FT-IR and FT-FIR studies of vanadium,molybdenum and tungsten oxides supported on different carriers

In the far IR region at low molybdenum loadings, Mo-SiO₂ catalysts present a pseudomolybdate or a polymolybdate species, while bulk-like MoO₃ appears at loadings close to the geometrical monolayer coverage. W-SiO₂ and V-SiO₂ spectra show bands close to those observed on the corresponding bulk oxides.In the case of TiO₂, Al₂O₃, ZrO₂ supported catalysts, a band is observed near 1000 cm^–1 which is assigned to the Mo=O stretching vibration of coordinatively unsaturated Mo ⁿ⁺ ions showing a stronger interaction with the support than one observed on silica.     

Shallow Water equations for Non-Newtonian fluids

The purpose of this paper is to provide a consistent thin layer theory for some Non-Newtonian fluids that are incompressible and flowing down an inclined plane under the effect of gravity. We shall provide a better understanding of the derivation of Shallow Water models in the case of power-law fluids and Bingham fluids. The method is based on asymptotic expansions of solutions of the Cauchy Momentum equations in the Shallow Water scaling and in the neighbourhood of steady solutions so that we can close the average equations on the fluid height h and the total discharge rate q. Such a method has been first introduced in the case of Newtonian fluids where the computations are proved to be rigorous (Vila, in preparation [20]; Bresch and Noble, 2007 [9]) whereas the more complex case of arbitrary topography has been treated formally (Boutounet et al., 2008 [5]). The well posedness of the free surface Cauchy Momentum equations for these Non-Newtonian fluids is still an open problem: the computations carried out here are only formal.     

Amino acid functionalisation of water soluble carbon nanotubes

High solubility of SWNTs and MWNTs in water is obtained by organic functionalisation; derivatisation with N-protected glycine is also easily achieved.     

A new supramolecular assembly obtained from the combination of silver(I) cations with a thiophosphorylated cavitand

The new tetra-thiophosphonatocavitand 1 in its iiii configuration extracts quantitatively Ag+ ions from aqueous solutions; the tetranuclear complex [1(2).Ag4Pic4] was selectively formed and characterized in the solid state by X-ray diffraction which revealed the formation of a new dimeric assembly through Ag+ coordination.     

A readily-accessible (+)-sparteine surrogate

A "(+)-sparteine-like" chiral diamine, readily synthesized in three steps from (-)-cytisine, has been evaluated in four different asymmetric transformations; in each case, selectivity in an enantiocomplementary fashion to (-)-sparteine was observed.     

Metallation des halogenures d'aryle par le tributylstannyllithium dans le tetrahydrofuranne

The metallation of aryl halides with tributylstannyllithium in THF proceeds via at least three different mechanisms whose relative rates depend on the nature of the halogen, the substrate and the experimental conditions. In the case of aryl bromides, a halogenmetal exchange (major process) is competing with a radical mechanism. With aryl chlorides, an arynic process, a halogenmetal exchange and a radical mechanism are involved. Finally, with aryl fluorides, the arynic process is usual, but it may be strongly competed by a radical mechanism whenever suitable experimental conditions are arranged.     

Leed and Aes study of the Au/AuPb2 interface

The adsorption of lead on gold at room temperature in UHV conditions has been studied by LEED and AES. We review some of the data obtained on the Au(100), (111), and (110) faces, published elsewhere, and we give some new experimental results on the stepped Au(S) [n(100) × (111)] (with n = 3, 4, 5, and 6) faces. On all these faces, as lead is deposited on the gold substrate it first forms a monolayer of lead, then a compound AuPb₂. Using the LEED and Auger data we give a model of the epitaxy with a layer-by-layer growth mechanism. We propose a model which involves a transition alloy wich forms at the interface Au/AuPb₂. This model is in agreement with the LEED diagrams observed before the one corresponding to bulk AuPb₂. In the case of the epitaxy of lead on gold (100), we calculate the Auger peak-to-peak ] heights of the gold (72 eV) and lead (93 eV) transitions versus coverage. We obtain good agreement with the experimental data, assuming that the first and last layers of the alloy are lead monolayers and diffusion of lead in gold as well as gold in lead.     

Molecular Structure of the Ethylenediammonium Complex of a Tetracarboxy-macrocyclic Receptor Molecule

The crystal and molecular structure of the complex formed by the ionized bistartro-[18]-crown-6 receptor molecule 1 with the ethylenediammonium cation, is described. The macrocycle is roughly planar, the carboxy groups of each tartaric acid residue being in a diaxial relationship and extending above and below this plane. This conformation allows ‘lateral’ interactions with bound species to occur. The substrate is sandwiched between two macrocycles, with one of its NH heads anchored to the polyether core, and the other one in contact with the two carboxy groups of the neighboring molecule.     

A new approach to A,B-difunctionalisation of cyclodextrins using bulky 1,3-bis[bis(aryl)chloromethyl]benzenes as capping reagents

1,3-Bis[bis(4-tert-butylphenyl)chloromethyl]benzene and 1,3-bis[bis(4-anisyl)chloromethyl]benzene were employed as regioselective capping reagents for the preparation of C-6A,C-6B-bridged, permethylated alpha- and beta-CD derivatives; isolated yields up to 55% of proximally capped, methylated CDs were obtained, thus opening the way to the straightforward preparation of a wide range of A,B-functionalised CDs. As revealed by a single crystal X-ray diffraction study, the benzene-1,3-bis[bis(4-tert-butylphenyl)methyl] spacer is perfectly suited for A,B-capping of beta-cyclodextrin.