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Deschenaux, Robert

Nom
Deschenaux, Robert
Affiliation principale
Fonction
Professeur.e ordinaire
Email
Robert.Deschenaux@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/384
_
0000-0002-1142-0022

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  • Publication
    Accès libre
    Highly Fluorescent Liquid-Crystalline Dendrimers Based on Borondipyrromethene Dyes
    (2009)
    Frein, Stéphane
    ;
    Camerel, Franck
    ;
    Ziessel, Raymond
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    Fluorescent mesomorphic materials have been synthesized by grafting difluoro-bora-diaza-s-indacene (F-Bodipy) onto first-, second-, and third-generation liquid-crystalline poly(aryl ester) dendrons functionalized with cyanobiphenyl units. The second- and third-generation dendrimers give rise to smectic A phases; the first-generation dendrimer shows a nematic phase and an unidentified phase. The supramolecular organization within the smectic A phase could be established from X-ray experiments: the dendritic core is oriented approximately parallel to the layer planes and the mesogenic units are oriented perpendicularly above and below the dendritic core; interdigitation occurs between neighboring layers. All the materials are highly fluorescent both in solution and in the mesophases. For the first-generation dendrimer, the formation of J-aggregates was detected. The higher-generation dendrons prevented the formation of aggregates. Therefore, the dendrons play the role of liquid-crystalline promoters and protective shells.
  • Publication
    Accès libre
    Conception de dendrimères liquides-cristallins pour la fonctionnalisation de nanoparticules d'or et de composés inorganiques et organiques
    (2009)
    Frein, Stéphane
    ;
    Deschenaux, Robert 
    Ce travail de thèse a pour sujet principal la synthèse et la caractérisation de dendrimères liquides-cristallins. Trois dendrimères ont été synthétisés. Le premier est un dendrimère poly(aryl ester) fonctionnalisé par des unités mésogènes cyanobiphényles et qui développe des phases lamellaires ou nématique. Il a été synthétisé jusqu’à la troisième génération, avec différents groupes fonctionnels sur son coeur (thiol, disulfure, alcool, acide, alcyne). Le deuxième dendrimère synthétisé est de type poly(benzyl éther) et s’organise en phases nématique discotique, cubique ou colonnaire. Il a lui aussi été synthétisé jusqu’à la troisième génération, avec différents groupes fonctionnels sur son coeur (thiol, disulfure, alcool, acide, alcyne). Finalement, un troisième dendrimère contenant un centre chiral a été synthétisé jusqu’à la deuxième génération, avec différents groupes fonctionnels sur son coeur (disulfure, alcool, acide, alcyne). Le but principal de cette thèse a été d’utiliser ces différents dendrons pour la fonctionnalisation de nanoparticules d’or. Ce projet a été réalisé via deux voies de synthèses : synthèse directe et estérification de nanoparticules d’or stabilisées par un dérivé alcool. Une organisation a été visible au TEM dans le premier cas et des phases mésomorphes nondéterminées ont été visibles par microscopie à lumière polarisée dans le deuxième cas. Les mêmes dendrimères ont ensuite été utilisés pour la fonctionnalisation d’autres composés inorganiques et organiques. Un complexe di-ruthénium de type chevalet, des composés dipyrrométhènes de bore, un hexa-adduit de fullerène et des nanotubes de carbone ont ainsi été fonctionnalisés par les différents dendrons. Les propriétés liquides-cristallines obtenues sont dans tous les cas en accord avec les propriétés des dendrimères, prouvant ainsi que le mésomorphisme est principalement dicté par le dendrimère. Les différents sujets de cette thèse ont souvent fait l’objet de publications scientifiques, ces dernières figurant dans les chapitres concernés., The main objective of the thesis is the design of liquid-crystalline dendrimers for the functionalization of various organic and organometallic moieties including gold nanoparticles, fullerene, diruthenium clusters, fluorescent dyes and carbon nanotubes. Three different families of dendrimers were prepared: poly(aryl ester) dendrimers functionalized with cyanobiphenyl mesogenic units (smectic and nematic phases), poly(benzyl ether) dendrimers functionalized with long alkyl chains (nematic discotic, cubic and columnar phases), and poly(aryl ester) dendrimers decorated with chiral mesogens (chiral nematic phase). For the gold nanoparticles, a supramolecular organization was observed when the particles were spread onto solid substrates. For the other organic and organometallic moieties, the liquid-crystalline phases observed were in agreement with the structure and nature of the dendrimers.
  • Publication
    Accès libre
    Mesomorphic Metallo-Dendrimers Based on the Metal−Metal Bonded Ru2(CO)4 Sawhorse Unit
    (2008)
    Frein, Stéphane
    ;
    Auzias, Mathieu
    ;
    Sondenecker, Aline
    ;
    Vieille-Petit, Ludovic
    ;
    Guintchin, Boris
    ;
    Maringa, Natacha
    ;
    Süss-Fink, Georg 
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    Dinuclear ruthenium complexes containing the stable metal−metal bonded Ru2(CO)4 sawhorse unit with two dendritic carboxylato bridges have been synthesized and characterized. All complexes Ru2(CO)4(O2CR)2L2 (R = R1, R2, R3) containing cyanobiphenyl-based poly(arylester) dendrons of first (R1), second (R2), and third (R3) generation and triphenylphosphine, pyridine, or 4-picoline ligands L proved to be mesomorphic, giving rise to smectic A or smectic A and nematic phases. The supramolecular organization within the smectic A phase is governed by the nature and structure of the mesogenic units and dendritic core. Such materials are of interest for the design of catalytically active anisotropic fluids.
  • Publication
    Accès libre
    Synthesis of dendrimer-carbon nanotube conjugates
    (2008)
    García, A.
    ;
    Herrero, M. A.
    ;
    Frein, Stéphane
    ;
    Deschenaux, Robert 
    ;
    Muñoz. R.
    ;
    Bustero, I.
    ;
    Toma, F.
    ;
    Prato, Maurizio
    We describe the coupling between Carbon Nanotubes (CNTs) and a second-generation cyanophenyl-based dendrimer. The goal of our work is the synthesis of highly functionalized CNTs without provoking damage to the conjugated π-system. One approach is the attachment of dendrimers with a high density of functional groups to the CNTs. These groups serve as anchor points for further reactions. With this aim, we have carried out a primary modification on CNTs by the use of 1,3 dipolar cycloaddition reaction. We have employed Single Wall Carbon Nanotubes (SWNTs) as well as Multi Wall Carbon Nanotubes (MWNTs) obtaining 238 μmol and 511 μmol of pyrrolidine groups per gram, respectively. The amount of amino groups introduced in the system was measured by the Kaiser test as well as thermogravimetric analyses. As a second step, dendrimer incorporation was performed by carbodiimide chemistry. Thermogravimetric Analysis, Raman Spectroscopy and Atomic Force Microscopy characterization techniques are reported for the characterization of the final CNT-dendrimer conjugate.
    The results show that the dendrimer has been attached covalently to the previously generated amine groups. Morphologically, the attached dendrimer with an estimated theoretical molecular length of 6.4 nm, generates a wrapping of 8 nm thick around the CNTs walls.
  • Publication
    Accès libre
    Liquid-Crystalline Thiol- and Disulfide-Based Dendrimers for the Functionalization of Gold Nanoparticles
    (2008)
    Frein, Stéphane
    ;
    Boudon, Julien
    ;
    Vonlanthen, Mireille
    ;
    Scharf, Toral
    ;
    Barberá, Joaquín
    ;
    Süss-Fink, Georg 
    ;
    Bürgi, Thomas
    ;
    Deschenaux, Robert 
    Liquid-crystalline dendrons carrying either a thiol or disulfide function which display nematic, smectic A, columnar, or chiral nematic phases have been synthesized. Their mesomorphic properties are in agreement with the nature of the mesogenic units and structure of the dendrons. The first-generation poly(aryl ester) dendron containing two cyanobiphenyl mesogenic units was used to functionalize gold nanoparticles. For full coverage, a smectic-like supramolecular organization on the nanometer scale is observed, when the gold nanoparticles are spread onto carbon-coated copper grids. This result indicates that the dendritic ligands reported here act as self-organization promoters.
  • Publication
    Métadonnées seulement
    Synthesis of dendrimer-carbon nanotube conjugates
    (: Wiley-V C H Verlag Gmbh, 2007)
    Garcia, A
    ;
    Herrero, M A
    ;
    Frein, Stéphane
    ;
    Deschenaux, Robert 
    ;
    Munoz, R
    ;
    Bustero, I
    ;
    Toma, F
    ;
    Prato, Maurizio
    We describe, the coupling between Carbon Nanotubes (CNTs) and a second-generation cyanophenyl-based dendrimer. The goal of our work is the synthesis of highly functionalized CNTs without provoking damage to the conjugated pi-system. One approach is the attachment of dendrimers with a high density of functional groups to the CNTs. These groups serve as anchor points for further reactions. With this aim, we have carried out a primary modification on CNTs by the use of 1,3 dipolar cycloaddition reaction. We have employed Single Wall Carbon Nanotubes (SWNTs) as well as Multi Wall Carbon Nanotubes (MWNTs) obtaining 238 mu mol and 511 mu mol of pyrrolidine groups per gram, respectively. The amount of amino groups introduced in the system was measured by the Kaiser test as well as thermogravimetric analyses. As a second step, dendrimer incorporation was performed by carbodiimide chemistry. Thermogravimetric Analysis, Raman Spectroscopy and Atomic Force Microscopy characterization techniques are reported for the characterization of the final CNT-dendrimer conjugate. The results show that the dendrimer has been attached covalently to the previously generated amine groups. Morphologically, the attached dendrimer with an estimated theoretical molecular length of 6.4 nm, generates a wrapping of 8 nm thick around the CNTs walls. [GRAPHICS] Scheme of the synthesized CNT-dendrimer conjugate. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Publication
    Accès libre
    Red and Blue Liquid-Crystalline Borondipyrromethene Dendrimers
    Mula, Soumyaditya
    ;
    Frein, Stéphane
    ;
    Russo, Virginie
    ;
    Ulrich, Gilles
    ;
    Ziessel, Raymond
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    We have designed a series of modular and fluorescent poly(arylester) dendrimers functionalized with cyanobiphenyl subunits and fluorescent borondipyrromethene (Bodipy) dyes. The green emitter is a Bodipy with four methyl groups, and the Bodipy dye possessing extended conjugation with two methyl and two vinyl groups acts as a red emitter. The design element of these architectures relates to a secondary amide linkers interposed between the conventional Bodipy and the dendrons. The second- and third-generation dendrimers give rise to nematic and/or smectic A phases, whereas the first-generation dendrimers show smectic A and C phases or an unidentified mesophase. The novel materials are highly fluorescent in solution and in the as-obtained powders but not in the mesophase. Dilution of the dendritic dyes with the nonfluorescent acid dendron in the solid phase shifted the fluorescence to higher energy, and demonstrated the presence of aggregates in the solid state. Mixing the red and blue materials in a solid phase led to the observation of effective electronic energy transfer from the red dye to the blue one. Increasing the proportion of the red dye (energy donor) from 1 to 250 molar with respect to the blue dye (energy acceptor) resulted in the observation of residual emission of the red dye in the solid state mixture. Increasing the proportion from 1 to 1000 resulted in equal emission in the 540 to 760 nm range.