Vol 59, No 8 (2018)

Complexes formed by leucine (Leu) and the dimer of sodium dodecyl sulfate (DDSNa)₂ are studied by the quantum chemical method DFT using the hybrid exchange-correlation functional B97 with Grimme's dispersion correction D2 and the 6-311++G(2d,2p) basic set. The complexes formed by Leu and the dimer of DDSNa (considered as a micelle fragment) are studied in terms of their spatial structures and the energies of intermolecular interactions Е_IMI, depending on the penetration depth of Leu inside the micelle model. The highest energy Е_IMI is exhibited by the complex formed by the zwitterionic form of the amino acid and the hydrophilic part of sodium dodecyl sulfate. When the hydrophilic environment is replaced by the hydrophobic one, the intramolecular hydrogen bond in the amino acid changes in terms of its type and strength: N–H…O (weak) → N…H…O (strong) → N…O–H (weak). The energies of frontier orbitals and, therefore, redox properties of leucine also undergo changes in the course of the process.

In the present research, the impact of the arene ligand on the dipole moment, electronic structure, hyperpolarizability, and frontier orbital energy in Cr(CO)₃(arene) complexes (arene = benzene, biphenyl, triphenly, tetraphenyl) is studied by MPW1PW91 quantum chemical computations. The chemical bond nature between the arene ligand and the Cr(CO)₃ fragment is demonstrated through the energy decomposition analysis (EDA). The percentage composition of frontier orbitals considering the specified groups of these complexes is obtained to investigate the features of metal–ligand bonds. The internal reorganization energy values are calculated to study the charges mobility. The quadrupole polarization magnitude of the carbonyl carbon atom is calculated as an assessment of the amount of pπ–dπ back donation in Cr–CO bonds. Moreover, the effect of aromatic ring numbers is calculated on the β_tot values for these complexes.

The title compound C₂₄H₁₈N₄O₂S₂ is synthesized via the azide method and its structure is redetermined at 100(2) K. The title structure, N,N′-(disulfanediyldibenzene-2,1-diyl)dipyridine-2-carboxamide is redetermined from the data published by Lumb, Hundal, and Hundal (Inorg. Chem., 2014, 53, 7770-7779). The redetermination is of significantly higher precision than a previous low-temperature structure and the improvement of the present redetermination consists in a released geometry of the 1,2-diphenyldisulfane group. The molecular structure crystallizes in the triclinic space group, P-1, with a = 7.3492(3) Å, b = 11.6753(5) Å, c = 13.1814(6) Å, α = 95.077(4)°, β = 105.316(4)°, γ = 100.759(4)°, and V = 1060.28(8) ų. The S–S bond length of 2.0758(4) Å and S–C distances of 1.7818(13) Å and 1.7767(13) Å for this redetermination are much closer to those observed in comparable structures. Intraand intermolecular N–H…S, N–H…N, C–H…O, C–H…S hydrogen bonds are present in the crystal structure. The molecular geometry of the title compound is optimized by the DFT method and the calculated geometrical parameters are compared with experimental ones. The NBO analysis of possible intramolecular hydrogen bonds is made on the optimized structure for comparison.

The mechanism and regioselectivity of the Diels–Alder cycloaddition reaction between 9- (methoxymethyl)anthracene and citraconic anhydride are explored using the valuable density functional theory (DFT) methods. The solvent effects are considered using the polarizable continuum model in the toluene solution. Due to a small electrophilicity difference of the reactants, the reaction has a low polar character. The investigated Diels–Alder reaction has a normal electron demand character. Depending on the respective position of substituents in the cycloadducts (head-to-head (ortho) or head-to-tail (meta)) the reaction can be progressed via two different pathways: ortho and meta. Due to a very high activation energy, the meta pathway is rejected. The product of the ortho pathway is demonstrated to be the final product of the reaction in the toluene solution. The obtained DFT results are in good agreement with the experimental results.

Ion mobility and a phase transition (PT) in the compound (NH₄)₆LiHf₂Zr₂F₂₃ are studied using ¹H NMR, ¹⁹F NMR, XRD, and DSC methods. The types of ionic motions in the fluoride and ammonium sublattices of this compound are determined at 150–450 K; their activation energies are estimated. It is shown that an order-disorder PT occurs in this compound at 400–450 K to form a metastable high-temperature modification, where ionic motions are represented mainly by the diffusion of fluoride and ammonium ions.

The products of mechanosynthesis in the systems “superstoichiometric fluorocarbon nanomaterial CF_1.2–thermally expanded graphite” are studied using X-ray photoelectron spectroscopy and low-temperature nitrogen adsorption to identify texture characteristics. A correlation is revealed between the conductivity of the composites and functional composition of their surface layers. The obtained results are explained by the fact that mechanosynthesis products contain mesoporous carbon-fluorocarbon nanocomposites consisting of micro- and nanoparticles CF_1+x coated by an outer nanolayer sp²-C–sp³-C–F.

A comprehensive study of the Jiddat Al Harasis 055 (L4-5 type) ordinary chondrite is conducted using 2D X-ray fluorescence spectroscopy, Mössbauer spectroscopy, X-ray absorption near edge structure (XANES) spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The content of Fe, Ni, Si, Mg, S, Ca, Al, Mn, Ti, and Cr is determined; several components and areas with increased content of S, Ti, Cr, and Ni are detected along with several Ca–Al inclusions. According to XANES data, the Jiddat Al Harasis 055 sample contains iron with the average oxidation state 2.4+. This result is consistent with the data of Mössbauer spectroscopy used to identify iron phases which testifis that 46% and 54% of iron ions appear in Fe²⁺ and Fe³⁺ states, respectively. By comparing the pre-edge energy position and the area under the preedge peak of XANES spectra with literature data reported for geological materials, the average coordination number in the first coordination sphere of iron is found to be 5.3. According to the data of Xray diffraction and Mössbauer spectroscopy, the iron-containing meteorite phases consist mainly of olivine, pyroxene, hematite, and goethite. The observed magnetic properties of the sample can be attributed to small inclusions of ferromagnetic phases such as nickel nanoparticles, which cannot be reliably identified using laboratory spectral methods.

The equilibrium and the rate of stepwise reactions in the course of pyridine (Py) coordination by oxo(5,10,15,20-tetraphenylporphinato)niobium(V) chloride ((Cl)О=NbTPP) in toluene and the chemical structure of reaction products are studied using time-dependent titration, chemical kinetics, UV/Vis, IR, ¹H NMR, and mass spectrometry methods. The interaction with Py is a complex system of simple, fast, reversible reactions of pyridine coordination (K₁ = 2.2.10⁵ l²/mol², K² = 5.2 l/mol) with subsequent nonreversible displacement of chloride ions into the second coordination sphere and cis–trans isomerization of axial ligands. A complete quantitative description of the interaction is obtained and spectral parameters were determined for intermediate and final products. Based on these data, the chemical structure of the latter is determined. The prospect of using (Cl)₃NbTPP as a receptor for nitrogenous bases, the “building blocks” of pharmaceuticals and food components, as well as environmental pollutants, is substantiated. The obtained results are useful for the design of dye-sensitized solar cells (DSSCs), since the above reaction is a model of the self-assembly process of dipolar systems based on metalloporphyrins and pyridyl derivatives of carbon nanoforms.

The synthesis method for [NiEn₃]WO₄ complex salt is described. Data of single crystal X-ray diffraction at 115 K are: space group \(p\bar 3\), a = 15.9633(5) Å, c = 9.9446(4) Å, V = 2194.6(1) ų, Z = 6, d_x = 2.210 g/cm³, Ni–N is 2.120(2)-2.149(2) Å, ∠N–Ni–N is 80.69(7)-82.28(7)°. From the differential scanning calorimetry data it is found that a phase transition occurs at 269 K. The crystal structural characteristics at 298 K are as follows: space group \(p\bar 31c\), a = 9.2641(3) Å, c = 9.9817(3) Å, V = 741.89(4) Å3, Z = 2, d_x = 2.179 g/cm³, Ni–N is 2.128(2) Å, ∠N–Ni–N is 81.05(12)°. The phase transition is shown to correspond to the disordering of tungstate anions over three positions. The comparative analysis of N–H…O and C–H…O interionic contacts is performed.

We report a novel three-component condensation of benzalacetophenone, ethyl acetoacetate, and malonodinitrile in a 1:1:1 molar ratio respectively, involving an equimolar amount of morpholine acetate to form ethyl-4,6(R,S)-diphenyl-2-dicyanomethylenecyclohex-3-ene-1(R,S)-carboxylate whose crystal structure is determined by single crystal XRD. The intermolecular interaction is analyzed using an atomatom potential model, and infinite chains of energetically tightly coupled molecules in the crystal structure are identified and described. A weak hydrogen bond of the C_Ar–H…O type is found.

A binuclear Zn(II) complex [Zn₂(SDBA)₂(DPA)₂.2H₂O] (1) (DPA = di-2-pyridylamine, H₂SDBA = 4,4′- sulfonyldibenzoic acid) is synthesized and characterized using single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The single crystal X-ray diffraction analysis reveals that complex 1 is a binuclear zinc(II) complex. The binuclear molecules are further connected by three types of N–H...O, C–H...O, and O–H...O hydrogen bonds, generating a three-dimensional supramolecular structure. Meanwhile, S–O...π interactions further consolidate the three-dimensional supramolecular framework of 1. In addition, the thermal stability and luminescent properties of the title complex are briefly investigated. The luminescence measurements reveal that complex 1 exhibits fluorescent emission in the solid state at room temperature.

A new samarium Schiff base complex with the formula [Sm^III(NO₃)₃(H₂O)L₂].EtOH, where L = {(E)-2- (((4-(ethoxycarbonyl)phenyl)iminio)-methyl)phenolate}, is synthesized. Its molecular structure is determined by means of single crystal X-ray diffraction (XRD). The complex crystallizes in the orthorhombic space group Pbca with the following unit cell dimensions: a = 14.1304(19) Å, b = 18.0218(13) Å, and c = 31.246(2) Å. Photoluminescence characteristics of the complex are investigated experimentally in the solid state and obtained theoretically using the Sparkle/PM7 modeling. Moreover, several methods such as powder XRD, FT-IR and UV-Visible spectroscopy are utilized to confirm the structure of the complex.

We consider our variants of applying a molecular dynamics method to quantitatively calculate adsorption isotherms of gases and vapor and their mixtures on microporous active coals in a wide temperature range (lower and higher than the critical one for adsorptives) and the dependence of adsorbate densities on the width of slit-like micropores.

Henry constants K₁ are calculated for stable conformers of isobutanol, tert-butano, and tert-amyl alcohol molecules on graphitized thermal carbon black (GTCB). Parameters of the atom-atom potential taking into account the formation of a hydrogen bond between the adsorbate OH group with GTCB π electrons with regard to the direction are found. By density functional theory (DFT) and molecular statistical theory of adsorption the ratio between conformers stable in the gas phase and the adsorbed state are determined. The experimental Henry constants are compared with the results of the molecular statistical calculation for stable conformers of alcohols forming the bond OH...π_GTCB.

FeBO₃ and Fe₃BO₆ are antiferromagnets with T_N ≈ 348 K and 508 K respectively. This work presents the results of the study of the thermal expansion and phase transitions occurring in these borates by hightemperature X-ray powder diffraction and Mössbauer spectroscopy in a wide temperature range. Unit cell parameters are refined by the Rietveld method at different temperatures. For both compounds an abrupt change in thermal expansion coefficients α is revealed near the magnetic antiferromagnet–paramagnet phase transition.

Structural deformations and phase transformations of Rb-boroleucite RbBSi₂O₆ obtained by crystallization from glass at 1000 °C are studied by high-temperature X-ray powder diffraction and differential scanning calorimetry in the range 25–1200 °C. At 345 °C the compound undergoes a reversible cubic-cubic polymorphic transition with increasing symmetry \(I\bar 43d \leftrightarrow Ia\bar 3d\). The crystal structure of RbBSi₂O₆ is refined by the Rietveld method at temperatures of 25 °C, 100 °C, 200 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 380 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, and 900 °C, according to the powder X-ray diffraction data.

The structure and morphology of CdS nanoparticles obtained by the hydrothermal synthesis are studied at temperatures of 80 °С, 100 °С, 120 °С, and 140 °С. The analysis is performed by calculating X-ray diffraction patterns by the Debye formula followed by the optimization of model parameters of nanocrystals. It is shown that with increasing temperature the CdS structure gradually transforms from a very defective sphalerite-like structure to very defective wurtzite-like one. At all temperatures the particles are ellipsoids stretched along the perpendicular to packing defects. An increase in the temperature causes a gradual enlargement of nanoparticles.

Magnetic and structural transitions in NdBaMn_2−xTi_xO₆ (x = 0, 0.2) samples obtained by the topotactic procedure at 1373 K and lgPO₂=−19 atm are studied by low-temperature X-ray diffraction and magnetometry in 1–5 T fields. Undoped double manganite undergoes a reversible ferromagnet—antiferromagnet magnetic phase transition at Т_N = 278 K without changing symmetry. The 20 mol.% titanium substitution for manganese causes a decrease in symmetry from the tetragonal space group P4/mmm to the orthorhombic space group Pmmm and a shift of magnetic transitions to lower temperatures. Oxide NdBaMn₂O₆ demonstrates high values of the magnetocaloric effect in the temperature range 250–315 K.