Journal of Structural Chemistry最新文献

The influence of hydrothermal synthesis conditions on the structural characteristics and photoelectrochemical properties of synthesized materials are studied using bismuth nitrate (Bi(NO₃)₃) and thiourea (CS(NH₂)₂) as precursors of bismuth oxysulfide (Bi₂O₂S). The influence of the following synthesis parameters is considered: solution′s pH, alkali type, time and temperature of the hydrothermal treatment, posttreatment conditions. The synthesized materials are characterized by powder XRD analysis, UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, thermogravimetric analysis, and photoelectrochemical methods to determine the photocurrent and flat-band potential. The conducted physico-chemical study reveals the importance of using excess alkali for formation of the oxysulfide phase, dependence of particle size on the time of hydrothermal treatment, and the influence of additional calcination conditions on the presence of photoactive surface defects.

Crystal structures of one imidazolinone based ligand L and one perchlorate salt (Salt 1) and one nitrate salt (Salt 2) of L have been reported. All the compounds were characterized with different spectroscopic tools such as NMR spectroscopy, mass spectroscopy and IR spectroscopy. The detailed elucidation of their solid-state structures was achieved through single crystal X-ray diffraction, offering comprehensive insights into their molecular arrangements. In their crystal structure, the asymmetric unit of L contains the whole molecule while in salt 2 the asymmetric unit contains one protonated L (HL⁺) and one nitrate ion. The crystallographic asymmetric unit of salt 1 comprises a solitary diprotonated L (H₂L²⁺) ion. Various non covalent interactions including bi and trifurcated intermolecular motifs are observed in case of L and in salt 1 while unique rare pentafurcated C–H⋯O/N–H⋯O intermolecular motifs are observed in salt 2 which was further supported by computational studies. Besides these interactions, C–H⋯O, C–H⋯π and O⋯π intermolecular interactions are also present in the crystal structures. UV-Vis absorption spectra show absorption of all of them around 420 nm. Steady state fluorescence spectra show that all the three compounds emit blue light. Hirshfeld surface analysis and 2D-FP analysis were used to quantitatively explore the noncovalent interactions responsible for crystal packing.

New cobalt(II) and copper(I) complexes, [CoCl₂(L¹)₂] (1) and [CuClL²(Ph₃P)₂]·CH₃CN (2), where L¹ = 1-(4-bromobenzylidene)thiosemicarbazide, L² = 1-(2,4-dichlorobenzylidene)thiosemicarbazide, PPh₃ == triphenylphosphine, were synthesized and characterized by elemental analysis and physico-chemical method, as well as single crystal X-ray diffraction. The complexes were also tested for their urease inhibitory properties. The cobalt complex has strong activity (IC₅₀ = 5.7 μM). Enzymatic kinetics research suggested that the cobalt complex is a non-competitive urease inhibitor.

A method of preparing tomographic images of multielectron (molecular) systems is theoretically substantiated. According to the current concepts, spin-spin coupling between resonating nuclei manifested in the NMR spectra is due to the electron motion inside the space of the molecule. Thus, it can be assumed that the interaction-containing space corresponds to the molecule′s size. Modern high-resolution NMR spectrometers allow studying low-energy (<1 Hz) interactions. From the experimental viewpoint, the inherently incorrect J → F(r, θ, φ, E) inverse problem should be solved. At the first stage, points of space occupied by some molecular (multielectron) system can be visualized using spin-spin coupling constants. At the next stage, tomographic images can be obtained from the calculated “exact” wave functions. This requires quite powerful computers and corresponding software programs. We propose a block diagram of a device for implementing a theoretically substantiated fundamentally new method of retrieving information about the spatial structure of substance at the molecular level.

The influence of weak microwave and ultraviolet radiation on the structure formation of zirconium oxyhydroxide prepared at different nucleation and growth rate ratios is studied. Thermal behavior, heat-induced phase changes, and morphology of the synthesized samples are studied by thermogravimetry, differential scanning calorimetry and mass spectrometry of gaseous thermolysis products, as well as by powder XRD and high-resolution transmission electron microscopy. It is established that such radiation promotes the decrease of the temperature of amorphous zirconium dioxide crystallization, formation of well-crystallized zirconium dioxide nanoparticles and can be therefore be used in the directed synthesis of nanocrystalline materials based on such compounds. The irradiation effect is most pronounced in the case of long-term hydrolysis of aqueous zirconium oxychloride.

A series of zinc complexes with 3-arylidene-1-pyrrolines and acetic or trifluoroacetic acid anions is obtained. Molecular and crystal structures are investigated and non-covalent interactions are analyzed for all synthesized compounds. The molecular structures of the complexes are shown to be similar. Minor differences are due to non-covalent interactions whose nature and amount is determined by the occurrence of active centers in the ligand compositions. It is revealed that for 3-arylidene-1-pyrroline complexes the main structure-forming interaction is π⋯π interactions of different topologies. The exceptions are only the crystals of compounds containing groups being donors of hydrogen bonds (e.g., hydroxyl groups), which results in the formation of hydrogen-bonded associates that in turn form the crystal packing mainly by π⋯π interactions. The molecular docking-modeling with the HER2 human receptor kinase domain indicates that the obtained complexes can bind with HER2 with an energy gain comparable with that for the previously studied copper trifluoroacetate complexes with 3-arylidene-1-pyrrolines. This fact suggests that they are effective in anticancer therapy.

The effect is studied of modifying dopants M = Fe, Cr, Ni, and Ga on the physicochemical and catalytic properties of copper-manganese catalysts for low-temperature CO oxidation under dry and wet reaction conditions. By means of X-ray diffraction and X-ray photoelectron spectroscopy the phase compositions and structural bulk characteristics of all catalysts before and after tests, as well as their surface compositions and states, are determined and compared. The catalysts are modified at the stage of preparing CuMn_1–xM_xO₂ nanocrystallites of the crednerite structure type with partial substitution at manganese positions. The final catalyst is obtained directly under the reaction conditions by pre-treatment at 350 °C that results in the phase transition of crednerite particles to cubic spinel structure (Cu,Mn,M)₃O₄. It is found that under dry conditions only nickel and gallium modifications substantially increase the specific rate of low-temperature CO oxidation whereas in the presence of water vapor, all CuMn catalysts studied are deactivated regardless of the nature of the modifying dopant.

This work discusses a mesoscale computer model based on the dissipative particle dynamics method. The model is aimed at studying the processes occurring at the initial stage of forming polyacrylonitrile-based chemical fibers by dry-jet wet spinning method. The model represents the appearance of structural inhomogeneities on the surface of a polymer solution jet as it passes through the air gap between the spinneret and the coagulation bath. According to the calculation results, a high-density polymer layer appears on the surface of the forming fiber the as a result of solvent evaporation, and this layer can significantly affect the polymer′s coagulation rate. The estimations of the layer thickness show that a ~0.5 µm thick layer is sufficient for making the spinning solution jet maintain in air for ~0.6 s. The obtained results can be useful in tuning the technological process of dry-jet wet method of chemical fiber spinning.

For the first time, the dependence of luminescent properties on temperature was investigated for the compound TbAl₃(BO₃)₄ with a huntite-like structure. Samples synthesized by the solution combustion synthesis (SCS) and grown from the flux were used for the study. There are significant differences in the thermal quenching behavior between the two types of materials. It was shown that the onset of thermal quenching strongly depends on the synthesis method: powders prepared by SCS exhibit higher luminescence efficiency at lower temperatures compared to flux-grown single crystals. The branching ratios for the ⁵D₄ to ⁷F₅ transition exceeded 50% under certain conditions, highlighting the potential of material for laser applications.

The existence of zero-dimensional layered bismuth(III) iodide hollow nanostructures is predicted; their models are constructed. Thermodynamic stability and electronic properties of BiI₃ fullerenes with tetrahedral, octahedral, and icosahedral morphologies and the number of atoms up to ~1000 are studied by the density functional theory method. The strain energy of BiI₃ fullerenes decreases with their increasing size, tetrahedral and octahedral morphologies being the most stable ones. Independently of the size and morphology, all the considered BiI₃ fullerenes are semiconductors with a bandgap smaller by 0.6-1.9 eV than that of the BiI₃ monolayer.