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Thomas C.,Texas A&M University | Bibal B.,CNRS Institute of Molecular Sciences
Green Chemistry | Year: 2014

In the ring-opening polymerization (ROP) of cyclic esters and carbonates, hydrogen-bonding organocatalysis offers an interesting alternative to metal-based and enzymatic catalysis to access biocompatible and biodegradable polymers. The design of catalysts, strategies of activation and mechanistic elucidations are highlighted. Recent developments with functionalized monomers for applications in nanomaterials and biomedicine have opened perspectives to broaden the scope of future catalytic systems. In the field of sustainable chemistry, hydrogen-bonding structures devoted to ROP have become a full-fledged class of catalysts. © the Partner Organisations 2014.


Llevot A.,University of Bordeaux 1 | Astruc D.,CNRS Institute of Molecular Sciences
Chemical Society Reviews | Year: 2012

This critical review focuses on the anti-cancer fight using gold nanoparticles (AuNPs) functionalized with chemotherapeutic drugs in so-called "complexes" (supramolecular assemblies) and "conjugates" (covalent assemblies) as vectors. There is a considerable body of recent literature on various tumor-imaging techniques using the surface plasmon band (SPB) and the "passive" and "active" vectorization of anti-cancer drugs. This article reviews the main concepts and the most recent literature data with emphasis on AuNP preparation, cytotoxicities and use in selective targeting of cancer cells with over-expressed receptors for diagnosis and therapy (108 references).


Sibi M.P.,North Dakota State University | Landais Y.,CNRS Institute of Molecular Sciences
Angewandte Chemie - International Edition | Year: 2013

Totally rad: Synthetic methods have been developed for the formation of Csp3-F bonds by reaction of C-centered radicals with fluorine sources. Three complementary strategies, which differ in the mode of generation of the alkyl radical intermediate, are described. These include olefin hydrofluorination, decarboxylative fluorination, and aliphatic C-H fluorination. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vincent J.-M.,CNRS Institute of Molecular Sciences
Chemical Communications | Year: 2012

In recent years, there has been an increasing interest in exploiting fluorous derivatives/moieties for applications that are not only related to reaction mixture purification issues and catalyst recycling, but to confer unique/improved properties to materials. Herein we will focus on the recent advances of fluorous chemistry in material sciences, with special emphasis on applications in organic electronics, crystals/metal-organic frameworks (MOFs) engineering and surface modification chemistry, in particular SiO 2 surfaces. By selecting major contributions in these areas, we wish to highlight the benefits imparted by the introduction of fluorous tags within/onto materials, such as favouring the self-organisation of charge-carrier compounds in bulk heterojunctions, improving the hydrophobicity and/or stability of coordination polymer networks, facilitating solid-state structural rearrangement of large magnitude within crystals or the modification of surfaces through adsorption processes. © 2012 The Royal Society of Chemistry.


Deraedt C.,CNRS Institute of Molecular Sciences | Astruc D.,CNRS Institute of Molecular Sciences
Accounts of Chemical Research | Year: 2014

Catalysis by palladium derivatives is now one of the most important tools in organic synthesis. Whether researchers design palladium nanoparticles (NPs) or nanoparticles occur as palladium complexes decompose, these structures can serve as central precatalysts in common carbon-carbon bond formation. Palladium NPs are also valuable alternatives to molecular catalysts because they do not require costly and toxic ligands.In this Account, we review the role of "homeopathic" palladium catalysts in carbon-carbon coupling reactions. Seminal studies from the groups of Beletskaya, Reetz, and de Vries showed that palladium NPs can catalyze Heck and Suzuki-Miyaura reactions with aryl iodides and, in some cases, aryl bromides at part per million levels. As a result, researchers coined the term "homeopathic" palladium catalysis. Industry has developed large-scale applications of these transformations.In addition, chemists have used Crooks' concept of dendrimer encapsulation to set up efficient nanofilters for Suzuki-Miyaura and selective Heck catalysis, although these transformations required high PdNP loading. With arene-centered, ferrocenyl-terminated dendrimers containing triazolyl ligands in the tethers, we designed several generations of dendrimers to compare their catalytic efficiencies, varied the numbers of Pd atoms in the PdNPs, and examined encapsulation vs stabilization. The catalytic efficiencies achieved "homeopathic" (TON = 540 000) behavior no matter the PdNP size and stabilization type. The TON increased with decreasing the Pd/substrate ratio, which suggested a leaching mechanism.Recently, we showed that water-soluble arene-centered dendrimers with tri(ethylene glycol) (TEG) tethers stabilized PdNPs involving supramolecular dendritic assemblies because of the interpenetration of the TEG branches. Such PdNPs are stable and retain their "homeopathic" catalytic activities for Suzuki-Miyaura reactions for months. (TONs can reach 2.7 × 106 at 80 C for aryl bromides and similar values for aryl iodides at 28 C.) Sonogashira reactions catalyzed by these PdNPs are quantitative with only 0.01% Pd/mol substrate. Kato's group has reported remarkable catalytic efficiencies for mesoporous catalysts formed by polyamidoamine (PAMAM) dendrimer polymerizations. These and other mesoporous structures could allow for catalyst recycling, with efficiencies approaching the "homeopathic" behavior.In recent examples of Suzuki-Miyaura reactions of aryl chlorides, chemists achieved truly "homeopathic" catalysis when a surfactant such as a tetra-n-butylammonium halide or an imidazolium salt was used in stoichiometric quantities with substrate. These results suggest that the reactive halide anion of the salt attacks the neutral Pd species to form a palladate. In the case of aryl chlorides, the reaction may occur through the difficult, rate-limiting oxidative-addition step. © 2013 American Chemical Society.


Van Melderen L.,CNRS Institute of Molecular Sciences
Current Opinion in Microbiology | Year: 2010

Toxin-antitoxin (TA) systems are small genetic modules that are abundant in bacterial genomes. Three types have been described so far, depending on the nature and mode of action of the antitoxin component. While type II systems are surprisingly highly represented because of their capacity to move by horizontal gene transfer, type I systems appear to have evolved by gene duplication and are more constrained. Type III is represented by a unique example located on a plasmid. Type II systems promote stability of mobile genetic elements and might act at the selfish level. Conflicting hypotheses about chromosomally encoded systems, from programmed cell death and starvation-induced stasis to protection against invading DNA and stabilization of large genomic fragments have been proposed. © 2010 Elsevier Ltd.


Astruc D.,CNRS Institute of Molecular Sciences
Nature Chemistry | Year: 2012

The extraordinary development of the design and synthesis of dendrimers has allowed scientists to locate redox sites at precise positions (core, focal points, branching points, termini, cavities) of these perfectly defined macromolecules, which have generation-controlled sizes and topologies matching those of biomolecules. Redox-dendrimer engineering has led to fine modelling studies of electron-transfer metalloproteins, in which the branches of the dendrimers hinder access to the active site in a manner reminiscent of that of the protein. It has also enabled the construction of remarkable catalysts, sensors and printboards, including by sophisticated design of the interface between redox dendrimers and solid-state devices-for example by functionalizing electrodes and other surfaces. Electron-transfer processes between dendrimers and a variety of other molecules hold promising applications in diverse areas that range from bio-engineering to sensing, catalysis and energy materials. © 2012 Macmillan Publishers Limited. All rights reserved.


Bonnet L.,CNRS Institute of Molecular Sciences
International Reviews in Physical Chemistry | Year: 2013

Molecular beam experiments provide fascinating data on how atoms move in the course of chemical reactions. In order to theoretically reproduce these data at relatively low computational cost and to interpret them, nuclei are often treated as classical particles, even though we have known for about a century that, in the range of energies usually available to chemical systems, their motion is best described by the laws of quantum mechanics. Nevertheless, over the last decade this approximation has been shown to work unexpectedly well, provided that a few constraints are introduced into the calculations in order to take into account the quantisation of product internal motions. Why this is so and the nature of the previous constraints are the central issues of this review article. © 2013 Copyright Taylor and Francis Group, LLC.


Astruc D.,CNRS Institute of Molecular Sciences
New Journal of Chemistry | Year: 2011

In this Perspective article, the assembly of ferrocenyl dendrimers, from small to giant sizes, is shown to provide a variety of key properties resulting from multi-electron-transfer. Remarkable features are the chemical and electrochemical reversibility, fast electron-transfer to electrodes, "near" equivalence of the redox potential of all the dendritic redox centers and the "redox breathing" of giant dendrimers. Under certain conditions, which are discussed (in particular the electrostatic effect), these properties lead to applications in the field of redox recognition and sensing, with these nanomaterials functioning as exo-receptors, redox catalysts with biochemical applications and, potentially, molecular batteries. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.


Vincent J.-M.,CNRS Institute of Molecular Sciences
Topics in Current Chemistry | Year: 2012

Among the various strategies developed in the last two decades to recycle catalysts, fluorous catalysis has emerged as one of the most powerful approaches as it combines the advantages of homogeneous catalysis for reactivity (molecular catalysts, most often reactions conducted in one-phase homogeneous conditions) and heterogeneous catalysis for catalyst recovery (liquid/liquid-or solid/liquid-phase separation protocols). Of particular interest is the general character of this approach and the variety and efficiency of separation protocols available to recover catalysts. © 2011 Springer-Verlag Berlin Heidelberg.

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