Spectral-purity-enhancing layer for multilayer mirrors

We demonstrate, both theoretically and experimentally, that special spectral-purity-enhancing multilayer mirror systems can be designed and fabricated to substantially reduce the level of out-of-band radiation expected in an extreme ultraviolet lithographic tool. A first proof of principle of applying such spectral-purity-enhancement layers showed reduced out-of-band reflectance by a factor of five, while the in-band reflectance is only 4.5% (absolute) less than for a standard capped multilayer.     

Regio- and stereospecific ring-opening reactions of 4-substituted basketanes and seco-basketanes

Homoketonization of basketane acetates6 and 10 on brief treatment with NaOMe in MeOH afforded the seco-basketanones7 and11, respectively, in a stereo-and regiospecific cage opening reaction. As shown by deuterium labeling experiments, both for 6 and 10, this homoketonization proceeds with retention of configuration. Prolonged basic treatment of10 led to the exclusive formation of bicyclo[2.2.2]octenyl-acetates12. Under identical conditions6 produced a complex mixture of products. Upon treatment of seco-basketanones7 and 11 with aq HC1 in MeOH, a rapid regiospecific cationic rearrangement to homobrendanone 14 was observed. This structure was established by X-ray analysis. The effect of a one carbon cage expansion on the base induced cage opening process by extension of the methylene bridge in the homocubane system into an ethylene bridge in the basketane system, is discussed.     

A new HPLC method for the simultaneous determination of fluazifop-butyl and fluazifop in soil samples

Summary The analytical method presented here enables the extraction of fluazifop-butyl and fluazifop from soil samples avoiding hydrolysis of the ester and allowing a better release of the acid form. Then the quantitative determination of both the compounds can be performed in one run by means of RP-HPLC. This is achieved by using a phenyl phase and an ion-pair reagent (tetrabutylammonium hydrogensulfate).     

Synthesis of functionalized basketanes by a regiospecific cage expansion of homocubanones

The synthesis of 4-substituted basketanes 11 is realized by a regiospecific one carbon-homologation of the readily available 4-substituted homocubanones 10 Subsequent group transformations, starting from basketanone 4-carboxylic acid 11a, leads to an efficient synthesis of basketane 4-acetates 16.     

Synthesis of 4-functionalized terdendate pyridine-based ligands

Four different 4-functionalised pyridine-based ligands were synthesized with aminomethyl, oxazolinyl, pyrazolyl and methylimidazolyl groups at the 2- and 6-position. The nitrogens of these groups together with the pyridine nitrogen can act as terdendate ligands for metal ions. Synthetic handles on the 4-position of the pyridine group were introduced via ether or ester bonds leading to monofunctional, bifunctional and amphiphilic ligands.     

Analysis of N-acylhomoserine lactones after alkaline hydrolysis and anion-exchange solid-phase extraction by capillary zone electrophoresis-mass spectrometry

A quantitative, specific, and sensitive method for the determination of N-acylhomoserine lactones (HSLs - a group of bacterial semiochemicals) in the form of their hydrolysis products (N-acylhomoserines, HSs) is presented. Real samples were analyzed by capillary zone electrophoresis-mass spectrometry (CZE-MS) after alkaline lactonolysis and extraction by mixed-mode anion-exchange solid-phase extraction. The presented cleanup significantly speeds up the HSL extraction procedure, strongly reduces sample consumption, and is more selective compared to the commonly used liquid/liquid extraction. Completeness of the hydrolysis reaction was examined by nuclear magnetic resonance spectroscopy. This CZE-MS method complements recently published capillary separation techniques (nano liquid chromatography-MS, partial-filling micellar electrokinetic chromatography-MS, gas chromatography-MS) and provides a possibility to differentiate quantitatively between the homoserines (as naturally occurring degradation products) besides the intact homoserine lactones. The method was found to be quantitative down to a concentration of 0.05 microg/mL (limit of quantification), while the limit of detection was determined with 0.01 microg/mL - sufficient for the analysis of culture supernatants.     

Separation of metal ions by capillary electrophoresis--diversity, advantages, and drawbacks of detection methods

Capillary electrophoresis (CE) has been applied to metal-ion analysis during the last 10 years. To improve sensitivity and selectivity different modes of detection have been adapted or developed. The selection of commercially available detection systems for metal-ion analysis is still primarily limited to UV-Vis detection, although other commercial systems, e.g. fluorescence, conductivity, or interfaces for coupling to mass spectrometry (MS) or inductively coupled plasma mass spectrometry (ICP-MS) are becoming available. High demands are made on any detector used in CE, because the analytical signal has to be extracted from less than 1 nL of sample, which corresponds to a total amount of < or = 10(-12) to 10(-15) mol analyte. This paper compares currently available and recently developed detection methods for CE as applied to the analysis of metal ions. Commercially available techniques, for example UV-Vis, fluorescence, or mass spectrometry, and other new detection methods including electrochemistry, radioactivity, and XRF, are discussed and future trends are anticipated.     

Geminal bis-ureas as gelators for organic solvents: gelation properties and structural studies in solution and in the gel state

Several geminal bis-urea compounds were synthesised by means of an acid-catalysed condensation of various benzaldehydes with different monoalkylureas. Many of these compounds form thermoreversible gels with a number of organic solvents at very low concentrations (<3mM) and which are stable to temperatures higher than 100 degrees C. Electron microscopy revealed a three-dimensional (3D) network of intertwined fibres, which are several tens of micrometers long and have a width ranging from approximately 30 to 300 nm. The possible aggregate forms and aggregate symmetries were evaluated by means of molecular mechanics calculations. 1H NMR, 2D NMR, 13C NMR and 13C-CP/MAS NMR techniques were used to obtain information about the aggregation and possible aggregate symmetry of geminal bis-ureas in solution, in the gel state, and in the solid state.