Voici les éléments 1 - 4 sur 4
  • Publication
    Métadonnées seulement
    1,3-Disubstituted ferrocene-containing thermotropic liquid crystals: synthesis, mesomorphic properties and the crystal and molecular structure
    (1993) ;
    Kosztics, Isabelle
    ;
    Marendaz, Jean Luc
    ;
    Two families of 1,3-disubstituted ferrocene derivs. were synthesized and their liq.-crystal behavior investigated. Compds. of series I, (?5-C5H5)Fe[(?5-C5H3)-1,3-(COOC6H4OOCC6H4OCnH2n+1)2] (n = 1-14, 16, 18), exhibited remarkable mesomorphic properties. Indeed, nematic and/or smectic C phases, assocd. with large anisotropic domains, were obsd. Derivs. of series II, (?5-C5H5)Fe[?5-C5H3)-1,3-(COOC6H4OCnH2n+1)2] (n = 1-9), were nonmesogenic. The crystal and mol. structure of Ih (n = 8) was detd. by x-ray anal. The compd. is orthorhombic, space group Pnma, with a 7.602(1), b 57.538(3), and c 10.760(1) Å; Z = 4, dc = 1.302; R = 0.102, Rw = 0.132 for 1401 reflections. The crystallog. data confirmed both a highly anisometric structure for Ih and a compact arrangement of the mols. in the crystal. The present results show that a crit. length/depth ratio of approx. 5-7 must be passed for obtaining liq.-crystal properties. [on SciFinder(R)]
  • 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
    ;
    ;
    Saez, Isabel M.
    ;
    Goodby, John W.
    ;
    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
    An amphiphilic trinuclear cobalt cluster-containing molecular unit: synthesis, characterization and Langmuir-Blodgett films
    (1994) ;
    Masoni, Claudio
    ;
    ;
    Vaucher, Sebastien
    ;
    Ketterer, Jurgen
    ;
    Steiger, Rolf
    ;
    Weisenhorn, Albrecht L.
    An amphiphilic polynuclear transition-metal cluster has been prepd. and its capability for forming layers at the air-water interface and Langmuir-Blodgett films on different substrates investigated. The compd. was obtained by linking a Co3(CO)9 cluster to a hydrophobic cholesterol framework. A polar head was introduced by substituting one CO ligand by an isocyanide deriv. bearing a hydrophilic functional group. The surface pressure and surface potential vs. area isotherms and Brewster-angle microscopy indicated the formation of stable Langmuir films. Up to thirty-six transfer were performed on hydrophobized solids (mica, glass, quartz and silicon wafers). Structural characterization of the transferred films (UV and IR spectroscopy, at. force microscopy, small-angle x-ray scattering) demonstrated the formation of stable, highly organized crystals. The results represent a novel strategy towards the development of supramol. assemblies from polynuclear transition-metal compds. and organometallic surfaces. The structure of [Co3(CO)8(CCO2Me)(CNC6H4CN)] has been established by x-ray crystallog. [on SciFinder(R)]
  • Publication
    Accès libre
    Optically active liquid-crystalline fullerodendrimers from enantiomerically pure fulleropyrrolidines
    (2010)
    Lincker, Frédéric
    ;
    Bourgun, Philippe
    ;
    ;
    Saez, Isabel M.
    ;
    Goodby, John W.
    ;
    A synthetic methodology based on the 1,3-dipolar cycloaddition reaction was developed to design enantiomerically pure liquid-crystalline fullerodendrimers.