Acta crystallographica Section B, Structural science, crystal engineering and materials最新文献

Diacetylenedisalicylic acid is a new rigid linker molecule, capable of forming strong chelate bonds with metal cations. Its monosubstituted salts with dimethylamine and sodium form 1D and 2D coordination polymers, whose structures were solved from single crystals, along with the dimethyl ester of diacetylenedisalicylic acid. The structure of the dimethyl ester is characterized by a dense co-facial π-stacking of molecules with a dominance of van der Waals interactions between the stacks. The angle between the stack direction and the butadiyne groups does not meet the Enkelmann criterion for polymerization in a crystal. In contrast to the dimethyl ester, both salts have a rigid framework with channels filled with disordered solvent molecules. Photoluminescence spectra of the acid and its dimethyl ester have been studied. Thermal analysis of the acid confirms its high thermal stability to 286°C. The acid and its dimethyl ester are prone to polymerization on further heating followed by 50-52% mass loss, forming an amorphous carbon residue at 1000°C.

The interaction of intense synchrotron radiation with molecular crystals frequently modifies the crystal structure by breaking bonds, producing fragments and, hence, inducing disorder. Here, a second-rank tensor of radiation-induced lattice strain is proposed to characterize the structural susceptibility to radiation. Quantitative estimates are derived using a linear response approximation from experimental data collected on three materials Hg(NO₃)₂(PPh₃)₂, Hg(CN)₂(PPh₃)₂ and BiPh₃ [PPh₃ = triphenylphosphine, P(C₆H₅)₃; Ph = phenyl, C₆H₅], and are compared with the corresponding thermal expansivities. The associated eigenvalues and eigenvectors show that the two tensors are not the same and therefore probe truly different structural responses. The tensor of radiative expansion serves as a measure of the susceptibility of crystal structures to radiation damage.

2-Iminocoumarin-3-carboxamide (2-imino-2 H-chromene-3-carboxylic acid) is a perspective compound for use in the pharmaceutical industry. This compound crystallized from several solvents as two concomitant polymorphic forms. The monoclinic polymorph, crystallized initially, is formed due to strong N-H...O hydrogen bonds, weak C-H...O and C-H...N(π) hydrogen bonds, and stacking interactions of `head-to-head' type. The triclinic polymorphic form obtained due to slow evaporation of the same solution is formed due to only strong intermolecular interactions, N-H...O hydrogen bonds of two types, and stacking interactions of two types. Analysis of pairwise interaction energies showed that the monoclinic structure is columnar while the triclinic one is layered. Calculations in a periodic approximation of their lattice energies confirmed that the monoclinic polymorphic crystals are metastable as compared to the stable triclinic polymorph. Further quantum chemical modeling of possible structure deformations proved that both concomitant polymorphs can not be transformed into a new polymorphic form under external influence.

This work analyzes the effects of a nearby Hf or Zr dopant on the electron density trapped at an oxygen vacancy site. The two metals are among the dopants used to achieve thermoluminescence and energy storage in phosphors based on cubic lutetium oxide (c-Lu₂O₃). The presence of oxygen vacancies is anticipated in those phosphors. If the dopant is located outside the immediate surroundings of the vacancy site, the resulting optical trap depth is similar to that of the isolated oxygen vacancies (1.6-1.7 eV versus 1.7 eV). If the dopant is one of the four metal cations surrounding the vacancy site, the corresponding trap depth is 2.0-2.1 eV. Using time-dependent density-functional theory calculations, it was found that the excitation of the vacancy-trapped electrons can take two forms: a local excited state at the vacancy site can be formed, or an electron transfer to Hf might occur. With charge compensation in mind, several structures with three defects were analyzed: the dopant cation, the vacancy and an interstitial oxygen (Hf/Zr plus a Frenkel pair). These last two systems with the dopant in a +4 oxidation state and a single electron trapped at the vacancy site correspond to zero total charge, while another electron can be trapped. The vacancy site is expected to trap the electron, not the dopant. The composite defects of the dopant and Frenkel pair are thus considered the most likely electron traps in cubic Lu₂O₃:Hf and cubic Lu₂O₃:Zr.

The crystal structure of potassium guaninate hydrate, K⁺·C₅H₄N₅O^-·H₂O, was studied in the pressure range of 1 atm to 7.3 GPa by single-crystal diffraction using synchrotron radiation and a laboratory X-ray diffraction source. Structural strain was compared to that of the same salt hydrate on cooling, and in 2Na⁺·C₅H₃N₅O^2-·7H₂O under hydrostatic compression and on cooling. A polymorphic transition into a new, incommensurately modulated, phase was observed at ∼4-5 GPa. The transition was reversible with a hysteresis: the satellite reflections disappeared on decompression to ∼1.4 GPa.

The co-crystal of phenazine and chloroanilic acid is known to display paraelectric properties at room temperature. It shows a paraelectric to ferroelectric phase transition at 253 K and has an incommensurately modulated ferroelectric phase below 137 K. High-resolution synchrotron X-ray data were collected at 160 K to model the experimental electron-density distributions, and derived topological properties from the electron density were used to quantify the weak interactions responsible for the origin of the ferroelectric phase. The structure and non-covalent interactions are analysed using Hirshfeld surfaces and energy frameworks. The topological properties, energies, atomic charges and molecular electrostatic potential surfaces are determined from the experimental data, further supported by theoretical calculations. The results from the ferroelectric phase are compared with the paraelectric phase. Although the structural descriptions indicate neutral phenazine and chloroanilic acid molecules in the ferroelectric phase, the topological properties of the electron density indicate a considerable amount of proton transfer in the O-H...O hydrogen bond. Indeed, the displaced H atom in the O-H...O hydrogen bond suggests a mixed covalent/polar nature of chemical bonding. Subtle changes in the chemical bonding and proton-transfer pathways could be detected from the high-resolution electron-density studies.

K₃FeTe₂O₈(OH)₂(H₂O)₂ was synthesized under hydrothermal conditions from Te(OH)₆, FeSO₄·7H₂O and 85 wt% KOH in a 1:2:6 molar ratio. The crystal structure is built of a triperiodic network. One disordered water molecule per formula unit is located in a channel and can be partially removed by heating. Systematic one-dimensional diffuse scattering indicates a polytypic character, which is best described by application of the order-disorder theory. The major polytype is monoclinic with pseudo-orthorhombic metrics. It is interrupted by fragments of an orthorhombic polytype. The diffraction intensities are analyzed using structure factor calculations.

The structure of (R)-rasagiline mesylate [(R)-RasH⁺·Mes^-], an active pharmaceutical ingredient used to treat Parkinson's disease, is presented. The structure was determined from laboratory and synchrotron powder diffraction data, refined using the Rietveld method, and validated and optimized using dispersion-corrected DFT calculations. The unit-cell parameters obtained in both experiments are in good agreement and the refinement with both datasets converged to good agreement factors. The final parameters obtained from laboratory data were a = 5.4905 (8), b = 6.536 (2), c = 38.953 (3) Å, V = 1398.0 (4) ų and from synchrotron powder data were a = 5.487530 (10) Å, b = 6.528939 (12) Å, c = 38.94313 (9) Å, V = 1395.245 (5) ų with Z = 4 and space group P2₁2₁2₁. Preferred orientation was properly accounted for using the synchrotron radiation data, leading to a March-Dollase parameter of 1.140 (1) instead of the 0.642 (1) value obtained from laboratory data. In the structure, (R)-RasH⁺ moieties form layers parallel to the ab plane connected by mesylate ions through N-H...O and C-H...O hydrogen bonds. These layers stack along the c axis and are further connected by C-H...π interactions. Hirshfeld surface analysis and fingerprint plot calculations indicate that the main interactions are: H...H (50.9%), H...C/C...H (27.1%) and H...O/O...H (21.1%).

By employing time-dependent density functional theory for solid-state chemistry, the research presented by Andrii Shyichuk [Acta Cryst. (2023), B67, 437-449] significantly contributes to the understanding of electron/hole traps in doped materials.

Four new coordination polymers, including 1D, 2D and 3D structures, were synthesized via a hydrothermal method using Cd²⁺/Zn²⁺/Cu²⁺ metal salts as nodes. These polymers were formed through self-assembly of four different dicarboxylic acid ligands, namely adamantane-1,3-dicarboxylic acid (H₂adc), glutaric acid (H₂glu), 5-hydroxyisophthalic acid (H₂hip) and fumaric acid (H₂fum), in conjunction with the auxiliary ligand [1,4-bis(pyridin-4-ylmethyl)piperazine (bpmp). The corresponding formulae are [Cd₃(adc)₂(bpmp)Cl₂(H₂O)₂]_n (1), {[Cd₂(glu)₂(bpmp)₂(H₂O)₂]·8H₂O·2CH₃OH}_n (2), [Zn(hip)(bpmp)(H₂O)]_n (3) and [Cu(fum)(bpmp)(H₂O)₂]_n (4). Single-crystal X-ray diffraction studies revealed that the Cd²⁺ centers in complex 1 all adopt a six-coordinate mode but two distinct {CdO₂N₂Cl₂} and {CuO₅Cl} units. The 3D network of complex 1 can be simplified to a binodal (4.6)-connected underlying net with the point symbol (3·4²·5·6²)⁴(3²·6²·7²·8⁸·10). Each Cd²⁺ cation in complex 2 adopts a seven-coordinate {CdO₅N₂} center, forming an asymmetric pentagonal bipyramidal coordination. Its stacking structure is formed by the interaction of hydrogen bonds between 2D supramolecular layers, with the adjacent layers exhibiting mirror symmetry. Each Zn²⁺ ion in complex 3 displays a {ZnO₃N} four-coordinate unit. Its stacking structure is formed by one-dimensional [Zn(hip)(bpmp)(H₂O)]_n chains connected through hydrogen bonds. On the other hand, complex 4 features a Jahn-Teller distorted {CuO₄N₂} octahedral coordination. Subsequently, the thermal stability of these complexes was investigated. The solid-state fluorescence spectroscopy was employed to analyze complexes 1, 2 and 3. Additionally, a Hirshfeld surface analysis was performed on complex 3.