Vincent Collière

Catalytic investigation of rhodium nanoparticles in hydrogenation of benzene and phenylacetylene

Nanoparticles of rhodium embedded in polyvinylpyrrolidone (PVP), as catalyst, were investigated in the hydrogenation of different substrates (benzene, phenylacetylene, norbornene, quinoline, adiponitrile). The solid was used as a heterogeneous catalyst or as a soluble heterogeneous catalyst in biphasic conditions (liquid/liquid) when the catalyst was dissolved in water. In both cases, the kinetics of the catalytic reaction were found to be zero-order in respect to the substrate and first-order with respect to hydrogen and catalyst. The higher hydrogenation reaction rate was found for benzene by using biphasic conditions. The [Rh-PVP] catalyst has shown an efficient activity for the catalytic hydrogenation of norbornene, quinoline and adiponitrile into norbornane, tetrahydroquinoline and 6-aminocapronitrile.

Synthesis and use of a novel SnO2 nanomaterial for gas sensing

Abstract Decomposition of the organometallic precursor [Sn(NMe 2 ) 2 ] 2 in a controlled water/anisol mixture leads to the formation of monodisperse nanocomposite particles of Sn/SnO x . Full oxidation of the particles into SnO 2 occurs at 600°C without size or morphology change. These particles can be deposited onto silicon nitride covered microelectronic platforms and used as sensitive layers of gas sensors. Doping of the sensors with palladium can be achieved either by co-decomposition of organometallic precursors (doping in volume) or by deposition of palladium on preformed SnO 2 nanoparticles (doping in surface). The doped sensors display an unusually high sensitivity for CO sensing.

Pyrene‐Tagged Dendritic Catalysts Noncovalently Grafted onto Magnetic Co/C Nanoparticles: An Efficient and Recyclable System for Drug Synthesis

The reuse of catalysts is highly desirable for economic and ecological reasons, and to this day constitutes an important challenge. Along these lines, magnetic nanoparticles (MNP) are increasingly recognized as appealing supports for catalytic systems in the development of more efficient and green processes. Contrary to conventional supports, such as polymers or silica, which require time-consuming precipitation and filtration steps, their separation can easily be achieved by magnetic decantation. Moreover, MNPs are mechanically robust and can be easily agitated during a reaction by application of an external magnetic field. Generally, MNPs are stabilized by coating the magnetic core with polymer or silica shells, which are used for the covalent immobilization of homogeneous catalysts. Magnetic carbon-coated nanoparticles have also been used as reusable supports for the covalent immobilization of catalysts; however, their graphene-like shell offers the unique possibility for non-covalent catalyst attachment by p–p stacking, a concept that was recently demonstrated with pyrene-tagged Pd monomeric complexes. Covalently immobilized dendronized catalysts, which possess an anchoring site and branches terminating with active sites, represent another promising strategy for recoverable catalysts, as they were shown to afford enhanced surface functionalization and better catalytic activity than corresponding monomeric catalysts. Combining both strategies, we planned to graft pyrene-tagged dendritic Pd-phosphine catalysts onto Co/C MNPs by p–p stacking, and to evaluate the activity and recyclability of the resulting composites in Suzuki reactions. Pyrene derivative 3 was prepared in high yield (91%) from commercial 1 and tyramine 2 (Scheme 1). 3 was allowed to react with N3P3Cl6 and Cs2CO3 to afford 4-G0 in 81% yield. The growth of this dendron was achieved by using the reactivity of the P Cl bonds towards phenolic group of 4-OH-

Organometallic approach for the synthesis of nanostructures

Nanostructures are considered as chemical systems of high potential owing to their unusual properties at the interface of those of molecular species and bulk metals. Consequently, they are promising candidates for application in different domains such as catalysis, magnetism, medicine, opto-electronics or sensors. The control of the characteristics of nanostructures is a fundamental prerequisite if one envisages exploring their physical or chemical properties since they vary dramatically with size, shape and surface state. Thus, the development of efficient methods leading to reproducible nanostructures is presently one of the main objectives in the nanochemistry community. Although organometallic chemistry has been early involved, it arises only marginally in the field. Nevertheless, the concepts and techniques of organometallic chemistry appear to be well-adapted for the growth of well-controlled nanostructures. This will be discussed through recent advances in the synthesis of metal and metal oxide nanoparticles in terms of size dispersion, chemical composition, surface state, shape or organization, pointing out the role of ligands. Moreover their characterization at a molecular level and the development of their chemical/physical properties towards applications will be described. This review reflects more than 20 years of efforts of our team to achieve these goals.

Platinum N‐Heterocyclic Carbene Nanoparticles as New and Effective Catalysts for the Selective Hydrogenation of Nitroaromatics

In this communication, we report the first synthesis of Pt NPs stabilized with NHC ligands and their investigation as catalysts in the chemoselective hydrogenation of nitroarenes. The results in catalysis show that by a proper choice of the NHC stabilizer and the adjustment of the NHC/metal ratio, these NHC‐capped Pt NPs exhibit high levels of activity and selectivity in the hydrogenation reactions. In particular, Pt NPs stabilized with 2 equiv. of IPr carbene (PtIPr0.2) catalyze the chemoselective reduction of a series of functionalized nitroarenes under mild conditions (1 bar H2, 30 °C). This catalyst tolerates the presence of a range of functional groups including hydroxyl, benzyloxy, carbonyl and olefinic moeities as well as halogens.

Gold nanoparticles from self-assembledgold(I) amine precursors

The reaction of AuCl(THT) (1) with long chain primary amines (CnH2n+1NH2; n = 8, 12, 16) leads to the formation of the complexes AuCl(NH2R) (R = C8H17, 2; C12H25, 3; C16H33, 4) which are characterized by classical methods and shown to self-organize in the solid state into a fibrous material; decomposition of the complexes inside the supramolecular framework yields a monolayer of ordered gold nanoparticles.

Novel super-structures resulting from the coordination of chiral oxazolines on platinum nanoparticles

The reaction of Pt2(dba)3 with CO in toluene leads rapidly to the formation of platinum nanoparticles which can be further stabilized by addition of aminoalcohol or oxazoline ligands. The coordination of the oxazoline ligands at the surface of the particles is demonstrated by IR after purification of the colloids. The fcc structure of the particles is evidenced by WAXS investigations, a statistical method which also gives information about the degree of crystallinity of the particles. TEM and HREM micrographs reveal surprising organisations of the particles into super-structures depending on the nature and/or position of the substituents present on the ligands. In addition, these particles are catalytically active in the hydrogenation of ethyl pyruvate, even if the preliminary results are modest.

Antischistosomal activity of trioxaquines: in vivo efficacy and mechanism of action on Schistosoma mansoni.

Schistosomiasis is among the most neglected tropical diseases, since its mode of spreading tends to limit the contamination to people who are in contact with contaminated waters in endemic countries. Here we report the in vitro and in vivo anti-schistosomal activities of trioxaquines. These hybrid molecules are highly active on the larval forms of the worms and exhibit different modes of action, not only the alkylation of heme. The synergy observed with praziquantel on infected mice is in favor of the development of these trioxaquines as potential anti-schistosomal agents.

An Organometallic Approach for Very Small Maghemite Nanoparticles: Synthesis, Characterization, and Magnetic Properties

Maghemite (gamma-Fe(2)O(3)) nanoparticles stabilized by long-alkyl-chain amines are synthesized by using an organometallic approach. This method consists of the hydrolysis and oxidation of an organometallic precursor, Fe[N(SiMe(3))(2)](2), in the presence of amine ligands as stabilizing agent in an organic solvent, namely tetrahydrofuran or toluene. Whatever the experimental conditions, particles with a diameter of 2.8 nm are obtained. The use of high-resolution transmission electron microscopy and wide-angle X-ray scattering, together with Mössbauer spectroscopy and SQuId magnetometry, allows a complete characterization of these particles. Herein, we show that their structure is composed of a well-ordered core surrounded by a more disordered shell. The size of the latter varies from 0.65 to 0.50 nm depending on the experimental conditions and is of prime importance for the understanding of the magnetic properties. We demonstrate that the shorter the alkyl chain length of the amine 1) the better the crystallinity of the particles core and 2) the stronger the interparticle interactions.

PPH dendrimers grafted on silica nanoparticles: surface chemistry, characterization, silver colloids hosting and antibacterial activity

Polyphosphorhydrazone (PPH) dendrimers have been grafted on silica nanoparticles, and the surface functions of the dendrimers have been derivatized to phosphonates with lateral poly(ethyleneglycol) (PEG) chains. All materials have been thoroughly characterized by MAS NMR, FT-IR, electron microscopy, TGA and elemental analysis. These materials successfully hosted silver and silver oxide nanoparticles. The resulting composites exhibit antibacterial activity.