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Deschenaux, Robert

Nom
Deschenaux, Robert
Affiliation principale
Fonction
Professeur ordinaire
Email
Robert.Deschenaux@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/384

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  • Publication
    Accès libre
    Conception de matériaux dendritiques chiraux mésomorphes pour l’élaboration de commutateurs électroactifs basés sur le couple ferrocène/ferrocenium
    (2010)
    Kopp, Cyril
    ;
    Deschenaux, Robert 
    ;
    Süss-Find, Georg
    Ce travail de thèse traite de la conception de nouveaux matériaux mésomorphes. Deux dendrimères chiraux ont été synthétisés dans le but de transmettre leurs propriétés liquides-cristallines à un dérivé du ferrocène. Une évolution vers les ferrocènes peralkylés a permis d‟obtenir des ferrocéniums stables montrant une modification (commutation) des propriétés mésomorphes. Puis, grâce à une variation dans la construction du cœur dendritique, nous avons mis en évidence de manière distincte le rôle du dendrimère ainsi que de l‟oxydation. Ces mêmes dendrimères ont également trouvé d‟autres utilisations. Les fonctions se trouvant au cœur du dendrimère ont été modulées par des réactions d‟estérification avec différentes petites chaînes. Dès lors, ces nouveaux composés ont été utilisés dans la conception de composés de « type Janus » ayant comme partie centrale soit un malonate soit un cycle triazole. Ces composés ont montré d‟intéressantes propriétés liquides-cristallines., This thesis focuses on the design of new mesomorphic materials. Two chiral dendrimers were synthesized with the aim to transfer their liquid-crystalline properties to ferrocene derivatives. An evolution towards peralkylated ferrocene gave stable ferrocenium derivatives showing a switch between liquid-crystalline phases. The role of the dendritic structure and oxidation could be explained. Then, the functions located at the focal point of the dendrimers were modulated by esterification reactions. Therefore, these new compounds were used in the design of “Janus type” compounds having as central units a malonate or a triazol ring. These compounds showed interesting liquid-crystalline properties.
  • 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.
  • Publication
    Accès libre
    A Mixed Fullerene-Ferrocene Thermotropic Liquid Crystal: Synthesis, Liquid-Crystalline Properties, Supramolecular Organization and Photoinduced Electron Transfer
    (2001)
    Even, Michaël
    ;
    Heinrich, Benoît
    ;
    Guillon, Daniel
    ;
    Guldi, Dirk M.
    ;
    Prato, Maurizio
    ;
    Deschenaux, Robert 
    Grafting of a ferrocene-containing liquid-crystalline malonate derivative to C60 led to the mixed fullerene-ferrocene material 1 which gave rise to a smectic A phase. Cholesterol was used as liquid-crystalline promoter. X-ray diffraction experiments and volumetric measurements indicated that 1 is organized in double layered structures. The corresponding supramolecular organization within the mesomorphic lamellar phase is characterized by a microsegregation of the different units (ferrocene, fullerene, and cholesterol) in distinct sublayers. In such a smectic A phase, C60 imposes the arrangement of the other molecular moieties. Photophysical studies revealed that electron transfer occurs from the donor ferrocene to the electron accepting fullerene. The formation of a long-lived radical pair, with lifetimes of the order of several hundred nanoseconds, was confirmed by time-resolved spectrometry, especially in the near infrared region, in which the radical anion of the fullerene moiety displays its characteristic fingerprint absorption.
  • Publication
    Accès libre
    Columnar Phases from Covalent and Hydrogen-Bonded Liquid-Crystalline Ferrocene Derivatives
    (1998)
    Deschenaux, Robert 
    ;
    Monnet, Florence
    ;
    Serrano, Elisabeth
    ;
    Turpin, François
    ;
    Levelut, Anne-Marie
    The synthesis and liquid-crystalline properties of tetracatenar covalent and H-bonded bis-ferrocene derivatives 1 and 2, respectively, are reported. Both compounds gave rise to enantiotropic columnar liquid-crystalline behavior with a hexagonal molecular organization. To explore the possibility to obtain also calamitic liquid-crystalline phases from H-bonded ferrocene-containing liquid crystals, a rod-shaped ferrocene mesogen 3 was synthesized, which gave rise to enantiotropic smectic C and smectic A phases. For the first time, a rational synthetic design at the ferrocene level led to ferrocene-based liquid-crystals with columnar behavior and to H-bonded metallomesogens.