Journal of Structural Chemistry最新文献

Single crystals of a new acentric barium iodide-thiocyanate tetrahydrate Ba(SCN)I·4H₂O (1) are prepared by the isothermal evaporation of aqueous solutions containing Ba(SCN)₂·3H₂O and BaI₂·2H₂O in the 1:1 molar ratio. The crystal structure of 1 is determined by XRD. The substance crystallizes in the orthorhombic unit cell, the I2mb space group, a = 7.4803(2) Å, b = 16.0959(4) Å, c = 24.0037(5) Å. The crystal motif is pseudo-layered and is formed by a packing of two types of layers, cationic and anionic ones, parallel to (010). The cationic layer is composed of distorted [BaS₂N₂(H₂O)₆] face-sharing 10-vertex polyhedra forming zigzag chains along the [100] axis. The neighboring chains are combined into a layer through common vertices corresponding to sulfur atoms. The anionic layer is formed by iodine atoms combined with the cationic layer into a 3D framework by O–H⋯I hydrogen bonds.

The {[CuCl(L)]·DMF}_n complex compound is prepared by the interaction of (E)-N′-(pyridin-2-ylmethylene)isonicotinohydrazide (L) with CuCl₂·2H₂O in ethanol. The obtained compound is characterized by elemental analysis and IR spectroscopy; its crystal structure is determined by XRD. The compound has a polymeric structure and is composed of {CuCl(L)} fragments connected into zigzag chains due to the coordination of the pyridine nitrogen of the L ligand of one fragment to the copper atom of the neighboring fragment. The copper ion has a distorted square-pyramidal coordination environment (∠NCuO = 155.71° and ∠NCuCl = 101.16°). The unit cell containing four {[Cu(L)Cl]·DMF} fragments is calculated within the quantum chemical approach of the density functional theory. The electronic structure is analyzed; the band structure and density of states diagrams are constructed. It is shown that the electronic structure has no band gap: the Fermi level virtually coincides with the highest occupied crystal orbital (HOCO) and is equal to –5.733 eV. The HOCO and the lowest unoccupied crystal orbital (LUCO) have similar compositions, but the contribution of p orbitals of the organic ligand is higher for the LUCO. The electron density Laplacian values at the critical points of Cu–N, Cu–Cl, and Cu–O bonds indicate that these bonds belong to the intermediate type with a predominant contribution of ionic bonding.

The crystal structure of a new complex of gold(III) with tetrakis-(4-cyanophenyl)porphyrin of composition [Au(TCNPP)][AuCl₄]·DMF is determined by single crystal X-ray diffraction. The structure contains a complex [Au(TCNPP)]⁺ cation and a complex [AuCl₄]^– anion in which the gold(III) atom is in the typical square environment; AuN₄ and AuCl₄ coordination cores respectively. Short intermolecular Au⋯Au and Au⋯Cl contacts are revealed between the mentioned complex ions whose nature is studied by quantum chemical calculations within the density functional theory (ωB97XD/DZP-DKH) and Bader’s topological analysis of the electron density distribution (QTAIM).

POMs modified with lanthanide metals combine the advantages of POMs and lanthanide metals, and show promising properties in the fields of luminescence, magnetism, catalysis, etc. Comparing with the classical Keggin-type POMs, the Preyssler-type POMs with larger size exhibit a rich spatial structure evolution, thereby offering potential for the synthesis of polyoxometalates with excellent properties. In this paper, the Preyssler-type POMs K_12.5Na_1.5[NaP₅W₃₀O₁₁₀] (P₅W₃₀) were selected as the research object, five polyoxometalates KNa{[Tb₄(H₂O)₃₂](NaP₅W₃₀O₁₁₀)}·24H₂O(1), KNa{[Eu₄(H₂O)₃₂](NaP₅W₃₀O₁₁₀)}· ·19H₂O(2), KNa{[La₄(H₂O)₂₄](NaP₅W₃₀O₁₁₀)}·22H₂O(3), KNa{[Gd₄(H₂O)₃₀](NaP₅W₃₀O₁₁₀)}·20H₂O(4), KNa{[Sm₄(H₂O)₂₄](NaP₅W₃₀O₁₁₀)}·21H₂O(5) were designed and synthesized with different lanthanide metals by hydrothermal synthesis method. The effects of pH value, stoichiometric ratio and reaction temperature on the synthesis were summarized. The crystal structures of five polyoxometalates were described, and the coordination environment of lanthanide metals was analyzed. PXRD, infrared spectra, thermogravimetric and fluorescence properties of these compounds were studied.

The influence of the size of the β-diketonate ligand substituent on the structure and thermal properties of volatile Ni(II) complexes is determined. To this aim, a corresponding heptanedione-3.5 (Hhd) derivative is prepared. The structures of [Ni₃(hd)₆] and its derivatives [Ni₄(OMe)₄(hd)₄(MeOH)₄] and [Ni₃(OH) (hd)₅(H₂O)]₂ are studied by XRD. The trinuclear complex is similar to its simplest β-diketonate analogue. Such a tetranuclear structure is typical for mixed-ligand alkoxy-β-diketonate divalent metal complexes, whereas the hexuclear structure is unique. Thermal properties of Ni(II) β-diketonates in the series L = RC(O)CHC(O)R, R = Me, Et, tBu are compared by the thermogravimetry method.

The shape of ions of quaternary ammonium bases should be known to correctly interpret the properties of their salts; however, there is almost no available numerical data on geometric parameters of their molecules. We report ab initio (HF/6-31G) calculation data on the structure of an all-atom model of the cluster containing one ion pair of tetrabutylammonium bromide TBA⁺Br^– in a vacuum and in a water environment. The same calculations are performed for its neutral structural analogue tetrabutylmethane (TBM). The following geometric parameters are reported: distances from the central atom to the terminal carbon and hydrogen atoms; distances between terminal atoms; excess charges on hydrogen atoms and angles between atoms characterizing the structure; volumes of structures approximating real species; average numbers and lengths of hydrogen bonds in water molecules depending on the distance to the central atom of the species. It is shown that the determined shapes correspond to irregular tetrahedra with densely packed hydrocarbon radicals. The shape and size of TBA⁺ and TBM are almost identical and do not depend on the environment or the electric charge on the central atom.

An all-atom model of the furfural molecule is proposed. The model is a system of two formally independent configurationally rigid fragments linked by a single covalent bond with a limited range of deformations. Using this model, structural and thermophysical characteristics (density, heat of evaporation, specific isobaric heat capacity, coefficients of isothermal compressibility and volumetric thermal expansion, dielectric constant) of liquid furfural at 298 K under atmospheric pressure are calculated by the Monte Carlo method. It is established that the fraction of trans-conformers at 298 K is 84.5% in the gas phase and as low as 32.3% in the liquid phase. The analysis of instantaneous and vibrationally averaged structures of the simulated system shows that the fraction of molecules participating in the formation of stack-type associates is 15-16%.

The effect of fluorination of boron nitride fullerene B₁₂N₁₂ on its activity towards the favipiravir molecule (a drug against the COVID-19 virus) is studied by the density functional theory. Two types of fullerene fluorination are considered: external doping with the formation of the B₁₂N₁₂F₂ structure and endohedral doping with the formation of the F^–@B₁₂N₁₂ complex. It is shown that fluorinated clusters can attach favipiravir by the same mechanism as initial fullerene. It is found that the interaction between the drug and the endohedral complex is too weak, while external doping by fluorine increases the binding energy between the cluster and the drug.

We report a two-step synthesis of benzyl diffractate ethers through the preparation of intermediate benzyl diffractate ethers with an alkyl substituent containing a terminal bromine atom. A series of new diffractaic acid based ethers are synthesized by replacing the bromine atom with various N- and S-nucleophiles. It is shown that benzyl diffractate derivatives exhibit pronounced antiviral in vitro activity against the strain A2 respiratory syncytial virus in a low micromolar concentration range. The dependence of the antiviral activity and cytotoxicity on the compound structure is determined. The analysis of biological activity data revealed two compounds of the active antiviral agents category with the selectivity indices 11.0 and 31.3.

A universal technique is described for producing nanostructured indium, gallium, and zinc oxides by the sol-gel method from respective metal nitrates with ethylene glycol as a complexing agent. The powder X-ray diffraction analysis of the samples obtained evidences that they do not contain noticeable concentrations of impurities, and their unit cell parameters are typical of these compounds. The microstructures of the samples are studied by electron microscopy. The band gap is determined based on diffuse reflectance of the samples using the Kubelka–Munk method, and it is shown that its boundaries correspond to the available literature data.