Journal of Structural Chemistry最新文献

Two new complexes of nickel(II) benzoylhydrazone 2-(N-tosylamino)benzaldehyde (H₂L) with additional heterocyclic donor ligands L¹ = 2,2′-bipyridine and L² = 1,10-phenanthroline are synthesized. Structures and compositions of the obtained compounds are determined by elemental analysis, ¹H NMR, and IR techniques. Crystal and molecular structures of the Ni(II) complexes are determined by single crystal X-ray diffraction. The adducts are shown to have dimeric structures: Ni₂L₂L¹(CH₃OH) and Ni₂L₂L²(CH₃OH). In both adducts, one of nickel(II) ions is in a distorted square-planar environment while another is in the octahedral environment due to additional coordination of 2,2′-bipyridine or 1,10-phenanthroline and a methanol molecule. The biological activity of the complexes is studied. It is found that both adducts exhibit the protistocidal activity against Colpoda steinii, with Ni₂L₂L¹(CH₃OH) being twice less active and Ni₂L₂L²(CH₃OH) being twice more active than the chloroquine reference.

The work considers the synthesis of thin films of vanadium oxides by plasma-enhanced atomic layer deposition (PE-ALD). A procedure is proposed to obtain thin films of amorphous vanadium dioxide. The hydrogen effect on the composition of deposited films during PE-ALD is analyzed. Hydrogen is shown to decrease the vanadium oxidation state in the deposited films and amorphize the structure. The mechanism of amorphization is discussed. The application of plasma enhancement promotes the hydrogen reducing activity. Calcination of films consisting of a mixture of vanadium oxides in hydrogen plasma enables the preparation of films of solely amorphous vanadium dioxide.

The key findings and significance of this report is the synthesis and characterization of two mononuclear nickel(II) complexes, [Ni(L)(val)].0.5MeOH (1) and [Ni(HL)₂](ClO₄)₂ (2) derived from a tetradentate Schiff base ligand HL and two different nickel(II) salts. These complexes were thoroughly characterized using techniques such as elemental analysis, IR spectroscopy, single crystal X-ray diffraction, and Hirshfeld surface analysis. The results revealed distinct coordination modes of the ligands in the complexes, leading to different non-covalent interactions and packing arrangements in their crystal structures. Specifically, complex 1 exhibited tetradentate coordination in addition to the bidentate o-vanillinate ligand, while complex 2 featured tridentate coordination with the zwitterionic form of the ligand. Hirshfeld surface analysis provided insights into the relative contributions of various intermolecular interactions, highlighting the significance of hydrogen bonding, tetrel bonding, and other non-covalent interactions in stabilizing the crystal structures. In general, this study contributes to the differences in structural integrity on variation in metal salts and the understanding in depth of various non-covalent interactions using Hirshfeld surface analysis tool.

A layered compound of molybdenum disulfide with cationic molecules of the medication lamivudine (Lam) is prepared by the monolayer dispersion method. The structure of this compound is determined by modeling the powder XRD pattern using the supercell method followed by a quantum chemical optimization of the obtained structural model using the electron density functional method. The AIM (Atoms in Molecules) topological analysis of the calculated electron density distribution reveals interatomic bonding interactions between Lam and MoS₂ monolayers. The energies of these interactions are estimated. It is shown that the interaction is mainly due to the NH⋯S hydrogen bonds between Lam and the sulfide layer and that these bonds determine the position of molecules in the MoS₂ interlayer The features of bonding between Lam and the surface of MoS₂ monolayer particles are determined using a computational model of exfoliated compound.

An aroylhydrazone compound N’-(2-hydroxy-4-methoxybenzylidene)-4-nitrobenzohydrazide (HL) was prepared. Reaction of the aroylhydrazone compound with zinc iodide afforded a dinuclear zinc(II) complex [Zn₂I₂L₂]∙2DMF. The aroylhydrazone compound and the zinc complex were characterized by CHN elemental analyses and infrared spectroscopy. Detailed structures are further confirmed by single crystal X-ray determination. The Zn atom in the complex is in square pyramidal coordination, with the phenolate O, imino N and carbonyl O atoms of one L ligand, and the phenolate O atom of the other L ligand in the basal plane, and with one I ligand at the apical position. The crystal structures of the aroylhydrazone and the zinc complex are stabilized by hydrogen bonds. The two compounds have been tested for their Jack bean urease activity. As a result, the zinc complex has effective activity with IC₅₀ value of 1.7 ± 0.3 μmol/L.

We report a comparative crystal chemical analysis of volatile homoligand complexes of Co(II), Ni(II), Cu(II), Pd(II), and Pt(II) with β-ketoimines utilized as precursors in the preparation of oxide and metal film coatings for various purposes using chemical vapor deposition. The crystal structures and intermolecular interactions of β-ketoiminates with the general formula M(L)₂ (L = (R1-C(O)CH-C(N-R3)-R2)₂; R1, R2 = CH₃, CF₃, C(CH₃)₃, C(OCH₃)(CH₂)₂ in various combinations; R3 = H, CH₃) are studied.

The key to the modification of the properties of carbon fibers is to understand how to control the structure of polyacrylonitrile-based precursors. Results of a mesoscale modeling of the structure formation processes in a mixture of polyacrylonitrile, dimethyl sulfoxide, and water (good and poor solvents for polymers) are reported. The system′s composition is chosen using the composition of precursor fibers at the later formation stages under coagulation bath conditions. All calculations are performed using the dynamic density functional theory. The proposed model considers effects caused by changes in the system composition, carbon nanotube filler, temperature, and shear flow. It is shown that the polymer structure can be significantly changed by varying the amount of water in the system (determined by the coagulation bath composition) and by introducing a carbon filler.

Results are reported about the molecular mechanics simulation of the structures of carbon–nitrogen solid solutions obtained by pyrolysis of a molten mixture of melamine with 50-100 wt.% high-temperature coal-tar pitch upon their slow heating to 500 °C. It is shown experimentally that the electrical conductivity of the solid solutions formed increases by several orders of magnitude with an increase in the nitrogen concentration from 0.4 wt.% to 22 wt.%. Structure simulation is the research stage required for understanding the conductivity mechanism. Starting data for the simulation are elemental, powder X-ray diffraction, pycnometric, simultaneous thermal analysis, infrared (IR) and X-ray photoelectron spectroscopy (XPS) results obtained for the materials under study. Apart from nitrogen and carbon atoms, hydrogen and oxygen atoms are present in the samples, which is explained by the presence of these elements in the initial components. According to XPS and Raman spectroscopy data, the materials have the graphite-like structure with carbon atoms that are mainly in the sp² hybridization state. The occurrence of four nitrogen atoms with different environments is detected by the XPS technique: graphite-, pyridine-, and pyrrole-like, and oxidized. The thermal analysis data support the conclusion about the absence of triazine islands in the samples prepared from mixtures with 80-100 wt.% coal-tar pitch and about their presence in the samples with 50-70 wt.% coal-tar pitch. The IR spectroscopic data confirm the absence of amino and cyano groups in all solid solutions. Based on the available experimental data, structure models are proposed for the materials studied, and common structural patterns are found.

Five new metal-organic frameworks based on 4,8-disulfo-2,6-naphthalenedicarboxylic acid (H₄dsndc) are obtained: [Cd₂(dsndc)(dmf)₆] (1), [Mn₂(dsndc)(dmf)₆] (2), [Zn₂(dsndc)(dmf)₆] (3), [Co₂(dsndc)(dmf)₆] (4), and [Cd₂(dsndc)(dma)₆] (5) (DMF = N,N-dimethylformamide, DMA = N,N-dimethylacetamide). The four of them (1–4) are isostructural layered coordination polymers. The structures of all compounds are determined by the single crystal X-ray diffraction analysis. Compounds 1–3 and 5 are obtained as chemically and phase-pure and are characterized by the standard complex of physicochemical techniques (powder XRD, IR, TGA, and CHN). Photoluminescence excitation and emission spectra are recorded for compound 3, and a quantum yield of 18% is obtained.

An original procedure is proposed to refine unit cell parameters (UCPs) of single crystals in Bond’s scheme. The procedure involves the use of a modern laboratory diffractometer equipped with a 2D detector and a three-circle goniometer. At the first stage, preliminary UCPs, diffraction class, and crystal orientation relative to goniometer axes are determined. Then φ and ω angles are calculated to bring an appropriate (occurrence of a well-resolved doublet, intensity) reflection hkl on the equatorial plane. The measurement in Bond’s scheme is carried out at two symmetric positions of the detector ±2θ_D ≈ 2θ_hkl. The principal difference from the measurement on a single crystal spectrometer consists in refusing to plot the reflection profile I(ω) and passing to ω-scans with a width of 3-4°, which allows the measurement of the Kα₁/Kα₂ doublet profile. After its processing by two independent 2D functions, coordinates of the maxima are determined, and then the 4θ_hkl. Angle is found based on angular sizes of the detector pixel and the difference in the coordinates of X Kα₁-component reflections obtained in symmetric positions. In this approach, measurement errors are related to the accuracy of placing the detector in two symmetric positions and the correctness of processing 2D reflection profiles. In the study of reference Si and Ge single crystals in the range of 2θ_D angles close to 100°, UCP deviations from the theoretical values are found to not exceed 0.0004 Å, and the relative measurement accuracy is 6·10^–5. The refinement of UCPs of single crystals grown in the Y₂O₃–Eu₂O₃ system by the melt-solution technique indicates the formation of the (Y_1–xEu_x)₂O₃ solid solution with the x value range of 0.27-0.40. A scheme is proposed to improve the measurement accuracy when the procedure is transferred to the diffractometer with synchrotron radiation.