Journal of Structural Chemistry最新文献

Fundamental research is essential for developing new generation catalysts and optimizing the characteristics of existing catalytic systems, because it allows establishing key parameters determining the activity and selectivity of the studied reactions. In this work, the activity of supported platinum-titanium catalysts in the selective oxidation of ammonia is studied. The influence of modifying additives (potassium chloride and tungsten oxide) on the physicochemical and catalytic properties of the Pt/TiO₂ system is considered. Structural methods such as powder XRD and transmission electron microscopy showed that the studied catalysts contain highly dispersed platinum particles. The effect of oxidation-reduction treatment on the oxidation state of platinum on the surface of modified and unmodified catalysts is determined by ex situ X-ray photoelectron spectroscopy. It is shown that doping the samples by tungsten oxide and potassium chloride stabilizes the metallic platinum state and the oxidized Pt²⁺ state, respectively. The correlation between the active component state and catalytic properties shows that the activity of samples below 180 °C improves upon the introduction of tungsten oxide and their selectivity to molecular nitrogen below 250 °C increases upon the introduction of potassium chloride.

Owing to its semiconductor properties, tin(IV) oxide is widely used in gas sensors, photo- and electrocatalysis, fuel cells, electrolyzers etc. In this work, macroporous SnO₂ samples are synthesized by impregnating polystyrene (PS) microspheres with sols containing SnCl₄ and alcohol (96% ethanol, isopropanol, or n-butanol). After impregnation, the composites undergo drying and annealing. After drying, the same samples are washed with water for more complete hydrolysis followed by annealing. The resulting SnO₂ samples are studied by powder X-ray diffraction, X-ray photoelectron spectroscopy, X-ray fluorescence analysis, low-temperature N₂ adsorption (77 K), mercury porosimetry, and scanning electron microscopy. The effect of washing with alcohol and water on the porous characteristics and electrical conductivity of the materials is studied.

4-((5,7-Dimethyl-1,3-diazaadamantan-6-yl)amino)-2,3,5,6-tetrafluorobenzonitrile, 5,7-dimethyl-N-(2,3,5,6-tetrafluoro-4-nitrophenyl)-1,3-diazaadamantane-6-amine, 4-((1,3,5-triaza-adamantan-7-yl)amino)-2,3,5,6-tetrafluorobenzonitrile, and N-(2,3,5,6-tetrafluoro-4-nitrophenyl)-1,3,5-triaza-adamantane-7-amine are prepared by the interaction of 5,7-dimethyl-1,3-diazaadamantane-6-amine or 1,3,5-triazaadamantane-7-amine with the corresponding polyfluorinated aromatic compound (perfluorobenzonitrile or perfluoronitrobenzene). All the compounds are structurally characterized by NMR and IR spectroscopy, high-resolution mass spectrometry, and XRD. The structures of triazaadamantane derivatives, in contrast to substituted diazaadamantanes, contain multiple short F⋯F contacts.

5-Hydroxy-2-{[(propane-2-yl)iminio]methyl}phenolate with an empirical formula of C₁₀H₁₃NO₂ was synthesized by a reaction between 2,4-dihydroxybenzaldehyde and isopropyl amine in an aqueous ethanolic medium. The Schiff base compound was characterized by elemental analysis, IR spectroscopy, NMR, mass-spectrometry, thermogravimetry (TG), and single-crystal X-ray diffraction (XRD). The compound was crystalized in an orthorhombic crystal system with a space group of Pna2₁. The azomethine functional group (–HC=N–) was confirmed by the band at 1638 cm^–1 in its IR spectrum. The compound is thermally stable from 40-154 °C losing only 0.2% of its weight. The thermogram indicated the absence of hydration or lattice water. The compound exhibits keto-enol tautomerism with a zwitterionic structure. The non-covalent interactions (NCI) were studied by various computational methods such as Hirshfeld surface analysis, NCI plot, and scatter plot (RDG vs sign (λ₂)ρ). The major contributors to the Hirshfeld surface contacts are O⋯/H⋯O (21.5%) and C⋯/H⋯C (25.3%). The non-covalent interactions and the crystal parameters are: a = 10.3839(9) Å, b = 9.9442(8) Å), c = 9.2223(8) Å, α = β = γ = 90°, Z = 4.

Titanium dioxide TiO₂ films are obtained from titanium tetrachloride and water by atomic layer deposition. A change in the phase composition of the films is found when the deposition and annealing temperatures are varied. At a deposition temperature of 150 °C amorphous films are formed; at 200-400 °C films containing the anatase phase are formed; a mixture of anatase and rutile phases is formed in high-temperature films (deposition temperatures of 450 °C and 500 °C). Annealing of high-temperature films at 400 °C and 500 °C increases the relative intensity of rutile reflections. The film morphology is analyzed by scanning electron and atomic force microscopy techniques. As the deposition temperature increases, grains enlarge on the film surface.

The previously synthesized 4-(2,4,5-triphenyl-1H-imidazol-1-yl)benzoic acid (THBA) structure was characterized by single crystal and finally confirmed by single crystal X-ray diffraction method. This molecule crystallizes in the orthorhombic crystal system, P2₁2₁2₁ space group, with crystal parameters found a = 9.3659(8) Å, b = 10.9060(8) Å, c = 21.2433(18) Å, Z = 4 and V = 2169.9(3) Å³. A single-crystal X-ray investigation of the compound revealed that hydrogen bonds and Van der Waals interactions play a crucial role in the stability of the crystal packing. At this point, comparative studies on crystallographic properties and Hirshfeld surface analysis have been carried out to characterize the binding states and crystal structure of THBA at molecular stability. The supramolecular features contain N–H⋯O (inter) and C–H⋯O (inter and intra) hydrogen bonding interactions, which are supported using Hirshfeld surface and 2D fingerprint analysis.

Two new tetranuclear ({text{Mn}_{2}^{text{II}}text{Mn}_{2}^{text{III}}}) clusters are obtained and studied by single crystal X-ray diffraction. They have similar coordination motifs involving p-H-calix[4]arene HCA or p-adamantylcalix[4]arene AdCA and 2,2′-bipyrimidine as N,N-donor chelating coligand. Two factors affecting the controlled cluster core deformation are revealed: the involvement of 2,2′-bipyrimidine in coordination with Mn(II) ions decreases the Mn^II–Mn^II distance; the introduction of bulky p-adamantyl groups along the calix[4]arene upper rim increases the Mn^III–Mn^III distance. Moreover, the presence of bulky substituents at the macrocycle platform is shown to change the molecular arrangement in the crystal, which leads to the formation of a porous crystal structure.

Novel optically active thioethers and sulfones based on 2(5H)-furanone, 4-aminothiophenol, and two monoterpene alcohols l-menthol and l-borneol are synthesized. The crystal structures of two optically active sulfonyl derivatives of the furanone series are studied by single crystal X-ray diffraction (XRD). In both crystals, the compound is presented by independent molecules A and B having radical differences in conformations and hydrogen bond systems. The efficiency of the approach involving a detailed examination of all stereochemical features of a molecule in a crystal is demonstrated based on single crystal XRD data with the use of the Hirshfeld surface analysis.

Preparation, X-ray crystal structure, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis of complexes 1, 2 from the pyridine and the mono- and dicarboxylic acids are reported. XRD and FTIR analysis demonstrate that both belong to the organic salt. The salt 1 crystallizes in the triclinic, space group (Pbar{1}), with a = 7.271(3) Å, b = 9.548(4) Å, c = 14.698(7) Å, α = 78.435(6)°, β = 85.975(7)°, γ = 71.492(6)°, V = 948.0(8) Å³, Z = 2. The salt 2 crystallizes in the orthorhombic, space group P2₁2₁2₁, with a = 7.9476(6) Å, b = 11.6756(9) Å, c = 25.686(2) Å, α = β = γ = 90°, V = 2383.4(3) Å³, Z = 4. In this study, the pyridine at 1, 2 were both involved in the classical ionic N–H⋯O H-bonds. The O–H⋯O H-bonds were also present in both salts. Apart from the classical H-bonds, the auxiliary interactions of CH⋯O, CH₃–O, CH₃–CH_3, CH–π, and O–π also helped the stabilization and expansion of the whole high-dimensional (3D) packings. Hirshfeld surface analysis provides additional views into the prevalence of the various short contacts in the crystal structure. On account of the subtle balance of the various nonbonding associations the synthons (R_{2}^{2})(7), (R_{2}^{2})(10), (R_{3}^{2})(8), (R_{3}^{2})(10), (R_{3}^{3})(9), (R_{3}^{3})(19), (R_{4}^{3})(15), (R_{4}^{4})(17), (R_{5}^{4})(12) and (R_{6}^{4})(18) were noted at the salts. For the combination of the classical H-bonds plus the various non-covalent contacts, the salts adopted the 3D net. In conclusion, we have shown that 3D structures can be constructed by the collective non-covalent interactions.

A new aroylhydrazone compound 2-chloro-N′-(2-hydroxy-5-methoxybenzylidene)benzohydrazide (H₂L) was synthesized. With the aroylhydrazone compound and 2-hydroxybenzohydroxamic acid (HL^a) or maltol (HL^b) as ligands, two new oxidovanadium(V) complexes [VOLL^a]∙CH₃OH (1) and [VOLL^b] (2) were synthesized. Both the aroylhydrazone and the complexes have been characterized by elemental analysis, IR, UV-Vis and ¹H NMR spectra, as well as single crystal X-ray determination. X-ray analysis indicates that the V atoms in the complexes are in octahedral coordination. Crystal structures of H₂L and the complexes are stabilized by hydrogen bonds. Thermal analysis of the complexes was performed. The complexes show effective catalytic property for the epoxidation of styrene, with conversion over 80% and selectivity over 90%.