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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
    Métadonnées seulement
    [60]fullerene-containing thermotropic liquid crystals
    (: Wiley-VCH Verlag GmbH & Co. KGaA, 2012)
    Guillon, Daniel
    ;
    Donnio, Bertrand
    ;
    Deschenaux, Robert 
    A review. [60]Fullerene-contg. liq. crystals have reached a high degree of sophistication from the point of view of both their structure and mesomorphic properties. Owing to their unique photophys. and electrochem. characteristics, [60]fullerene-based liq. crystals are promising compds. for the development of nanotechnol. by the bottom-up approach. Indeed, good studies have shown that liq.-cryst. fullerenes can play a major role in electron transport and photoconduction, and photoinduced electron and/or energy transfer has been achieved in donor-acceptor dyads when combined with ferrocene, tetrathiafulvalene, or oligophenylenevinylene. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-crystalline fullerodendrimers and fullero(codendrimers)
    (: Wiley-VCH Verlag GmbH & Co. KGaA, 2009)
    Guillon, Daniel
    ;
    Donnio, Bertrand
    ;
    Deschenaux, Robert 
    This review highlights with selected examples some relevant results in the field of fullerene-contg. thermotropic liq.-cryst. dendrimers. These examples demonstrate the wide application of dendrimers in designing supramol. fullerene materials. Structures and properties are presented according to the nature of dendrimers and mesogenic units. [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
    Ferrocene-containing optically active liquid-crystalline side-chain polysiloxanes with planar chirality
    (2006)
    Brettar, Julie
    ;
    Burgi, Thomas
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    ;
    Scharf, Toralf
    ;
    Deschenaux, Robert 
    Optically active liq.-cryst. side-chain polysiloxanes have been prepd. by grafting planar chiral ferrocene-based vinyl monomers onto com. available polyhydrosiloxane. Two ferrocene monomers have been synthesized: a linear-type monomer, which displays a monotropic chiral smectic C (SC*) phase and enantiotropic smectic A (SA) and chiral N (N*) phases, and a laterally branched monomer, which shows an enantiotropic N* phase. X-ray diffraction anal. indicates a monomol. organization of the monomeric units within the smectic layers. The polymers retain the liq.-cryst. phases of their corresponding monomers. The UV-vis and CD (CD) spectra are in agreement with the structure of the monomers and polymers. The molar absorption coeff. (?) and molar circular dichroic absorption coeff. (??) values of the polymers are proportional to the no. of monomeric units grafted onto them. The abs. configuration of the ferrocene carboxylic acid intermediate, used to synthesize the monomers, has been detd. on the basis of CD spectra. The helical twisting power (HTP) of the nematogenic monomer and polymer have been detd. in E7, and indicate that such materials could be used as chiral dopants. Finally, this study demonstrates that the nature of chiral phases can be controlled by structural engineering of the org. groups only, with ferrocene acting as the source of chirality. [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
    Aromatic Bent-Core Liquid Crystals: an Opportunity for Introducing Terdentate Binding Units into Mesophases
    (2002)
    Nozary, Homayoun
    ;
    Piguet, Claude
    ;
    Rivera, Jean-Pierre
    ;
    Tissot, Paul
    ;
    Morgantini, Pierre-Yves
    ;
    Weber, Jacques
    ;
    Bernardinelli, Gerald
    ;
    Buenzli, Jean-Claude G.
    ;
    Deschenaux, Robert 
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    Lipophilic linear semirigid side arms contg. two or three successive Ph rings sepd. by carboxylate spacers were connected to the 5 or 6 positions of bent arom. terdentate 2,6-bis(benzimidazol-2-yl)pyridine binding units to give extended V-shaped (L11) and I-shaped receptors (L12, L12b, and L13). The carboxylate spacers limit the flexibility of the side arms and provide crossed arrangements of the successive arom. rings in the crystal structure of L12b (C63H61N5O10; triclinic, space group P?1, Z = 2) in agreement with semiempirical calcns. performed on optimized gas-phase geometries. also, the carboxylate spacers in L11-L13 prevent efficient electronic delocalization between the connected arom. rings and act as weak ? acceptors producing a slight increase of the energy of the 1??* and 3??* levels centered on the terdentate binding unit. Intermol. ?-stacking interactions obsd. in the crystal of L12b are invoked to rationalize (i) the peculiar excimer emission of L11 in the solid state and (ii) the rich and varied calamitic (I-shaped L12, L12b, and L13) and columnar (V-shaped L11) mesomorphism obsd. at high temp. The ColR mesophase detected for L11 demonstrates that V-shaped bent terdentate binding units are compatible with liq.-cryst. behavior. Complexation of L11 with lanthanide(III) produces I-shaped complexes [Ln(L11)(NO3)3] (Ln = La, Eu, Gd, Tb, and Lu) possessing a large axial anisometry as found in the crystal structure of [Lu(L11)(CF3CO2)3(H2O)] (LuC81H87N5O17F9; triclinic, space group P?1, Z = 2), which exists in the solid state as H-bonded dimers. No mesomorphism is detected for the complexes as a result of the large perpendicular expansion brought by the metallic coordination site, but the high energy of the ligand-centered 3??* prevents Eu(5D0) ? L11 back transfer in the Eu(III) complex, which thus exhibits sizable red luminescence at room temp., a crucial point for the design of luminescent materials. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    A Ferrocene-Containing Carbohydrate Surfactant: Thermotropic and Lyotropic Phase Behavior
    (2000)
    Donnio, Bertrand
    ;
    Seddon, John M.
    ;
    Deschenaux, Robert 
    A ferrocene-contg. carbohydrate surfactant has been synthesized and shown by polarized optical microscopy, differential scanning calorimetry, and x-ray diffraction to exhibit both thermotropic and lyotropic liq.-cryst. phase behavior. This new class of materials should prove useful for the design of redox-active lyotropic liq. crystals, allowing fine electrochem. control of the phase structure and symmetry. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Calamitic liquid crystals containing metal-metal bonds: design of mesomorphic materials based on the Ru2(CO)4(?-?2-O2CR)2L2 sawhorse unit
    (1997)
    Deschenaux, Robert 
    ;
    Donnio, Bertrand
    ;
    Rheinwald, Gerd
    ;
    Stauffer, Frederic
    ;
    Süss-Fink, Georg 
    ;
    Velker, Jorg
    Complexes based on the stable [Ru2(CO)4(?-?2-O2CR)2L2] sawhorse unit were prepd. and characterized. [Ru2(CO)4(?-?2-O2CR)2{NC5H4(CO2C6H4OCnH2n+1-p)-p}2] (R = H, n = 10; R = C6H5, n = 6, 10, 12, 14 or 16; R = C6H4CH3-p, n = 10; R = C6H4OCH3-p, n = 6, 10 or 16) proved to be mesomorphic, giving rise to nematic phases. [on SciFinder(R)]
  • Publication
    Métadonnées seulement