Journal of Structural Chemistry最新文献

We propose a new reactive force field of the ReaxFF family. It is based on computations of model structures with a small number of atoms (no more than four) by density functional theory with dispersion corrections. Unlike the existing force fields, our force field provides the correct description of two polymorphs of crystalline oxide B₂O₃ that qualitatively differ in the coordination of boron atoms (triangularly and tetrahedrally coordinated boron atoms). The force field application is exemplified by the derivation of the atomic model of borate glass as a result of imitating the melt cooling process. The model quality is verified by comparing with the reported experimental neutron diffraction data.

Changes in the surface resistance of polyethylene based composite films modified by multi-walled carbon nanotubes (MWCNTs) as a result of laser treatment are studied. Composites containing uniformly distributed nanotubes throughout their volume are prepared by mechanical melt mixing. The composite surfaces are treated by a 1064 nm fiber laser while varying the pulse duration within the 3-120 ns range and the source power within the 0.6-21 W range, so that the surface energy density during processing is 0.1-18.3 J/cm². The influence of laser treatment parameters on the surface structure of composites is studied by scanning electron microscopy and Raman spectroscopy, and the surface resistance is determined using a four-electrode circuit. It is established that the surface resistance of the MWCNT-modified polymer composites can be either decreased by 30-50 times or increased by up to 140 times by tuning the laser treatment parameters.

The crystal structure of allobetulin contained in birch bark as a minor component is determined. Allobetulin crystallizes in the monoclinic system in the space group P2₁, Z = 4. The unit cell parameters are determined as follows: a = 13.2600(9) Å, b = 12.6245(10) Å, c = 15.4702(11) Å; β = 95.425(7)°, V = 2578.1(3) Å³. Allobetulin molecules form a layered crystal packing of supramolecular chains.

The disordered structure of metallic cobalt nanoparticles prepared by the in situ Co₃O₄ and Co_2.95Al_0.05O₄ reduction at different temperatures is characterized. According to the transmission electron microscopy data, individual particles have a stripe contrast indicating that they consist of plate-like domains with different structures. The main feature of the recorded XRD patterns is the anisotropic peak broadening. The Rietveld analysis shows that the model represented by homogeneous particles with hcp and/or fcc structures does not agree well with the experiment. The XRD patterns calculated using statistical models of 1D disordered crystals show that metallic cobalt particles are heterogeneous and consist of plate-like domains with hcp and fcc structures. The dependences of diffraction peak parameters on the thickness of two types of domains are determined; the corresponding calibration graphs are constructed. The phase composition and domain structure parameters are determined as functions of temperature for two series of metallic particles.

One salt and three cocrystals of 2,7-bis(3-(1H-imidazol-1-yl)propyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (L) have been synthesized and reported. 3-Nitro benzoic acid (3NBA) forms salt with L and 4-Nitro benzoic acid (4NBA), 4-hydroxy benzoic acid (4HBA) and 4-amino benzoic acid (4ABA) form cocrystals with L. L forms 1:1 salt with 3-NBA and 1:1 cocrystal with 4-NBA, 4-HBA and 4-ABA, respectively. All the complexes were formed in a warm solvent condition. The solid-state structures were determined by single crystal X-ray diffraction method. Salt 1 exhibits zig zag tetrameric water cluster in the solid-state structure. Various types of supramolecular interactions such as O–H⋯O, C–H⋯O, π⋯π, and C–H⋯π were observed in the X-ray structures and all these interactions guide the formation of 3D supramolecular architecture in the solid state of all the complexes. Besides, the 2D fingerprint (2D-FP) and Hirshfeld surface analysis (HSA) computations were served to prove the 2D network packed crystal lattice interactions.

One of the most studied compound families in the field of crystallography is the Schiff-based compounds. The basis of this research article is a newly synthesized Schiff-base compound. This research aims to investigate the synthesized (E)-3-(5-bromo-3-fluoro-2-hydroxybenzilide amino)benzaldehyde phenol compound using experimental methods. FTIR, UV-Vis and X-ray diffraction methods were used to elucidate the structural properties of the compound synthesized at the end of chemical processes. The structure solution was carried out from the data obtained as a result of X-ray analysis. According to these results, a molecule was formed in the asymmetric cell. The resulting structure has shaped in enol-imine form. The number of molecules in the unit cell was also determined as 4 (Z = 4). According to the results obtained as a result of UV-Vis spectroscopy, the structure revealed that the enol-imine form was dominant. The reasons for this situation were explained.

A new Schiff base, paeonol-[1,4-bis(3-aminopropyl)piperazine], was synthesized for the first time by the condensation reaction of paeonol and 1,4-bis(3-aminopropyl)piperazine through solution method. The product was characterized by the methods of melting point, IR, UV-Vis, fluorescence spectrum, ¹H NMR, elemental and thermal analysis, and its crystal structure was analyzed by single crystal X-ray diffraction method, which indicated that it belongs to triclinic system, (Pbar{1}) group, a = 6.836(14) Å, b = 7.729(17) Å, c = 12.28(3) Å, α = 87.25(2)°, β = 85.53(2)°, γ = 88.74(2)°. The antioxidant and in vitro antibacterial activities of the product were investigated by DPPH method and agar plate diffusion method, respectively. Moreover, the interaction of the product with biomacromolecule DNA was studied by the electronic spectroscopy and viscosity method.

The micro- and nanostructure of the surface of polycrystalline platinum foil (Pt(poly)) after annealing in the O₂ atmosphere at P_O2 = 0.2 bar and 1 bar and T = 1000-1400 K is analyzed by scanning electron microscopy (SEM), powder X-ray diffraction, and electron backscatter diffraction (EBSD). With an increase in the temperature from 1000 K to 1400 K the main part of grains maintains the surface structure close to the (110) face, with the grain surface rearranging from the (311) stair structure to the (100) surface structure, and partially to (111). At these temperatures the values of unit cell parameter a almost do not change in coherence scattering region D and appear to be close to those obtained for initial Pt(poly) (3.925 Å, 25 nm). In the electron secondary and backscatter mode, SEM images in the magnification range from ×100 to ×300k at E₀ of 5 keV, 10 keV, and 20 keV demonstrate the microgranular structure with 10-150 µm (~30 µm) grains and different brightness levels, as well as the 10-100 nm high facet on the grain surface. The neighboring grains with different brightness contain facets of different shapes, sizes, and orientations. After annealing at 1100 K layered structures with a layer thickness up to 100 nm are found on the surface of bright grains while square and rectangular facets with step heights up to 100 nm and 25 nm respectively are observed on the surface of grains with gray and dark levels of brightness. The fixed level of brightness and the structure of facets can be related to the grain surface structure close to (111), (100), and (110) crystallographic planes respectively. At high temperatures (1000-1400 K) and O₂ pressure (~1 bar) the surface can be densely covered with adsorbed O_ads atoms stimulating the release of adsorbed Pt_ads atoms from the bulk to the surface. The high concentration of mobile Pt_ads atoms causes the surface rearrangement involving the formation of facets on the grain surface, which decrease the surface energy and form the stable surface structure.

Molecular and crystal structures of the novel [Pd{(PhO)₂PS₂}₂] complex and the known [Pd{(EtO)₂PS₂}₂] complex are studied. According to the XRD data, [Pd{(RO)₂PS₂}₂] (R = Et, Ph) compounds crystallize in centrosymmetric space groups, and their crystal structures consist of mononuclear complex molecules. The ({{(text{EtO})}_{2}}text{PS}_{2}^{-}) and ({{(text{PhO)}}_{2}}text{PS}_{2}^{-}) ions perform an S,S′-donor bidentate-chelating function leading to the formation of square-planar PdS₄ coordination cores. The electronic absorption spectra of the solutions of these complexes are studied; the influence of the ({{(text{RO})}_{2}}text{PS}_{2}^{-}) ligand structure and the solvent polarity on the observed optical properties of the studied compounds is considered.

A fine crystalline sample of the cubic modification (space group (Iabar{3}), Z = 16) of gadolinium oxide (C-Gd₂O₃) is grown by the solution–melt technique. The single crystal X-ray diffraction analysis performed at 150 K and 298 K reveals a relative increase in the unit cell parameter by 0.08%. The parameter at 300 K is refined by two independent procedures: in Bond’s scheme (a = 10.8152(9) Å, relative error Δa/a = 8·10^–5) and by calibrating the equatorial circumference according to the external reference (a = 10.8145(6) Å, relative error Δa/a = 5.1·10^–5). The values obtained coincide within the experimental error with data for the polycrystalline reference described by the National Bureau of Standards of the United States. The dependence a(T) is studied in the range of 90-490 K with a step of 10 K. Experimental points are described by second degree polynomial a = 10.801 + 2.7·10^–5T + 6.0·10^–8T².