抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution

A kinetic and mechanistic study is reported of the oxidation of a number of azonaphthol dyes with hydrogen peroxide in aqueous solution, catalysed by some mono and dinuclear manganese(IV) complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN). The results of UV-Vis investigations, augmented by EPR and ESI-MS studies, are described for a series of experiments in which concentrations, pH and ionic strength have been varied. The reactions are characterised by an induction period followed by a relatively rapid oxidation. For the dinuclear manganese complex 2, these are consistent with an initial perhydrolysis of the manganese complex involving both the dye anion and HO2-, to give mononuclear manganese species and the operation of a catalytic cycle incorporating MnIIIL(OH)3, O = MnVL(OH)2 and MnIVL(OH)3 (L = Me3TACN) (cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of MnIVL(OH)3. With the mononuclear manganese complex MnIVL(OMe)3, there is a short lag-phase attributed to perhydrolysis by HO2- followed by the same catalytic cycle.     

Evaluation of multiple solid-phase microextraction as a technique to remove the matrix effect in packaging analysis for determination of volatile organic compounds

Multiple solid-phase microextraction (SPME) is an useful technique for the direct quantification of solid samples removing any matrix effect. The volatile organic compounds formed in the extrusion-coating process of multilayer packaging materials have already been quantified by multiple HS-SPME coupled to gas chromatography (GC)-mass spectrometry (MS) using volatile organic compound (VOC) solutions in hexadecane for calibration. In this article, water is proposed as solvent to prepare the calibration solutions because it provides a shorter calibration time, better linearity, better reproducibility, and lower detection limits than hexadecane. Besides, the extraction of VOCs from aqueous solutions is exhaustive and avoids the extrapolations needed to calculate the total peak areas, as they can be calculated as the sum of the individual areas of each extraction. Finally, it is checked whether the two solvents provide the same mean values for the total peak areas.     

High-spin structure of yrast-band in 78Kr

Lifetime of levels up to 22⁺, have been measured in ⁷⁸Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations. Calculations further show that ⁷⁸Kr is highly γ-soft nucleus. The experimental Q _t values coupled with theoretical calculations indicate an oblate shape for ⁷⁸Kr at low spins and triaxial shape at higher spins     

Stereoisomerism of molecular multipropellers. 1. Static stereochemistry of bis- and tris-triaryl systems

The static stereoisomerism of bis- and tris-triaryl systems has been analyzed by a systematic stereochemical analysis, and the resulting theoretical predictions have been experimentally confirmed by using reversed-phase HPLC and ESR and (1)H NMR spectroscopies with a family of seven distinct polychlorinated aromatic multipropellers. To analyze the static stereochemistry of these molecules, we have developed a specific procedure that uses a symmetry-adapted symbolic notation, allowing the theoretical prediction of both the number and symmetry of the isomers of the investigated molecules. Due to the steric hindrance introduced by the presence of bulky chlorine substituents, (all) conformational isomers can be characterized experimentally by several independent techniques confirming the theoretical stereochemical predictions. The different propeller moieties that constitute the molecule appear to be nearly independent of each other. Consequently, most of the observed isomers show comparable populations in solution at room temperature.     

Behaviour of solid adsorbents for the sampling of atmospheric organochlorine compounds

The behaviour of Tenax(R) GC, Polyurethane foam (density 0.022 g/cm(3)), Amberlite(R) XAD-2 and Amberlite(R) XAD-4 alone or in combination has been studied. Standard atmospheres containing different concentration levels of hexachlorocyclohexane and chlorobenzene isomers were generated and trapped in adsorbent cartridges. The generation of the atmosphere, the adsorption by the cartridges, the extraction of the compounds, the evaporation of the final solution and the analysis of GC/ECD have been studied. The most efficient system for trapping the test gases is the use of two cartridges connected in series, one containing Polyurethane foam and the second one containing Tenax GC. Recovery values ranging from 72% for 1,3-dichlorobenzene to 98% for gamma-hexachlorocyclohexane are obtained, most of them >90%. The SD values for all the compounds under study are around 4% for a total sampled amount of 0.5 mug of each compound.     

Recent advances in UV-visible reflectance spectroelectrochemistry

UV-visible spectroelectrochemistry is used in situ during electrochemical experiments to examine chemical processes occurring either in solution or at the electrode surface. The technique has recently been applied to the study of polymer modified electrodes, surface adsorbed species and surface plasmons, and soluble reactive organic intermediates, in addition to many other areas of general interest. Substantial improvements have been made recently in the sensitivity of the method, which allow electrochemical kinetic and mechanistic studies on very small concentrations of electrogenerated chromophores.