Home – Home – Jornals – Advanced Search

The complex [Pd(bipy)Cl₂] (1) (bipy = 2,2′-bipyridyl) has been synthesized and characterized by NMR spectroscopy, elemental analysis and X-ray diffraction method. The first step hydrolysis reaction kinetics for the complex was studied by UV-absorption spectroscopy; the speed constant (k₁) was found to be 3.0×10^-4 s^-1. The fluorescence spectra have been collected to investigate the interaction of complex (1) with fish sperm DNA (FS-DNA) and the results indicate that the complex (1) has an effective intercalation within DNA. The reaction of complex (1) with adenine in ethanol/water results in the compound [Pd₂(bipy)₂(ade)₂]Cl₂⋅3H₂O (2) (ade = adenine) whose crystal structure was determined by X-ray diffraction method. The structure is orthorhombic, Pmmn, a = 12.993(4), b = 14.512(5), c = 9.837(3) Å, V =
1854.8(11) ų, Z = 2 (C₃₀H₃₀Cl₂N₁₄O₃Pd₂), final R₁ = 0.0675. The palladium complex is a binuclear cation, where two ade ligands bridge two Pd(II) centers, while each Pd(II) is also chelated by one bipy ligand.

Nature of the kinematic shear viscosity of water ν is discussed in the work. Dependences of ν on temperature t, reduced volume ν, and the average number of hydrogen bonds per one molecule n_H (t =
T/T_c, = T_c and are critical values of temperature and reduced volume) are analyzed in detail on a liquid-vapor coexistence curve. It is shown that at T < T_H (T_H ≈ 310 K is the characteristic temperature of water) the formation of the kinematic shear viscosity is induced by activation. At T > T_H, the shear viscosity of water is the sum of two contributions. One of them is of the same nature as in simple liquids, and another is caused by effects of hydrogen bonds. The temperature dependence of ν in this temperature region has nothing in common with exponential formulas of activation theory. The explicit form of the functional dependence of the kinematic shear viscosity on t, , and _νn_H is found and substantiated. It is shown that the value and temperature dependence of n_H resulting in the experimental values of the kinematic shear viscosity of water agree well with the values corresponding to density and evaporation heat data.

Crystals of Y_0.90Tb_0.10Ba₂Cu₃O_6.75 have been prepared by spontaneous crystallization from slowly cooled non-stoichiometric melt of the system Y-Tb-Ba-Cu-O. Average size of platelet crystals having mirror surface is 2×2, the largest - 8×9 mm with thickness 0.1-0.2 mm. The crystals have been characterized by powder X-ray diffraction and electron microprobe analysis. Tetragonal symmetry of the crystals has been determined by X-ray diffraction. Magnetic susceptibility measurements have revealed that the crystals manifest transition to superconducting state without additional annealing (Т_с = 60 K). Structures and compositions - Y/Tb ratio (σ = 0.01) and oxygen content (σ = 0.04) - have been refined for two single crystals. Possibility of rhombic distortion of the tetragonal symmetry is discussed.

Crystals of LuBaCo₄O_7+δ (114Lu) have been obtained by spontaneous crystallization of slowly cooled non-stoichiometric melt of the system Lu-Ba-Co-O. The crystals have been characterized by EDX microprobe and synchrotron radiation powder diffraction. Structure refinement has been carried out (automated diffractometer Bruker X8 APEX with a CCD detector, МоK_α, graphite monochromator, θ_max = 32.54°). Parameters of the hexagonal unit cell: space group P6₃mc, a = 6.2601(1) Å, c = 10.2017(3) Å, V =
346.23(1) ų, Z = 2, d_calc = 6.331 g/cm³. Framework structure of the wurtzite type has been refined anisotropically to R-factor 0.0174. Charge balance in the compound and geometrical matching of structural fragments are discussed.

In the present study high-temperature X-ray diffraction, thermal analysis, and mass-spectrometry have been employed for investigation of samples in the La_1-xSr_xFeO_3-δ family (0 ≤ x ≤ 1), the materials being solid solutions having perovskite structure. It has been shown that the loss of oxygen by the samples on heating to 1200°C in air (0 ≤ x ≤ 1) or in vacuum (х < 0.75) does not result in structural rearrangement of the solid solutions, but causes an increase in the lattice parameters. Heating of the compositions with x ≥ 0.75 in vacuum affords phases with ordered vacancies. The observed structural evolutions (growth of the unit cell parameter and vacancy ordering) are reversible, and on re-oxidation (on cooling in air or additional heating of the "vacuum" samples in air atmosphere) the original parameters of the oxides are recovered. The amount of oxygen evolved on heating increases in vacuum or in helium atmosphere, as compared to air, and also grows with rising strontium content, but under experimental conditions does not reach the maximum possible value (δ = x/2).

A solvate [Cu(CF₃COCHCOCH₃)₂(CH₃COCH₃)] has been synthesized and characterized for the first time. According to X-ray structural data (diffractometer X8 APEX BRUKER, radiation MoK_α, T = 150 K), it crystallizes in the monoclinic crystal system, space group P2₁/c, a = 8.9940(4) Å, b = 22.3966(11) Å, c = 8.1884(3) Å, β = 92.705(2)°, V = 1647.59(12) ų, Z = 4, d_calc = 1.725 g/cm³, final R = 0.0272. The structure is molecular. In the equatorial plane the atom Cu(II) is surrounded with four oxygen atoms of two chelating ligands (CF₃COCHCOCH₃)^-; Cu-O distances 1.927-1.937 Å, O-Cu-O angles 86.18-93.30° and 170.18-175.67°. Square coordination of Cu is complemented to the square-pyramidal one by the oxygen atom of an acetone molecule behaving as an axial ligand; Cu-O_acetone 2.342 Å, O-Cu-O_acetone 89.66-100.11°. In the studied compound disorder of one of the chelate ligands implies the co-existance of the molecules in the cis- and trans-configuration in the crystal under ratio 54.6:45.4. In air the solvate rapidly degrades losing acetone, while in a sealed vessel melts around 313 K. Temperature dependence of equilibrium vapor pressure of acetone over the complex was measured with the static spoon gauge technique, thermodynamic characteristics of its dissociation process being derived: [Cu(CF₃COCHCOCH₃)₂(CH₃COCH₃)]_s = [Cu(CF₃COCHCOCH₃)₂]_s + CH₃COCH_3g, ΔH = 49.6(3) kJ/mol, ΔS = 152(1) J/(mol K), ΔG = 4.30(2) kJ/mol.

A DTA study of thermal decomposition of (NH₄)₂[Ru(NO)Cl₅] in helium atmosphere has been carried out, a synthetic procedure for preparation of the trans-diammine complex mer-[Ru(NO)(NH₃)₂Cl₃] (I) with yield ~70% has been developed. On re-crystallization of I from aqueous solution a trans-aquanitroso complex [Ru(NO)(NH₃)₂Cl₂(H₂O)]Cl⋅H₂O (II) has been isolated. The structures of the compounds have been determined by single crystal X-ray diffraction: space group Pbcn, a = 6.607(1) Å, b = 11.255(2) Å, c = 9.878(2) Å (I) and space group Ima2, a = 8.3032(3) Å, b = 8.0890(2) Å, c = 15.9192(5) Å (II).

Synthesis and single crystal X-ray diffraction study of hafnium(IV) dipivaloylmethanate Hf(dpm)₄ and chloro-tris-(dipivaloylmethanato)hafnium(IV) Hf(dpm)₃Cl have been carried out. Crystal data: a =
22.6606(5) Å, b = 11.3990(4) Å, c = 19.8513(7) Å, β = 106.458(1)°, Рс, Z = 4, d_calc = 1.231 g/cm³, R = 0.075 for C₄₄H₇₆HfO₈; a = 10.6376(13) Å, b = 10.6701(10) Å, c = 19.4400(22) Å, α = 74.970(3)°, β = 75.672(3)°, γ = 61.725(2)°, P-1, Z = 2, d_calc = 1.366 g/cm³, R = 0.031 for C₃₃H₅₇ClHfO₆. The structures are molecular and are built from discrete mononuclear complexes joined by van der Waals interactions. Disordering of carbon atoms preserving at low temperature is observed for the compound Hf(dpm)₄. It has been found out that the structure contains two crystallographically unique complexes of hafnium(IV) with central atoms coordinated with eight oxygen atoms of four dipivaloylmethane ligands, bond lengths Hf-O fall within 2.084-2.222 Å, the distances Hf…Hf between the molecules are 10.07-13.87 Å. In Hf(dpm)₃Cl the hafnium atom is seven-coordinated with six oxygen atoms of three β-diketonate ligands and one chlorine atom, the distances Hf-O fall within 2.087-2.179 Å, the lengths of the bond Hf-Cl for two crystallographically independent molecules Hf(1) and Hf(2) are 2.466 Å and 2.442 Å, respectively.

Molecular and crystal structures of a new complex compound of copper(II) with 3-methyl-5-carboxylatopyrazole (СН₃PzCOO^-) with the composition Cu(СН₃PzCOO)₂⋅H₂O have been determined by single crystal XRD. It has been demonstrated that the carboxylate ion performs the bridging tridentate function. In the equatorial plane coordination occurs through the pyridine N atom of the pyrazole and one of O atoms of the carboxylate group yielding a five-membered metallocycle CuNOC₂. The second О atom of one of the ligands is bound to the neighboring copper(II) ion affording an infinite linear chain. The coordination polyhedron of the copper atom is a square pyramid, coordination core CuN₂O₃.

Results of a quantum-chemical study of the molecular structure of dimerization products of saturated 1,3-butadiene and hexafluoro-1,3-butadiene (tricyclo[3.3.0.0^2.6]octane, dodecafluorotricyclo[4.2.0.0^2.5]octane (I), and dodecafluorotricyclo[3.3.0.0^2.6]octane (II)) are presented. The calculated symmetry of the molecule of I in vacuum (C₂) differs from its symmetry in the single crystal (C_i, XRD). The most stable of dimers (II) contains C-C bonds with a length of up to 1.573 Å and a four-atom cycle with angles of 82.3°.