Partial orientation of nitroxide biradicals in the plastic phase of cyclohexane and in frozen toluene solution

Several nitroxide biradicals have been studied by electron spin resonance, in cyclohexane solution at ?10°C and in toluene solution at ?150°C. The ESR spectra change when the sample orientation in the spectrometer cavity is changed: under favourable circumstances oriented spectra are obtained.     

Distribution angulaire des électrons secondaires émis par des monocristaux de cuivre sous bombardement ionique

Energy angular distributions of the secondary electronic emission from copper single crystals bombarded by 40 keV Ar⁺ ions are studied. These distributions, recorded as a function of the reception azimuth angle, with fixed polar angle, show an anisotropy which is both characteristic of the target cristalline structure and of the collected electron energy. We interpret these result in terms of bulk electron diffraction.     

How M?ssbauer spectroscopy can improve Li-ion batteries

In the domain of Li-ion batteries, M?ssbauer spectroscopy is mainly used for the characterization of electrode materials and the analysis of electrochemical reactions. Depending on the properties under investigation, different approaches are often considered, which are based on ex situ, in situ and operando measurements. The specific electrochemical cells and sample preparations used for such measurements are described in this paper. Applications to selected examples of cathode and anode materials are presented in order to show how M?ssbauer spectroscopy, when associated with other techniques, provides essential information to understand the mechanisms and improves the performances of Li-ion batteries.     

Recherches sur les substances mesomorphes—IX : Smectiques “fourchus”. organisation moleculaire dans les phases smectiques a

The synthesis and the mesomorphic properties of new branched smectogenic A derivatives of fluorene are described. The observation that branched chain compounds form a smectic A phase allows conclusions to be drawn on molecular arrangements in smectic A layers.     

Recherches sur les substances mesogenes—VIII : Preparation et proprietes mesomorphes de series isometriques

The synthesis and the mesomorphic properties of various series of isometric mesogenic compounds are described. It is confirmed that isometric mesogenic molecules may be nematogenic and/or smectogenic according to the position of the polar rigid core.     

Un nouvel hétérocycle telluré: le benzisotellurazole-1,2. 2. Structure cristalline et moléculaire du benzisoselenazole-1,2 et du benzisotellurazole-1,2

Anomalous physical properties (solubility and melting point) of 1,2-benzisotellurazole are explained by very short intermolecufar Te…N bonds (2.4 Å) found in the crystal structure. Such bonds are not present in the crystal structure of 1,2-benzisoselenazole and the physical properties are those expected.     

Spectrophotometric determination of hydroxylamine alone and in the presence of monochloramine

Hydroxylamine (< 3 × 10^?3 mol l^?1) is quantified by ultraviolet spectrophotometry after reaction with an excess of formaldehyde in buffered solution at pH 12.2. The absorbance of the formaldoxime produced is measured at 218 nm (? = 5480 l mol^?1 cm^?1) when hydroxylamine is alone but at 230 nm (? = 3230 l mol^?1 cm^?1) when monochloramine is present.     

General access to polyhydroxylated nortropane derivatives through hetero diels-alder cycloaddition. Part II: Synthesis of (±) calystegine B2.

Calystegine B₂ was prepared by the intramolecular cyclisation of a polyhydroxylated 4-amino-cycloheptanone. This intermediate results from a heteroycloaddtion between an acylnitroso compound and a cyclohepta-1,3-diene. The diene is in turn obtained from iron-complexed tropone.     

Speleands. Macropolycyclic receptor cages based on binding and shaping sub-units. Synthesis and properties of macrocycle cyclotriveratrylene combinations. Preliminary communication

Combination of a receptor unit with a rigid shaping unit produces a new type of receptor molecules of the cryptand class, hollow macropolycyclic molecules termed speleands, capable of substrate inclusion. Two members of this category of compounds 1 and 2 , have been synthesized by connecting in a single step, a macro-cyclic [18]-N₃O₃ binding unit with a rigid cyclotriveratrylene unit via three bridges. Compound 1 binds the rnethylammonium cation forming both external and internal complexes; for the latter a ‘speleme’ structure, schematically represented by 15 , may be proposed.