Publications

URI permanent de cette collection

https://libra.unine.ch/handle/123456789/2

Parcourir par

Parcourir la collection Publications par Titre

Voici les éléments 1 - 20 sur 19071
  • Publication
    Accès libre
    0.35 μm 22μW Multiphase Programmable Clock Generator for Circular Memory SC FIR Filter For Wireless Sensor Applications
    (2006-03-06)
    Dlugosz, Rafal Tomasz
    ;
    Iniewski, K.
    ;
    Talaśka, T.
    The paper presents the programmable multiphase clock generator for switched-capacitor finite impulse response (SC FIR) circular memory filters. The proposed programmable clock circuit enables easy division of such kind of filters into different orders smaller sections, which when connected in series, lead to increase in filter efficiency: reduction of chip area, power dissipation, and rising up of the speed. The proposed clock generator enables adjustment of the impulses width, that simplifies design process and leads to structure, which is more robust to process variation. The clock circuit realized in CMOS 0.35μm technology, dissipates 22 μW from 2 V power supply.
  • Publication
    Métadonnées seulement
    1,1'-Dimethyl-2,2'-biimidazole
    (1999)
    Therrien, Bruno 
    ;
    Beauchamp, Andre L.
    Crystals of the title compd. are monoclinic, space group P21/n, with a 6.6760(10), b 5.5670(9), c 11.471(3) Å, ? 103.88(4)°; Z = 2, dc = 1.302; R = 0.036, Rw(F2) = 0.084 for 779 reflections,. The two rings are approx. coplanar. The mol. lies on a crystallog. inversion center and it adopts the anti conformation keeping the Me groups apart. [on SciFinder(R)]
  • Publication
    Accès libre
    1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester: A new bidentate ligand in arene ruthenium chemistry
    (2007)
    Auzias, Mathieu
    ;
    Therrien, Bruno 
    ;
    Süss-Fink, Georg 
    1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester (1) is prepared from 1,1′-ferrocene dicarbonyl chloride and 4-hydroxypyridine. This new bidentate ferrocenoyl ligand reacts with the monocationic complex [(η6-p-cymene)2Ru2 (μ-OH)3]+ to give the dicationic complex [(η6-p-cymene)2Ru2(μ-OH)2(1,1′- (NC5H4–OOC)2–Fc)]2+ (2) (Fc: C5H4–Fe–C5H4), isolated as a tetrafluoroborate salt. The single-crystal X-ray structure analysis of [2][BF4] 2 reveals the ferrocenoyl pyridine ligand 1 to act as μ2-η2 chelating ligand in the dinuclear complex, having replaced a μ2-η1-hydroxo ligand.
  • Publication
    Accès libre
    1,2-Bis-N-[2’-(diphenylphosphanyl)benzoyl]diaminobenzene, a New Chelating Ligand with Versatile Coordination Properties
    (2003)
    Burger, Sylvain
    ;
    Therrien, Bruno 
    ;
    Süss-Fink, Georg 
    1,2-Bis-N-[2’-(diphenylphosphanyl)benzoyl]diaminobenzene (dppbH; 1) was prepared by peptidic coupling and shown to exist, in the solid state, in the form of hydrogen-bonded dimers by single-crystal X-ray structure analysis. As expected, 1 reacts with [MCl2 (cod)] (M = Pd, Pt; cod = cyclooctadiene) to form square-planar complexes. However, in the case of palladium [PdCl2 (dppbH)] (2) is obtained, while in the case of platinum [Pt(dppb)] (3) is formed. Thus, the nature of the metal induces a completely different coordination mode: In 2, the dppbH ligand only coordinates through the two phosphorus atoms, while in 3 a dppb ligand, formed by deprotonation of the two amino functions in dppbH, coordinates through the two phosphorus atoms and through the two nitrogen atoms. The single-crystal X-ray analyses of the two square-planar complexes reveal 2 to contain the two phosphorus atoms in a trans coordination mode and 3 to contain the two phosphorus atoms in a cis coordination mode.
  • Publication
    Métadonnées seulement
  • Publication
    Accès libre
    1,3-Butadienyl-thiocyanate in der Diels-Alder-Reaktion mit anschliessender [3,3]-sigmatroper Umlagerung
    (1986)
    Huber, Stefan
    ;
    Stamouli, Peristera
    ;
    Jenny, Titus
    ;
    Neier, Reinhard 
    (E)- and (Z)-1,3-Butadienyl thiocyanates 3, 4, and 12-15 have been synthesized selectively. Their use as dienes for Diels-Alder reactions followed by a [3,3]-sigmatropic shift to obtain an isomeric isothiocyanate has been studied. The butadienyl thiocyanates are, unfortunately, not very reactive in Diels-Alder reactions. This disadvantage can be overcome, if a trapping reaction with EtOH is added to the two-step sequence. This sequence allows to get good yields of the O-ethyl thiocarbamates 18-23, even if the first two reactions have not favorable equilibrium constants.
  • Publication
    Accès libre
    1,3-Dipolar cycloadditions: click chemistry for a new synthesis of 5-substituted tetrazoles and applications in organocatalysis
    (2007)
    Aureggi, Valentina
    ;
    Neier, Reinhard 
    ;
    Sedelmeier, Gottfried
    Les besoins récents en chimie organique de synthèse appliquée focalisent les efforts des chercheurs au développement de nouvelles voies efficaces et versatiles pour la préparation de molécules bioactives, en prenant en comptes en particulier les critères économiques et environnementaux. Nous avons développé une méthode novatrice et écologique pour la préparation de tetrazoles 141,142. Ce groupe fonctionnel trouve des applications dans des domaines variés allant des matériaux aux explosifs, et est d’un intérêt tout particulier en chimie médicinale 1. Cette importance a conduit au développement de diverses méthodes de préparation des tétrazoles, toutes présentant cependant des désavantages majeurs comme l’utilisation de réactifs toxiques ou explosifs, entre autres. La méthode alternative que nous avons développée permet la formation de tétrazoles à partir de nitriles en utilisant des azides de dialkylaluminium, qui possèdent l’avantage d’être des réactifs bon marché et non toxiques et permettent la préparation d’une large variété de tétrazoles de façon très efficace, adaptable à l’échelle industrielle. Nous avons ensuite appliqué cette méthodologie à l’organocatalyse 142, c'est-à-dire à la préparation et l’étude de molécules organiques ayant la faculté de catalyser des transformations chimiques très sélectives, procédé particulièrement attractif d’un point de vu environnemental et économique en constant développement., Tetrazoles are a class of heterocycles with a wide range of applications in medicinal chemistry and in material sciences 1. However a versatile method to synthesize tetrazoles through safe protocols is still highly desirable. Indeed each of the general known procedures uses either toxic metals, expensive reagents, harsh reaction conditions and may lead to the formation of dangerous hydrazoic acid or explosive sublimates. We report herein the discovery and development of a novel efficient process for transforming a wide variety of nitriles into the corresponding tetrazoles in high yield, using a simple and safe protocol. It has been found that the organoaluminum azides are affective reagents for the direct conversion of nitriles to tetrazoles. The organic soluble dialkylaluminum azides are prepared in a short time (4-6 h, r.t.) from the corresponding cheap dialkylaluminum chlorides. The cycloaddition occurs under mild conditions, and it is possible to synthesize a broad range of tetrazole derivatives with a high selectivity. This methodology can be applied to the synthesis of the pyrrolidine tetrazole, a versatile alternative of proline in organocatalysis. A variety of new catalysts based on pyrrolidine tetrazole skeleton are therefore efficiently prepared and tested.
  • Publication
    Métadonnées seulement
    1,3-Disubstituted ferrocene-containing thermotropic liquid crystals of form (?5-C5H5)Fe[(?5-C5H3)-1,3-(CO2C6H4CO2C6H4OCnH2n+1)2]
    (1994)
    Deschenaux, Robert 
    ;
    Santiago, Julio
    ;
    Guillon, Daniel
    ;
    Heinrich, Benoit
    The title compds. were synthesized and their liq.-crystal properties studied. The reported ferrocene derivs. exhibited enantiotropic nematic and/or smectic A phases assocd. with broad anisotropic domains. The mol. arrangement within the smectic A phases was studied by x-ray diffraction. The exptl. data, compared to the values obtained from CPK models, suggested a monolayer mol. organization with a pronounced chain disorganization for the medium- and long-chain derivs. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    1,4-Bis(hex-yloxy)-2,5-diiodo-benzene
    (2010)
    Thevenet, Damien 
    ;
    Neier, Reinhard 
    ;
    Sereda, Olha
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    The centrosymmetric title compound, C(18)H(28)I(2)O(2), crystallized in the monoclinic space group P2(1)/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosymmetric bromo analogue [Li et al. (2008 (black right triangle)). Acta Cryst. E64, o1930] that crystallized in the triclinic space group P. The difference between the two structures lies in the orientation of the two alkyl chains with respect to the C(aromatic)-O bond. In the title compound, the O-C(alk-yl)-C(alk-yl)-C(alk-yl) torsion angle is 55.8 (5)°, while in the bromo analogue this angle is -179.1 (2)°. In the title compound, the C-atoms of the alkyl chain are almost coplanar [maximum deviation of 0.052 (5) Å] and this mean plane is inclined to the benzene ring by 50.3 (3)°. In the bromo-analogue, these two mean planes are almost coplanar, making a dihedral angle of 4.1 (2)°. Another difference between the crystal structures of the two compounds is that in the title compound there are no halide(midline ellipsis)halide inter-actions. Instead, symmetry-related mol-ecules are linked via C-H(midline ellipsis)? contacts, forming a two-dimensional network.
  • Publication
    Métadonnées seulement
    1,4-Bis[4-(tert-butyl-diphenyl-silyl)buta-1,3-diyn-yl]benzene
    (2010)
    Thevenet, Damien 
    ;
    Neier, Reinhard 
    ;
    Stoeckli-Evans, Helen 
    The title centrosymmetric mol-ecule, C(46)H(42)Si(2), is composed of a central benzene ring with buta-1,3-diynyl chains at positions 1 and 4. These chains are terminated by tert-butyl-diphenyl-silyl groups, hence the molecule is dumbbell in shape. The mol-ecules are connected via C-H(midline ellipsis)? inter-actions in the structure, so forming an undulating two-dimensional network in the bc plane. There is also a weak ?-? inter-action involving centrosymmetrically related phenyl rings with a centroid-centroid distance of 3.8359 (11) Å.
  • Publication
    Accès libre
    1-Methoxycarbonyl-substituiertes 2,3-Dihydropyridin-4(1H)-on (= Methyl-1,2,3,4-tetrahydro-4-oxopyridin-1-carboxylat) als Chromophor für die photochemische [2 + 2]-Cycloaddition
    (1991)
    Guerry, Philippe
    ;
    Blanco, Philippe
    ;
    Brodbeck, Heinz
    ;
    Pasteris, Olivier
    ;
    Neier, Reinhard 
    With olefins having an electron-acceptor as well as with olefins having an electron-donor substituent, 1-methoxycarbonyl-substituted dihydropyridinone 12 undergoes [2 + 2] cycloaddition in good preparative yields. The photochemical cycloaddition is highly regioselective. For preparative purposes, the ring junction can be equilibrated to the thermodynamically more stable cis-junction. Only the ’endo’/’exo’ selectivity at the C-atom bearing the olefin substituent cannot be controlled. The photodimerization of 12 is the only side reaction. Using a slight excess of the olefin, the photodimerization can be suppressed. The protecting group at the N-atom of the dihydropyridinone can be varied in order to introduce an internal sensitizer, as shown with 1-acyl-substituted compound 29, which underwent the cycloaddition process even with sunlight.
  • Publication
    Accès libre
    1-Octen-3-Ol Isolated from Bont Ticks Attracts Amblyomma variegatum
    (2001)
    McMahon, Conor
    ;
    Guerin, Patrick 
    ;
    Syed, Zainulabeudin
    Volatiles from various life-stages of the bont ticks Amblyomma variegatum and A. hebraeum were collected by using solid-phase microfibers and charcoal traps. An octenol isomer was found to be a major constituent of most of the tick material sampled and was identified as 1-octen-3-ol by gas chromatography–mass spectrometry and by using antenna of the tsetse fly Glossina brevipalpis in gas chromatography-linked antennogram detection. Release of this compound increased during molt to adulthood and following mechanical disturbance of adult ticks. (R)-(–)-1-Octen-3-ol and racemate 1-octen-3-ol both induce an increase in upwind walk to the odor source from A. variegatum in an airstream on a servosphere. Volatiles from tick exuviae plus feces and from dead ticks also attracted A. variegatum, suggesting that 1-octen-3-ol may contribute to the aggregation response of Amblyomma spp. on such substrates. 2,6-Dichloroanisol and 2,5-dimethylpyrazine also were detected in volatiles from the ticks but induced no behavioral responses on the servosphere. The suspected tick pheromone component, 2,6-dichlorophenol, was detected from A. variegatum adults cut into pieces but had no effect on the behavior of A. variegatum on the servosphere at a range of doses.
  • Publication
    Accès libre
    1.55 µm InAs/GaAs Quantum Dots and High Repetition Rate Quantum Dot SESAM Mode-locked Laser
    Zhang, J. Y
    ;
    Oehler, A. E. H
    ;
    Resan, B
    ;
    Kurmulis, S
    ;
    Zhou, K. J
    ;
    Wang, Q
    ;
    Mangold, Mario
    ;
    Südmeyer, Thomas 
    ;
    Keller, Ursula
    ;
    Weingarten, K. J
    ;
    Hogg, R. A
    High pulse repetition rate (≥10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.55 µm In(Ga)As QDs on GaAs substrates, their incorporation into a SESAM, and the realization of the first 10 GHz repetition rate QD-SESAM modelocked laser at 1.55 µm, exhibiting ∼2 ps pulse width from an Er-doped glass oscillator (ERGO). With a high areal dot density and strong light emission, this QD structure is a very promising candidate for many other applications, such as laser diodes, optical amplifiers, non-linear and photonic crystal based devices.
  • Publication
    Accès libre
    10 kHz linewidth mid-infrared quantum cascade laser by stabilization to an optical delay line
    Shehzad, Atif 
    ;
    Brochard, Pierre 
    ;
    Matthey-De-L'Endroit, Renaud 
    ;
    Südmeyer, Thomas 
    ;
    Schilt, Stephane 
    We present a mid-infrared quantum cascade laser (QCL) with a sub-10 kHz full width at half-maximum linewidth (at 1 s integration time) achieved by stabilization to a free-space optical delay line. The linear range in the center of a fringe detected at the output of an imbalanced Mach–Zehnder interferometer implemented with a short free-space pathlength difference of only 1 m is used as a frequency discriminator to detect the frequency fluctuations of the QCL. Feedback is applied to the QCL current to lock the laser frequency to the delay line. The application of this method in the mid-infrared is reported for the first time, to the best of our knowledge. By implementing it in a simple self-homodyne configuration, we have been able to reduce the frequency noise power spectral density of the QCL by almost 40 dB below 10 kHz Fourier frequency, leading to a linewidth reduction by a factor of almost 60 compared to the free-running laser. The present limits of the setup are assessed and discussed.
  • Publication
    Métadonnées seulement
  • Publication
    Accès libre
    100 numéros, ça se… pense
    (2014)
    De Pietro, Jean-François
    ;
    Duchêne, Alexandre
    ;
    Kamber, Alain 
  • Publication
    Métadonnées seulement
  • Publication
    Accès libre
  • Publication
    Accès libre
    13C- and 15N‑Isotope Analysis of Desphenylchloridazon by Liquid Chromatography−Isotope-Ratio Mass Spectrometry and Derivatization Gas Chromatography−Isotope-Ratio Mass Spectrometry
    (2019-1)
    Melsbach, Aileen
    ;
    Ponsin, Violaine 
    ;
    Lihl, Christina
    ;
    Torrento Aguerri, Clara 
    ;
    Hofstetter, Thomas B.
    ;
    Hunkeler, Daniel 
    ;
    Elsener, Martin
    The widespread application of herbicides impacts surface water and groundwater. Metabolites (e.g., desphenylchloridazon from chloridazon) may be persistent and even more polar than the parent herbicide, which increases the risk of groundwater contamination. When parent herbicides are still applied, metabolites are constantly formed and may also be degraded. Evaluating their degradation on the basis of concentration measurements is, therefore, difficult. This study presents compound-specific stableisotope analysis (CSIA) of nitrogen- and carbon-isotope ratios at natural abundances as an alternative analytical approach to track the origin, formation, and degradation of desphenylchloridazon (DPC), the major degradation product of the herbicide chloridazon. Methods were developed and validated for carbon- and nitrogen-isotope analysis (δ13C and δ15N) of DPC by liquid chromatography−isotope-ratio mass spectrometry (LC-IRMS) and derivatization gas chromatography−IRMS (GC-IRMS), respectively. Injecting standards directly onto an Atlantis LC-column resulted in reproducible δ13C-isotope analysis (standard deviation <0.5‰) by LC-IRMS with a limit of precise analysis of 996 ng of DPC on-column. Accurate and reproducible δ15N analysis with a standard deviation of <0.4‰ was achieved by GC-IRMS after derivatization of >100 ng of DPC with 160-fold excess of (trimethylsilyl)diazomethane. Application of the method to environmental-seepage water indicated that newly formed DPC could be distinguished from “old” DPC by the different isotopic signatures of the two DPC sources.