Temperature effect on the competition between the processes of 9-cyanophenanthrene exciplex decay

The activation parameters of internal conversion, intersystem crossing, and dissociation into radical ions were determined for the exciplexes of 9-cyanophenanthrene with 1,3,5- and 1,2,3-trimethoxybenzene. The activation enthalpies for the different processes of exciplex decay were found to be close for a given exciplex in a given solvent, thus allowing a linear approximation for the temperature dependence of the logarithm of the exciplex lifetime.Translated from Khimiya Vysokikh Energii, Vol. 39, No. 1, 2005, pp. 26–31.Original Russian Text Copyright © 2005 by Dogadkin, Dolotova, Soboleva, Kuzmin, Plyusnin, Pozdnyakov, Grivin.     

Synthesis and Properties of Scandium and Alkaline-Earth Double Borates M<Subscript>3</Subscript>Sc(BO<Subscript>3</Subscript>)<Subscript>3</Subscript>

Compounds M₃Sc(BO₃)₃ (M = Ba, Sr) were prepared by solid-phase reactions and studied by X-ray diffraction (XRD) analysis and IR spectroscopy. The structural type of the compounds was determined and their unit cell parameters were refined.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 25–27.Original Russian Text Copyright © 2005 by Khamaganova, Khrushcheva.     

The Mechanism of Action of a Multicomponent Co-Mo-Bi-Fe-Sb-K-O Catalyst for the Partial Oxidation of Propylene to Acrolein: II. Changes in the Phase Composition of the Catalyst under Reaction Conditions

The structures of a complex multicomponent Co-Mo-Fe-Bi-K-Sb-O catalyst for the oxidation of propylene to acrolein and simpler catalysts from which some catalyst components were absent were studied by X-ray diffraction analysis. The phases of α-CoMoO₄, β-CoMoO₄, Fe₂(MoO₄)₃, Bi₂O₃ ⋅ MoO₃, Bi₂O₃ ⋅ 2MoO₃, Bi₂O₃ ⋅ 3MoO₃, oxidized molybdenum oxide, and reduced molybdenum oxide are the main components of the catalyst. Ternary compounds were not detected. Under catalytic reaction conditions, the relative amounts of the phases changed; this change suggests the occurrence of redox transformations with the participation of these phases, probably, at the interface.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 580–584.Original Russian Text Copyright © 2005 by Shashkin, Udalova, Shibanova, Krylov.     

Stress-induced crystallization of poly(ethylene terephthalate)

Quenched amorphous films of poly(ethylene terephthalate) (PET) are stretched at temperatures less than T_g; changes in density, wide-angle x-ray diffraction, and small-angle light scattering are observed. The density increase upon stretching is attributed to an increase in crystallinity accompanied by an increase in the intensity of somewhat diffuse wide-angle x-ray diffraction and of both V_V and H_V small-angle light scattering patterns. The formation of oriented rodlike superstructure may be discerned from small-angle light scattering. Annealing of these samples increases the crystallinity as measured from density and leads to an increase in the perfection of crystalline and supercrystalline structure as measured by wide-angle x-ray diffraction and small-angle light scattering. The rodlike morphology changes to form spherulitelike aggregates as observed by small-angle light scattering and light micrographs. A model is proposed to explain the observations. Studies are extended to stretching films of PET above their T_g and observing changes in birefringence, density, wide-angle x-ray diffraction and small-angle light scattering as a function of elongation and stretching temperature. The formation of defomed spherulitelike superstructure may be discèrned from light micrographs. Results are compared with those obtained upon stretching films below T_g.     

Molecular Structure of Bis(trimethylsilyl) Hypophosphite HP(OSiMe3)2 by Gas-Phase Electron Diffraction and Quantum Chemistry

Geometric parameters and conformation of the bis(trimethylsilyl)hypophosphite molecule were determined by gas-phase electron diffraction and quantum-chemical calculations. The molecule has an asymmetric structure, including an asymmetric P(OSiMe₃)₂ group. The principal geometric parameters are as follows: (r _a; in parentheses are standard deviations): bond lengths: P-O 1.616 and 1.633(1), Si-O 1.670(1), Si-C 1.892(1), C-H 1.097(3) Å; bond angles: OPO 100.8(8), POSi 133.3, and 138.4(3)°; torsion angles about P-O bonds 120(2) and 41.(3)°; and torsion angles about Si-O bonds are 145 and −178(4)°.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 897–902.Original Russian Text Copyright © 2005 by Naumov, Oberhammer, Tafipol’skii.     

Synthesis and X-ray diffraction analysis of {Perchlorato-bis[benzimidazole-2-<Emphasis Type="Italic">N</Emphasis>-(4-methoxyphenyl)carbothioamidato]copper(III)} hydroperchlorate

Conditions for the formation of the complex [CuL₂(ClO₄)] · HClO₄ (where L is the deprotonated molecule of benzimidazole-2-N-(4-methoxyphenyl)carbothioamide) are determined and its crystal and molecular structures are studied by X-ray diffraction analysis.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 1, 2005, pp. 43–47.Original Russian Text Copyright © 2005 by Panasyuk, Ranskii, Aliev.     

Nanostructured material based on Tin and Titanium Oxides: A potentiodynamic study

Films of a nanostructured material containing 90% SnO₂ and 10% TiO₂ (material ST10) are exhaustively studied by a potentiodynamic method in a lithium imide solution in dioxolane. The results are compared with x-ray diffraction data for freshly prepared and cycled samples.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 76–82.Original Russian Text Copyright © 2005 by Kulova, Roginskaya, Skundin.     

X-ray diffraction study of pore structure of pyrocarbon coatings obtained at various temperatures

X-ray diffraction (large- and small-angle scattering) has been used in an investigation of the pore structure and crystal structure of pyrocarbon coatings obtained by pyrolysis of a number of gaseous hydrocarbons at temperatures of 1300–2000°C. The coatings have a well-developed pore structure. The pore dimensions cover a range from fractions of a nanometer to hundreds of nano-meters. The pore volume and distribution depend primarily on the temperature of deposition. This relationship is extremal in nature. The volume of small pores (R=0.5-3.0 nm) is the greatest when T_d=1500°C; owing to the closed nature of the pores, this leads to an anomalous decrease in pycnometric density, the minimum density being observed at this same temperature. With T_d > 1500°C, growth of the crystals is observed, correlating with the decrease in volume of small pores.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya; No. 5, pp. 982–987, May, 1990.     

Synthesis and Structure of Heterometallic Chromium(III) Complexes with Ethylenediaminetetraacetic Acid

The complexes [M(Tsc)₂][Cr(Edta)]₂, where M is Ni, Cu; Tsc is thiosemicarbazide; Edta^4– is the ethylenediaminetetraacetate anion, were synthesized and characterized by X-ray diffraction. The ionic structures are composed of the [M(Tsc)₂]²⁺ cations and [Cr(Edta)]^– anions with a component ratio of 1 : 2. The cation has a distorted trans-square coordination. The carboxyl groups of the H₄Edta molecule are deprotonated and the ligand is attached to the Cr atom in the hexadentate chelating mode. The cations and anions are linked by a system of hydrogen bonds.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 370–375.Original Russian Text Copyright © 2005 by Ciornea, Filippova, Gulea, Shova, Borta, Simonov.     

Study of the Solid—Liquid Equilibrium in Mixed Alkaline Earth Fluorohalides

We have studied the solid-liquid equilibrium of the system Sr_1–yBa_yFCl_1–xBr_x using DTA and X-ray diffraction techniques. The entire composition range in this system yields solid solutions which crystallize in the PbFCl (Matlockite) structure type. The melting points of the entire composition range have been parametrized (within 5°C rms error) using a biquadratic fit of the available data obtained by experiment and from the literature.This revised version was published online in November 2005 with corrections to the Cover Date.     

Cordierite-Like Catalyst Supports Based on Clay Materials

The possibility of lowering the temperatures of crystallization of spinel-like cordierite, mullite, MgAl₂O₄, and corundum was studied. The following naturally occurring clay materials were used for the synthesis of supports: bentonite, clay, and kieselguhr. The effect of the preparation procedure on the structure and texture characteristics of the resulting supports was found. The composition of the resulting samples varied over the following ranges: clay material, from 45 to 60%; Al₂O₃, from 30 to 42%; and MgO, from 10 to 20%. Conditions responsible for spinel formation in cordierite and mullite phases over the temperature range 1050–1150°C were found. At the same parent composition, the thermal stability of supports prepared by coprecipitation was higher than that of composites prepared by mechanical mixing, as found using X-ray diffraction analysis and measuring specific surface areas and mechanical strength. The supports synthesized are promising for the preparation of supported catalysts for high-temperature processes.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 648–651.Original Russian Text Copyright © 2005 by Stoyanova, Vladov, Kasabova, Mekhandzhiev.     

Synthesis of hollow spherical silica with MCM-41 mesoporous structure

Hollow spherical mesoporous silica was synthesized by using sodium silicate as a precursor and a low concentration of cetyltrimethylammonium bromide (CTAB) (0.154 mol dm^–3). The resulting hollow spherical particles were characterized with scanning electron microcopy (SEM), small-angle X-ray diffraction (SXRD), transmission electron microscopy (TEM), and N₂ gas adsorption and desorption techniques. The results showed that regular spherical mesoporous silica could be obtained only if the molar ratio of propanol to CTAB was in the range of approximately 8:1–9:1. The spherical particles were hollow (inside), and the shell consisted of smaller particles with a pore structure of hexagonal symmetry. With an increase of the molar ratio of propanol to CTAB, the distance (a value) between centers of two adjacent pores increased, and the pore structure of mesoporous silica became less ordered. N₂ adsorption–desorption curves revealed type IV isotherms and H1 hysteresis loops; with an increase of the molar ratio of propanol to CTAB, the pore size with Barrett–Joyner–Halenda (BJH) diameter of the most probable distribution decreased, but the half peak width of the pore size distribution peak increased     

Crystal Structure of Sodium Perchloratotriacetatoneptunate(V) Monohydrate Na<Subscript>3</Subscript>NpO<Subscript>2</Subscript>(OOCCH<Subscript>3</Subscript>)<Subscript>3</Subscript>ClO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O

The crystal structure of Na₃NpO₂(OOCCH₃)₃ClO₄ · H₂O was studied by single-crystal X-ray diffraction method. The structure is composed of the complex anions NpO₂(OOCCH₃)₃]²⁻, perchlorate anions, Na cations, and water molecules. The oxygen environment of Np(V) is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of three acetate ions. In addition to the acetate anions, the structure contains the perchlorate ion whose oxygen atoms, except for one, are included in the coordination environment of Na⁺ cations.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 636–640.Original Russian Text Copyright © 2005 by Charushnikova, Fedoseev, Starikova.     

Dependences on the Composition and a Comparison of Electrolytic Properties of Some Germanium-Containing Quasi-binary Salt Systems

Germanium-containing quasi-binary salt systems GeSe-GeI₂ and NaI-GeI₂ (GeI₂ is a dopant) are studied by methods of electroconductance and x-ray diffraction analysis (XRDA). The conductivity isotherms combined with the XRDA data show that the domain of restricted solid solutions in these systems comes to 3 and 1 mol % GeI₂, respectively. The maximal electrolytic admittance is observed at 2 and 0.25 mol % GeI₂ in GeSe-GeI₂ and NaI-GeI₂ systems. The GeSe system has better ceramic properties, is less susceptible to water traces, and has higher conductivity and lower activation energy for conduction.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 616–619.Original Russian Text Copyright © 2005 by Leushina, Danilov, Zlomanov.     

Structure and Properties of Solid Solutions in the System YBaCuFeO<Subscript>5</Subscript>-YBaCuCoO<Subscript>5</Subscript>

The crystal structure parameters of solid solutions YBaCuFe_{1 − x} Co_xO₅ (0 ≤ x ≤ 1) were determined, and their thermal stability, thermal expansion, conductance, thermoelectromotive force, dielectric properties, and magnetic sensibility were studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 716–720.Original Russian Text Copyright © 2005 by Chizhova, Klyndyuk, Bashkirov, Petrov, Yanushkevich.     

Formation of Composites Based on CsHSO<Subscript>4</Subscript> and Cs<Subscript>5</Subscript>H<Subscript>3</Subscript>(SO<Subscript>4</Subscript>)<Subscript>4</Subscript> and Mechanism of Their Protonic Conduction

Vibrational spectra of finely divided amorphous CsHSO₄,Cs₅H₃(SO₄)₄ · H₂O, and composites based on these are measured and analyzed. An analysis of the spectra indicates the occurrence of substantial changes in the system of hydrogen bonds and in the spectral range of the sulfate group of acid sulfates in the composites. Structural dynamics of the SO₄ tetrahedrons is in full conformance with protonic conduction and the data of x-ray diffraction analyses accompanied by differential scanning calorimetry. It is shown that mobility of protons in the composites increases. A mechanism of the formation of the composites and their conduction is proposed.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 640–645.Original Russian Text Copyright © 2005 by Ponomareva, Lavrova, Burgina.     

Solid Electrolytes Based on KAlO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript>: The Crystalline Structure and Conduction

The structure of solid high-conductance potassium electrolytes K_{1 − x} Al_{1 − x} Ti_xO₂ (x = 0.1; 0.2) at 25 and 575°C is studied by a powder neutron diffraction analysis with the application of full-profile Rietveld analysis. Inserting titanium ions removes in potassium aluminate the phase transition at 540°C and the conductance anisotropy typical for its low-temperature form. Both structures are identical (fcc lattice, space group Fd3m). Experiment and calculation coincide best under the assumption that the potassium sublattice is disordered. The conductance increase upon inserting ions Ti⁴⁺ is due, apart from stabilization of the fcc structure, to formation of additional potassium vacancies and larger channels for the migration of potassium cations (ions Ti⁴⁺ are larger than ions Al³⁺).__________Translated from Elektrokhimiya, Vol. 41, No. 7, 2005, pp. 878–883.Original Russian Text Copyright © 2005 by Burmakin, Voronin, Akhtyamova, Berger, Shekhtman.     

New Metal Chelates with Sterically Hindered Azo Ligands: Synthesis and Physicochemical Properties

Metal chelates based on 3,5-di-(tert-butyl)-2-hydroxyazobenzene are synthesized and their physicochemical properties were studied. Four alternative structures and isomeric transformations between these structures were suggested on the basis of NMR data, electric dipole and magnetic moments, X-ray diffraction and quantum-chemical data. The change in stereochemistry of a complex through introduction of tert-butyl substituents was found to give unusual (for metal chelates with azo ligands (MN₂O₂)) dome-shaped isomers with the trans-planar coordination core at a vertex or with a distorted cis-structure.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 563–571.Original Russian Text Copyright © 2005 by Kogan, Lyubchenko, Shcherbakov, Ionov, Tkachev, Shilov, Aldoshin.     

The Mechanism of Selective NO<Subscript>x</Subscript> Reduction by Hydrocarbons in Excess Oxygen on Oxide Catalysts: III. Adsorption Properties of the Commercial STK Catalyst

According to X-ray diffraction data, the STK catalyst is a mixture of Fe₂O₃ and Cr₂O₃. The temperature-programmed reduction spectrum exhibited two reduction peaks: one, with T _max = 250°C, corresponds to the reduction process Cr₂O₃ → CrO and the other, with T _max = 360°C, corresponds to the reduction Fe₂O₃ → Fe₃O₄. The results of thermal desorption measurements suggest that the individual adsorption of oxygen on the surface of the STK catalyst is low; in this case (according to IR-spectroscopic data), an atomic form is the main species. Surface nitrite-nitrate complexes are formed upon the adsorption of NO. Nitrite and nitrate complexes desorbed at maximum rates at 105 and 160°C, respectively. Unlike the NTK-10-1 catalyst, the NO species, which desorbed at high temperatures (250–400°C), was absent from the surface of STK. Propane adsorbed at room temperature to form surface compounds containing an acetate group. The interaction of propane with the surface of the STK catalyst at reaction temperatures resulted in strong surface reduction.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 550–558.Original Russian Text Copyright © 2005 by Tret’yakov, Burdeinaya, Zakorchevnaya, Matyshak, Korchak.     

Crystal structure of <Emphasis Type="Italic">N</Emphasis>-Furfuryl-1-(2-Thienyl)but-3-en-1-Ammonium Chloride

The crystal structure of (H₂L)⁺Cl^-(HL is N-furfuryl- 1-(2-thienyl)but-3-en-1-amine) was studied by X-ray diffraction analysis. In the crystal, (H₂L)⁺ cations and Cl^- anions are united through N-HCl hydrogen bonds into polymer chains.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 1, 2005, pp. 69–71.Original Russian Text Copyright © 2005 by Antsyshkina, Egorova, Sergienko, Sadikov.