On the way of understanding the behavior of nanometer-scale metallic particles toward the adsorption of CO and NO molecules

Previously, we have proposed a relationship between the adsorption modes of a simple molecule (NO) and the behavior of the nanometer-scale monometallic clusters after this adsorption. More precisely, a set of experiments seems to show that dissociative adsorption of NO leads to the sintering of nanometer-scale metallic particles (NSMPs), whereas molecular adsorption is related to the oxidation. Although numerous investigations have been published on catalytic or electrocatalytic reactions where the interaction between carbon monoxide and NSMPs is involved, only a few studies have been dedicated to the adsorption of CO on NSMPs. This purely energetic approach is discussed through different results already published in the literature and through some recent theoretical calculations related to solid state physics. Although interesting and systematic results are gathered here and are partly explained, this adsorption process still remains a challenge.     

A Photoreducible Copper(II)‐Tren Complex of Practical Value: Generation of a Highly Reactive Click Catalyst

A detailed study on the photoreduction of the copper(II) precatalyst 1 to generate a highly reactive cuprous species for the copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC) click reaction is presented. For the photoactive catalyst described herein, the activation is driven by a photoinduced electron transfer (PET) process harnessing a benzophenone‐like ketoprofenate chromophore as a photosensitizer, which is equally the counterion. The solvent is shown to play a major role in the Cu^II to Cu^I reduction process as the final electron source, and the influence of the solvent nature on the photoreduction efficiency has been studied. Particular attention was paid to the use of water as a potential solvent, aqueous media being particularly appealing for CuAAC processes. The ability to solubilize the copper‐tren complexes in water through the formation of inclusion complexes with β‐CDs is demonstrated. Data is also provided on the fate of the copper(I)‐tren catalytic species when reacting with O₂, O₂ being used to switch off the catalysis. These data show that partial oxidation of the secondary benzylamine groups of the ligand to benzylimines occurs. Preliminary results show that when prolonged irradiation times are employed a Cu^I to Cu⁰ over‐reduction process takes place, leading to the formation of copper nanoparticles (NPs). Finally, the main objective of this work being the development of photoactivable catalysts of practical value for the CuAAC, the catalytic, photolatent, and recycling properties of 1 in water and organic solvents are reported.     

Changes in the structure of MgxAly(OH)z layered double hydroxides during the adsorption of organic compounds

Changes in the structure of synthetic Mg _x Al _y (OH) _z layered double hydroxides are studied during the sorption of organic compounds.     

Reaction of Hexamethyldisilazane with Diacylhydrazines : An Easy 1,3,4-Oxadiazole Synthesis

The reaction of diacylhydrazines with hexamethyldisilazane in the presence of tetrabutylammonium fluoride as catalyst results in cyclisation to give 1,3,4-oxadiazoles in good yield.     

Syntheses of N-Acyl and N-Alkoxycarbonyl Derivatives of 2-Alkoxycarbonylamino-2-deoxy-D-glucose

Abstract

N-Acyl and N-alkoxycarbonyl derivatives of l, 3, 4, 6-tetra-O-acetyl-2-alkoxy-carbonylamino-2-deoxy-β-D-glucopyranose have been synthesized using mixed anhydrides and symmetrical or disymetrical pyrocarbonates. These derivatives have been used as donors in 1, 2-trans-glycosylation reactions promoted by Lewis acids. Besides the expected (β-D-glycosides, cyclisation and rearrangement side-products were often encountered in such glycosylations.