has an infinite two-dimensional network structure. The asymmetric unit is composed of two crystallographically independent CdIIatoms, one of which is located on a twofold rotation axis. There are two independent ethylenediamine (en) ligands, one of which bis-chelates to the Cd atom that sits in a general position, while the other bridges this Cd atom to that sitting on the twofold axis. The Cd atom located on the twofold rotation axis is linked to four equivalent CoIIIatomsviacyanide bridges, while the Cd atom that sits in a general position is connected to three equivalent CoIIIatomsviacyanide bridges. In this way, a series of trinuclear, tetranuclear and pentanuclear macrocycles are linked to form a two-dimensional network structure lying parallel to thebcplane. In the crystal structure, these two-dimensional networks are linkedviaN—H...N hydrogen bonds involving an en NH2H atom and a cyanide N atom, leading to the formation of a three-dimensional structure. This coordination polymer is only the second example involving a cyanometallate where the en ligand is present in both chelating and bridging coordination modes.

Structural Systematics of 2/4-Nitrophenoxide Complexes of Closed-Shell Metal Ions. VII Acid Salts of the 4-Nitrophenoxides of Group 2

1998 ◽  
Vol 51 (8) ◽  
pp. 785 ◽  
Author(s):  
Jack M. Harrowfield ◽  
Raj Pal Sharma ◽  
Brian W. Skelton ◽  
Allan H. White
Keyword(s):  
Room Temperature ◽  
Calcium Salt ◽  
Three Dimensional ◽  
Closed Shell ◽  
The Other ◽  
X Ray ◽  
C 23 ◽  
Structure Determinations ◽  
Group 2 ◽  
Acid Salts

Room-temperature single-crystal X-ray structure determinations are recorded for a number of Group 2 4-nitrophenoxide acid salts, variously hydrated M(4-np)2.x(4-npH).yH2O. Ca(4-np)2.2(4-npH).8H2O is monoclinic, P 21/n, a 30·52(1), b 10·027(1), c 23·65(2) Å, β 116·3(5)°, Z = 8, conventional R on |F| being 0·058 for No 5092 independent ‘observed’ (I > 3s(I)) reflections. Sr(4-np)2.2(4-npH).8H2O, based on a subcell of the former, is monoclinic, P 21/c, a 15·576(5), b10·081(6), c 24·20(2) Å, β 117·99(5)° , Z = 4, R 0·054 for No 2908. Ba(4-np)2.2(4-npH).4H2O is orthorhombic, Fdd2, a 28·01(1), b 19·90(1), c 10·692(7)Å, Z = 8, R 0·028 for No 1967. The strontium array (and that of the calcium salt developed from it) may be represented as [(H2O)6Sr(4-npH.4-np)] (4-npH.4-np), a neutral ligand being unsymmetrically chelated to the strontium through the nitro group, with a quasi-parallel counter ion hydrogen-bonded to it by phenoxide confrontation. The other two 4-np residues make up a similar phenoxide-confronting pair (4-npH.4-np), the hydrogen being more intimately associated with one moiety. The barium salt is also an interesting array: the 10-coordinate barium lies on a crystallographic 2 axis, in an environment of two pairs of symmetry-related nitro-chelating ligand anions, and a pair of nitro-O coordinating neutral 4-npH ligands; the whole [(H2O)4Ba(4-np)2(4-npH)2] array may be envisaged as a single neutral (super)molecule. Hydrogen bonds between confronting phenoxides of the neutral 4-npH components of the parent and the 4-np- components of neighbouring molecules link the whole into a three-dimensional array.

Three Dimensional Structure-Electrical Properties of Oriented PPV and PANI Films

2003 ◽  
Author(s):  
Runqing Ou ◽  
Robert J. Samuels ◽  
Rosario A. Gerhardt
Keyword(s):  
Electrical Properties ◽  
Three Dimensional ◽  
The Other ◽  
Planar Structure ◽  
Dimensional Structure ◽  
Phenylene Vinylene ◽  
Random Orientation ◽  
Waveguide Coupler ◽  
Impedance Measurements ◽  
Oriented Films

In this paper the influence of anisotropic molecular structure on the three dimensional electrical properties of both poly(phenylene vinylene), (PPV), and polyaniline, (PANI) oriented films is investigated. The anisotropic structure of the stretched PPV and PANI EB films were examined using a modified waveguide coupler while three dimensional impedance spectroscopy measurements were made using specially designed test fixtures that allowed the in-plane as well as the through-plane impedance to be measured. The unstretched PANI EB film has a random orientation and one-way stretching leads to a uniaxial structure. The unstretched PPV film, on the other hand, was found to have a highly planar structure and oneway stretching converts the planar structure to a uniaxial structure. Impedance measurements were made on PANI after it was doped with HCl while PPV films were measured in the undoped state. For HCl-doped PANI films, the conductivity along the stretch direction was found to increase with orientation. For undoped PPV films, the conductivity through the film thickness direction decreased with increasing orientation. For both polymers, the in-plane conductivity was significantly greater than the through-plane conductivity.

Incommensurately modulated phase of Rb2CoBr4 at 295 and 200 K

2000 ◽  
Vol 56 (1) ◽  
pp. 17-21 ◽  
Author(s):  
K. Friese ◽  
G. Madariaga ◽  
T. Breczewski
Keyword(s):  
Crystal Structure ◽  
Close Relationships ◽  
Room Temperature ◽  
Lattice Parameters ◽  
Modulated Structure ◽  
Space Group ◽  
Average Structure ◽  
First Order ◽  
Modulation Function ◽  
Modulated Phase

The crystal structure of Rb_2CoBr_4 at 295 and 200 K has been determined. At these temperatures Rb_2CoBr_4 exhibits an incommensurately modulated structure with wavevector {\bf q} = (1/3+\delta){\bf a}^*. At room temperature only the average structure was refined. Lattice parameters are a = 9.732 (3), b = 13.328 (4), c = 7.654 (3) Å, space group Pnam. The R(F) value was 0.0414 for 286 observed reflections (0.0778 for all 477 reflections). At 200 K the lattice parameters are a = 9.691 (4), b = 13.278 (5), c = 7.630 (6) Å, superspace group P:Pnam:\overline{1}ss. Main reflections and satellite reflections of first order were measured. The refinement converged at R(F) = 0.052 for 309 observed reflections (255 main reflections and 54 satellites) and 0.2971 for all reflections (1849; 695 main reflections and 1154 satellites). Amplitudes and phases of the modulation function as well as bond distances show close relationships to those observed in the incommensurately modulated phase of Rb_2ZnBr_4.

A three-dimensional zinc-based coordination polymer built from 5-carboxylato-1-carboxylatomethyl-2-oxidopyridinium with a 4-connectedsratopology

2014 ◽  
Vol 70 (8) ◽  
pp. 801-804
Author(s):  
De-Yun Ma ◽  
Jing Zheng ◽  
Jie-Qiong Cao ◽  
Xu-Min Lin ◽  
You-Biao Ling
Keyword(s):  
Coordination Polymer ◽  
Luminescence Spectrum ◽  
Room Temperature ◽  
Three Dimensional ◽  
The Other ◽  
Planar Structure ◽  
Zigzag Chain ◽  
Carboxylate Group ◽  
Aromatic Carboxylate ◽  
Bidentate Mode

A novel three-dimensional ZnIIcomplex, poly[aqua(μ4-5-carboxylato-1-carboxylatomethyl-2-oxidopyridinium)zinc(II)], [Zn(C8H5NO4)(H2O)]n, has been prepared by hydrothermal assembly of Zn(CH3COO)2·2H2O and 5-carboxy-1-(carboxymethyl)pyridin-1-ium-2-olate (H2ccop). The ccop2−anions bridge the ZnIIcations in a head-to-tail fashionviamonodentate aromatic carboxylate and phenolate O atoms to form an extended zigzag chain which runs parallel to the [011] direction. One O atom of the aliphatic carboxylate group of the ccop2−ligand coordinates to the ZnIIatom of a neighbouring chain thereby producing undulating layers which lie parallel to the (01-1) plane. A similar parallel undulating planar structure can be obtained if a path involving the other O atom of the aliphatic carboxylate group is considered. Thus, the aliphatic carboxylate group acts in a bridging bidentate mode to give extended –Zn–O–C–O–Zn– sequences running parallel to [001] which link the layers into an overall three-dimensional framework. The three-dimensional framework can be simplified as a 4-connected sra topology with a Schläfli symbol of 42.63.8 if all the ZnIIcentres and ccop2−anions are regarded as tetrahedral 4-connected nodes. The three-dimensional luminescence spectrum was measured at room temperature with excitation and emission wavelengths of 344–354 and 360–630 nm, respectively, at intervals of 0.15 and 2 nm, respectively.

The crystal chemistry of duftite, PbCuAsO4(OH) and the β-duftite problem

1998 ◽  
Vol 62 (1) ◽  
pp. 121-130 ◽  
Author(s):  
Kharisun ◽  
Max R. Taylor ◽  
D. J. M Bevan ◽  
Allan Pring
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Chemistry ◽  
Three Dimensional ◽  
The Other ◽  
Orthorhombic Space Group ◽  
Teller Distortion ◽  
Modulated Structure ◽  
Dimensional Network ◽  
Jahn Teller ◽  
Jahn Teller Distortion

AbstractDuftite, PbCu(AsO4)(OH) is orthorhombic, space group P212121 with a = 7.768(1), b = 9. 211(1), c = 5.999(1) Å, Z = 4; the structure has been refined to R = 4.6% and Rw = 6.5% using 640 observed reflections [F> 2σ(F)]. The structure consists of chains of edge-sharing CuO6 ‘octahedra’, parallel to c; which are linked via AsO4 tetrahedra and Pb atoms in distorted square antiprismatic co-ordination to form a three dimensional network. The CuO6 ‘octahedra’ show Jahn-Teller distortion with the elongation running approximately along <627>. The hydrogen bonding network in the structure was characterized using bond valence calculations. ‘β-duftite’ is an intermediate in the duftite-conichalcite series, which has a modulated structure based on the intergrowth of the two structures in domains of approximately 50 Å. The origin of the modulation is thought to be associated with displacements in the oxygen lattice and is related to the orientation of the Jahn-Teller distortion of CuO6 ‘octahedra’. Approximately half of the strips show an elongation parallel to <627> while the other strips are elongated parallel to [010]. This ordering results in an increase in the b cell repeat compared to duftite and conichalcite.

Sign in / Sign up

Export Citation Format

Share Document