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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
    Accès libre
    Aromatic Bent-Core Liquid Crystals:  an Opportunity for Introducing Terdentate Binding Units into Mesophases
    (2012)
    Nozary, Homayoun
    ;
    Piguet, Claude
    ;
    Rivera, Jean-Pierre
    ;
    Tissot, Paul
    ;
    Morgantini, Pierre-Yves
    ;
    Weber, Jacques
    ;
    Bernardinelli, Gérald
    ;
    Bünzli, Jean-Claude G.
    ;
    Deschenaux, Robert 
    ;
    Donnio, Bertrand
    ;
    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
    Accès libre
    Encapsulation of Pyrene-Functionalized Poly(benzyl ether) Dendrons into a Water-Soluble Organometallic Cage
    (2011)
    Pitto-Barry, Anaïs
    ;
    Barry, Nicolas P. E.
    ;
    Zava, Olivier
    ;
    Deschenaux, Robert 
    ;
    Therrien, Bruno 
    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
    Accès libre
    Double Targeting of Tumors with Pyrenyl-Modified Dendrimers Encapsulated in an Arene-Ruthenium Metallaprism
    (2011)
    Pitto-Barry, Anais
    ;
    Barry, Nicolas P. E.
    ;
    Zava, Olivier
    ;
    Deschenaux, Robert 
    ;
    Dyson, Paul J.
    ;
    Therrien, Bruno 
    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
    ;
    Deschenaux, Robert 
    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
    (2011)
    Furrer, Julien
    ;
    Guerra, Sebastiano 
    ;
    Deschenaux, Robert 
    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.
  • Publication
    Accès libre
    Double Targeting of Tumours with Pyrenyl-Modified Dendrimers Encapsulated in an Arene–Ruthenium Metallaprism
    (2011)
    Pitto-Barry, Anaïs
    ;
    Barry, Nicolas P. E.
    ;
    Zava, Olivier
    ;
    Deschenaux, Robert 
    ;
    Dyson, Paul J.
    ;
    Therrien, Bruno 
    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-containing dendrimers of different generations (P0, P1 and P2), affords the triangular prismatic host–guest compounds [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 solution by NMR and UV/Vis spectroscopic methods, allowing the determination of their affinity constants (Ka). Moreover, the ability of these water-soluble host–guest systems to carry the pyrenyl-containing 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 μM), with the most active compound, [P0⊂1][CF3SO3]6, being an order of magnitude more cytotoxic.
  • Publication
    Accès libre
    Optically active liquid-crystalline fullerodendrimers from enantiomerically pure fulleropyrrolidines
    (2010)
    Lincker, Frédéric
    ;
    Bourgun, Philippe
    ;
    Stoeckli-Evans, Helen 
    ;
    Saez, Isabel M.
    ;
    Goodby, John W.
    ;
    Deschenaux, Robert 
    A synthetic methodology based on the 1,3-dipolar cycloaddition reaction was developed to design enantiomerically pure liquid-crystalline fullerodendrimers.
  • Publication
    Accès libre
    Influence of a Mesogenic Dendrimer on the Morphology of Polymer–Fullerene Composites for Photovoltaics
    (2010)
    Kasdorf, Olga
    ;
    Kitzerow, Heinz-Siegfried
    ;
    Lenoble-Zwahlen, Julie
    ;
    Deschenaux, Robert 
    The efficiency of "bulk hetero junction"-type plastic solar cells depends crucially on the morphology of an entangled network of two immiscible compounds that serve as electron donor and electron acceptor, respectively. The present work describes preliminary results about the question how the luminescence and the morphology of a composite containing a fullerene C60 derivative and a p-phenylene vinylene (PPV) derivative are altered, when a dendrimer with a fullerene core and mesogenic side-chains is added. Fluorescence quenching and surface topography of the composites indicate that adding the mesogenic dendrimer can result in smaller domain sizes, which may be useful for photovoltaic applications.
  • Publication
    Accès libre
    Highly Fluorescent Liquid-Crystalline Dendrimers Based on Borondipyrromethene Dyes
    (2009)
    Frein, Stéphane
    ;
    Camerel, Franck
    ;
    Ziessel, Raymond
    ;
    Barberá, Joaquín
    ;
    Deschenaux, Robert 
    Fluorescent mesomorphic materials have been synthesized by grafting difluoro-bora-diaza-s-indacene (F-Bodipy) onto first-, second-, and third-generation liquid-crystalline poly(aryl ester) dendrons functionalized with cyanobiphenyl units. The second- and third-generation dendrimers give rise to smectic A phases; the first-generation dendrimer shows a nematic phase and an unidentified phase. The supramolecular organization within the smectic A phase could be established from X-ray experiments: the dendritic core is oriented approximately parallel to the layer planes and the mesogenic units are oriented perpendicularly above and below the dendritic core; interdigitation occurs between neighboring layers. All the materials are highly fluorescent both in solution and in the mesophases. For the first-generation dendrimer, the formation of J-aggregates was detected. The higher-generation dendrons prevented the formation of aggregates. Therefore, the dendrons play the role of liquid-crystalline promoters and protective shells.
  • Publication
    Accès libre
    Mesomorphic Poly(aryl ester)/Poly(benzyl ether) Dendrimers/co-Dendrimers with C60 as the Core
    (2009)
    Yevlampieva, Natalia
    ;
    Beljaev, Nikolai
    ;
    Lavrenko, Peter
    ;
    Deschenaux, Robert 
    Structure-properties relations of liquid crystalline fullerene-containing poly(aryl ester)/poly(benzyl ether) dendritic compounds with variation of C60 linkage type have been analyzed based on experimental data on their total polarity and electro–optical Kerr effect in benzene solutions. There was established that fulleropyrrolidine as the core of dendrimer strongly restricts rotational freedom of dendrons, in contrast to methanofullerene. A conclusion that not only terminal mesogenic groups and dendrons' generation number, but a manner of C60 incorporation into the dendritic matrix also influences on the mesomorphic behavior of these multicomponent hybrid-type liquid crystalline compounds had been made.