Crystal Engineering最新文献

X-ray structures of four substituted azobenzene-carboxylic acids have been determined. The crystal packing of the compounds has been analyzed in terms of three main features: parallel placement of the long molecular axes, lateral contacts of (offset) face to face and face to edge types among aromatic rings and hydrogen bonding between carboxy and/or alcoholic hydroxy groups. Hydrogen bonding patterns of the dimer, catemer and expanded dimer types have been found, as well as supramolecular architectures such as chains, rows, sheets and networks.

Thin vacuum sublimed films composed of planar metallophthalocyanines in various proportions have been studied by means of X-ray diffraction. Formation of stable solid solution is proposed from experimental data.

The hybrid density functional/Hartree-Fock methods (DF/HF) UB3LYP and UB1LYP with 6–31 G(d) basis set have been applied to the atomic spin densities and isotropic hyperfine coupling constants (hfcc’s) calculations of the NS, ONS, NN and NO bridged radicals. The calculated hfcc’s are in a good agreement with the experimental values. The results are explained in terms of the molecular geometries and the influence of the substituents.

The previously unknown crystal structure of cyclohexane-1, 3cis, 5cis-tricarboxylic acid (CTA) has been solved from laboratory X-ray powder diffraction data using a simulated annealing algorithm followed by restrained Rietveld refinement (reduced-χ²=8.531 for the refined crystal structure). The structure is triclinic $\text{(}\text{P}\text{1}\text{̄}\text{,}\text{Z=4}\text{).}$ Five out of six of the CO₂H groups in the asymmetric unit form R₂²(8) hydrogen bond motifs with neighbouring CO₂H groups. The motifs connect molecules to form pseudo-hexagonal, ten-molecule rings that fuse into supramolecular buckled honeycomb sheets, which stack and are linked by O–H⋯O hydrogen bonds.

The solid-state packing arrays of ten 4-chloro substituted 2-aminopyrimidines have been examined and the occurrence of N—H—Cl hydrogen-bonding associations in those structures discussed. The ten compounds were 4,6-dichloropyrimidine 1, 2-amino-4-chloro-6-(4-carbamoylpiperidinyl)pyrimidine hemihydrate 2, 2-amino-4-chloro-6-(4-fluorophenylthio)pyrimidine 3, 2-amino-4-chloro-6-(1-phenylethylamino)pyrimidine 4, 2-amino-4-chloro-6-benzylaminopyrimidine $\text{1}\text{6}$ hydrate 5, 2-amino-4-chloro-6-isopropylaminopyrimidine 6, 2-amino-4-chloro-6-(4-(2,3-dimethylphenyl)piperizino)pyrimidine hydrate 7, 2-amino-4,6-dichloro-5-phenylpyrimidine 8, 2-amino-4-chloro-6-dimethylamino-5-phenylpyrimidine 9 and 2-amino-4-chloro-5-phenyl-6-thiomorpholinopyrimidine 10. The single-crystal x-ray structures of 1–4 have been previously reported while the structures of 5–10 are presented in this paper. All packing motifs, except compound 2, exhibit characteristic R₂²(8) hydrogen-bonded 2-aminopyrimidine dimers, to varying degrees of polymerisation. Only compounds 8 and 9 include N—H—Cl interactions, which for compound 8 is a three-center association in addition to a N—H—N interaction.

The crystal structure of the 2:1 1,6-diamino-hexane: para-H-calix-4-arene-25,27-di-phosphonate complex shows a designed encapsulation of a calix-arene dimer within a three-dimensional matrix formed by the diamine molecules, the slight mismatch in the length of the diamine molecules compared to the size of the calix-arene molecule is compensated by chain folding in the diamine

Comparison of conformational features on halogen substitution in 1, 2-diaryl-6-methoxy-1, 2, 3, 4-tetrahydroisoquinolines based on crystal structures indicate that the derivatives with fluorine differ significantly from those of chlorine and bromine. The packing of the molecules in the lattice are nearly identical for derivatives of chlorine and bromine while the fluorine derivatives display C-F...F, C-H...F and C-F...π interactions.

In this contribution, we apply orientation imaging microscopy (OIM) to melt-textured, bulk YBa₂Cu₃O_y (YBCO) samples, which require to perform an automated two-phase analysis. Both YBCO and the green phase Y₂BaCuO₅ (Y-211) are of orthorhombic crystal structures, but with clearly distinct unit cell parameters. We obtain the orientations of the individual crystallites and the misorientation distributions for both YBCO and Y-211. From the obtained data, we calculate the orientation distribution functions.

Epitaxial thin films of RMnO₃ (R=Sm, Eu, Gd, Dy) were prepared using liquid injection MOCVD and studied by XRD. The formation of high-temperature hexagonal polymorphic structure of DyMnO₃ and non-existing-as-bulk hexagonal EuMnO₃, GdMnO₃ and SmMnO₃ (traces) was observed on ZrO₂(Y₂O₃) (111) substrates at 900 °C due to epitaxial stabilization. For the thickness exceeding the critical one the oriented stable perovskite form grew on the hexagonal phase. Parallel deposition on perovskite or non-coherent substrates gave only the stable perovskite phase, epitaxially grown in the former case or oriented in the latter.