d-f heterobimetallic association between ytterbium and ruthenium carbon-rich complexes: redox commutation of near-IR luminescence

We describe how the association between an ytterbium ion and a ruthenium carbon-rich complex enables the first switching of the near-IR Yb(III) luminescence by taking advantage of the redox commutation of the carbon-rich antenna.     

Représentations de Gelfand–Graev pour les groupes réductifs non connexesGelfand–Graev representations for non connected reductive groups

Let G be a connected reductive group defined over $\text{F}{}_{\mathrm{q}}$ and let F be the corresponding Frobenius endomorphism. Let σ be a quasi-central rational automorphism of G. We define in this article Gelfand–Graev representations of the group $\text{G}{}^{\mathrm{F}}\text{=G}{}^{\mathrm{F}}\text{.〈σ〉}$ when σ is unipotent and when it is semi-simple. We show that they have similar properties to Gelfand–Graev representations of the group G^F. To cite this article: K Sorlin, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 179–184.     

Sol-Gel Coatings on Non-Oxide Planar Substrates and Fibers: A Protection Barrier Against Oxidation and Corrosion

Sol-gel coatings on non-oxide substrates can be used to prevent high temperature degradation and to improve wet corrosion resistance. Alumina coatings were investigated. The starting precursor was aluminium sec-butoxide, modified with chelating ligands such as 2,4-pentanedione or acrylic acid to prevent its precipitation in the presence of water. Stainless steel plates and Hi-Nicalon SiC fibers are often utilized in different kinds of applications and thus were selected as substrates. Thin films were deposited from the modified alkoxide solutions using dip-coating techniques. The parameters governing the process such as the aging of the sols, the viscosity, the withdrawal rate and the thermal treatment were investigated. The films were characterized (morphology, thickness) and showed an interesting behaviour as protection barrier in an aggressive medium.     

The new pentaborate Na3SrB5O10

Sodium strontium pentaborate, Na₃SrB₅O₁₀, maintains the same, previously unobserved, structure type at 200, 250 and 293 K. The fundamental building units are anionic [B₅O₁₀]⁵⁻ groups distorted from mm2 point symmetry. The Sr atoms are eightfold coordinated by O atoms, forming trigonal dodecahedra. The Na atoms appear in three crystallographically different environments. The present single‐crystal results correct a previous report in which a monoclinic cell was deduced for this compound on the basis of powder diffraction data. The structure of the title compound is discussed in the crystalochemical context of other borates with the same formula type. Although the unit cell of the present compound is similar to that determined in a previous study of the analogous Ca‐containing compound, this study demonstrates that the structures of the two are different. These novel alkali–alkaline earth borates are considered as potential host materials for optical applications (fluorescence materials or phosphors).     

Free Superoxide is an Intermediate in the Production of H2O2 by Copper(I)‐Aβ Peptide and O2

Oxidative stress is considered as an important factor and an early event in the etiology of Alzheimer's disease (AD). Cu bound to the peptide amyloid‐β (Aβ) is found in AD brains, and Cu‐Aβ could contribute to this oxidative stress, as it is able to produce in vitro H₂O₂ and HO^. in the presence of oxygen and biological reducing agents such as ascorbate. The mechanism of Cu‐Aβ‐catalyzed H₂O₂ production is however not known, although it was proposed that H₂O₂ is directly formed from O₂ via a 2‐electron process. Here, we implement an electrochemical setup and use the specificity of superoxide dismutase‐1 (SOD1) to show, for the first time, that H₂O₂ production by Cu‐Aβ in the presence of ascorbate occurs mainly via a free O₂^.? intermediate. This finding radically changes the view on the catalytic mechanism of H₂O₂ production by Cu‐Aβ, and opens the possibility that Cu‐Aβ‐catalyzed O₂^.? contributes to oxidative stress in AD, and hence may be of interest.     

X‐ray absorption spectroscopy study of buried Co layers in the Co/Mo2C multilayer mirrors

X‐ray absorption spectroscopy at the Co K edge was applied to investigate the chemical environment of Co atoms inside Co/Mo₂C periodic multilayers. The results show a mixing between Co and Mo₂C layers prior to any annealing process, whereas following annealing from 300 °C pure Co layers are observed. X‐ray absorption spectroscopy results are in agreement with previous nuclear magnetic resonance spectroscopy results. They indicate that the pure Co content increases upon annealing, while it is absent in the as‐deposited samples. The comparison of the results, based on the analysis of the data obtained on the multilayer samples and some reference materials, reveals that the ordering of Co atoms inside the Co layers increases upon annealing. Copyright © 2016 John Wiley & Sons, Ltd.     

Efficient conversion of aromatic amines into azides: a one-pot synthesis of triazole linkages

[reaction: see text] An efficient and improved procedure for the preparation of aromatic azides and their application in the Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition ("click reaction") is described. The synthesis of aromatic azides from the corresponding amines is accomplished under mild conditions with tert-butyl nitrite and azidotrimethylsilane. 1,4-Disubstituted 1,2,3-triazoles were obtained in excellent yields from a variety of aromatic amines without the need for isolation of the azide intermediates.     

Identification of novel circulating coffee metabolites in human plasma by liquid chromatography-mass spectrometry

This study reports a liquid chromatography-mass spectrometry method for the detection of polyphenol-derived metabolites in human plasma without enzymatic treatment after coffee consumption. Separation of available standards was achieved by reversed-phase ultra performance liquid chromatography and detection was performed by high resolution mass spectrometry in negative electrospray ionization mode. This analytical method was then applied for the identification and relative quantification of circulating coffee metabolites. A total of 34 coffee metabolites (mainly reduced, sulfated and methylated forms of caffeic acid, coumaric acid, caffeoylquinic acid and caffeoylquinic acid lactone) were identified based on mass accuracy (<4 ppm for most metabolites), specific fragmentation pattern and co-chromatography (when standard available). Among them, 19 circulating coffee metabolites were identified for the first time in human plasma such as feruloylquinic acid lactone, sulfated and glucuronidated forms of feruloylquinic acid lactone and sulfated forms of coumaric acid. Phenolic acid derivatives such as dihydroferulic acid, dihydroferulic acid 4'-O-sulfate, caffeic acid 3'-O-sulfate, dimethoxycinnamic acid, dihydrocaffeic acid and coumaric acid O-sulfate appeared to be the main metabolites circulating in human plasma after coffee consumption. The described method is a sensitive and reliable approach for the identification of coffee metabolites in biological fluids. In future, this analytical method will give more confidence in compound identification to provide a more comprehensive assessment of coffee polyphenol bioavailability studies in humans.     

Synthesis and growth regulatory activity of pyrazolesulfanyl‐ and isoxazolesulfanyl‐1H‐[1,2,4]triazoles and their azinyl derivatives

By cyclocondensation of 3‐(1H‐[1,2,4]triazol‐3‐ylsulfanyl)‐pentane‐2,4‐dion with hydroxylamine, hydrazine, methylhidrazine, and arylsulfonyl‐hydrazides, the 3‐(3,5‐dimethyl‐isoxazol‐4‐ylsulfanyl)‐1H‐[1,2,4]triazole ( 2 ) and 3‐(3,5‐dimethyl‐1‐R‐pyrazol‐4‐ylsulfanyl)‐1H‐[1,2,4]triazoles ( 3a , 3b , 3c , 3d ) are synthesized. Under the action of quaternary ammonium salts of azines with limited heating in acetone they form a series of compounds ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h ), which molecules simultaneously contain three different heterocyclic rings. Structures of compounds were confirmed by ¹H and ¹³C NMR, MS, and elemental analysis. The plants growth regulatory activities of compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h were investigated. Data of biological tests testify that these compounds can be of interest to search for new growth stimulators. J. Heterocyclic Chem., (2010).