Solid-state detection of gases by use of thin films based on pyrazole units, and morphological characterization of the films by AFM

Synthesis of a series of heterocyclic compounds based on pyrazole units is reported. The possibility of using these compounds, as solid-state thin layers deposited on quartz substrates, for optical recognition of hazardous pollutant gases was investigated. The gases SO₂, NO₂, CO, CH₄, and NH₃ were studied. Two of the ligand layers had reversible sensitivity toward SO₂, with good reaction time. The presence of CO, CH₄ NO₂, and NH₃ had no effect on the optical properties. Morphological characterization by use of AFM microscopy was also investigated.     

Influence of Vertical Vibrations on the Stability of a Binary Mixture in a Horizontal Porous Layer Subjected to a Vertical Heat Flux

Macroscale three-dimensional modeling of fluid flow in a thin porous layer under unsaturated conditions is a challenging task. One major issue is that such layers do not satisfy the representative elementary volume length-scale requirement. Recently, a new approach, called reduced continua model (RCM), has been developed to describe multiphase fluid flow in a stack of thin porous layers. In that approach, flow equations are formulated in terms of thickness-averaged variables and properties. In this work, we have performed a set of experiments, where a wet \(260\hbox {-}\upmu \hbox {m}\)-thin porous layer was placed on top of a dry layer of the same material. We measured the change of average saturation with time using a single-sided low-field nuclear magnetic resonance device known as NMR-MOUSE. We have employed both RCM and the traditional Richards equation-based models to simulate our experimental results. We found that the traditional unsaturated flow model cannot simulate experimental results satisfactorily. Very close agreement was obtained by including the dynamic capillary term as postulated by Hassanizadeh and Gray in the traditional equations. The reduced continua model was found to be in good agreement with the experimental result without adding dynamic capillarity term. Moreover, the computational effort needed for RCM simulations was one order of magnitude less than that of traditional models.     

Théorème de Hoffmann-Jorgensen et application aux amarts multivoques

Annali di Matematica Pura ed Applicata (1923 -) - On présente ici des versions univoques et multivoques d'un résultat de Hoffmann-Jorgensen ([10]). Ces résultats permettent...     

Efficient solution phase combinatorial access to a library of pyrazole- and triazole-containing compounds

An efficient method for the synthesis of multidentate molecules, with various building blocks, such as pyrazolyl, triazolyl, pyridyl, furyl, or bispinidyl derivatives, is reported. This approach is based on the condensation of easily available N-alkyl heteroarylamines with N-hydroxymethyl pyrazoles or triazoles.     

Synthesis of 2-(fluorinated aryl)pyridine derivatives via palladium-catalyzed CH bond arylation of fluorobenzenes using 2-halopyridines as aryl sources

We report herein on palladium-catalyzed direct arylation of (poly)fluorobenzene derivatives in the presence of 2-halopyridines for the one-step synthesis of 2-[(poly)fluorinated aryl]pyridine derivatives. The reactivity of 2-bromopyridines strongly dependents on its substituents at C6 position. The reaction proceeds nicely using a diphosphine palladium catalyst, and potassium pivalate/dimethylacetamide (PivOK/DMA) as catalytic system. The reaction was regioselective and occurred at the ortho-position of fluorine atoms.     

Effect of two isomeric tetrapyrazolyl ligands on the catalytic oxidation of 3,5-di-tert-butylcatechol

Copper(II) salts were combined with a tetrapyrazolyl ligand ({N,N,N’,N’-tetrakis-[(3,5-dimethylpyrazol-1-yl)methyl)-1,4-phenylenediamine}L1 or {N,N,N’,N’-tetrakis-[(1,5-dimethylpyrazol-3-yl)methyl)-1,4-phenylenediamine}L2) and assessed as oxidation catalysts. The corresponding dioxygen complexes were generated in situ by mixing the copper salt and the pyrazolyl donor ligand in air. The oxidation of 3,5-di-tert-butylcatechol (DTBC), which affords 3,5-di-tert-butylquinone (DTBQ), was studied. The reaction rate was found to depend essentially on the nature of the junction linking two pyrazolyl neighbours.     

An optimal order finite element method for elliptic interface problems

A specific finite element method for problems involving interfaces is presented. The method allows for non fitted meshes and is well adapted for elliptic problems with jumps of coefficients along a closed curve. Error bounds for the presented method show optimal convergence. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of high added value compounds through catalytic oxidation of 2-phenylethanol: A Kinetic study

An effective procedure was developed to produce high-value added phenolic compounds through the conversion of 2-phenylethanol (2-PhEt) by using acid-activated clays KSF for the hydrogen peroxide. Owing to KSF's ability to catalyze a variety of complex oxidations, it was likely to convert 2-PhEt to hydroxytyrosol (HTY) and tyrosol (TY) derivatives. The analyses of catalytic solution revealed that the optimum conditions, giving a higher concentration of oxidation products such as HTY, were as follows: 2-PhEt concentration 10⁻² mol/L, the hydrogen peroxide concentration 5.05 × 10⁻² and 0.6 g L^–1 of KSF clays . The yield during the conversion reaction into HTY was around 25%. All compounds in the reaction mixture were identified by mass spectrophotometry using a LC-MS apparatus. HTY, TY, meta-tyrosol and ortho-tyrosol were the major compounds. The antioxidant activity was realized by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. In fact, it is revealed that the strongest inhibition percentage (PI = 96) was detected with the increase in the concentration of HTY. The approach proposed in the present work presents an environment friendly method.     

Blue Highly Fluorescent Boranil Derived From Anil Ligand: Synthesis,Characterization, Experimental and Theoretical Evaluation of Solvent Effect on Structures and Photophysical Properties

In this study, we report the design and the synthesis of a Schiff base; Anil and its corresponding Boron Difluoride complexe; Boranil. The synthesis procedure was carried out adopting new, optimized reaction conditions. The Boranil dye presents the advantage to be emissive in solution. 1H and 19F NMR along with FTIR confirmed both compound's structure. To gain a better understanding of the solvatochromic behavior of Anil and Boranil, the dependence of the absorption spectra on the solvent's polarity was studied in depth. Thus, UV–Vis spectroscopy was performed in five selected solvents. In addition to the solvent's polarity effect, the influence of BF2 moiety introduction on the molecule's photophysical properties was also evaluated. When examining different absorption spectra, we found that the title fluorescent dye exhibited weak solvatochromic (11 nm in THF) as well as a slight redshift broader and relatively more structured absorption spectra after complexation. Besides, we investigate the obtained key structure–property relationships through DFT and TD-DFT calculations using a 6–311++ G (d, p) basis set. Quantum chemical calculations allowed confirming proposed structures and understanding their electronic structure in larger details. Theoretical results also showed good agreement with the experimental findings. Finally, the frontier molecular orbitals were investigated to illustrate the pi-conjugation and charge transfer effect.