Laser-Induced Electron-Transfer Processes in a Pyrene–β-Cyclodextrin Complex in Titanosilicate Systems

We have used fluorescent spectroscopy and laser flash photolysis to investigate the photonics of pyrene molecules in a pyrene–-cyclodextrin inclusion complex in various media. We have observed a protective effect of -cyclodextrin relative to solubilized pyrene molecules during quenching of fluorescence by Ti ions (or titanium dioxide particles) in mixed colloids. In the presence of a precursor of silica (a TEOS solution), the pyrene molecules react with the colloidal silica particles formed, and the reaction is accompanied by decomposition of the pyrene–-cyclodextrin inclusion complex and efficient photoionization of pyrene.     

Researches on furan compounds

This paper gives the results obtained by liquid phase catalytic hydrogenation under pressure, over ruthenium catalysts, of furan aldehydes, ketones, and carboxylic acids. It is shown that the ruthenium catalysts are highly effective for hydrogenating the furan ring, ethylenic double bonds, and the carbonyl group, though they are not selective with respect to them. At room temperature the furan ring is mostly reduced to a tetrahydrofuran one. It is confirmed that compounds containing the 1, 6-dioxaspiro [4, 4]-nonane grouping are formed by hydrogenating furfurylidene aldehydes and ketones, and -furylalkanols.For Part XXX see [15].     

(CuO-CeO2)/glass cloth catalysts for selective CO oxidation in the presence of H2: The effect of the nature of the fuel component used in their surface self-propagating high-temperature synthesis on their properties

The potential of surface self-propagating high-temperature synthesis (SSHS) for obtaining (CuO-CeO₂)/glass cloth catalysts is demonstrated. The dependence of the structural and catalytic properties of the catalysts on their preparation conditions (nature of the fuel component) is considered. X-ray diffraction, electron microscopy, and EXAFS data suggest that the short-term action of high temperature in the SSHS leads to the complete decomposition of the precursors and has an effect on the distribution of the resulting phases. According to H₂ TPR and XPS data, the degree of dispersion of CuO and the electronic state of the reacting CuO and CeO₂ phases depend on the choice of fuel. This is likely due to fuels varying in the amount of heat released in their combustion. The degree of dispersion of CuO and the total contribution from Cu¹⁺ and Ce⁴⁺ to the electronic state of the active component increase as the standard enthalpy of combustion increases in the urea < glycerol < citric acid order. This leads to an increase in the catalytic activity of the (CuO-CeO₂)/glass cloth system in selective CO oxidation.     

Study of the structure of (carbamimidoylsulfanyl)acetic (“pseudothiohydantoic”) acid by XRD and PM6 methods

It was shown by the method of powder X-ray diffraction analysis that in the crystalline state the product of the reaction of thiourea with chloroacetic acid in water, (carbamimidoylsulfanyl)acetic acid, existed in the zwitter-ion tautomeric form. The structure consists of virtually planar infi nite layers normal to the c axis of the unit cell which are bound by van der Waals interactions. The layers are formed by infi nite rows elongated along the b axis of the unit cell consisting of materially planar zwitter-ionic molecules linked by strong bifurcated hydrogen bonds. The results of quantum-chemical calculations by PM6 method are in agreement with the XRD results: whereas an isolated molecule exists in nonzwitter-ionic tautomeric form, in the crystal only the zwitterionic tautomer is present.     

Catalytic activity of Co/SiO2 and Co/TiO2 nanosized systems in the oxidation of carbon monoxide

The effects of the preparation procedure, active component concentration, and conditions of formation of nanosized cobalt-containing systems based on TiO₂ and SiO₂ mesoporous powders on their catalytic activity in the oxidation of carbon monoxide were studied. The active phase in the systems was cobalt spinel CoCo₂O₄ found in all samples. High catalytic activity was found in the samples characterized by relatively high contents of surface active centers (cobalt cations with octahedral surroundings).     

Effect of thermal aging on the mechanical characteristics of a composite of a polyimide with an organosilicon resin

The effect exerted by thermal aging in air at 350°C on the thermal and mechanical properties of composite films prepared on the basis of heat-resistant polyimide PM and non-film-forming polymethylphenylsiloxane (PMPS) was examined. The phase segregation of polymeric composites of various compositions and the thermal aging rate were evaluated.     

Thermodynamics of hard poly(phenylene-pyridyl) dendrimers

The temperature dependences of heat capacity C ^○ _p = f(T) of hard poly(phenylene-pyridyl) dendrimers of the first and the second generations based on 1,3,5-triethynylbenzene were studied over the temperature range from 7–180 to 455–470 K for the first time. Over the range 290–350 K, the relaxation transition supposedly caused by sample devitrification was detected and characterized for the dendrimer of the first generation. The experimental results were used to calculate the standard thermodynamic functions, namely, heat capacity, enthalpy, entropy, and change in the Gibbs energy on heating. The standard entropy of formation of the compounds under study was determined at T = 298.15 K. The qualitative and quantitative dependences of the thermodynamic properties of the poly(phenylene-pyridyl) dendrimers on their composition and structure were revealed by comparison of the determined parameters with similar data for the earlier studied dendrimers of this series.     

Calorimetric study of poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K

For the first time, the heat capacity $ C_{\text{p}}^{^\circ } $ of poly(2-ethylhexyl acrylate) has been studied in an adiabatic vacuum calorimeter between 7 and 350 K, the standard thermodynamic functions: heat capacity $ C_{\text{p}}^{^\circ } $ (T), enthalpy H°(T) ? H°(0), entropy S°(T) ? S°(0), Gibbs function G°(T) ? H°(0) have been calculated from T → 0 to 350 K. The energy of combustion Δ_c U of the compound under study has been measured in a calorimeter with a stationary bomb and an isothermal shell. The standard enthalpy of combustion Δ_c H° and thermodynamic parameters of formation—enthalpy Δ_f H°, entropy Δ_f S°, Gibbs function Δ_f G°—at T = 298.15 K have been calculated. The results have been used to calculate the thermodynamic characteristics of 2-ethylhexyl acrylate bulk polymerization into poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K.     

Standard thermodynamic functions of CaNi0.5Zr1.5(PO4)3 crystalline phosphate in the range of T → 0 to 640 K

The temperature dependence of the heat capacity C _p ^○ = f(T) of CaNi_0.5Zr_1.5(PO₄)₃ crystalline phosphate is studied by precision adiabatic vacuum and differential scanning calorimetry over the temperature range of 7–640 K. Its standard thermodynamic functions C _p ^○ (T), H ^○(T)-H ^○(0), S ^○(T), and G ^○(T)-H ^○(0) for the region T → 0 to 640 K and the standard entropy of formation at T = 298.15 K are calculated from the obtained experimental data. Using data on the low-temperature (30–50 K) heat capacity, the D fractal dimension of phosphate is determined and conclusions about the character of the topology of its structure have been made. The final results are compared to data from thermodynamic investigations of the structurally related crystalline phosphates Zr₃(PO₄)₄, Ni_0.5Zr₂(PO₄)₃, and Ca_0.5Zr₂(PO₄)₃.