A five-dimensional structural investigation of the misfit layer compound [Bi_0.87SrO₂]₂[CoO₂]_1.82

A structural study of the misfit layer compound [BiSrO][CoO] was carried out from single-crystal X-ray diffraction data. The main results concern both the existence of vacant bismuth sites regularly distributed in the crystal and the setting up of strong bonds between the [BiSrO] and [CoO] subsystems.

Structure of the defect perovskite Ce_1/3NbO₃: a redetermination by electron and neutron powder diffraction

The crystal structure of the defect perovskite Ce_1/3NbO₃ has been re-examined by neutron powder and electron diffraction. The structure is described in P2/m, rather than the previously reported Pmmm. The reduction in symmetry arises from subtle tilting of NbO₆ octahedra, which was not detected by X-ray diffraction data.

High-pressure transformations of NbO₂F

High-pressure synchrotron X-ray powder diffraction data show a cubic to rhombohedral transition for NbO₂F between ambient pressure and 0.47 GPa. At pressures above 18 GPa the structure becomes X-ray amorphous.

Electron density of KNiF₃: analysis of the atomic interactions

Atomic interactions in the perovskite KNiF₃ are examined in terms of the topological analysis of the electron density. Comparison with the classical crystal chemistry description has been performed.

Structure of the alums. I. On the sulfate group disorder in the α-alums

The crystal structures at room (296 K) and low (173 K) temperature of several α-alums have been refined by single-crystal X-ray structure analysis. In all the α-alums studied a disorder of the sulfate group is evident, but the degree of disorder decreases with lowering of the temperature.

Two phases of {[CsPH(η⁶-2,4,6-^tBu₃C₆H₂)]₂(η³-toluene)_0.5}_x: their structures and interconversions

The crystal structure of {[CsPH(η⁶-2,4,6-^tBu₃C₆H₂)]₂(η³-toluene)_0.5}_x has been shown to undergo a reversible solid-state, order–disorder phase transition at 278 (2) K. This transformation results in the doubling of a unit-cell vector, resulting in the doubling of the unit cell of the system.

X-ray diffraction study of the phase transitions of (CH₃)₄NCdCl₃ between 293 and 80 K: a qu­antitative analysis of the ferroelastic domains distribution below 118 K

The X-ray diffraction study of the chain compound [N(CH)][CdCl] in the range 80–293 K is reported. A maximum entropy model for the disorder of the organic groups at room temperature is proposed. A quantitative analysis of the domain structure in the low-temperature phases (stable below 118 and 104 K, respectively) is given.

Packing effects on the geometry of neutral platinum(II) complexes due to solvate molecules: the structure of trans-di­chlorobis(tri­phenylarsine)platinum(II)

Four different solvates of trans-[PtCl₂(AsPh₃)₂] have been obtained and their different geometries are analysed by half-normal probability plots and root-mean-square calculations.

Dimorphism and inclusion compounds of N,N′-di(benzene­sulfonyl)-p-phenylenedi­amine

The crystal structures, phase transformation behavior and crystallization conditions of two polymorphs, as well as two solvates, of N,N′-di(benzenesulfonyl)-p-phenylenediamine are investigated and discussed.

Direct observation of deuterium migration in crystalline-state reaction by single-crystal neutron diffraction. II. 3–1 Photoisomerization of a cobal­oxime complex

Single crystal neutron diffraction analysis of photo-exposed (3-cyanopropyl-d₂^α,α)-[(R)-1-phenylethylamine-d₁₁]bis(dimethylglyoximato-d₁₄)cobalt(III) revealed that the crystalline-state 3–1 photoisomerization of the 3-cyanopropyl group proceeded in two steps, 3–2 and 2–1 isomerizations. Moreover, it was indicated that the 2–1 process was irreversible.

Short N⁺—H⋯Ph hydrogen bonds in ammonium tetra­phenylborate characterized by neutron diffraction

In the neutron diffraction crystal structure of ammonium tetraphenylborate, all N—H vectors of the ammonium ion are involved in short N—H⋯Ph hydrogen bonds with N⋯M(Ph) separations of 3.023 Å. The H-atom displacement parameters are very high.

Hydrogen-bonding behaviour of benzene-1,2,4,5-tetra­carboxylic acid: supramolecular structures of different dimensionality in the 2:1 adducts formed with 4,4′-bi­pyridyl and hexa­methylene­tetramine

Benzene-1,2,4,5-tetracarboxylic acid forms 2:1 adducts with 4,4′-bipyridyl and with hexamethylenetetramine: the 4,4′-bipyridyl adduct contains a chain-of-rings built from (C₁₀H₉N₂)⁺ and (C₁₀H₄O₈)²⁻ ions, while in the hexamethylenetetramine adduct the dominant structural motif is a three-component aggregate [(C₆H₁₃N₄)⁺][(C₁₀H₄O₈)²⁻][(C₆H₁₃N₄)⁺]. In each compound the primary structural motifs are further linked by soft C—H⋯O hydrogen bonds.

Oligosiloxanediols as building blocks for supra­molecular chemistry: hydrogen-bonded adducts with amines form supramolecular structures in zero, one and two dimensions

Oligosiloxanediols HO(SiPh₂O)_nH (n = 2 or 3) form hydrogen-bonded adducts with the following cyclic and cage amines: pyridine, pyrimidine, pyrazine, 2,2′-bipyridyl and hexamethylenetetramine. The structures exhibit molecular aggregation in zero, one or two dimensions by means of O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds.

3,6,9,16,19,22-Hexa­azatri­cyclo[22.2.2.2^11,14]triconta-1(26),11(29),12,14(30),24,27-hexa­ene­, C₂₄H₃₈N₆, as a building block in supramolecular chemistry: structures in two and three dimensions

The adducts of the hexaaza macrocycle C₂₄H₃₈N₆ with 4,4′-sulfonyldiphenol and with 4,4′-biphenol are both salts containing centrosymmetric (C₂₄H₄₀N₆)²⁺ cations which exhibit a variety of different conformations. Extensive hydrogen bonding links the molecular components into sheets in the 4,4′-sulfonyldiphenol adduct and into a three-dimensional framework in the 4,4′-biphenol adduct.

Anisotropic crystal structure distortion of the monoclinic polymorph of acetaminophen at high hydrostatic pressures

Despite the overall decrease in the molar volume with pressure, the structure expanded in particular crystallographic directions. The anisotropy of structural distortion was analysed in detail in relation to the pressure-induced changes in the molecular conformations, to the compression of the hydrogen-bond network and to the changes in the orientation of molecules with respect to each other in the pleated sheets in the structure.

Bulk modulus and high-pressure crystal structures of tetra­kis­(tri­methylsilyl)methane C[Si(CH₃)₃]₄ determined by X-ray powder diffraction

The pressure dependence of the crystal structure of cubic tetrakis(trimethylsilyl)methane C[Si(CH₃)₃]₄ is reported, as determined from high-resolution X-ray powder diffraction at room temperature. The material undergoes three phase transitions up to a pressure of 16.0 GPa.

Molecular analysis of the β-polymorphic form of trielaidin: crystal structure at low temperature

The polymorphism of trielaidin, a trans unsaturated triglyceride, was analyzed and the crystal structure of the β-form was solved at low temperature.

Structure of the inclusion complex of β-cyclodextrin with 1,12-do­decanedioic acid using synchrotron radiation data; a detailed dimeric β-cyclodextrin structure

The quality of the data made possible the location of the H atoms of the dimeric host. Thus, it was revealed for the first time that the host monomers self-assemble through hydrogen bonds of the O3 hydroxyl groups only.

Structure and thermal behavior of the new superprotonic conductor Cs₂(HSO₄)(H₂PO₄). Erratum

Erratum to Acta Cryst. (1999). B55, 937–946.

The weak hydrogen bond in structural chemistry and biology