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11.
A novel solid-phase strategy allows the efficient preparation of "traceless" sulfahydantoins. A total of 28 derivatives, with crude purity generally higher than 85%, were prepared by parallel synthesis. Through reductive alkylations, Mitsunobu reactions, and sulfamoylation reactions on oxime resin, the synthetic strategy affords sulfahydantoin derivatives selectively substituted at N(2), N(5) and N(2), N(5) positions, although yields of disubstituted compounds are lower. The mild reaction conditions involved lead to sulfahydantoins without racemization. 相似文献
12.
Sihem Hessainia Malika Berredjem Souad Ouarna Zinelaabidine Cheraiet Nour-Eddine Aouf 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):719-725
Abstract The synthesis of two new series of functionalized phosphonates is described. A new entry for the synthesis of 5-phosphonoalkyl cyclosulfamides and bis(phosphonoalkyl) sulfamides starting from dihalogeno bis(amino) sulfone has been developed. These compounds have been synthesized in good yields. Triethylphosphite has been used to introduce the phosphonate moiety into sulfamides and cyclosulfamides via Arbuzov reaction. 相似文献
13.
Hureau C Groni S Guillot R Blondin G Duboc C Anxolabéhère-Mallart E 《Inorganic chemistry》2008,47(20):9238-9247
The two pentadentate amino-pyridine ligands L5(2) and L5(3) (L5(2) and L5(3) stand for the N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine and the N-methyl-N,N',N'-tris(2-pyridylmethyl)propane-1,3-diamine, respectively) were used to synthesize four mononuclear Mn(II) complexes, namely [(L5(2))MnCl](PF6) (1(PF6)), [(L5(3))MnCl](PF6) (2(PF6)), [(L5(2))Mn(OH2)](BPh4)2 (3(BPh4)2), and [(L5(3))Mn(OH2)](BPh4)2 (4(BPh4)2). The X-ray diffraction studies revealed different configurations for the ligand L5(n) (n = 2, 3) depending on the sixth exogenous ligand and/or the counterion. Solid state high-field electron paramagnetic resonance spectra were recorded on complexes 1-4 as on previously described mononuclear Mn(II) systems with tetra- or hexadentate amino-pyridine ligands. Positive and negative axial zero-field splitting (ZFS) parameters D were determined whose absolute values ranged from 0.090 to 0.180 cm(-1). Density-functional theory calculations were performed unraveling that, in contrast with chloro systems, the spin-spin and spin-orbit coupling contributions to the D-parameter are comparable for mixed N,O-coordination sphere complexes. 相似文献
14.
Sihem Khaddar-Zine Abdelhamid Ghorbel Claude Naccache 《Journal of molecular catalysis. A, Chemical》1999,150(1-2):223-231
The oxidation state, the mobility and the molecular structure of chromium species present on CrOx–Al2O3 catalysts have been studied by combined diffuse reflectance spectroscopy, EPR and reduction–extraction by ethane 1,2 diol. CrO42− species exist on the alumina surface in the form of loosely-interacting species on hydrated surface (species A) and in the form of strongly bonded species on dehydrated Al2O3 surface (species B). The CrO42− species show high mobility and are probably responsible for the formation of CrOx clusters. 相似文献
15.
Quartz crystal microbalance determination of organophosphorus and carbamate pesticides 总被引:1,自引:0,他引:1
Nikolaos G Karousos Sihem AouabdiAllan S Way Subrayal M Reddy 《Analytica chimica acta》2002,469(2):189-196
We have developed a quartz crystal microbalance (QCM) biosensor for the determination of organophosphorus and carbamate pesticides. A change in resonant frequency is observed as a result of mass adsorption, and we have used this as the basis for sensor development. Specifically, we have used a two-enzyme system (acetylcholine-esterase and choline oxidase) which converts acetylcholine to betaine producing hydrogen peroxide as a by-product. In a third enzyme reaction (peroxidase), the peroxide is able to oxidise benzidines (3,3′-diaminobenzidine) into an insoluble product that precipitates out and can adsorb to surfaces. Non-ionic surfactants have been used for the first time to enhance the surface deposition of suspended precipitate, thereby improving sensor sensitivity. Pesticides are known to inhibit esterase activity (thereby reducing the amount of QCM-detectable precipitate produced). We have shown that the QCM-enzyme sensor system can be used to determine carbaryl and dichlorvos down to 1 ppm. 相似文献
16.
The morphology of silicon nanowire (SiNW) layers formed by Ag-assisted electroless etching in HF/H2O2 solution was studied. Prior to the etching, the Ag nanoparticles were deposited on p-type Si(1 0 0) wafers by electroless metal deposition (EMD) in HF/AgNO3 solution at room temperature. The effect of etching temperature and silicon resistivity on the formation process of nanowires was studied. The secondary ion mass spectra (SIMS) technique is used to study the penetration of silver in the etched layers. The morphology of etched layers was investigated by scanning electron microscope (SEM). 相似文献
17.
Stefan Benndorf Dr. Sihem Groni Leanne M. Stafast Dr. Helmar Görls Dr. Claire Fave Prof. Dr. Bernd Schöllhorn Prof. Dr. Wolfgang Weigand 《欧洲无机化学杂志》2023,26(10):e202200684
[FeFe] hydrogenase (H2ase) mimicking complexes containing lipoic and selenolipoic acid moieties connected to 2-hydroxy-1,3-dithiopropane and 2-hydroxy-1,3-diselenopropane bridging ligands were synthesized and characterized using different spectroscopic methods. X-ray diffraction analysis was utilized to determine the molecular structure of a triphenylphosphane substituted analogue. Cyclic voltammetry (CV) investigations on the redox chemistry in presence and absence of acetic acid (AcOH) revealed differing behaviours among the mimics. IR spectroelectrochemistry (IR SEC) enabled deeper insights of structural changes during electrochemical measurements. The elaboration of surface confined systems was studied in preliminary experiments. CV experiments showed that the lipoic acid derivatives of the [FeFe] H2ase mimics formed well-organized self-assembled monolayers (SAMs) on Pt electrodes, a promising result for future work. 相似文献
18.
Imen Essouissi Nadia Malek Saied Najoua Mejri Sihem Guizani Hadeer Lazim Mouldi Saidi 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(3):987-996
In this work we propose a technetium-99m-labeled derivative from Ethionamide (ETH), further referred to as 99mTc-ECF for tuberculosis diagnosis. The biological features of this radioactive agent have been studied. The 2-ethylpyridine-4-carbothioamide-ferrocène (ECF) was chemically synthesized and then labeled with technetium-99m. It has been confirmed through this work that 99mTc-ECF is obtained with high radiolabelling yield (>90 %). Radiochemical analysis of 99mTc-ECF revealed that the molecule was efficiently labeled with a little free remaining pertechnetate. Only 1–2 % of the tracer was leached out from the complex at 24 h when incubated in serum at 37 °C which confirmed its high stability. The sensitivity test of ECF showed that the group of grafted ferrocenyl does not seem to have largely altered the active site of the molecule. In-vitro investigations were conducted using BCG (Bacille Calmette-Guérin) as analogue of Mycobacterium Tuberculosis and Listeria Monocytogenes as negative control. It was proved that for BCG, ECF has kept the bacteriostatic properties of the parent compound (ETH). In physiological conditions, the measured up-take of the tracer with live bacteria was about 24.1 and 7.1 % for BCG and Listeria Monocytogenese, respectively. The comparison of the 99mTc-ECF accumulation at sites of BCG infected animals, which is expressed as target-to-non-target ratio (found to be equal to 2.15) with other radiotracers was discussed. This allowed us to consider that 99mTc-ECF could be a reasonable radiotracer for mycobacterial infections. Obtained results were good and encourage to undergo a similar labeling for the Mycobacterium tuberculosis as perspective of this work. 相似文献
19.
This paper presents an analysis of how to obtain narrow transmission band in the centre of the spectrum of the arbitrary chirped fiber Bragg grating (ACFBG). Grating chirp coefficient and refractive index profile are the critical parameters in contributing to performance of fiber Bragg grating. The reflection spectra and transmission band were analyzed with different refractive index profile. Apodization techniques are used to get optimized reflection spectra. The simulations are based on solving coupled mode equations by transfer matrix method that describes the interaction of guided modes. 相似文献
20.
In this paper, the effect of various taper profiles on dispersion slope compensation in optical fiber links is studied. Theoretical and numerical investigation of the linear and nonlinear group delays of tapered fiber Bragg grating's (T-FBG) under strain is made. Calculation is performed using Matlab code based on solving the coupled mode equation using transfer matrix method. Our study shows that the linear tapered FBG profile provide the best result than the linear-exponential profile which can compensate up to 500 km. As result, the spectral characteristics of tapered grating allow them to be used efficiently in high bit rates WDM and long-haul optical communication systems for chromatic dispersion of single-mode fiber. 相似文献