Journal of Structural Chemistry最新文献

A mixture of two structurally different cluster phases I and II with the general chemical formula W₅Br₁₂·BiBr₃ is obtained as a product of the WBr₆ reduction reaction with elemental bismuth at 280 °C. The elemental composition of the mixture is determined by the energy-dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectrometry. For the single crystals selected from a mixture of phases I and II their crystal structures are determined, and the powder X-ray diffraction analysis is performed for the polycrystalline mixture. In the crystal structure of I, square-pyramidal cluster fragments are bridged by bromine atoms into infinite chains by the W–Br^a–a–W interaction. In the structure of II, BiBr₃ (W–{Br^aBiBrBr^a}–W) molecules incorporate into the chain instead of the bridging bromine atom.

A synthesis procedure for composite precursors of the composition yttrium-stabilized zirconia nanoparticles – 2,2,6,6-tetramethyl-3,5-heptandionato-hafnium(IV) is developed. The thermal behavior of the synthesized composites is studied by the complex thermal analysis up to 600 °C in a wide concentration range. Main components of thermolysis products are determined by the energy-dispersive X-ray (EDX) analysis. Features are revealed in TG curves for all compositions in the temperature range of 310-410 °C. From the IR, XPS, and EDX data it is found that the observed effects are due to low-temperature decomposition of a small part of the volatile metal-organic precursor irreversibly absorbed on the surface of nanoparticles. A hypothesis is put forward that irreversible adsorption is caused by Lewis acid centers on the surface of nanoparticles. The obtained information about the thermal properties of composite precursorscan facilitate the development of methods to control nanoparticle concentrations in the coating formed.

The possibility of forming molecular Ag(I) complexes with tris(3,5-dimethylpyrazol-1-yl)methane (HC(3,5-Me₂pz)₃) and fluorinated β-diketones (hexafluoroacetylacetone (Hhfac) and trifluoroacetylacetone (Htfac)) is tested to expand the library of potential precursors for the chemical vapor deposition of Ag containing materials. It is established that the interaction of HC(3,5-Me₂pz)₃ with silver β-diketonates leads to the formation of [Ag{HC(3,5-Me₂pz)₃}₂]⁺ cationic complexes. At the same time, a stable desired product [Ag{HC(3,5-Me₂pz)₃}hfac] (L = hfac) was isolated and characterized. The structures of [Ag{HC(3,5-Me₂pz)₃}₂](tfac) and as series of solvates [Ag{HC(3,5-Me₂pz)₃}(hfac)]·½THF and [Ag{HC(3,5-Me₂pz)₃}₂](L)Solv_x (L = hfac, Solv = Et₂O (x = ¼), C₇H₈ (x = ½), CHCl₃ (x = 1); L = tfac, Solv = THF (x = 1)) are determined by XRD. Structures of the cationic and molecular complexes are compared with those of related compounds.

Drug transport to specific areas of the body is accomplished by drug delivery systems. Components of these systems are often biodegradable and bioabsorbable polymers. The elaboration of effective drug delivery methods can, along with the search for new drugs, significantly enhance the development of corresponding therapeutic strategies. In the present work, the possibility of utilizing chitosan to deliver antiviral drugs is studied using the density functional theory (DFT, B3LYP-D3(BJ)/6-311+G(d,p)). The energies of frontier molecular orbitals and fundamental DFT indices are calculated, densities of electronic states are analyzed. The results indicate that medicinal compounds are adsorbed on chitosan by H-bonds, and the strongest bond energy between chitosan and ivermectin B1b is –34.83 kcal/mol. The analysis of reactivity descriptors for the interaction of chitosan with hydroquinone, chloroquine, and hydroxychloroquine reveals specific interactions indicating that these complexes are not stable. In view of the chitosan compatibility with the human body, its non-toxicity, and the possibility to control the release of medicinal compounds due to such factors as pH, solubility, and ionic strength, we propose to use this compound as a system for the delivery of medicinal compounds.

The ({{({{text{H}}_{3}}text{O})}_{2}}[text{Pt}_{2}^{text{III}}{{(text{S}{{text{O}}_{4}})}_{4}}{{({{text{H}}_{2}}text{O})}_{2}}]cdot 4{{text{H}}_{2}}text{O}) compound (1) is isolated by keeping sulfuric acid solutions of the [Pt^IV(H₂O)₂(OH)₄] platinum hydroxide with an addition of 18-crown-6-ether. The structure of 1 (C2/c, a = 20.276(1) Å, b = 7.5844(5) Å, c = 13.8876(9) Å; β = 113.466(4)°; V = 1959.0(2) Å³; Z = 4) is determined by XRD and is shown to be formed by binuclear anionic platinum(III) aquasulfate complexes (containing bridging sulfate ligands and axial aqualigands), hydronium cations, and water molecules. The ({{({{text{H}}_{3}}text{O})}_{2}}[text{Pt}_{2}^{text{III}}{{(text{S}{{text{O}}_{4}})}_{4}}{{({{text{H}}_{2}}text{O})}_{2}}]) (2) compound, containing no solvate water molecules, is prepared from a solution of the (Bu₄N)₂[Pt^IV(NO₃)₆] salt in strong sulfuric acid. The structure of 2 (P2₁, a = 7.4384(7) Å, b = 13471(1) Å, c = 7.566(1) Å; β = 101.419(4)°; V = 743.1(1) Å³; Z = 2), containing no solvate water molecules, is determined by XRD. The substances are characterized by Raman and NMR spectroscopy methods. The geometry of the ({{[text{Pt}_{2}^{text{III}}{{(text{S}{{text{O}}_{4}})}_{4}}{{({{text{H}}_{2}}text{O})}_{2}}]}^{2-}}) anion is additionally calculated by the DFT method; the optimized model agrees well with structural data and confirms a presence of Pt–Pt bonding. Possible mechanisms of the formation of platinum(III) complexes in sulfate solutions of platinum(IV) compounds are discussed.

The geometry and energy of (CH₃CN)_n (n = 2-8) and (CH₃CN)_m·H₂O (m = 4-7) clusters are calculated by the density functional theory with the B3LYP functional, the cc-pvdz basis set and Grimme’s dispersion correction D3. In (CH₃CN)_n clusters at n ≤ 4, acetonitrile molecules are arranged antiparallel; as n increases, cycles can be distinguished in the cluster structure with the head-to-tail orientation of molecules. Cycles can be distinguished where the molecules have a head-to-tail orientation. With the same number of molecules in a cluster the formation of clusters including a water molecule is more energetically favorable. Starting from m > 5, this molecule is located inside the cavity of acetonitrile molecules. The application of Grimme D3 correction allows us to refine the energy of the formation of (CH₃CN)₃ clusters.

Single crystals of hexahydrates of divalent fluoridotitanates MTiF₆·6H₂O (M = Mn, Co, Ni, Zn) are synthesized. Their crystal structures are determined by X-ray diffraction at room temperature (RT-structure) and below the phase transition (LT structure). The phase transition is accompanied by a transformation of the disordered trigonal lattice into the ordered monoclinic one. The initial RT-structures differ in the set and strength of O–H⋯F hydrogen bonds linking isolated [M(H₂O)₆]²⁺ and [TiF₆]^2– octahedra into a 3D framework. There is a correlation between the strength of hydrogen bonds and the thermal behavior of the complexes.

Neutral and zwitter-ionic conformers of glycine (Gly) and alanine (L-Ala) are quantum chemically calculated at the B3LYP+GD3/def2TZVPP level of density functional theory within the discrete-continuum model in the gas phase and with regard to the effect of the aqueous medium. Structures with the minimum dipole moments prove to be the most stable neutral conformers of Gly and Ala in the gas phase. When solvation effects are taken into account within the polarized continuum model, conformers with the maximum dipole moments become energetically favorable due to the dipole-dipole interaction with the medium. Reaction activation barriers of the intramolecular proton transfer in the formation of zwitter-ions studied are calculated depending on the number of water molecules in the first coordination sphere. The inclusion of seven water molecules saturating the hydrogen bond of –(text{NH}_{3}^{+}) and –COO^– functional groups into the discrete-continuum model of a water solvent is shown to significantly decrease the activation barrier to 0.02 kcal/mol for glycine and to 0.09 kcal/mol for alanine.

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.