Journal of Structural Chemistry最新文献

The 5-I-8-HqAc (1) and 5,7-I₂-8-HqAc (2) acyl derivatives are prepared by the interaction of 5-iodo-8-hydroxyquinoline (5-I-8-Hq) and 5,7-diiodo-8-hydroxyquinoline (5,7-I₂-8-HqAc) with acetic anhydride at 80 °C. Crystals of these compounds are obtained by the recrystallization from chloroform. The crystal structures of 1 and 2 are determined by XRD, the revealed structural features are discussed. The intermolecular contacts influencing the crystal packing are analyzed; Hirshfeld surfaces are constructed. It is shown that the monoiodide contains short I⋯N halogen bonds, whereas the diiodide contains only short I⋯I contacts.

Molecular and crystal structures of the following bispidine conjugates with stable TEMPO radicals and their synthetic precursors are described for the first time: 4-(2-bromacetoamido)-2,2,6,6-tetramethylpiperidine-1-oxyl (2), tert-butyl-3,7-diazabicyclo[3.3.1]nonan-3-carboxylate (4), 2-(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)acetamide (3,7-diazabicyclo[3.3.1]nonan-3-carboxylate (6) and 2,2′-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonan-3,7-diyl)bis[N-(2,2,6,6-tetramethyl-1-oxyl-piperidine-4-yl)acetamide] (7). These conjugates are prepared by the alkylation of bispidines using TEMPO bromo-derivatives.

The composite based on graphite-like carbon nitride and on yttrium ferrite doped by magnetic ions is a promising photocatalyst for energy consuming reactions such as decomposition of water into hydrogen. This system provides efficient charge separation and most productive light absorption. It is known that photocatalytic activity is affected by the bandgap, specific surface area, and crystallinity. Preparing composites based on graphite-like carbon nitride not only improves the above parameters but also creates additional properties, e.g. magnetic ones due to the doping by the Er³⁺ erbium magnetic ion. It is shown that the magnetization ability of the composite increases and its bandgap decreases from with 2.70 eV to 2.55 eV with increasing degree of ferrite substitution by the Er³⁺ magnetic ion, thus confirming the above hypotheses.

The crystal structure of the molecular iodine complex with 1,2-bis(pyridyl)ethane is determined for the first time by the single crystal X-ray diffraction analysis and the structure of the molecular complex of iodine with 1,2-bis(pyridyl)ethylene is refined. It is shown that regardless of the initial ratio of reagents, only 2:1 complexes are formed in the systems in which ligands act as bridging ones and coordinate two iodine molecules with the formation of molecular complexes I₂LI₂. The structural and energy characteristics of gas phase complexes are calculated by DFT at the M06-2X/def2-TZVP level of theory. On passing from the gas phase to the condensed one, an enhancement of the donor-acceptor interaction is observed in the complexes, which shortens the N–I bond and elongates the I–I bond.

Triple system BaB₂O₄–NaBaBO₃–BaMoO₄ is studied to optimize the growth of barium metaborate crystals (β-BaB₂O₄) - promising materials for nonlinear optics in visible and ultraviolet ranges. Main attention is paid to the phase equilibria and characteristics of crystallization in this system. It is shown that the addition of barium molybdate decreases the solution-melt viscosity, increasing the crystal yield and quality. The key parameters and β-BaB₂O₄ primary crystallization regions are determined by solid-phase synthesis, differential scanning calorimetry, and powder X-ray diffraction techniques. Experiments are performed on growing spontaneous β-BBO crystals. The results obtained demonstrate the promising application of compositions of this system as solvents for β-BBO crystal growth.

A new β-polymorph of hydrazinium salt of [1,2,3]triazolo[4,5-c][1,2,5]oxodiazol-5-oxide is obtained and characterized by single crystal X-ray diffraction. The new form crystallizes in chiral space group P1, as well as the previously described α-polymorph (P2₁). The analysis of crystal packings of polymorphs reveals that they have both cation-anion, anion-anion, and cation-cation contacts. Both forms contain identical H-bonded supramolecular synthons: the (text{R}_{2}^{2}(7)) cation-anion associate and infinite chains of hydrazinium cations formed by translation symmetry. The analysis of the Cambridge Crystallography Data Center shows that similar cationic chains occur in 29% of structures of hydrazinium salts, which indicates their abundance. Explanation is proposed for the crystallization of both polymorphs in non-centrosymmetric space groups, which is based on a combination of 1D and 2D non-centrosymmetric supramolecular synthons: chains and layers. The cohesion energies of polymorphs calculated by the quantum chemical simulation of crystals differ by 0.6 kcal/mol.

The interest in the preparation of nanoscale oxide semiconductors of the In–Ga–Zn–O system is due to the rapid development of printed electronics and solar cells. There are numerous methods for the synthesis of oxide nanomaterials (coprecipitation, sol-gel, self-combustion, etc), including a relatively novel reverse micelle synthesis. In the present study, In₂O₃, Ga₂O₃, ZnO oxides are prepared using self-combustion, and reverse micelle synthesis. The phase composition and morphology of the obtained oxides are described. The average size of their particles is determined from the XRD data, scanning electron microscopy, specific surface area, and dynamic light scattering of the suspensions of prepared powders. It is shown that the finest oxide powders are obtained by the reverse micelle synthesis.

Fractions of single-walled carbon nanotubes separated by diameter and conductivity type are obtained by aqueous two-phase extraction. In the case of the sodium cholate - Pluronic F127 pair of surfactants, the upper fraction is enriched with nanotubes of smaller diameters, while the lower fraction is enriched with nanotubes of larger diameters. In the case of the sodium cholate - sodium dodecylsulfate pair, the upper fraction is enriched with semiconducting nanotubes, while metallic nanotubes dominate in the lower fraction. The effect of the surfactant concentration on the purity of the fractions separated by conductivity type is studied. The concentrations of polymers and surfactants used in the one-step separation are found to provide the 97.6% purity of the metallic fraction and more than 99.9% of the semiconductor fraction.

Europium(III), terbium(III), samarium(III), and gadolinium(III) coordination compounds with 3,4-dichloroisothiazole-5-carboxylic acid of general formula [Ln(H₂O)₂L₂(OAc)]_n are obtained. The complexes are characterized by a number of physicochemical techniques: elemental analysis, powder and single crystal X-ray diffraction (XRD), and IR spectroscopy. According to the single crystal XRD data, these complexes have the polymeric structure formed by the bridging function of acetate ions. In the case of the deprotonated isothiazole derivative, only oxygen atoms of the carboxyl group participate in coordination (two coordination modes: bidentate cyclic or monodentate). When studying the photoluminescent properties of the obtained europium(III) and terbium(III) complexes, it is found that the quantum yield of terbium(III) compounds exceeds 9 times this parameter for the europium(III) complex. The excited state lifetimes are in the millisecond range.

The paper presents a molecular dynamics simulation of a three-dimensional fully silicified form of mordenite filled with a mixture of water and glycerol molecules at five different component ratios (20:1, 8:1, 4:1, 2:1, and the fully hydrated form). For comparative analysis, bulk phases of these mixtures are simulated with the same molecule ratios. Based on the simulation data, radial distribution functions between water atoms and glycerol molecules are calculated and changes in the local ordering of guest molecules in mordenite pores are described. The effect of spatial constraints on the conformations of the glycerol molecule and on translational and rotational mobilities of the mixture components are considered in detail.