新型的含硫族元素碳硼烷配体的三(3，5-二甲基-1-吡唑)硼氢钼配合物的合成和分子结构(英)

三齿单核三(3，5-二甲基-1-吡唑)硼氢钼配合物Tp^*Mo(O)Cl₂ (1)(Tp^*=三(3，5-二甲基-1-吡唑)硼氢HB(C₃H(Me₂)N₂)₃)与含硫族元素碳硼烷的锂盐[(THF)₂LiE₂C₂B₁₀H₁₀(THF)]<     

Determination of molecular orientation distribution of a stable paramagnetic probe in oriented 4-cyano-4’-<Emphasis Type="Italic">n</Emphasis>-pentylbiphenyl

The molecular orientation distribution function of a stable radical 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl in magnetic-field oriented 4-cyano-4’-n-pentylbiphenyl was determined from the angular dependence of the ESR spectra. The preferred molecular orientation of radical species in the liquid crystal matrix was determined. The temperature evolution of the orientation distribution function was studied.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 190–195, January, 2005.     

Study of the α-relaxation of PVC, EVA and 50/50 EVA70/PVC blend

The dipole dynamics and α-relaxation behaviour of polyvinyl chloride PVC, poly(ethylene-co-vinyl-acetate) EVA₇₀ and blend of them EVA₇₀/PVC have been investigated by differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The differential scanning calorimetry (DSC) thermograms measured on samples show a single glass transition in the analysed temperature range. These three polymers are wholly amorphous and pure PVC and pure EVA₇₀ are miscible in the ratio 1:1. The glass transition temperature T_g decreases significantly with presence of EVA₇₀. Furthermore, the values of apparent activation energies for molecular motions at the α-relaxation and the values of fragility index have also been determined for each sample using Moynihan expression for DSC results and Vogel-Fulcher-Tammann-Hesse (VFTH) form for DRS results. It is shown a large dependence of all the values of these parameters with the content of EVA₇₀. Comparing these three polymers, we found that the more fragile glass forming liquid is the PVC. Fragility decreases drastically with EVA₇₀ content. EVA₇₀ and EVA₇₀/PVC blend exhibit practically the same behaviour. The effect of inter- and intra-molecular interactions on fragility is discussed to explain these variations.     

A PMMA composite as an optical diffuser in a liquid crystal display backlighting unit (BLU)

The effect of thermo-physical properties, relative humidity and stiffness on the warpage of a poly(methyl methacrylate) (PMMA) diffusing plate modified with glass fibers in a direct-lit backlight unit (BLU) of a liquid crystal display (LCD) was investigated. The warpage of the PMMA diffusing composites modified with a glass fiber were significantly reduced relative to that of a conventional PMMA diffusing plate. Luminance and scattering characteristics of the PMMA diffusing composites having 5, 10, 20 vol% of glass fibers were measured. Although the luminance of the composite was lowered as increasing the volume fractions of glass fibers in the PMMA composites, good brightness uniformity of the composites on a light source was obtained.     

Characterization of high-temperature superconductors by electron microprobe analysis

In order to optimize the physical properties of HTSC small single crystals grown from a melt for basic studies of their physical properties the influence of the environment on their impurity content was investigated by EPMA. This requires quantitative analysis of all elements being present in the crystals. The accuracy of results was affected by problems with the choice and quality of standards, by contamination but also by malfunction of microprobe electronics. The HTSC materials were found to react with mills, milling balls, crucibles and the atmosphere. These problems are being discussed and some reactions being studied for Y₁Ba₂Cu₃O_6+x (0 < x < 1) HTSC in A1₂O₃ and ZrO₂ crucibles. The crystals grown contain reproducible amounts of impurities depending on boundary conditions and exhibit a zone structure in composition particularly for Y and Ba within their range of homogeneity.     

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.     

Structure of hydroxycinnamic acid derivatives established by high-perfomance liquid chromatography with photodiode-array detection

Summary The present paper describes the development of a method for the differentiation of hydroxycinnamic acid derivatives by HPLC with photodiode-array detection. Furthermore spectral data of the compounds under investigation are given. Whereas p-coumaric acid derivatives are distinguishable from caffeic and ferulic acid derivatives by the positions of their spectrum maxima and their convexity interval value, it is not possible to distinguish between caffeic and ferulic acid derivatives because of overlapping spectrum maxima and convexity interval values.     

Ein neues Kupfercobaltboratoxid mit isolierten B2O5-Baugruppen: Cu2Co(B2O5)O

On a New Copper Cobalt Borate Oxide with Isolated B₂O₅ Units: Cu₂Co(B₂O₅)O Single crystals of a new compound with the empirical formula Cu₂CoB₂O₆ were obtained by using a B₂O₃ flux technique. X-ray single crystal technique led to a new structure type. Cu₂CoB₂O₆ crystallizes monoclinic, space group C-P2₁/c (No. 14); a = 3.2250(6); b = 14.847(1); c = 9.1171(6) Å; β = 93.67°; Z = 4. All metal sites are octahedrally coordinated and form a two dimensional framework consisting of edge sharing octahedra ribbons. In addition one observes isolated B₂O₅-units and oxygen which is not coordinated to boron. The far relation to the crystal structure of the mineral Warwickite is illustrated.     

Addition of diazocyclopropane generatedin situ to vinyl bromide and chemical transformations of the resulting 5-bromospiro(1-pyrazoline-3,1′-cyclopropane)

The reaction of diazocyclopropane generatedin situ with vinyl bromide occurs as regioselective 1,3-dipolar cycloaddition to give 5-bromospiro(1-pyrazoline-3,1′-cyclopropane) in ∼60% yield. Reactions of the latter with nucleophilic reagents, which can occur both with retention and opening of the cyclopropane ring, were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 688–690, April 1998.     

A new convenient synthesis of N-acyl-2-(dimethoxyphosphoryl)glycinates

Easily accessible N-acyl-2-triphenylphosphonioglycinate tetrafluoroborates react smoothly with trimethylphosphite in the presence of methyltriphenylphosphonium iodide to give N-acyl-2-(dimethoxyphosphoryl)glycinates in good or very good yields. The dimethoxyphosphorylglycinates may be isolated by column chromatography, or used directly for the Wadsworth-Emmons synthesis of α,β-dehydro-α-amino acids in a one-pot procedure without purification.