Vignette d'image

Deschenaux, Robert

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

Résultat de la recherche

Filtres

1494
7574
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 10 sur 149
  • Publication
    Métadonnées seulement
    Ferrocene-containing thermotropic liquid crystals: influence of polysubstitution on the mesomorphic properties
    (1995)
    Deschenaux, Robert 
    ;
    Kosztics, Isabelle
    ;
    Nicolet, Blaise
    The synthesis, characterization and mesogenic properties of a new family of 1,3-disubstituted ferrocene derivs. and of the 1st trisubstituted ferrocene-contg. thermotropic liq. crystals (here functionalized in the 1,1',3-positions) are reported. The results confirmed the importance of the org. segment length for promoting mesomorphism in disubstituted systems and revealed the strong tendency of polysubstitution for generating liq.-cryst. materials. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Synthesis and characterization of the sodium and lithium cryptates of macrobicyclic ligands incorporating pyridine, bipyridine, and biisoquinoline units
    (1988)
    Alpha, Beatrice
    ;
    Anklam, Elke
    ;
    Deschenaux, Robert 
    ;
    Lehn, Jean Marie
    ;
    Pietraskiewicz, Marek
    Procedures were developed for the prepn. of Na and Li cryptates of macrobicyclic ligands contg. pyridine, bipyridine, and biisoquinoline groups. They involve stepwise construction of the bicyclic system as well as direct macrobicyclization procedures and give access to both sym. and dissym. structures. Marked cation template effects facilitate the cyclization processes. The ligands were isolated as their cryptates with Na+ or Li+ cations. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Crystal smectic-B phase from a mesomorphic ferrocene derivative
    (1995)
    Deschenaux, Robert 
    ;
    Marendaz, Jean-Luc
    ;
    Santiago, Julio
    ;
    Goodby, John W.
    The thermal properties of two ferrocene derivs., substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene deriv. was non-mesomorphic, the disubstituted ferrocene deriv. exhibited a crystal smectic-B phase. This result shows that ferrocene-contg. thermotropic liq. crystals, despite the bulkiness of the metallocene core, are not limited to disordered calamitic phases. [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
    Accès libre
    Bent Tridentate Receptors in Calamitic Mesophases with Predetermined Photophysical Properties:  New Luminescent Lanthanide-Containing Materials
    (American Chemical Society (ACS), 1998)
    Nozary, Homayoun
    ;
    Piguer, Claude
    ;
    Tissot, Paul
    ;
    Bernadinelli, Gérald
    ;
    Jean-claude G. Bünzli
    ;
    Deschenaux, Robert 
    ;
    Guillon, Daniel
    A new synthetic strategy has been developed to introduce bent and rigid tridentate 2,6-bis(benzimidazol-2‘-yl)pyridine cores into rodlike ligands L11-17. The crystal structure of the nonmesogenic ligand L13 (C39H37N5O4, triclinic, P1̄, Z = 2) shows the expected trans−trans conformation of the tridentate binding unit, which provides a linear arrangement of the semirigid aromatic sidearms. The crystal structure of the related mesogenic ligand L16 (C61H81N5O4, triclinic, P1̄, Z = 2) demonstrates the fully extended conformation adopted by the lipophilic side chains, leading to a slightly helically twisted I-shaped molecule. A rich and varied mesomorphism results which can be combined with the simultaneous tuning of electronic and photophysical properties via a judicious choice of the spacers between the rigid central core and the semirigid lipophilic sidearms. Ligands L13,14 react with Ln(NO3)3·xH2O to give quantitatively and selectively the neutral 1:1 complexes [Ln(Li)(NO3)3] (Ln = La to Lu), which are stable in the solid state at room temperature but partially dissociate in acetonitrile to give the cationic species [Ln(Li)(NO3)2]+. The crystal structure of [Lu(L13)(NO3)3]·3CH3CN (30, LuC45H46N11O13, monoclinic, C2/c, Z = 8) reveals a U-shaped arrangement of the ligand strand arising from the cis−cis conformation of the coordinated tridentate binding unit. This drastic geometric change strongly affects the thermal behavior and the photophysical and electronic properties of the lipophilic complexes [Ln(L14)(NO3)3]. Particular attention has been focused on structure−properties relationships, which can be modulated by the size of the lanthanide metal ions.
  • Publication
    Métadonnées seulement
    Unsymmetrically 1,1'-disubstituted ferrocene-containing thermotropic liquid crystals
    (1993)
    Deschenaux, Robert 
    ;
    Rama, Mafalda
    ;
    Santiago, Julio
    The synthesis and mesomorphic properties of the first family of unsym. 1,1'-disubstituted ferrocene-contg. liq. crystals are reported. All compds. have smectic phases. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    1,3-Disubstituted ferrocene-containing thermotropic liquid crystals: synthesis, mesomorphic properties and the crystal and molecular structure
    (1993)
    Deschenaux, Robert 
    ;
    Kosztics, Isabelle
    ;
    Marendaz, Jean Luc
    ;
    Stoeckli-Evans, Helen 
    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
    Ferrocene- and fullerene[60]-containing liquid-crystalline materials
    (1998)
    Chuard, Thierry
    ;
    Deschenaux, Robert 
    A review with 22 refs. showing the versatility of ferrocene and fullerene for the design of thermotropic liq.-cryst. materials: (i) the electrochem. properties of the ferrocene-ferrocenium system were exploited to design redox-active metallomesogens; (ii) ferrocene-contg. side-chain liq.-cryst. polysiloxane and polymethacrylates were synthesized by grafting a mesomorphic vinyl-ferrocene monomer onto com. available polysiloxane and by free-radical polymn. of mesomorphic methacrylate-ferrocene monomers, resp.; (iii) a 1st-generation ferrocene-contg. liq.-cryst. dendrimer was synthesized; and (iv) liq.-cryst. fullerene (10) and mixed fullerene-ferrocene (11) derivs. were obtained by functionalizing the C60 core with a twin cholesterol moiety. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Crystal structures of the lanthanum(III), europium(III), and terbium(III) cryptates of tris(bipyridine) macrobicyclic ligands
    (1991)
    Bkouche-Waksman, Itka
    ;
    Guilhem, Jean
    ;
    Pascard, Claudine
    ;
    Alpha, Beatrice
    ;
    Deschenaux, Robert 
    ;
    Lehn, Jean Marie
    The crystal structures of I.LaCl3.2H2O and I.TbCl3.4H2O (X = H) and I.EuCl3.4H2O (X = COOCH3) were detd. I.LaCl3.2H2O is triclinic, space group P?1, with a 18.602(5), b 17.342(5), c 14.130(5) Å, ? 99.98(2), ? 106.26(4), and ? 103.2(3)°; R = 5.8% (Rw = 5.6%). I.TbCl3.4H2O is orthorhombic, space group Cmca, with a 25.510(8), b 10.279(4), and c 31.021(9) Å; R = 5.0% (Rw = 7.3%). I.EuCl3.4H2O is monoclinic, space group C2/c, with a 30.715(8), b 14.121(5), c 23.813(8) Å, and ? 118.62(4)°; R = 5.9% (Rw = 6.2%). The structures confirm the cryptate nature of these species, the cations being bound to the 8 N sites of the ligand. The macrobicycle presents 2 open faces, thus allowing addnl. coordination of 2 species, Cl- ions or H2O mols., to the bound cations. These data provide structural support for the photophys. studies of the luminescent properties of the EuIII and TbIII cryptates, which indicated residual coordination of H2O mols. [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)]