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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
    Métadonnées seulement
    Diastereoisomerically Pure Fulleropyrrolidines as Chiral Platforms for the Design of Optically Active Liquid Crystals
    (2010)
    Campidelli, Stephane
    ;
    Bourgun, Philippe
    ;
    Guintchin, Boris
    ;
    Furrer, Julien
    ;
    Stoeckli-Evans, Helen 
    ;
    Saez, Isabel M.
    ;
    Goodby, John W.
    ;
    Deschenaux, Robert 
    Incorporation of [60]fullerene (C60) within self-organizing systems is conceptually challenging but allows us to obtain materials which combine the characteristics (anisotropy, organization) of condensed mesophases with the properties of C60 (photo- and electrochem. activity). Here, the authors report on the synthesis, characterization, and liq.-cryst. properties of four optically active fullerodendrimers, which are chiral at the point of conjunction between the fullerene scaffold and the mesogenic moieties. Thus, the novelty of this study is to take advantage of the asym. carbon atom created during the 1,3-dipolar cycloaddn. reaction on C60 in order to induce mesoscopic chirality in the materials. Four diastereoisomeric fulleropyrrolidines ((R,S)-1, (R,R)-1, (S,R)-1, and (S,S)-1) were synthesized and assocd. with a second-generation nematic (N) dendron to give fullerodendrimers ((R,S)-2, (R,R)-2, (S,R)-2, and (S,S)-2) which display chiral nematic (N*) phases. The abs. configurations of the stereogenic centers were detd. by X-ray crystallog., 1D and 2D NMR expts., and CD spectroscopy. The liq.-cryst. properties of the fullerodendrimers were studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The fulleropyrrolidine derivs. 2 exhibit supramol. helicoidal organizations with a right-handed helix for the (R,S)-2 and (R,R)-2 diastereoisomers and a left-handed helix for the (S,R)-2 and (S,S)-2 diastereoisomers. This result suggests that the self-organization of such supermol. materials can be controlled at the mol. level by the introduction of only one chiral center. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-Crystalline Janus-Type Fullerodendrimers Displaying Tunable Smectic-Columnar Mesomorphism
    (2007)
    Lenoble, Julie
    ;
    Campidelli, Stephane
    ;
    Maringa, Natacha
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    ;
    Yevlampieva, Natalia
    ;
    Deschenaux, Robert 
    Janus-type liq.-cryst. fullerodendrimers were synthesized via the 1,3-dipolar cycloaddtition of 2 mesomorphic dendrons and C60. By assembling poly(aryl ester) dendrons functionalized with cyanobiphenyl groups, displaying lamellar mesomorphism, with poly(benzyl ether) dendrons carrying alkyl chains, which display columnar mesomorphism, the authors could tailor by design the liq.-cryst. properties of the title compds. as a function of each dendron size. The liq.-cryst. properties were examd. by polarized optical microscopy, DSC, and x-ray diffraction. Depending on the dendrimer generations, smectic (SmC and/or SmA phases) or columnar (Colr-c2mm or Colr-p2gg phases) mesomorphism was obtained. The supramol. organization is governed by (1) the adequacy of the cross-sectional area of the dendrons, (2) the microsegregation of the dendrimer, (3) the deformation of the dendritic core, and (4) the dipolar interactions between the cyanobiphenyl groups. Comparison of the mesomorphic properties of 2 fullerodendrimers with those of model compds. (fullerene-free analogs) indicated that the C60 unit does not influence the type of mesophase that is formed. Mol. properties detd. in soln. (permanent dipole moment, specific dielec. polarization, molar Kerr const.) confirm that microsegregation persists in soln. and strengthen the models proposed for the structure of the mesophases. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-Crystalline Fullerodendrimers which Display Columnar Phases
    (2006)
    Lenoble, Julie
    ;
    Maringa, Natacha
    ;
    Campidelli, Stephane
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    ;
    Deschenaux, Robert 
    The title compds. were synthesized by applying the 1,3-dipolar cycloaddn. reaction of aldehyde-based poly(benzyl ether) dendrimers and sarcosine (N-methylglycine) to [60]fullerene (C60). The dendritic building blocks used to functionalize C60 displayed cubic and hexagonal columnar phases. The fullerene derivs. showed rectangular columnar phases of c 2. mm symmetry. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    A dendritic fullerene-porphyrin dyad
    (2006)
    Campidelli, Stephane
    ;
    Deschenaux, Robert 
    ;
    Swartz, Angela
    ;
    Rahman, G. M. Aminur
    ;
    Guldi, Dirk M.
    ;
    Milic, Dragana
    ;
    Vazquez, Ester
    ;
    Prato, Maurizio
    We describe the synthesis, characterization and photophys. properties of a fullerene deriv. whose structure includes a Zn-porphyrin and a second generation liq.-cryst. (LC) dendrimer. The size of the fullerene and porphyrin units with respect to the size of the LC dendrimer prevents the formation of liq.-cryst. phases. However, this system gives interesting photoinduced electron transfer phenomena. Compd. 1 has been investigated by steady state and time resolved fluorescence as well as transient absorption spectroscopy in polar and apolar solvents. We demonstrate that the fluorescence of the porphyrin unit in 1 is quenched compared to the Zn-tetraphenylporphyrin used as ref. Femto- and picosecond transient absorption permit to identify the formation of a radical ion pair while nanosecond expts. allowed the detn. of the charge recombination lifetimes. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Supramolecular fullerene materials: dendritic liquid-crystalline fulleropyrrolidines
    (2005)
    Campidelli, Stephane
    ;
    Lenoble, Julie
    ;
    Barbera, Joaquin
    ;
    Paolucci, Francesco
    ;
    Marcaccio, Massimo
    ;
    Paolucci, Demis
    ;
    Deschenaux, Robert 
    [60]Fullerene-contg. liq.-cryst. dendrimers were synthesized from the first to the fourth generation by applying the 1,3-dipolar cycloaddn. reaction from a mesomorphic dendritic-type aldehyde deriv., sarcosine (N-methylglycine) or glycine and C60. The cyanobiphenyl unit was used as a liq.-cryst. promoter. With the exception of the first-generation fullerene dendrimer, which was found to be nonmesomorphic, all fullerene-based dendrimers gave rise to a smectic A phase. The liq.-cryst. fullerenes led to two different supramol. organizations within the smectic layers: for the second-generation dendrimers, the mols. are oriented in a head-to-tail fashion within the layers; for each mol. the cyanobiphenyl units point in the same direction. For the dendrimers of third and fourth generations, the dendritic core extends laterally, parallel to the layer planes; the mesogenic units are oriented above and below the dendritic core. For the aldehyde precursors, only one organization inside the layers was obtained, similar to the one obsd. for the third and fourth fullerene-based dendrimers. Cyclic voltammetry investigations displayed several one-electron and multielectron redn. processes; no significant interaction in the ground state between the fullerene and the dendrimer was noticed. The title compds. showed the typical electrochem. stability of fulleropyrrolidines. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Dendritic liquid-crystalline fullerene-ferrocene dyads
    (: Molecular Diversity Preservation International, 2005)
    Campidelli, Stephane
    ;
    Perez, Laura
    ;
    Rodriguez-Lopez, Julian
    ;
    Barbera, Joaquin
    ;
    Langa, Fernando
    ;
    Deschenaux, Robert 
    First- and second-generation ferrocene-based dendrimers, fullerene and a second-generation liq.-cryst. poly(aryl ester) dendrimer carrying four cyanobiphenyl units were assembled to elaborate polyfunctional materials displaying mesomorphic and electronic properties. The targeted compds. gave rise to enantiotropic smectic A phases and organized into bilayer structures within the smectic layers. Cyclic voltammetry investigations revealed oxidn. and redn. 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 electron transfer from the ferrocene-based dendrimer to fullerene. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-crystalline fullerene-ferrocene dyads
    (2004)
    Campidelli, Stephane
    ;
    Vazquez, Ester
    ;
    Milic, Dragana
    ;
    Prato, Maurizio
    ;
    Barbera, Joaquin
    ;
    Guldi, Dirk M.
    ;
    Marcaccio, Massimo
    ;
    Paolucci, Demis
    ;
    Paolucci, Francesco
    ;
    Deschenaux, Robert 
    The 1,3-dipolar cycloaddn. reaction was used to assemble fullerene, ferrocene and a 2nd-generation liq.-cryst. cyanobiphenyl-based dendrimer. The targeted compd. displayed an enantiotropic smectic A phase from 40 to 135°. The d-layer spacing was detd. by x-ray diffraction, and is independent of temp. with a value of 95 Å. Mol. modeling and structural considerations suggested partial bilayer organization of the mesogenic mol. units within the smectic layers. Oxidn. or redn. processes of the basic components (ferrocene, fullerene, dendrimer) were studied by electrochem. techniques, and were in agreement with the structure. Photoinduced electron transfer from ferrocene to fullerene was identified, most likely with a through space mechanism. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Functional polypedes-chiral nematic fullerenes
    (2003)
    Campidelli, Stephane
    ;
    Eng, Carine
    ;
    Saez, Isabel M.
    ;
    Goodby, John W.
    ;
    Deschenaux, Robert 
    Self-organizing, functional materials created by bottom-up synthesis represent important steps forward in the development of novel materials. The authors report on the prepn. and properties of a chiral nematic tetrapedal liq. crystal that was functionalized with C60. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-crystalline fullerene-oligophenylenevinylene conjugates
    (2002)
    Campidelli, Stephane
    ;
    Deschenaux, Robert 
    ;
    Eckert, Jean-Francois
    ;
    Guillon, Daniel
    ;
    Nierengarten, Jean-Francois
    Functionalization of C60-oligophenylenevinylene derivs. with a cyanobiphenyl-terminated dendromesogen leads to new donor-acceptor systems with liq.-cryst. properties. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-crystalline fulleropyrrolidines. Preliminary communication
    (2001)
    Campidelli, Stephane
    ;
    Deschenaux, Robert 
    A fulleropyrrolidine showing a smectic A phase was synthesized by 1,3-dipolar cycloaddn. of a liq.-cryst. aldehyde deriv. and sarcosine to C60. [on SciFinder(R)]