Voici les éléments 1 - 10 sur 149
  • Publication
    Métadonnées seulement
    Macrocyclic Effects in the Mesomorphic Properties of Liquid-Crystalline Pillar[5]- and Pillar[6]arenes
    (2013)
    Nierengarten, Iwona
    ;
    ;
    Holler, Michel
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    Karmazin-Brelot, Lydia
    ;
    Barbera, Joaquin
    ;
    ;
    Nierengarten, Jean-Francois
    Whereas the reaction of 1,4-bis(2-bromoethyloxy)benzene (4) with paraformaldehyde in the presence of BF3·Et2O afforded exclusively the cyclopentameric pillar[5]arene deriv. (5), both cyclopenta- and cyclohexameric macrocycles 5 and 6 were obtained when the reaction of 4 with paraformaldehyde was performed at 45 °C in CHCl3 with FeCl3 as the catalyst. Treatment of compds. 4-6 with sodium azide provided the corresponding polyazides, to which a cyanobiphenyl building block was subsequently grafted to generate model compd. 1, pillar[5]arene 2, and pillar[6]arene 3, bearing two, ten and twelve mesomorphic subunits, resp. The liq.-cryst. and thermal properties of the compds. were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Comparison of the liq.-cryst. properties of macrocycles 2 and 3 with those of 1 revealed the strong influence of the macrocyclic pillar[n]arene core on the mesomorphic properties. Whereas only a monotropic mesophase was obsd. for 1, a broad enantiotropic mesophase was evidenced for both pillar[n]arene derivs. [on SciFinder(R)]
  • Publication
    Accès libre
    Aromatic Bent-Core Liquid Crystals:  an Opportunity for Introducing Terdentate Binding Units into Mesophases
    (2012)
    Nozary, Homayoun
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    Piguet, Claude
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    Rivera, Jean-Pierre
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    Tissot, Paul
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    Morgantini, Pierre-Yves
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    Weber, Jacques
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    Bernardinelli, Gérald
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    Bünzli, Jean-Claude G.
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    Donnio, Bertrand
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    Guillon, Daniel
    Lipophilic linear semirigid side arms containing two or three successive phenyl rings separated by carboxylate spacers have been connected to the 5 or 6 positions of bent aromatic 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 aromatic rings in the crystal structure of L12b (C63H61N5O10; triclinic, P1̄, Z = 2) in agreement with semiempirical calculations performed on optimized gas-phase geometries. Moreover, the carboxylate spacers in L11−L13 prevent efficient electronic delocalization between the connected aromatic rings and act as weak π acceptors producing a slight increase of the energy of the 1ππ* and 3ππ* levels centered on the terdentate binding unit. Intermolecular π-stacking interactions observed 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 observed at high temperature. The ColR mesophase detected for L11 demonstrates that V-shaped bent terdentate binding units are compatible with liquid-crystalline 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, P1̄, 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 3ππ* prevents Eu(5D0) → L11 back transfer in the Eu(III) complex, which thus exhibits sizable red luminescence at room temperature, a crucial point for the design of luminescent materials.
  • Publication
    Métadonnées seulement
    Design of liquid-crystalline gold nanoparticles by click chemistry
    Mesomorphic alkyne-based 1st- and 2nd-generation dendrons were grafted onto Au nanoparticles carrying azide groups under click reaction conditions. The nanoparticles decorated with the dendrons displayed liq.-cryst. properties and good thermal stability. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Fullerene-containing dendrimers: synthesis and properties
    (2012)
    Nierengarten, Jean-Francois
    ;
    Holler, Michel
    ;
    A review. The aim of this review is not to give an exhaustive review on fullerene-contg. dendrimers but to present examples to illustrate the current state-of-the-art of fullerene chem. for the development of new functional dendrimers. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Building liquid crystals from the 5-fold symmetrical pillar[5]arene core
    (2012)
    Nierengarten, Iwona
    ;
    ;
    Holler, Michel
    ;
    Nierengarten, Jean-Francois
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    Comparison of the liq.-cryst. properties of a pillar[5]arene core functionalized with 10 mesogenic cyanobiphenyl units with those of a corresponding model compd. revealed the strong influence of the macrocyclic pillar[5]arene core on the mesomorphic properties. [on SciFinder(R)]
  • Publication
    Accès libre
    Encapsulation of Pyrene-Functionalized Poly(benzyl ether) Dendrons into a Water-Soluble Organometallic Cage
    (2011)
    Pitto-Barry, Anaïs
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    Barry, Nicolas P. E.
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    Zava, Olivier
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    ;
    Two generations of lipophilic pyrenyl functionalized poly(benzyl ether) dendrimers (P1 and P2) have been synthesized. The thermal properties of the two functionalized dendrimers have been investigated, and the pyrenyl group of the dendritic molecules encapsulated in the arene–ruthenium metalla-cage, [Ru6(p-cymene)6(tpt)2(donq)3]6+ ([1]6+) (tpt=2,4,6-tri(pyridin-4-yl)-1,3,5-triazine; donq=5,8-dioxydo-1,4-naphthoquinonato). The host–guest properties of [P1⊂1]6+ and [P2⊂1]6+ were studied in solution by NMR and UV/Vis spectroscopic methods, thus allowing the determination of the affinity constants. Moreover, the cytotoxicity of these water-soluble host–guest systems was evaluated on human ovarian cancer cells.
  • Publication
    Métadonnées seulement
    A liquid-crystalline fullerene-oligophenylenevinylene dyad which displays columnar mesomorphism
    (2011)
    Hoang, Thi Nhu Y.
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    Pociecha, Damian
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    Salamonczyk, Miroslaw
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    Gorecka, Ewa
    ;
    The design, synthesis and liq.-cryst. properties of a family of hybrid compds. which are built from rod-like (oligophenylenevinylene) and disk-like [poly(benzyl ether)] units are reported. All compds. form columnar phases within broad temp. ranges; the mesophases are stable even below room temp. Weak photovoltaic effect was obsd. for the C60-OPV dyad. For the mol. having a terminal OH group, frustration of the hexagonal packing was obsd. and gave rise to a rare phase sequence. For this material, a columnar phase with trigonal symmetry and doubling of the crystallog. lattice was found below the hexagonal columnar phase. [on SciFinder(R)]
  • Publication
    Accès libre
    Double Targeting of Tumors with Pyrenyl-Modified Dendrimers Encapsulated in an Arene-Ruthenium Metallaprism
    (2011)
    Pitto-Barry, Anais
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    Barry, Nicolas P. E.
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    Zava, Olivier
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    Dyson, Paul J.
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    The self-assembly of 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine (tpt) triangular panels with p-cymene-ruthenium building blocks and 5,8-dioxido-1,4-naphthoquinonato (donq) bridges, in the presence of pyrenyl-contg. dendrimers of different generations (P0, P1 and P2), affords the triangular prismatic host-guest compds. [Pn?Ru6(p-cymene)6(tpt)2(donq)3]6+ ([Pn?1]6+). The host-guest nature of these systems, with the pyrenyl moiety being encapsulated in the hydrophobic cavity of the cage and the dendritic functional group pointing outwards, was confirmed by NMR spectroscopy (1H, 2D and DOSY). The host-guest properties of these systems were studied in soln. by NMR and UV/Vis spectroscopic methods, allowing the detn. of their affinity consts. (Ka). Moreover, the ability of these water-sol. host-guest systems to carry the pyrenyl-contg. dendrimers into cancer cells was evaluated on human ovarian cancer cells. The host-guest systems are all more cytotoxic than the empty cage [1][CF3SO3]6 (IC50?4 ?M), with the most active compd., [P0?1][CF3SO3]6, being an order of magnitude more cytotoxic. [on SciFinder(R)]
  • Publication
    Accès libre
    A liquid-crystalline fullerene–oligophenylenevinylene dyad which displays columnar mesomorphism
    (2011)
    Hoang, Thi Nhu Y
    ;
    Pociecha, Damian
    ;
    Salamonczyk, Miroslaw
    ;
    Gorecka, Ewa
    ;
    The design, synthesis and liquid-crystalline properties of a family of hybrid compounds which are built from rod-like (oligophenylenevinylene) and disc-like [poly(benzyl ether)] units are reported. All compounds form columnar phases within broad temperature ranges; the mesophases are stable even below room temperature. Weak photovoltaic effect was observed for the C60–OPV dyad. For the molecule having a terminal OH group, frustration of the hexagonal packing was observed and gave rise to a rare phase sequence. For this material, a columnar phase with trigonal symmetry and doubling of the crystallographic lattice was found below the hexagonal columnar phase.
  • Publication
    Accès libre
    Accordion-optimized DEPT experiments
    In this contribution, a pulse sequence is described for recording accordion-optimized DEPT experiments. The proposed ACCORDEPT experiment detects a wide range of one-bond coupling constants using accordion optimization. As a proof of concept, this strategy has been applied to a mesogen containing a large range of one-bond 1JCH coupling constants associated with the various structural elements. The ACCORDEPT experiment afforded significant enhancements for the resonances with the larger 1JCH couplings, similar SNR for aliphatic resonances, but reduced SNR for aliphatic resonances as compared with the standard DEPT experiment. In addition, the ACCORDEPT is straightforward to implement, does not require any supplementary calibration procedures and can be used under automated conditions without difficulty by inexperienced users.