Vol 57, No 6 (2016)

In the work the structural and thermodynamic characteristics of zirconium tetrahydroborate Zr(BH₄)₄ are considered. The initial compound organized in a cubic lattice was heated from absolute zero to temperatures exceeding the experimental boiling temperature. Temperature dependences of the parameters of the internal structure, energy, and density of molecules in bulk are obtained. It is found that on heating the compound to 300 K its structure is maintained and on further cooling it returns to the initial state. On heating above 400 K the irreversible destruction of the crystal lattice is observed. On further cooling the compound in the solid phase becomes amorphous. It is shown that in the new state the average binding energy is lower than that in the initial one and the cubic lattice has the highest binding energy among the considered Zr(BH₄)₄ structures.

Ab initio calculations are employed to investigate nitrogen inversion as a configuration change that can supply an infinitely useful switchable control mechanism for some complex systems. In this paper, the design of a new pedal-like nano-scale robot is discussed based on nitrogen inversion. This work introduces the design of a nano pedal in which different structures of the arms created two diverse kinds of pedals: a) nano pedal without intersectional motion and b) nano pedal with intersectional motion. In (a), due to stereo repellent in the two pedal arms, they were unable to pass each other and could only move back and forth in one direction. However, in (b), due to an increase in the axis connecting the two arms, the issue of stereo repellent of nitrogen was looked over and the arms could pass each other and moved in a larger domain.

The prilocaine is a significant amino amide local anaesthetic. This drug can exist as three possible tautomers. Herein, by using density functional theory (DFT), and handling the solvent effects with the PCM model, the structure, energetic behavior, kinetics and mechanism of tautomerization, as well as the natural bond orbital analysis (NBO) of the prilocaine are reported. P1 is the most stable tautomer of the prilocaine, which can be tautomerized to two other tautomers via the intramolecular-proton transfer. Good agreement between the calculated NMR chemical shifts and IR vibrational frequencies with the experimental values approves the suitability of the optimized geometry for the prilocaine. A large HOMO-LUMO energy gap implies a high stability of the prilocaine.

Captopril disulphide is obtained under hydrothermal conditions. The IR and Raman spectra data are in agreement with the X-ray diffraction results. The disappearance of the band at 2566 cm^–1 (ν(SH)) in both spectra of captopril disulphide is consistent with the formation of the S–S bond. The degradation of the captopril drug is investigated by Raman spectroscopy and the results indicate that after 6 weeks of air exposure, a band at 512 cm^–1, assigned as ν(SS), is observed, suggesting the formation of captopril disulphide. DFT calculations in the solid state are performed for captopril and captopril disulphide. The results indicate that captopril disulphide is approximately 30 kcal•mol^–1 more stable than captopril. The analysis of the total density of states (DOS) reveals that the captopril valence band contains a significant contribution from the S atom, whereas for captopril disulphide, the O atom is the most important for the valence band.

In the work the double differentiation of functions describing the Pt4f_7/2 band in the XPS spectra of model supported Pt/SiO₂ catalysts is performed in order to determine the number of different chemical states of platinum particles. The functions for the differentiation are obtained by the deconvolution of the experimental spectral contour into two spin-orbit components. As a result of the performed analysis of the number and position of the minima of the second derivative of the function of Pt43_7/2 the conditions of the oxidation of platinum particles in the Pt/SiO₂ sample on treating in a NO + O₂ mixture and the reduction of platinum oxide particles on interacting of the PtO_x/SiO₂ sample with hydrogen are determined.

The classical molecular dynamics method is used to simulate the structure of liquid chlorobenzene in the temperature range 293-363 K. Theradial angular distribution functions for the distances between the benzene molecular planes and the angle between them; the radial distribution functions for the distances between chlorine atoms; self-diffusion coefficients, local dipole moments, and permittivities are calculated. In the entire temperature range molecules are joined into agglomerates due to contacts between chlorine atoms (halogen aggregation) and to the specific interactions of benzene rings, which causes mainly parallel and perpendicular orientations of the rings in the first coordination sphere. The molecules in the agglomerates are mostly organized in the 1D motif: chains of chlorine atoms and stacks of benzene rings. With increasing temperature, the agglomerate structure is reorganized, with the most visible changes occurring in temperature ranges 293-298 K, 313-323 K, and 343-353 K.

Novel supramolecular networks based on an anionic polymolybdophosphate cluster Sr₁₀(H₂O)₁₂[Sr₂P₉HMo₁₂O₇₁] is hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction, thermogravimetric analysis, infrared, ultraviolet spectroscopy, and cyclic voltammetry in an aqueous solution. It crystallizes in the orthorhombic space group Pnmm (No. 59) with a = 12.699(1) Å, b = 14.914(1) Å, c = 23.851(2) Å and Z = 2. The compound is made up of unusual shaped-cage [Sr₂P₉HMo₁₂O₇₁]²⁰⁻. The strontium cations are divided in two kinds. The first occupy vacant sites in the [P₉Mo1_2O68]^n– polyoxoanions unit and the second [Sr(H₂O)₆]²⁺, [Sr(H₂O)₄]²⁺, and [Sr(H₂O)₂]²⁺ serve to bridge together the adjacent polymolybdophosphate clusters to yield unprecedented three-dimensional pure inorganic assemblies of the shaped-cage polymolybdophosphate clusters.

The syntheses and crystal structures of two one-dimensional coordination polymers, [Mn(C₅HO₂F₆)₂(C₁₆H₂₀N₂)]_n (1) and [Mn(C₅HO₂F₆)₂(C₂₀H₂₀N₂)]_n (2), are described, where C₅HO₂F₆⁻ is the hexafluoro acetylacetonate anion, C₁₆H₂₀N₂ is 1,6-bis(4-pyridyl)-hexane, and C₂₀H₂₀N₂ is 1,4-bis[2-(3-pyridyl)ethyl]-benzene. In both phases, the metal ion lies on a crystallographic twofold axis and is coordinated by two chelating C₅HO₂F₆⁻ anions and two bridging bipyridyl ligands to generate a cis-MnN₂O₄ octahedron. The bridging ligands, which are completed by crystallographic inversion symmetry in both compounds, connect the metal nodes into zigzag [20 1 ] chains in 1 and contorted [001] chains in 2. Intrachain C–H•••O interactions occur in 1 but not in 2, which may be correlated with the relative orientations of the ligands. Crystal data: 1, C₂₆H₂₂F₁₂MnN₂O₄, M_r = 709.40, monoclinic, C2/c (No. 15), a = 9.3475(2) Å, b = 16.6547(3) Å, c = 18.3649(4) Å, β = 91.1135(8)°, V = 2858.50(10) ų, Z = 4, R(F) = 0.030, wR(F²) = 0.075. 2, C₃₀H₂₂F₁₂MnN₂O₄, M_r = 757.44, monoclinic, C2/c (No. 15), a = 19.9198(2) Å, b = 10.6459(2) Å, c = 16.8185(3) Å, β = 119.8344(8)°, V = 3093.91(9) Å3, Z = 4, R(F) = 0.032, wR(F²) = 0.078.

After the addition of the saturated NaClO₄ solution to a solution of trans-[Ru(NO)(NH₃)₄SO₄]HSO₄•H₂O, trans-[Ru(NO)(NH₃)₄SO₄]ClO₄ perchlorate salt (I) is obtained with the yield of ~80%. The heating of trans-[Ru(NO)(NH₃)₄(H₂O)](HSO₄)SO₄ at a temperature of ~220 °C results in a complete removal of coordination water and a partial removal of ammonia molecules. Successive treatment of the thermolysis product with sulfuric and hydrochloric acids yields [Ru(NO)(NH₃)₄SO₄][Ru(NO)(NH₃)₃Cl(SO₄)]HSO₄•H₂O crystals (II). The single crystal X-ray diffraction method is used to determine the structure of the compounds obtained. For I: space group P2₁/c, a = 6.6949(9) Å, b = 13.7049(19) Å, c = 12.8641(17) Å, β = 101.028(4)°; for II: space group Р2₁/c, a = 14.1304(4) Å, b = 12.4908(3) Å,, c = 11.6264(3) Å, β = 94.1980(10)°.

By the single crystal X-ray diffraction analysis in combination with quantum chemical calculations the molecular and crystal structures of high-energy 2,4,6-triazidopyridine and 2,4,6-triazido-3,5- dibromopyridine are studied; the dependence of structural parameters of their azido groups on the size of substituents in β-positions of the pyridine ring is analyzed. The effect of the intramolecular contact involving the central nitrogen atom of γ-azido groups in substituted triazides on their structure and properties is revealed.

Films of hydrogenated SiC_xN_yO_z:H obtained by plasma-enhanced chemical vapor deposition from a mixture of 1,1,3,3-tetramethyldisilazane with oxygen and nitrogen (TMDS+ O₂+xN₂) in the temperature range 373-973 K are nanocomposites in whose amorphous part nanocrystals belonging to phases of the Si–C–N: α-Si_3–xC_xN₄ system and graphite are distributed. A change in the chemical composition of gas mixtures enables the preparation of SiC_xN_yO_z:H films with a broad variation range of functional properties, such as the 1.45-2.15 variation of the refractive index; the controlled transparency (T ~ 92-99.7%) in the UV, visible, and IR spectral ranges; tunable characteristics of the band gap (3.5-5.4 eV), and dielectric constants (5.2-5.8).

A motif of the supramolecular architecture of соcrystals of 18-crown-6 and polychloropolyfluoro-1,3- phenylenediamines or partially fluorinated 1,3-phenylenediamines (1:1 stoichiometry) is infinite 1D ensembles of alternating components. The mutual coordination of molecules in the ensembles is due to the hydrogen bond between crown ether oxygen atoms and hydrogen atoms of polyfluoroarene amino groups. Parameters of the architecture of соcrystals are determined by the effect of the number and arrangement of substituents (chlorine and fluorine atoms) in the polyhalogenated aromatic ring.

Mechanisms of radiation damages in minerals promising for the utilization of highly active radioactive waste (zircon ZrSiO₄, monazite LaPO₄, orthophosphate YbPO₄, lakargiite CaZr_0,8Sn_0,1Ti_0,1O, and Gd₂Zr₂O₇ and Gd₂Ti₂O₇ compounds with the pyrochlore structure) are studied by the computer simulation using the molecular dynamics method. The formation of a damaged region in the structures under study is considered along with the recovery (relaxation) processes in these structures. The number of Frenkel pairs and antistructural defects that form in the structure of these minerals after the pass of the knocked out thorium atom is calculated by the molecular dynamics method. A parameter is proposed that characterizes the mineral tendency to amorphization under the effect of the radiation damage. The obtained results show that one of the main factors determining the radiation stability of minerals is the crystal structure type, compounds with the monazite structure being more radiationally stable than compounds with the zircon structure. It is found that the Gd₂Zr₂O₇ compound and lakargiite have a weaker tendency to amorphization than other minerals such as zircon, monazite, and orthophosphate YbPO₄. A high radiation stability of the studied Gd₂Zr₂O₇ compound as well as a solid solution of the composition CaZr_0.8Sn_0.1Ti_0.1O₃ makes it possible to propose them as a possible matrix for the utilization of highly active radioactive waste.

The structure of ionic cocrystals of piperidinium 2-thiobarbiturate with 2-thiobarbituric acid PipeH⁺(HTBA⁻)H₂TBA (I) (H₂TBA is 2-thiobarbituric acid, Pipe is piperidine) is determined. The asymmetric unit of I contains a H₂TBA molecule in the form of thionemonocarbonyl tautomer, the HTBA^–ion, and the PipeH⁺ piperidinium ion. The structure is stabilized by the intermolecular O–H•••O, N–H•••S, and N–H•••O hydrogen bonds (HBs) forming a three-dimensional framework. The results of single crystal XRD and IR spectroscopy indicate the formation of strong O–H•••O HB. The topological analysis of the HB network in I is performed.

A new Cu(II) coordination polymer, namely {[Cu₂(btb)₂(sip)(OH)]•(H₂O)_0.25}_n (btb = 4,4′-bis(1,2,4- triazolyl-1-yl)-biphenyl, H₃sip = 5-sulfoisophthalic acid), is hydrothermally synthesized and characterized by elemental analyses, infrared (IR) spectroscopy, and single crystal X-ray diffraction. It crystallizes in the monoclinic space group P2_1/c, a = 14.9676(3) Å, b = 14.3478(3) Å, c = 21.2719(5) Å, β = 125.325(2)°, V = 3727.11(14) ų, Z = 4, C₄₀H_28.50Cu₂N₁₂O_8.25S, M_r = 968.39, D_c = 1.726 g/cm³, μ = 1.274 mm^–1. The structural analyses reveal that the compound displays a 2D binodal rarely (4,5)-connected network with 4,5L50 topology. Moreover, the thermal and catalytic properties of the complex for the degradation of the congo red azo dye in a Fenton-like process are investigated.