Etudes par RMN en serie heterocyclique–III. Non-equivalence magnetique et inversion de l'azote dans une serie d'heteocycles pentagonaux diazotes,pyrazolines-2 et 3, pyrazolidines et pyrazolidones

The non-equivalence of ethyl, benzyl and isopropyl groups fixed on nitrogen atoms in 2-and 3-pyrazolines, pyrazolidines and pyrazolidones depends on the assymetry existing in the molecule. The asymmetric centres are either a ring carbon atom, a quaternary nitrogen atom (protonation, quaternarization) or a tertiary nitrogen atom (slow nitrogen inversion). The nitrogen inversion process was observed only in the case of pyrazolidines (possibility of inversion at the two adjacent nitrogens) and of pyrazolidones (inversion of the ‘non-amidic’ nitrogen). The inversion is temperature-dependent and is affected by substituents.     

13C NMR spectra of s-triazolo-as-triazinones: Application to isomeric and tautomeric structure determination

¹³C NMR spectroscopic data are reported for the s-triazolo-as-triazinones of five isomeric series. Comparison of their ¹³C chemical shifts and CH coupling constants allows the determination of the type of ring junction of the two heterocycles, as well as the predominant tautomeric form in each system.     

Comparative 13C NMR study of deuteriated and undeuteriated dibenzothiophenes,dibenzofurans, carbazoles,fluorenes and fluorenones

The NMR assignments of all carbons of dibenzothiophene and its S-oxides, dibenzofuran, various carbazoles, fluorene and fluorenone have been carried out using deuteriated derivatives and lanthanide shift reagents. Chemical shifts and coupling constants are discussed as a function of the nature of the central ring.     

«Self-organized» InAs/GaAs quantum dots

Il Nuovo Cimento D - We discuss some specific properties of self-organized InAs-GaAs quantum dots grown by Molecular Beam Epitaxy. We report on the optical spectra obtained under resonant...     

Using Microfluidic Set-Up to Determine the Adsorption Rate of Sporosarcina pasteurii Bacteria on Sandstone

Transport in Porous Media - Microbial-induced carbonate precipitation (MICP) in porous media is a two-step procedure: First, the suspension of bacteria is injected and some of the bacteria get...     

Chiral macrocycles,part II: Transport of amino acid Li+ salts

Complexation of amino acids in both their zwitterionic and Li⁺ salt forms by macrocycles, and carrier-mediated transport of the Li⁺ salts through a CH₂Cl₂ membrane have been investigated: the transport study of four amino acids by a new series of tetrapyrazolic macrocycles with functionalized sidearms shows wide variations of the transport rates depending on both the macrocyclic sidearm and the amino acid structure.     

Chiral macrocycles,part I: Synthesis and enantioselective transport of carboxylic acids as their Li+ salts

A new series of tetrapyrazolic macrocycles with a functionalized sidearm has been prepared. Their capability to transport Li⁺ salts of carboxylic acids has been examined and is shown to be strongly dependent on the functionality of the macrocycle sidearm. In the case of the Li⁺ (D, L.)-mandelate, chiral recognition has been observed.     

Investigation of reactive ion etch-induced damage in InP surfaces using a noncontact photothermal radiometric probe

Process-induced damage in epitaxial InP films following CH₄/H₂ reactive ion etching has been studied using a noncontact photothermal radiometric (PTR) probe. A significant shift in measured PTR amplitude as a function of applied bias voltage has been observed. Results are correlated with both Raman and photoluminescence measurements.     

Development of a rotating reactor for uniform solid treatments: Application to the steaming of HY zeolites

A laboratory scale rotating reactor designed for high temperature treatments of powders under controlled atmosphere is described. It was used for HY zeolite steamings. This rotating reactor allowed the lattice dealumination level to be governed with a good accuracy and to minimize concomitant amorphization. A series of well-defined steamed HY zeolites characterized by their lattice Si/Al ratio varying from 7.6 to 40 was obtained.