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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
    Conception de bisfullérodendrimères liquides-cristallins par la réaction de métathèse croisée d'oléfines
    (2016)
    Russo, Virginie
    ;
    Deschenaux, Robert 
    Le fil conducteur de cette thèse, a été la conception de bisfullérodendrimères présentant des propriétés liquides-cristallines. En effet, les fullérodendrimères liquides-cristallins sont des sujets d’études très intéressants. En associant le [60]fullerène (C60) avec l’organisation des cristaux-liquides, les possibilités et applications dans le domaine des matériaux supramoléculaires auto-assemblés sont innombrables. Actuellement, les fullérodendrimères mésomorphes ne possèdent qu’une seule unité C60. En cause, la difficulté à incorporer cette sphère isotrope dans les organisations supramoléculaires. Si cette difficulté pouvait être surmontée, il serait intéressant de voir les modifications que la densité en C60 entrainerait sur la structure des mésophases.
    Nous nous sommes donc intéressés à la synthèse et l’étude de bisfullerènes, comme première avancée vers des composés liquides-cristallins riche en C60. Les propriétés mésomorphes des différents bisfullerènes obtenus ont été systématiquement étudiées mais également comparées avec des composés analogues possédant un seul C60 ou n’en possédant pas. Le but de ces comparaisons a été de montrer l’influence du nombre de C60 sur l’organisation supramoléculaire. La réaction de métathèse croisée d’oléfines a été sélectionnée comme étape clé de la synthèse, permettant, à partir de quatre oléfines, d’obtenir quatre composés finaux : le bisfullerène, deux monofullerènes et le bismalonate.
    Pour promouvoir les propriété liquides-cristallines, plusieurs dendrimères ont été utilisés : des dendrimères poly(arylesters) fonctionnalisés par des groupements cyanobiphényles, des dendrimères poly(benzyléthers) et des dendrimères nématiques chiraux. Chaque chapitre correspond aux synthèses relatives à une famille de dendrimère. De plus, deux chapitres correspondent à la synthèse de composés Janus. L’utilisation de différents dendrimères, promoteurs de mésophases aussi diverses que des phases lamellaires, colonnaires ou encore chirales, ont permis de mieux comprendre l’effet du C60 au sein de diverses organisations supramoléculaires., In this thesis, the topic was the design of liquid-crystalline bisfullerodendrimers. Indeed, the field of liquid-crystalline fullerodendrimers is being extensively investigated. Combining [60]fullerene (C60) with liquid crystal organization give numerous applications in the field of self-assembled supramolecular materials. Currently, the mesomorphic fullerodendrimers are made of only one C60 unit. This is due to the fact that the incorporation of several C60 units within liquid crystals is a difficult synthetic task.
    We have synthesized bisfullerenes and studied their liquid-crystalline properties. The latter were compared to the properties of mono-fullerene derivatives and fullerene-free materials. The purpose of such comparisons was to explore and understand the influence of the number of C60 units on the supramolecular organization. The olefin cross-metathesis reaction was selected as a key step in the synthesis of the target materials leading to four compounds from four different type I and type II olefins: the bisfullerene, two monofullerenes and the bismalonate.
    To promote liquid-crystalline properties, various dendrimers were used, including poly(aryl ester) dendrimers functionalized with cyanobiphenyl groups, poly(benzyl ether) dendrimers and chiral nematic dendrimers. Each chapter corresponds to the synthesis of a dendrimer. In addition, two chapters correspond to the synthesis of Janus-type compounds. The use of different dendrimers to promote lamellar, columnar or chiral phases led to a better understanding of the influence of C60 on the formation and structure of the mesophases.
  • Publication
    Accès libre
    Designing Supramolecular Liquid-Crystalline Hybrids from Pyrenyl-Containing Dendrimers and Arene Ruthenium Metallacycles
    Pitto-Barry, Anaïs
    ;
    Barry, Nicolas P. E
    ;
    Russo, Virginie
    ;
    Heinrich, Benoît
    ;
    Donnio, Bertrand
    ;
    Therrien, Bruno 
    ;
    Deschenaux, Robert 
    The association of the arene ruthenium metallacycle [Ru4(p- cymene)4(bpe)2(donq)2][DOS]4 (bpe = 1,2- bis(4-pyridyl)ethylene, donq = 5,8-dioxydo-1,4-naphtoquinonato, DOS = dodecyl sulfate) with pyrenyl-functionalized poly(arylester) dendrimers bearing cyanobiphenyl end- groups is reported. The supramolecular dendritic systems display mesomorphic properties as revealed by polarized optical microscopy, differential scanning calorimetry and small- angle X-ray scattering measurements. The multicomponent nature of the dendrimers and of the corresponding host–guest supramolecules (i.e., end-group mesogens, dendritic core, pyrene unit, aliphatic spacers, and metallacycle) leads to the formation of highly segregated mesophases with a complex multilayered structure due to the tendency of the various constitutive building-blocks to separate in different organized zones. The pyrenyl dendrimers exhibit a multilayered smectic A-like phase, thereafter referred to as LamSmA phase to emphasize this unaccustomed morphology. As for the corresponding Ru4–metallacycle adducts, they self-organize into a multicontinuous thermotropic cubic phase with the Im3¯m space group symmetry. This represents a unique example of liquid- crystalline behavior observed for such large and complex supramolecular host–guest assemblies. Models of their supramolecular organizations within both mesophases are proposed.
  • Publication
    Accès libre
    Design, Synthesis, and Self-Assembly Behavior of Liquid-Crystalline Bis-[60]Fullerodendrimers
    Russo, Virginie
    ;
    Pieper, Pauline
    ;
    Heinrich, Benoît
    ;
    Donnio, Bertrand
    ;
    Deschenaux, Robert 
    Bis-[60]fullerodendrimers were synthesized by assembling [60]fullerene-containing type I (terminal olefin) and type II (a,ß-unsaturated carbonyl olefin) olefins through the olefin cross-metathesis reaction. The synthetic modular approach developed in this study allowed the preparation of mono-[60]fullerodendrimers and their [60]fullerene-free analogues. First- and second-generation poly(aryl ester) dendrons carrying cyanobiphenyl mesogens were used as liquid-crystalline promoters. The liquid- crystalline properties were studied by polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. In agreement with the nature and structure of the dendrimers, nematic, smectic, and multisegregated lamellar phases were observed. Owing to its versatility and tolerance towards many functional groups, olefin cross-metathesis proved to be a reaction of choice for the elaboration of molecular materials with complex architectures.
  • Publication
    Accès libre
    Olefin Cross-Metathesis: a Versatile Synthetic Reaction for the Design of Janus Liquid Crystals
    Trinh, Thi Minh Nguyet
    ;
    Nguyen, Thanh Tung
    ;
    Kopp, Cyril
    ;
    Pieper, Pauline
    ;
    Russo, Virginie
    ;
    Heinrich, Benoît
    ;
    Donnio, Bertrand
    ;
    Nguyen, Thi Le Anh
    ;
    Deschenaux, Robert 
    The olefin cross-metathesis reaction using the second-generation Grubbs catalyst was employed to prepare non-symmetrical thermotropic liquid crystals from various mesomorphic or nonmesomorphic type I and type II olefinic constructs, including linear, chiral, dendritic and ferrocenyl olefins. Smectic C, smectic A and nematic phases, as well as chiral smectic A and chiral nematic phases were observed in agreement with the structure and nature of the mesogens. The olefin cross-metathesis proved to be a valuable chemical reaction in designing dimeric and Janus-like thermotropic liquid crystals built from two different molecular entities.
  • 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.