Vignette d'image

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

Résultat de la recherche

Filtres

12
12
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 10 sur 12
  • Publication
    Accès libre
    Piling Up Pillar[5]arenes To Self-Assemble Nanotubes
    (2016)
    Nierengarten, Iwona
    ;
    Guerra, Sebastiano 
    ;
    Ben Aziza, Haifa
    ;
    Holler, Michel
    ;
    Abidi, Rym
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    ;
    Nierengarten, Jean-François
    New liquid-crystalline pillar[5]arene derivatives have been prepared by grafting first- generation Percec-type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc-shaped structure perfectly suited for self-organization into a columnar liquid-crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6- dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Colh mesophase has been deduced from X-ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4-dimethoxypillar[5]arene and 1,6- dicyanohexane.
  • Publication
    Accès libre
    Liquid-Crystalline Dendrimers Designed by Click Chemistry
    (2016)
    Guerra, Sebastiano 
    ;
    Nguyen, Thi Le Anh
    ;
    Furrer, Julien
    ;
    Nierengarten, Jean-François
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    Liquid-crystalline dendrimers have been prepared from second-generation Percec- type poly(benzyl ether) dendrons or second-generation poly(aryl ester) dendrons carrying cyanobiphenyl mesogens. The Janus dendrimer, which combines the two types of dendromesogens, has also been synthesized. Those compounds have been prepared under copper-catalyzed azide–alkyne cycloaddition conditions. The mesomorphic properties have been studied by thermal analysis (POM, DSC) and small-angle X-ray scattering. Smectic A, nematic, and columnar phases have been observed depending on the dendritic building blocks. The click reaction has proven to be a powerful and elegant synthetic tool for the design of complex dendritic liquid- crystalline architectures.
  • Publication
    Accès libre
    Red and Blue Liquid-Crystalline Borondipyrromethene Dendrimers
    (2015)
    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.
  • Publication
    Accès libre
    Macrocyclic Effects in the Mesomorphic Properties of Liquid-Crystalline Pillar[5]- and Pillar[6]arenes
    (2013)
    Nierengarten, Iwona
    ;
    Guerra, Sebastiano 
    ;
    Holler, Michel
    ;
    Karmazin-Brelot, Lydia
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    ;
    Nierengarten, Jean-François
    Whereas the reaction of 1,4-bis(2-bromoethyloxy)benzene (4) with paraformaldehyde in the presence of BF3·Et2O afforded exclusively the cyclopentameric pillar[5]arene derivative (5), both cyclopenta- and cyclohexameric macrocycles 5 and 6 were obtained when the reaction of 4 with paraformaldehyde was performed at 45 °C in CHCl3 with FeCl3 as the catalyst. Treatment of compounds 4–6 with sodium azide provided the corresponding polyazides, to which a cyanobiphenyl building block was subsequently grafted to generate model compound 1, pillar[5]arene 2, and pillar[6]arene 3, bearing two, ten and twelve mesomorphic subunits, respectively. The liquid-crystalline and thermal properties of the compounds were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Comparison of the liquid-crystalline properties of macrocycles 2 and 3 with those of 1 revealed the strong influence of the macrocyclic pillar[n]arene core on the mesomorphic properties. Whereas only a monotropic mesophase was observed for 1, a broad enantiotropic mesophase was evidenced for both pillar[n]arene derivatives.
  • 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
    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
    [60]Fullerene-based liquid crystals acting as acid-sensitive fluorescent probes
    (2008)
    Pérez, Laura
    ;
    Lenoble, Julie
    ;
    Barberá, Joaquín
    ;
    de la Cruz, Pilar
    ;
    Deschenaux, Robert 
    ;
    Langa, Fernando
    Functionalization of [60]fullerene with liquid-crystalline dendrimers and a dibutylaniline-based phenylenevinylene moiety leads to supramolecular materials, the fluorescence of which responds to acid–base stimuli.
  • 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
    Accès libre
    Dendritic liquid-crystalline fullerene–ferrocene dyads
    (2006-02-25)
    Campidelli, Stéphane
    ;
    Pérez, Laura
    ;
    Rodríguez-López Julián
    ;
    Barberá, Joaquín
    ;
    Langa, Fernando
    ;
    Deschenaux, Robert 
    First- and second-generation ferrocene-based dendrimers, fullerene and a second-generation liquid-crystalline poly(arylester) dendrimer carrying four cyanobiphenyl units were assembled to elaborate polyfunctional materials displaying mesomorphic and electronic properties. The targeted compounds gave rise to enantiotropic smectic A phases and organized into bilayer structures within the smectic layers. Cyclic voltammetry investigations revealed oxidation and reduction processes in agreement with the presence of both ferrocene and fullerene units. Finally, strong quenching of the fluorescence was obtained for the fullerene–ferrocene dyads suggesting efficient elecron transfer from the ferrocene-based dendrimer to fullerene.
  • Publication
    Accès libre
    Dendritic liquid-crystalline fullerene–ferrocene dyads
    (2006)
    Campidelli, Stéphane
    ;
    Pérez, Laura
    ;
    Rodríguez-López Julián
    ;
    Barberá, Joaquín
    ;
    Langa, Fernando
    ;
    Deschenaux, Robert 
    First- and second-generation ferrocene-based dendrimers, fullerene and a second-generation liquid-crystalline poly(arylester) dendrimer carrying four cyanobiphenyl units were assembled to elaborate polyfunctional materials displaying mesomorphic and electronic properties. The targeted compounds gave rise to enantiotropic smectic A phases and organized into bilayer structures within the smectic layers. Cyclic voltammetry investigations revealed oxidation and reduction processes in agreement with the presence of both ferrocene and fullerene units. Finally, strong quenching of the fluorescence was obtained for the fullerene–ferrocene dyads suggesting efficient elecron transfer from the ferrocene-based dendrimer to fullerene.