Journal of Structural Chemistry最新文献

A comparative analysis of the properties of bulk and aluminum oxide supported Ce_1–xNi_xO_y oxides (x = 0.2-0.8; y = 1.2-1.8) exhibiting catalytic activity in reforming reactions is performed using a complex of physical and chemical methods (thermal analysis, low-temperature nitrogen adsorption, powder XRD, Raman spectroscopy, electron microscopy, hydrogen temperature-programmed reduction). It is shown that the obtained samples are mesoporous materials with a specific surface area of 100±10 m²/g, containing substitutional solid solutions with fluorite cubic structure in their composition. In contrast to bulk Ce_1–xNi_xO_y complex oxide samples, the Ce_1–xNi_xO_y/Al₂O₃ material exhibits resistance to sintering during high temperature treatments in the course of activation and the subsequent reaction. At the same time, the formation temperature of metal Ni particles increases (540 °C vs. 350 °C) and the dispersion of the Ni⁰ phase after the reaction is preserved (6.5 nm vs. 50 nm). A relationship between characteristics of these materials and their functional properties is revealed.

The Na₃Nd(BO₃)₂-NdBO₃ phase diagram was investigated by the solid-state synthesis and DSC methods. Na₃Nd(BO₃)₂, Na₃Nd₂(BO₃)₃ and NdBO₃ were grown by spontaneous crystallization from the Na₂O-B₂O₃-NaF flux. Typical Nd³⁺ luminescence of ⁴F_3/2 → ⁴I_9/2 and ⁴F_3/2 → ⁴I_11/2 electron transitions at 875 nm and 1054 nm were registered. Maximum integral intensity of the luminescence was observed for Na₃Nd₂(BO₃)₃ crystals, more than twice that of NdBO₃, Na₃Nd(BO₃)₂.

Isostructural binuclear complexes [Ln₂L₂(hfac)₆] (Ln = Eu, Tb; hfac^– = hexafluoroacetylacetonate ion) are synthesized by the interaction of [Ln(hfac)₃(H₂O)₂] with 3,6-bis(diphenylphosphinyl)pyridazine (L). According to the single-crystal XRD data, two Ln(hfac)₃ moieties in the complexes are connected by two O,O´-bidentate-bridging ligands L, and the coordination polyhedron Ln@O₈ has the geometry of a triangular dodecahedron. The Eu³⁺ and Tb³⁺ complexes exhibit characteristic lanthanide-centered photoluminescence in the solid state at 297 K with luminescence quantum yields of 31% and 2% and excited state lifetimes of 707 and 30 μs, respectively, thus indicating that luminescence sensitization by the ligand environment is more effective for Eu³⁺ than for Tb³⁺.

By the condensation of 4-amino-5-R-2,4-dihydro-3H-1,2,4-triazole-3-thiones with anthracene-9- carbaldehyde, respective 4-[(anthracene-9′-ylmethylene)amine)]-5-R-2,4-dihydro-3H-1,2,4-triazole-3-thiones are prepared and structurally characterized by NMR, UV, IR spectroscopies, high-resolution mass spectrometry, and single crystal XRD. The effect of a substituent at position 5 in triazole moieties of azomethines obtained on their head-to-head or head-to-tail crystal packings is determined.

The molecular structure of 3-cyano-4-amino-1,2,5-oxadiazole-2-oxide (3-cyano-4-aminofuroxan, CAFO) in the gas phase is studied for the first time by gas-phase electron diffraction (GED) and quantum chemical calculations, and the equilibrium parameters of this molecule are determined. The data obtained are compared with those of related compounds analyzed by GED and single crystal X-ray diffraction. It is shown that the best agreement with the experiment is obtained at the B3LYP/aug-cc-pVTZ level of theory. The information on the molecular structure of free CAFO will be useful for the structural studies of compounds containing furoxan moieties.

Film heterostructures of compositions Ag/Au/Ti and Ag/Au/CFR-PEEK are obtained by thermal evaporation with subsequent deposition of metallic gold sublayers and silver nanostructures on modern biomaterials (Ti-6Al-4V alloy, polyether ether ketone CFR-PEEK). Silver concentration is varied within 2.1-20.8 µg/cm² by changing the initial metal portion (1.2-5 mg) and the number of successive depositions (1–3). According to SEM data, Ag nanofilms with a thickness up to 10-15 nm are formed on the surface of gold sublayers. According to XPS results, gold is present in the metallic state on the surface of biomaterials whereas along with metal, the Ag₂O oxide phase is detected for silver. The dynamics of silver dissolution from the Ag/Au surface is analyzed by ICP-AES (2-48 h). It is found that regardless of the silver concentration, the samples demonstrate moderate dynamics of releasing metal ions; some amount of gold is detected together with silver in the solution. The absence of cytotoxicity of the synthesized film heterostructures in vitro (L-929 cells, viability >95-98%) is shown. Heterostructures completely suppress the growth of colonies of Gram-negative (P. aeruginosa) and Gram-positive (S. aureus) bacteria after 6 h and 24 h action respectively.

The (Bu₄N)₂[{Mo₆I₈}(CN)₅(OEt)]·2H₂O and (Bu₄N)₂[{W₆I₈}(CN)₄(OEt)₂]·H₂O·EtOH cluster complexes are prepared by the reaction of (Bu₄N)₂[{M₆I₈}I₆] (M = Mo, W) with NaCN in ethanol and subsequent recrystallization from an aqueous ethanol solution. The structure of both compounds is determined by XRD. The external ligand environment of the anions contains CN^– and OEt^– ligands. The behavior of the complexes in an aqueous solution is studied by electron spectroscopy.

The addition of tartrate, oxalate and citrate anions during the one-pot synthesis of 12-MC-4 metallacrown based on β-alaninehydroximate ligands leads, respectively, to dimeric complex Cu₁₀(β-alaha)₈ (tartrate)₂·10H₂O (1) and two one-dimensional coordination polymers, Cu₅(β-alaha)₄Cu(oxalate)₂·8H₂O (2) and Cu₁₀(β-alaha)₈Cu(citrate)₂·19H₂O (3). According to X-ray diffraction data for 2 and 3, in the presence of oxalate and citrate anions, infinite chains containing alternating molecules of cationic copper (II) 12 –MC-4 metallacrown and polycarboxylate cuprate anion are formed in crystals. The distance between the metallacrown molecules in the crystal depends significantly on the choice of the initial polycarboxylate anion. In contrast to the oxalate and citrate anions, the dibasic tartrate guest anion does not lead to the formation of endless one-dimensional chains in the crystal. In this case, dimeric complex 1 is formed, for which short Cu–O contacts occur between neighboring 12-MC-4 metallamacrocycles.