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Journal of Structural Chemistry

2008 year, number 6

1.
STUDY OF THE STRUCTURAL AND THERMODYNAMIC STABILITY OF PENTACOORDINATED NITROGEN COMPOUNDS NF2X3 (X = H, Cl, Br): AB INITIO CALCULATIONS

I. V. Getmanskii, R. M. Minyaev
Keywords: pentacoordinated nitrogen atom, thermodynamic stability, potential energy surface, reaction path, saddle point
Pages: 1013-1019

Abstract >>
Quantum chemical calculations of compounds with a pentacoordinated nitrogen atom such as NF2H3 (in the CCSD(Full)/6-311++G(d,p) approximation), NF2Cl3 and NF2Br3 (in the B3LYP/6-311+G(d) approximation) are carried out. It is found that NF2Cl3 and NF2Br3 molecules are structurally stable, but thermodynamically unstable, and are isomerized to NFCl2FCl and NFBr2FBr molecular complexes respectively. The total energy of NFCl2FCl and NFBr2FBr complexes is lower than the total energy of NF2Cl3 and NF2Br3 molecules by 62 kcal/mol and 64 kcal/mol respectively. The trigonal bipyramidal form of the NF2H3 molecule of D3h symmetry is structurally unstable: a first-order saddle point corresponds to it on the potential energy surface of the system. A second-order saddle point is found on the reaction path of NF2H3 isomerization.
																								



2.
AROMATIC STABILITY ENERGY STUDIES ON FIVE-MEMEBERED HETEROCYCLIC C4H4M (M = O, S, Se, Te, NH, PH, AsH and SbH): DFT CALCULATIONS

E. Vessally
Keywords: Aromatic character; isodesmic reaction; NICS; five-membered heterocycle; C4H4M
Pages: 1020-1025

Abstract >>
Energetic, geometric and magnetic criteria were applied to examine the stability and/or aromatic character for the cyclic molecules C4H4M (M = O, S, Se, Te, NH, PH, AsH and SbH)
at B3LYP/6-311++G** and MP2/6-311++G** levels of theory. The isodesmic reactions and nuclear independent chemical shifts (NICS) calculations were utilized to examine the molecules for energetic and magnetic criteria, respectively. The isodesmic reaction energies reveal that thiophene (C4H4S, -23.269 kcal/mol) and pyrrole (C4H4NH, -20.804 kcal/mol) have the greatest aromatic stabilization energies and tellurophene (C4H4Te, -15.114 kcal/mol) and stibole (C4H4SbH, -1.169 kcal/mol) have the lowest aromatic stabilization energies in their corresponding groups at MP2/6-311++G**. The NICS calculations confirmed the results obtained trough isodesmic reaction energies.
																								



3.
PREDICITION OF VAPORIZATION ENTHALPY BASED ON MODIFIED RANDIČ INDICES. ALKANES

. L. Krasnykh
Keywords: enthalpy of vaporization, topological index, binding index, alkanes, QSPR
Pages: 1026-1033

Abstract >>
Methods to calculate the enthalpy of vaporization of alkanes under normal conditions are considered using the classic Randič method and its modifications. The calculation based on modified methods is shown to be capable of predicting the vaporization enthalpy of alkanes with an error comparable with that of experimental measurements.
																								



4.
SIMULATION OF STRUCTURAL, ELASTIC, AND ELECTRONIC PROPERTIES OF NEW CUBIC CRYSTALS OF CARBON AND BN NANOTUBES

A. N. Enyashin, A. L. Ivanovskii
Keywords: crystals from carbon and BN nanotubes, structural, elastic, and electronic properties, simulation
Pages: 1033-1039

Abstract >>
Models of new cubic crystals from carbon and boron-nitrogen (BN) nanotubes are proposed. Within electronic density functional theory, their structural, elastic, and electronic properties are studied. These isotropic nanotubular crystals are found to have extremely high elastic modules B (~490-650 GPa) and low compressibility β (~0.0020-0.0015 1/GPa) and maintain the conductivity typical of their "building blocks," i.e. isolated carbon and BN nanotubes.
																								



5.
STRUCTURE AND ENERGY STUDY OF β-DIKETONATES. XV. COMPOSITION OF SUPERHEATED VAPORS AND STRUCTURE OF MONOMERIC MOLECULES OF Tris-HEXAFLUOROACETYLACETONATES OF DYSPROSIUM, HOLMIUM, ERBIUM, AND YTTERBIUM

N. V. Tverdova, G. V. Girichev, V. V. Rybkin, S. A. Shlykov, N. P. Kuzmina, I. G. Zaitseva
Keywords: gas-phase electron diffraction, DFT, mass-spectrometry, molecular structure, tris-hexafluoroacetylacetonate, REE
Pages: 1040-1050

Abstract >>
The molecular structure of tris-hexafluoroacetylacetonates of dysprosium, holmium, erbium, and ytterbium (M(hfa)3, M = Dy, Ho, Er, Yb) is studied in the framework of synchronous electron diffraction and mass-spectrometric experiment and also quantum-chemically. For all M(hfa)3 complexes structural parameters ra, rg, and rh1 are found. It is established that the coordination polyhedron LnO6 has a configuration of D3 symmetry. In experiments on superheated vapors of Dy(hfa)3, Ho(hfa)3, and Yb(hfa)3 the molecular forms present in the vapor at different degrees of superheat are determined.
																								



6.
STUDY OF THE TEMPERATURE EFFECT ON IR SPECTRA OF CRYSTALLINE AMINO ACIDS, DIPEPTIDS, AND POLYAMINO ACIDS. III. α-GLYCYLGLYCINE

Y. A. Chesalov, G. B. Chernobai, E. V. Boldyreva
Keywords: peptide bond, ?-glycylglycine, IR spectroscopy, hydrogen bond
Pages: 1051-1060

Abstract >>
The IR spectra of α-glycylglycine (H3+N-CH2-CO-NH-CH2-COO-) are studied in the temperature range of 93 to 413 K. Changes in the spectra due to temperature variation are correlated with the previously obtained X-ray diffraction data on anisotropic compression of the structure and changes in the parameters of hydrogen bonding. Changes in the vibrational frequencies of NH+3 and COO groups in the IR spectrum of α-glycylglycine are compared to changes in the vibrational frequencies of the same groups in the IR spectra of polymorphs of glycine, L- and DL-serine.
																								



7.
STUDY OF THE TEMPERATURE EFFECT ON IR SPECTRA OF CRYSTALLINE AMINO ACIDS, DIPEPTIDES, AND POLYAMINO ACIDS. IV. L-CYSTEINE AND DL-CYSTEINE

V. S. Min'kov, Y. A. Chesalov, E. V. Boldyreva
Keywords: cysteine, optical isomers, IR spectroscopy, hydrogen bonds
Pages: 1061-1073

Abstract >>
A study of the IR spectra of L- and DL-cysteine is carried out in a range of frequencies from 4000 cm-1 to 600 cm-1 and temperatures from 333 K to 83 K. Changes in the spectra of L- and DL-cysteine (NH+3-CH(CH2SH)-COO-) on cooling are analyzed in comparison with the spectra of L- and DL-serine (NH+3-CH(CH2OH)-COO-) and three polymorphs of glycine (NH+3-CH2-COO-) previously studied under temperature variation. Changes in the IR spectr at variable temperatures are correlated with previously obtained diffraction data on anisotropic compression of the structure and changes in the geometric parameters of hydrogen bonds. Special attention is paid to temperature regions in which anomalies were detected by vibrational spectroscopy, X-ray diffraction, and calorimetry.
																								



8.
INFRARED SPECTROSCOPY AND THE STRUCTURE OF POLYTYPIC MODIFICATIONS OF RM3(BO3)4 BORATES (R - Nd, Gd, Y; M - Al, Ga, Cr, Fe)

V. S. Kurazhkovskaya, . Y. Borovikova, N. I. Leonyuk, . V. Koporulina, . L. Belokoneva
Keywords: infrared spectroscopy, factor group analysis of vibrations, rare-earth orthoborates, polytypic modifications
Pages: 1076-1080

Abstract >>
By means of IR spectroscopy with the use of factor group analysis for vibrations of the B-O bond, rare-earth borates with a general formula of RM3(BO3)4 (R is Nd, Gd, and Y; M is Al, Ga, Cr, and Fe) and related polytypic structures are assigned to space groups R32 or 2/c. Compounds with both almost homogeneous structures and with inclusions of the monoclinic polytype are revealed among rhombohedral borates. The latter is most typical of phases with a small octahedral Al cation. It is shown that in the monoclinic modification of NdAl and NdCr borates fragments of the rhombohedral phase are always present. Alternation of differently ordered structural fragments is determined by temperature conditions of crystallization.
																								



9.
IONIC MOBILITY IN AMMONIUM-RUBIDIUM HEPTAFLUOROZIRCONATE (NH4)2.4Rb0.6ZrF7 BY (1H, 19F) NMR DATA

V. Y. Kavun, I. A. Tkachenko, N. A. Didenko, V. I. Sergienko
Keywords: NMR (19F, 1H) spectra, ammonium-rubidium heptafluorozirconate, ionic mobility, ionic conductivity
Pages: 1081-1085

Abstract >>
NMR (19F, 1H) methods are used to study ionic mobility in heptafluorozirconate (NH4)2.4Rb0.6ZrF7 in a range of temperatures from 150 K to 430 K. Types of ionic movements are determined, and their activation energy is evaluated. As a result of a phase transition a modification forms in which diffusion in the ammonium sublattice and isotropic reorientations of ZrF3-7 complex anions are observed. According to preliminary data, due to diffusion of ammonium ions the compound has relatively high ionic conductivity (σ ≈ 8.3×10-5 S/cm at 423 K).
																								



10.
STUDY ON THE INTERACTION OF A PALLADIUM COMPLEX WITH DNA

E.J. Gao, H.X. Yin, M.C. Zhu, Y.G. Sun, X.F. Gu, Q. Wu, L.X. Ren
Keywords: palladium(II) complex, adenine, interaction mechanism, kinetics, crystal structure
Pages: 1086-1091

Abstract >>
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) Å3, 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.
																								



11.
NATURE OF THE KINEMATIC SHEAR VISCOSITY OF WATER

N. P. Malomuzh, A. V. Oleinik
Keywords: water, argon, kinematic shear viscosity, hydrogen bonds, structural functions
Pages: 1092-1100

Abstract >>
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 nH (t =
T/Tc, = Tc 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 < TH (TH ≈ 310 K is the characteristic temperature of water) the formation of the kinematic shear viscosity is induced by activation. At T > TH, 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 νnH is found and substantiated. It is shown that the value and temperature dependence of nH resulting in the experimental values of the kinematic shear viscosity of water agree well with the values corresponding to density and evaporation heat data.
																								



12.
COMPOSITION AND STRUCTURE REFINEMENT OF SUPERCONDUCTING CRYSTALS Y1-xTbxBa2Cu3O6+δ ( = 0.10; δ = 0.75)

L. P. Kozeeva, N. V. Podberezskaya, N. V. Kuratieva, M. Y. Kamaneva, A.G. Blinov
Keywords: superconducting crystals Ln123, (Y/Tb)123 crystals, crystallization, structure, solid solutions, superconductivity
Pages: 1101-1107

Abstract >>
Crystals of Y0.90Tb0.10Ba2Cu3O6.75 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 ( = 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.
																								



13.
CRYSTAL STRUCTURE OF A COBALT OXIDE LuBaCo4O7

L. P. Kozeeva, M. Y. Kamaneva, A. I. Smolentsev, V. S. Danilovich, N. V. Podberezskaya
Keywords: barium lutetium cobalt oxide, ternary oxides, high-temperature crystallization, structure of cobalt oxides
Pages: 1108-1113

Abstract >>
Crystals of LuBaCo4O7+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, Kα, graphite monochromator, θmax = 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) Å3, Z = 2, dcalc = 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.
																								



14.
WEAKLY BOUND OXYGEN AND ITS ROLE IN STABILITY OF SOLID SOLUTIONS La1-xSrxFeO3-δ

A. N. Nadeev, S. V. Tsybulya, V. D. Belyaev, I. S. Yakovleva, L. A. Isupova
Keywords: perovskite, weakly bound oxygen, DTA, high-temperature powder X-ray diffraction
Pages: 1114-1121

Abstract >>
In the present study high-temperature X-ray diffraction, thermal analysis, and mass-spectrometry have been employed for investigation of samples in the La1-xSrxFeO3-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 1200C in air (0 ≤ x ≤ 1) or in vacuum ( < 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).
																								



15.
CRYSTAL STRUCTURE AND THERMODYNAMIC STABILITY OF AN ACETONE SOLVATE OF BIS(TRIFLUOROACETYLACETONATO)COPPER(II)

P. A. Stabnikov, G. I. Zharkova, A. I. Smolentsev, É. A. Ukraintseva, D. V. Soldatov
Keywords: copper(II), ?-diketonates, acetone, cis-trans isomerization, crystal structure, weak interactions, vapor pressure
Pages: 1122-1127

Abstract >>
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 MoKα, 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) Å3, Z = 4, dcalc = 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-Oacetone 2.342 Å, O-Cu-Oacetone 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 + CH3COCH3g, ΔH = 49.6(3) kJ/mol, ΔS = 152(1) J/(mol K), ΔG = 4.30(2) kJ/mol.
																								



16.
STRUCTURE AND SYNTHESIS OF NITROSORUTHENIUM trans-DIAMMINES [Ru(NO)(NH3)2Cl3] AND [Ru(NO)(NH3)2(H2O)Cl2]Cl⋅H2O

M. A. Il'in, V. A. Emel'yanov, I. A. Baidina
Keywords: ruthenium, nitroso complexes, ammine complexes, chloro complexes, single crystal X-ray diffraction, thermogravimetric analysis
Pages: 1128-1136

Abstract >>
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).
																								



17.
X-RAY DIFFRACTION STRUCTURAL INVESTIGATION OF TWO HAFNIUM(IV) COMPLEXES WITH DIPIVALOYLMETHANE

K. V. Zherikova, I. A. Baidina, N. B. Morozova, N. V. Kuratieva, I. K. Igumenov
Keywords: hafnium(IV) β-diketonates, synthesis, single crystal X-ray diffraction, mononuclear complex, mass-spectrometry study
Pages: 1137-1142

Abstract >>
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), , Z = 4, dcalc = 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, dcalc = 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 HfHf 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.
																								



18.
THE STRUCTURE OF A NEW COPPER(II) COMPLEX WITH 3-METHYL-5-CARBOXYLATOPYRAZOLE

L. G. Lavernova, E. V. Peresypkina, A. S. Zhilin, O. G. Shakirova, M. N. Novikov, S. F. Vasilevskii
Keywords: crystal and molecular structure, complex, copper, pyrazole derivatives
Pages: 1143-1146

Abstract >>
Molecular and crystal structures of a new complex compound of copper(II) with 3-methyl-5-carboxylatopyrazole (3PzCOO-) with the composition Cu(3PzCOO)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 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.
																								



19.
QUANTUM CHEMICAL STUDY OF THE STRUCTURE OF TRICYCLIC SATURATED HEXAFLUORO-1,3-BUTADIENE DIMERS

K. K. Kalninsh, S. G. Semenov
Keywords: equilibrium structure, B3LYP/6-311G**, tricyclo-C8F12
Pages: 1147-1149

Abstract >>
Results of a quantum-chemical study of the molecular structure of dimerization products of saturated 1,3-butadiene and hexafluoro-1,3-butadiene (tricyclo[3.3.0.02.6]octane, dodecafluorotricyclo[4.2.0.02.5]octane (I), and dodecafluorotricyclo[3.3.0.02.6]octane (II)) are presented. The calculated symmetry of the molecule of I in vacuum (C2) differs from its symmetry in the single crystal (Ci, 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.
																								



20.
MOLECULAR STATISTICAL MODEL OF SPIN CROSSOVER EQUILIBRIUM IN THE CRYSTAL STATE TAKING INTO ACCOUNT THE PHENOMENON OF ORDERING

A. B. Koudriavtsev, W. Linert
Keywords: spin crossover, statistical thermodynamics, molecular interactions, ordering
Pages: 1150-1153

Abstract >>
Formalism is developed in which contributions of binary and ternary interactions towards free energy of a mixture of low-spin (A) and high-spin (B) isomers of spin crossover compounds as well as effects of ordering are taken into account. Parameters characterising non-ideality in this formalism are the excess free energy (ΔFex) and absolute asymmetries (ΔA, ΔB) of splittings of free energy levels. The excess free energy characterises the effects of binary interactions whereas asymmetries arise from ternary interactions. According to this model, the plateau in the spin crossover transition curve originates from the phenomenon of ordering taken into account in the Gorsky-Bragg-Williams approximation.
																								



21.
WHY THE MODEL OF NON-INTERACTING CHAINS YIELDS ADEQUATE DESCRIPTION OF SPIN CROSSOVER IN SPACE STRUCTURES?

A. B. Koudriavtsev, W. Linert
Keywords: spin crossover, many-body interactions, ordering
Pages: 1154-1158

Abstract >>
Considering many-body interactions in tetrahedral structures as perturbations of binary potentials by third bodies yields a free energy functional of the binary mixture equivalent to one earlier derived for spin crossover equilibrium in one-dimensional chains. Formal non-ideality parameters of this functional, the excess energy and asymmetries of splittings can be expressed in terms of molecular parameters based on binary potentials.
																								



22.
1 NMR SPECTROSCOPIC STUDY OF THE FORMATION OF MOLECULAR COMPLEXES OF METHANOL WITH BENZENE AND PHENANTHRENE

R. S. Kumeev, M. Y. Nikiforov, E. D. Totchasov, G.A. Al'per
Keywords: solutions of non-electrtolytes, molecular association, NMR spectroscopy, polyaromatic hydrocarbons
Pages: 1159-1162

Abstract >>
Chemical shifts (c.s.) of 1 nuclei in methanol are measured for methanol-benzene and methanol-phenanthrene systems. A method to determine the equilibrium constant of the molecular association reaction by NMR spectroscopy data is proposed for systems with low solubility of a compound when the dependence of c.s. on the composition is close to a straight line. The equilibrium constants for the formation of molecular complexes in methanol-benzene and methanol-phenanthrene systems are found.
																								



23.
THE STRUCTURE OF A NEW OCTAHEDRAL FLUORIDE COMPLEX OF NIOBIUM (Me4N)2[Nb6F6Br6(H2O)2Cl4]⋅6H2O

N. G. Naumov, S. Cordier, C. Perrin, S.B. Artemkina
Keywords: niobium, fluorides, cluster, synthesis, crystal structure
Pages: 1163-1166

Abstract >>
The substitution reaction of thiocyanide groups of the complex K4[Nb6F6Br6(NCS)6] in aqueous hydrochloric acid has afforded a new fluoride cluster anion [Nb6FBrCl(H2O)]2- isolated as the salt (Me4N)2[Nb6F6Br6Cl4(H2O)2]⋅6H2O (space group R3m, a = 11.230(5) Å, c = 26.230(5) Å, V = 2865(2) Å3, Z = 3, R1 = 0.0362, R2w = 0.0886). The anion contains the cluster core Nb6F6Br6 having ordered "inner" ligands. Difference in the atomic radii of "inner" ligands causes a significant distortion of the metal cluster along the three-fold axis.
																								



24.
CRYSTAL STRUCTURE OF Cs[Gd(H2O)4Re6Te8(CN)6]⋅4H2O

M. S. Tarasenko, N. G. Naumov, A. V. Virovets, S.-J. Kim, V. E. Fedorov
Keywords: rhenium, octahedral cluster, cyanide complex, gadolinium, crystal structure
Pages: 1167-1170

Abstract >>
The structure of the salt Cs[Gd(H2O)4Re6Te8(CN)6]⋅4H2O (space group P-1, a = 9.436(5) Å, b =
12.365(7) Å, c = 15.187(8) Å, α = 89.104(10), β = 86.996(10), γ = 82.304(9)) has been established by single crystal XRD. The structure of the compound features layers involving Gd3+ cations bound to cluster anions [Re6Te8(CN)6]4- through cyanide groups. The interlayer space contains cesium cations and crystallization water molecules.
																								



25.
INGLE CRYSTAL XRD STUDY OF 4,4′-DIPYRIDYL-p-ETHOXYBENZOIC ACID AND N,N′-DIPYRIDYLPIPERAZINE- p-ETHOXYBENZOIC ACID CO-CRYSTALS: DIRECT EVIDENCE OF H-BOND INTERACTION IN THE CORRESPONDING LIQUID-CRYSTALLINE MESOGENIC PHASES

L.-L. Lai1, L.-J. Lee2, D.-W. Luo3, Y.-H. Liu4, Y. Wang5
Keywords: bipyridine, molecular crystals, liquid crystals, neumatic, mesogenic
Pages: 1175-1178

Abstract >>
Supramolecular H-bonded complexes formed between p-ethoxybenzoic acid and 4,4′-dipyridyl or N,N′-dipyridylpiperazine were obtained as nematic liquid-crystalline phases. The corresponding crystals suitable for single crystal X-ray analysis were isolated and investigated. The stoichiomtery of complex 1 is (4,4′-dipyridyl)⋅2(p-ethoxybenzoic acid) and that of complex 2 is (N,N′-dipyridylpiperazine)⋅2(p-ethoxybenzoic acid). The molecular packing observed in the crystal structures investigated indicates that the mesogenic phases of the complexes are induced by H-bond interactions.
																								



26.
MOLECULAR STRUCTURE OF 8-CARBOXY-18-CHLORO-14-HYDROXY-20-ISOPROPYL-16-METHOXY-4,8-DIMETHYL-15-OXAOCTACYCLO-[11.7.1.03,1204,9012,19014,18016,21017,20]HENICOSANE

R. R. Fazlyev, G. F. Vafina, F. Z. Galin
Keywords: "cage" compound, photocyclization, structure, single crystal X-ray diffraction
Pages: 1179-1181

Abstract >>
The structure of 8-carboxy-18-chloro-14-hydroxy-20-isopropyl-16-methoxy-4,8-dimethyl-15-oxaocta-
cyclo[11.7.1.03,1204,9012,19014,18016,21017,20]henicosane has been determined by single crystal X-ray diffraction.
																								



27.
X-RAY STRUCTURAL INVESTIGATION OF THE PRODUCTS OF RING CLOSURE OF 2-ALKENYLTHIO-PYRIDINES UPON TREATMENT WITH MERCURY IODIDE

P. A. Slepukhin, D. G. Kim, V. N. Charushin
Keywords: 2-aleknylthiopyridines, mercury iodide, mercury iodide promoted ring closure, organomercury compounds, salts of 2, 3-dihydrothiazolo[3, 2-a]pyridinium
Pages: 1182-1186

Abstract >>
The products of the reaction of 2-alkenylthiopyridines with mercury iodide have been studied by single crystal X-ray diffraction. It has been demonstrated that the products are organomercury derivatives of salts of 2,3-dihydrothiazolo[3,2-a]pyridinium.
																								



28.
ELECTROSTATIC MoO (METHANOL) BOND IN BENZYLTRIPHENYLPHOSPHONIUM trans−TETRACHLORO(METHANOL)OXOMOLYBDATE(V)

M. Holynska1, T. Lis2
Keywords: Crystal structure; electrostatic bond; Mo(V) complex; oxomolybdates
Pages: 1187-1190

Abstract >>
Benzyltriphenylphosphonium trans-tetrachloro(methanol)oxomolybdate(V) has been obtained from methanol suspension of benzyltriphenylphosphonium molybdate(VI) saturated with hydrogen chloride. The crystal structure comprises discrete trans-tetrachloro(methanol)oxomolybdate(V) anions and benzyltriphenylphosphonium cations. The anion has distorted octahedral geometry of central atom with visible trans influence imposed by short Mo-O bond (1.659(2) Å). The methanol O atom is bonded to the Mo atom, the bond being mostly electrostatic in character. A comparison with previously reported structures indicates that the methanol methyl moiety can switch between different positions with respect to the chloride ligands.