39 research outputs found
A comparative study of non-covalent encapsulation methods for organic dyes into silica nanoparticles
Numerous luminophores may be encapsulated into silica nanoparticles (< 100 nm) using the reverse microemulsion process. Nevertheless, the behaviour and effect of such luminescent molecules appear to have been much less studied and may possibly prevent the encapsulation process from occurring. Such nanospheres represent attractive nanoplatforms for the development of biotargeted biocompatible luminescent tracers. Physical and chemical properties of the encapsulated molecules may be affected by the nanomatrix. This study examines the synthesis of different types of dispersed silica nanoparticles, the ability of the selected luminophores towards incorporation into the silica matrix of those nanoobjects as well as the photophysical properties of the produced dye-doped silica nanoparticles. The nanoparticles present mean diameters between 40 and 60 nm as shown by TEM analysis. Mainly, the photophysical characteristics of the dyes are retained upon their encapsulation into the silica matrix, leading to fluorescent silica nanoparticles. This feature article surveys recent research progress on the fabrication strategies of these dye-doped silica nanoparticles
Crystallographic, spectroscopic and electrochemical characterization of pyridine adducts of magnesium(II) and zinc(II) porphine complexes
Modular Functionalized Polyphosphines for Supported Materials: Previously Unobserved 31P-NMR "Through-Space" ABCD Spin Systems and Heterogeneous Palladium-Catalyzed C-C and C-H Arylation
Aromatic Nucleophilic Substitution (SNAr) of meso-Nitroporphyrin with Azide and Amines as an Alternative Metal Catalyst Free Synthetic Approach To Obtain meso-N-Substituted Porphyrins
International audienceAromatic nucleophilic substitution reaction of the nitro group of meso-nitroporphyrins with azide and various amines was achieved and represents an alternative procedure to C-N coupling reactions usually needed to obtain such meso-N-substituted porphyrins in good yields
Investigation of the Redox Properties of a Cp*Co(dithiolene) Complex. Evidence of the Formation of a Dimeric Dicationic Species:Â [Cp*Co(dddt)] 2
Functionalized Tri- and Tetraphosphine Ligands as a General Approach for Controlled Implantation of Phosphorus Donors with a High Local Density in Immobilized Molecular Catalysts
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Electrochemical deposition of a luminescent alkoxysilyl-based fluorenone film exhibiting halide sensitivity
International audienc
Kinetic and Electrochemical Studies of the Oxidative Addition of Demanding Organic Halides to Pd(0): the Efficiency of Polyphosphane Ligands in Low Palladium Loading Cross-Couplings Decrypted
International audienceOxidative addition (OA) of organic halides to palladium(0) species is a fundamental reaction step which initiates the C–C bond formation catalytic processes typical of Pd(0)/Pd(II) chemistry. The use of structurally congested polyphosphane ligands in palladium-catalyzed C–C bond formation has generated very high turnover numbers (TONs) in topical reactions such as Heck, Suzuki, Sonogashira couplings, and direct sp2C–H functionalization. Herein, the OA of aryl bromides to Pd(0) complexes stabilized by ferrocenylpolyphosphane ligands L1 (tetraphosphane), L2 (triphosphane), and L3 (diphosphane) is considered. The investigation of kinetic constants for the addition of Ph–Br to Pd(0) intermediates (generated by electrochemical reduction of Pd(II) complexes coordinated by L1–L3) is reported. Thus, in the OA of halides to the Pd(0) complex coordinated by L1 the series of rate constants kapp is found (mol–1 L s–1): kapp(Ph–Br) = 0.48 > kapp(ClCH2–Cl) = 0.25 ≫ kapp(p-MeC6H4–Br) = 0.08 ≈ kapp(o-MeC6H4–Br) = 0.07 ≫ kapp(Ph–Cl). Kinetic measurements clarify the influence that the presence of four, three, or two phosphorus atoms in the coordination sphere of Pd has on OA. The presence of supplementary phosphorus atoms in L1 and L2 unambiguously stabilizes Pd(0) species and thus slows down the OA of Ph–Br to Pd(0) of about 2 orders of magnitude compared to the diphosphane L3. The electrosynthesis of the complexes resulting from the OA of organic halides to [Pd(0)/L] is easily performed and show the concurrent OA to Pd(0) of the sp3C–Cl bond of dichloromethane solvent. The resulting unstable Pd/alkyl complex is characterized by NMR and single crystal X-ray structure. We additionally observed the perfect stereoselectivity of the OA reactions which is induced by the tetraphosphane ligand L1. Altogether, a clearer picture of the general effects of congested polydentate ligands on the OA of organic halides to Pd(0) is given
High temperatures and Raman scattering through pulsed spectroscopy and CCD detection
International audienceA Raman scattering system devoted to high temperatures is presented. It is based on a pulsed system to remove thermal emission with retaining charge-coupled device (CCD) detection. Two types of optical gating are used: a Pockels switch or an intensified CCD (ICCD), combining in this case the optical gate and the CCD detection. The performances of both systems are presented and their respective advantages are discussed and compared. The ICCD device allows recording of spectra in the 2000°C range, and typical results obtained on alumina and zirconia ceramics are shown
Electron-Sponge Behavior and Electronic Structures in Cobalt-Centered Pentagonal Prismatic Co11Te7(CO)10 and Co11Te5(CO)15 Cluster Anions (lien).
International audienc