Deschenaux, Robert

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.

2008, Frein, Stéphane, Auzias, Mathieu, Sondenecker, Aline, Vieille-Petit, Ludovic, Guintchin, Boris, Maringa, Natacha, Süss-Fink, Georg, Barberá, Joaquín, Deschenaux, Robert

Dinuclear ruthenium complexes containing the stable metal−metal bonded Ru₂(CO)₄ sawhorse unit with two dendritic carboxylato bridges have been synthesized and characterized. All complexes Ru₂(CO)₄(O₂CR)₂L₂ (R = R¹, R², R³) containing cyanobiphenyl-based poly(arylester) dendrons of first (R¹), second (R²), and third (R³) generation and triphenylphosphine, pyridine, or 4-picoline ligands L proved to be mesomorphic, giving rise to smectic A or smectic A and nematic phases. The supramolecular organization within the smectic A phase is governed by the nature and structure of the mesogenic units and dendritic core. Such materials are of interest for the design of catalytically active anisotropic fluids.

2005, Campidelli, Stéphane, Lenoble, Julie, Barberá, Joaquín, Paolucci, Francesco, Marcaccio, Massimo, Paolucci, Demis, Deschenaux, Robert

[60]Fullerene-containing liquid-crystalline dendrimers were synthesized from the first to the fourth generation by applying the 1,3-dipolar cycloaddition reaction from a mesomorphic dendritic-type aldehyde derivative, sarcosine (N-methylglycine) or glycine and C₆₀. The cyanobiphenyl unit was used as a liquid-crystalline promoter. With the exception of the first-generation fullerene dendrimer, which was found to be nonmesomorphic, all fullerene-based dendrimers gave rise to a smectic A phase. The liquid-crystalline fullerenes led to two different supramolecular organizations within the smectic layers:  for the second-generation dendrimers, the molecules are oriented in a head-to-tail fashion within the layers; for each molecule the cyanobiphenyl units point in the same direction. For the dendrimers of third and fourth generations, the dendritic core extends laterally, parallel to the layer planes; the mesogenic units are oriented above and below the dendritic core. For the aldehyde precursors, only one organization inside the layers was obtained, similar to the one observed for the third and fourth fullerene-based dendrimers. Cyclic voltametry investigations displayed several one-electron and multielectron reduction processes; no significant interaction in the ground state between the fullerene and the dendrimer was noticed. The title compounds showed the typical electrochemical stability of fulleropyrrolidines.

, Guerra, Sebastiano, Nguyen, Thi Le Anh, Furrer, Julien, Nierengarten, Jean-François, Barberá, Joaquín, Deschenaux, Robert

Liquid-crystalline dendrimers have been prepared from second-generation Percec- type poly(benzyl ether) dendrons or second-generation poly(aryl ester) dendrons carrying cyanobiphenyl mesogens. The Janus dendrimer, which combines the two types of dendromesogens, has also been synthesized. Those compounds have been prepared under copper-catalyzed azide–alkyne cycloaddition conditions. The mesomorphic properties have been studied by thermal analysis (POM, DSC) and small-angle X-ray scattering. Smectic A, nematic, and columnar phases have been observed depending on the dendritic building blocks. The click reaction has proven to be a powerful and elegant synthetic tool for the design of complex dendritic liquid- crystalline architectures.

2008, Pérez, Laura, Lenoble, Julie, Barberá, Joaquín, de la Cruz, Pilar, Deschenaux, Robert, Langa, Fernando

Functionalization of [60]fullerene with liquid-crystalline dendrimers and a dibutylaniline-based phenylenevinylene moiety leads to supramolecular materials, the fluorescence of which responds to acid–base stimuli.

2006-02-25, Campidelli, Stéphane, Pérez, Laura, Rodríguez-López Julián, Barberá, Joaquín, Langa, Fernando, Deschenaux, Robert

First- and second-generation ferrocene-based dendrimers, fullerene and a second-generation liquid-crystalline poly(arylester) dendrimer carrying four cyanobiphenyl units were assembled to elaborate polyfunctional materials displaying mesomorphic and electronic properties. The targeted compounds gave rise to enantiotropic smectic A phases and organized into bilayer structures within the smectic layers. Cyclic voltammetry investigations revealed oxidation and reduction processes in agreement with the presence of both ferrocene and fullerene units. Finally, strong quenching of the fluorescence was obtained for the fullerene–ferrocene dyads suggesting efficient elecron transfer from the ferrocene-based dendrimer to fullerene.

2004, Campidelli, Stéphane, Vázquez, Ester, Milic, Dragana, Prato, Maurizio, Barberá, Joaquín, Guldi, Dirk M., Marcaccio, Massimo, Paolucci, Demis, Paolucci, Francesco, Deschenaux, Robert

The 1,3-dipolar cycloaddition reaction was used to assemble fullerene, ferrocene and a second-generation liquid-crystalline cyanobiphenyl-based dendrimer. The targeted compound displayed an enantiotropic smectic A phase from 40 to 135 °C. The d-layer spacing was determined by X-ray diffraction, and was found to be independent of temperature with a value of 95 Å. Molecular modeling and structural considerations suggested partial bilayer organization of the mesogenic molecular units within the smectic layers. Oxidation or reduction processes of the basic components (ferrocene, fullerene, dendrimer) were investigated by electrochemical techniques, and were in agreement with the structure. Photoinduced electron transfer from ferrocene to fullerene was identified, most likely with a “through space” mechanism.

2008, Frein, Stéphane, Boudon, Julien, Vonlanthen, Mireille, Scharf, Toral, Barberá, Joaquín, Süss-Fink, Georg, Bürgi, Thomas, Deschenaux, Robert

Liquid-crystalline dendrons carrying either a thiol or disulfide function which display nematic, smectic A, columnar, or chiral nematic phases have been synthesized. Their mesomorphic properties are in agreement with the nature of the mesogenic units and structure of the dendrons. The first-generation poly(aryl ester) dendron containing two cyanobiphenyl mesogenic units was used to functionalize gold nanoparticles. For full coverage, a smectic-like supramolecular organization on the nanometer scale is observed, when the gold nanoparticles are spread onto carbon-coated copper grids. This result indicates that the dendritic ligands reported here act as self-organization promoters.

2006, Campidelli, Stéphane, Pérez, Laura, Rodríguez-López Julián, Barberá, Joaquín, Langa, Fernando, Deschenaux, Robert

First- and second-generation ferrocene-based dendrimers, fullerene and a second-generation liquid-crystalline poly(arylester) dendrimer carrying four cyanobiphenyl units were assembled to elaborate polyfunctional materials displaying mesomorphic and electronic properties. The targeted compounds gave rise to enantiotropic smectic A phases and organized into bilayer structures within the smectic layers. Cyclic voltammetry investigations revealed oxidation and reduction processes in agreement with the presence of both ferrocene and fullerene units. Finally, strong quenching of the fluorescence was obtained for the fullerene–ferrocene dyads suggesting efficient elecron transfer from the ferrocene-based dendrimer to fullerene.

, Nierengarten, Iwona, Guerra, Sebastiano, Ben Aziza, Haifa, Holler, Michel, Abidi, Rym, Barberá, Joaquín, Deschenaux, Robert, Nierengarten, Jean-François

New liquid-crystalline pillar[5]arene derivatives have been prepared by grafting first- generation Percec-type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc-shaped structure perfectly suited for self-organization into a columnar liquid-crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6- dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Colh mesophase has been deduced from X-ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4-dimethoxypillar[5]arene and 1,6- dicyanohexane.