Micro- and nanocomposites of Keggin heteropolymetalates in cellulose esters

Composites of Keggin heteropolymetalates have been prepared and characterized by SEM, XPS, ³¹P-magic angle spinning/nuclear magnetic resonance and differential scanning calorimetry. The phosphotungstic acid and phosphomolybdic acid form nanocomposites where the oxocluster structure is preserved and is highly dispersed over the material, probably inserted between the polymeric chains. Phosphovanadotungstic clusters suffer partial decomposition during composite formation, resulting in a biphasic microcomposite. The decomposition product, phosphotungstic acid presents surface segregation as shown by comparison of XPS and nuclear magnetic resonance results. Copyright © 2002 John Wiley & Sons, Ltd.     

Identifizierung organischer Säuren durch thermische Analyse und Bestimmung des Säuregehaltes in Anhydriden

Zusammenfassung Ein thermisches Analysenverfahren wurde ausgearbeitet, das die Identifizierung einiger organischer Säuren nebeneinander und zugleich deren sehr empfindliche Bestimmung in kleinen Einwaagen ermöglicht. Die dazu entwickelte Anlage verwendet einen Gaschromatographendetektor.

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Identification of organic acids through thermoanalysis and determination of the acid content of anhydrides

Summary A thermoanalytic procedure has been developed which permits to identify several organic acids in the presence of one another, and at the same time to determine them in very small samples. The apparatus employs a gaschromatograph-detector.

     

Anion-pi interactions in a carousel copper(II)-triazine complex

Unprecedented anion-pi interactions are revealed for the electron-poor triazine rings in [L2(CuCl)3][CuCl4]Cl (L = hexakis(pyridin-2-yl)-[1,3,5]-triazine-2,4,6-triamin), where both the chloride ion and a Cl atom of [CuCl4]2- are located approximately 3.15 A above the ring centroids, in excellent agreement with theoretical predictions for a Cl-...triazine complex. This confirms the importance of attractive anion-pi interactions for the supramolecular assembly of complexes with pi-electron-deficient heteroaromatics.     

High-performance liquid chromatographic method for the determination of nefazodone and its metabolites in human plasma using laboratory robotics.

A quantitative analytical method, using high-performance liquid chromatography and ultraviolet detection, has been established for the determination of nefazodone (NEF) and its metabolites, m-chlorophenylpiperazine (mCPP),p-hydroxynefazodone (PHN), and hydroxynefazodone (HO-NEF), in human plasma. The fully automated, robotic procedure consisted of addition of internal standard (aprindine), extraction with butyl chloride, followed by phase separation, organic phase evaporation, reconstitution of the residue, and injection onto the chromatographic system. The limits of detection for NEF, mCPP, PHN, and HO-NEF were 5, 1, 10, and 5 ng/ml, respectively, at a signal-to-noise ratio of 4. The method had a linear range of 10-1000 ng/ml for NEF and HO-NEF, 20-2000 ng/ml for PHN, and 2.5-250 ng/ml for mCPP. Correlation coefficients of 0.996 or greater were obtained during validation and study sample analysis.     

The Purification of PCl3 from Pv by interaction with active silica

It was found, that the addition of silica gel to PCl₃ prevents its oxidation and acts as an adsorbent of P^v impurities. The concentration of P^v impurities is diminished below 0,1% calculated as H₃PO₄. The velocity of purification depends on the kind of silica gel, on its amount and on the volume of the liquid above the adsorbent layer. For the purification of technical grade PCl₃ with an impurity level below 1% H₃PO₄ the small pore or middle pore silica gel in amounts of 10% in relation to PCl₃ may be used. In case of PCl₃, oxidated to a level of 2.6% P^v, as H₃PO₄, the velocity of purification was higher for the middle pore silica gel. An attempt is made to explain the action of silica gel on theoretical backgrounds.     

Hypergeometric series,modular linear differential equations and vector-valued modular forms

We survey the theory of vector-valued modular forms and their connections with modular differential equations and Fuchsian equations over the three-punctured sphere. We present a number of numerical examples showing how the theory in dimensions 2 and 3 leads naturally to close connections between modular forms and hypergeometric series.     

An unusually stable octanuclear sigma-mesityl-bridged mu4-oxo-copper(I) complex encapsulated by a pyrazolate-based compartmental ligand scaffold

A new compartmental pyrazole-derived chelating ligand, four equivalents of mesitylcopper and stoichiometric amounts of dioxygen lead to the formation of a remarkably stable organometallic framework that can be described as a heteroleptic O-centered cuprate anion [(MesCu(I))(4)(mu(4)-O)](2-) linked via sigma-mesityl-bridges to two surrounding binuclear Cu(I)-pyrazolate clamps.