On Some Features of X-Ray Powder Patterns of OD Structures

X-ray powder data of OD crystals may be misinterpreted, if the OD character of the substance is not taken into account. For some typical OD structures, problems in connection with their identification and the determination of lattice parameters are discussed. Some features of X-ray powder patterns, which — on principle — are relevant to all OD crystals are summarized.     

X-Ray Crystal Structures of Two Monopentamethylcyclopentadienylhafnium(IV) Complexes

Crystallography Reports - The crystal structures of two monopentamethylcyclopentadienylhafnium(IV) derivatives have been determined by X-ray diffraction analysis. The [Hf(η5-C5Me5)Cl3] complex...     

Synchrotron White Beam X-Ray Topography Characterization of Defect Structures in 2,10-Undecanedione/Urea Inclusion Compounds

Abstract

The defect structure of a crystal of the urea inclusion compound (UIC) of 2,10-undecanedione was investigated using Synchrotron White Beam X-ray Topography. X-ray transmission topographs recorded from different regions show that the crystal is divided into several twin domains. Each region in the crystal is revealed on the topographs by orientation contrast arising from the mutual misorientation of adjacent regions. Using a combination of pinhole Laue pattern analysis and topographic orientation contrast analysis, the twin operation was determined to be consistent with an approximately 60° rotation about the orthorhombic c-axis. Possible twin boundary structures are also presented. Other defects such as dislocations and inclusions are also characterized.     

Crystal structure and thermal analysis of an inclusion compound of a chiral sexipedal host with 1,4-dioxane

The crystal structure of the 16 inclusion compound of the chiral host, hexakis[3-o-chlorophenyl)-3-(phenyl-3-hydroxy-1-propynyl]benzene with 1,4-dioxane shows that both O–H...O and C–H...O hydrogen bonds are used to bind the guests.     

The X-ray Structures of Sulfones

Abstract  

The X-rays structures of diphenyl sulfone 1, bis(3-aminophenyl) sulfone 2, bis(4-nitrophenyl) sulfone 3, 2-nitrophenylphenyl sulfone 4, benzylphenzyl sulfone 5, 4-nitrobenzylphenyl sulfone 6, 4-methylphenylbenzyl sulfone 7, dibenzyl sulfone 8, benzylisopropyl sulfone 9, and methylacetate,ethyl sulfone 10, are reported. B3PW91 DFT calculations were performed on selected sulfones for comparison. The S = O distances in these compounds range from 1.392(5) to 1.463(3) Å and S–C bond distances range from 1.743(7) to 1.790(3) Å. The C–S–C bond angles vary from 101.1(3)° to 106.80(14)° and the O–S–O bond angles vary from 116.7(2)° to 120.61(8)°. Using data obtained here and comparison with published structural data no evidence was found for para substituents on aryl groups influencing S–O bond distances, however, small changes on S–C bond distances were noted. Additionally, if the sulfur is flanked by an alkyl group the S–C distance is slightly larger than when it is flanked by an aryl group. Most of the sulfone compounds studied here display intermolecular soft hydrogen bonding interactions which influence their solid state packing. Furthermore, in dialkyl sulfone compounds these interactions appear to be strong enough to overcome conformational barriers calculated to be ca. 6 kJ mol⁻¹.     

On the Application of Direct Methods in X-Ray Structure Analysis: Survey on Number and Kind of Solved Acentric Equal Atom Structures

A statistical analysis of all acentric equal atom structures solved by direct methods and reported in Acta Crystallographica from January 1968 to November 1978 has been carried out. The most frequently applied direct methods programs are the MULTAN, SAP and SHELX. About 80% of all considered structures belong to the space groups P2₁2₁2₁ and P 2₁. Problems with direct methods can arise if the number of the nonhydrogen atoms per asymmetric unit is greater then about 40 and/or the space group belongs to a category in which the definition of the enantiomorph is difficult.     

The Syntheses and Crystal Structures of Metronidazole-derived Compounds

Abstract Metronidazole (MET-OH), widely used as an antibacterial agent, is found to have some side effects on human bodies. Due to these disadvantages, people have been looking for its modification compounds for substituents. In this article, four MET-OH derivatives were designed, prepared, and structurally characterized by single crystal X-ray diffraction. These compounds are MET-OTs (1), MET-Br (2), MET-Cl (3), and MET-I (4). X-ray structure analyses revealed that, 1 crystallized in the monoclinic system with space group P2 ₁ /c, with a = 16.1178, b = 7.5473, c = 13.4161 ?, V = 1520.3 ?³, β = 111.3210^o and Z = 4. 2 crystallized in the monoclinic system with space group P2 ₁ /c, with a = 12.079, b = 11.089, c = 6.380 ?, V = 847.1 ?³, β = 97.57^o and Z = 4. 3 crystallized in the monoclinic system with space group P2 ₁ /c, with a = 12.098, b = 11.007, c = 6.295 ?, V = 830.3 ?³, β = 97.886^o and Z = 4. 4 crystallized in the triclinic system with space group P1, with a = 6.192, b = 7.740, c = 10.001 ?, V = 457.9 ?³, α = 89.073, β = 86.903, γ = 73.097^o and Z = 2. Index Abstract In this article, metronidazole-derived compounds were prepared and structurally characterized by single crystal X-ray diffraction      

Supramolecular Interactions in the Adduct of Di-triethylammonium,tetrachlorobenzene-1,4-dicarboxylate and tetrachlorobenzene-1,4-dicarboxylic acid

Abstract  The adduct of di-triethylammonium, tetrachlorobenzene-1,4-dicarboxylate and tetrachlorobenzene-1,4-dicarboxylic acid, i.e. {2(C₂H₅)₃NH⁺ C₈Cl₄O₄²⁻ H₂C₈Cl₄O₄}, crystallizes in triclinic, P-1 with cell dimensions of a = 8.5080(5) ?, b = 8.9789(6) ?, c = 12.5212(8) ?, α = 93.301(1)°, β = 109.107(1)°, γ = 103.565(1)°, V = 869.2(1) ?³ and Z = 2. The C₈Cl₄O₄²⁻ and H₂C₈Cl₄O₄ moieties link with each other by O–H···O along c axis, C–Cl···O=C along b axis and C–Cl···Cl–C along a axis to form the 3D framework of the crystal structure. The (C₂H₅)₃NH⁺ cations reside in the cavities of the 3D framework via various intermolecular interactions such as N–H···O, C–H···O and C–H···π. Index Abstract  In the title compound, tetrachlorobenzene-1,4-dicarboxylates and tetrachlorobenzene-1,4-dicarboxylic acids form 3D framework by hydrogen bonds and halogen bonds, and triethylammoniums reside in the voids of the framework via supramolecular interactions .     

Liquid crystalline G phase of self assembled donor-acceptor molecules by intermolecular hydrogen bonding

The interaction with donor p-n-alkylbenzoic acid and acceptor nonyl-p-hydroxy benzoate molecules was studied. The likely association of these molecules to complexes is studied by intermolecular hydrogen bonding. The textures are observed by polarizing optical microscope with corresponding transitions confirmed by differential scanning calorimetry. The molecular complexes exhibited enantiotropic crystal G phases in both heating and cooling cycles. The relevant functional groups C═O, C-O and OH in formation of molecular complexes are attributed with spectral shifts in infrared spectra and further with absorption studies. The proton NMR studies convinced the structural aspects of hydrogen bonded structure. Crystal parameters were studied with powdered X-ray diffraction. The results show that constituent molecules self organize through intermolecular hydrogen bonding in the formation of crystal G phase.     

Cu(II) Compounds with Pyrimidine-Based Chelating Ligands,Bridged by a Flexible Alkyl Spacer: Synthesis,Characterisation and X-Ray Structures of Methoxide-Bridged Dinuclear-Based Species

Abstract  The synthesis and full structural characterisation is described of 3 dinuclear-based Cu(II) compounds bridged by methoxide anions, and flexible linear bis(pyrimidine)-α,ω-diaminoalkane ligands. The structures are dinuclear based in all cases, in which the bis(pyrimidine)diaminoalkane ligand chelates to 2 Cu(II) ions in the same dinuclear unit (N–C–C–C–C–C–N linker), or to two different dinuclear units (with the short N–C–C–N linker), thereby generating a polymeric chain. The magnetic exchange in the compounds is dominated by the alkoxido-bridged ligands, which generate a very strong antiferromagnetic coupling between the Cu(II) ions, resulting in diamagnetism at room temperature and below, and EPR silent behaviour. Index Abstract  Dinuclear-based Cu(II) compounds with pyrimidine-based chelating ligands flexible linear bis(pyrimidine)-α,ω-diaminoalkane ligands are described, bridged by methoxide anions. The structures are dinuclear based in all cases, with the ligand chelating to 2 Cu(II) ions in the same dinuclear unit (N–C–C–C–C–C–N linker), or to 2 different dinuclear units (with short N–C–C–N linkers). The very strong antiferromagnetic magnetic exchange in all compounds is caused by the alkoxido-bridged ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Influence of Interstitials and Growth Conditions on the X-Ray Colorability of Synthetic Quartz Crystals

The saturation colorability of quartz crystals depends not only on the contamination of the material but also on the regarded growth sector. But even in the same sector the colorability varies locally. Investigations of crystals with induced growth striations and defined local growth rate showed that the dependence of the colorability on the growth conditions is very complex. The growth rate to colorability characteristics may have positive or negative slopes regarding e.g. —x-or z-sections. Optical investigations of —x-sections prove that under certain circumstances light and/or dark striations may occur or even uncolorable regions may be observed, althought the contamination is sure. We explain this by the interaction of the coloration centres with interstitials. That effect might be of importance for the evaluation of the impurity by means of the coloration of natural or synthetic quartz crystals.     

The Use of X-Ray Diffraction in the Study of Thermotropic Liquid Crystals With Rod-Like Molecules

The paper first reviews briefly the various kinds of information that can be obtained from x-ray diffraction studies. Next, specific examples are given from the literature of determinations of each of the different kinds of data.