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Deschenaux, Robert

Nom
Deschenaux, Robert
Affiliation principale
Fonction
Professeur.e ordinaire
Email
Robert.Deschenaux@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/384
_
0000-0002-1142-0022

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  • Publication
    Accès libre
    Photophysical, electrochemical, and mesomorphic properties of a liquid-crystalline [60]fullerene–peralkylated ferrocene dyad
    (2008)
    Campidelli, Stéphane
    ;
    Séverac, Marjorie
    ;
    Scanu, David
    ;
    Deschenaux, Robert 
    ;
    Vázquez, Ester
    ;
    Milic, Dragana
    ;
    Prato, Maurizio
    ;
    Carano, Maurizio
    ;
    Marcaccio, Massimo
    ;
    Paolucci, Francesco
    ;
    Rahman, G. M. Aminur
    ;
    Guldi, Dirk M.
    Two fullerene–peralkylated ferrocene derivatives were synthesized: (1) a liquid-crystalline dyad (compound 1) was obtained by introduction of nonamethyl ferrocene into a liquid-crystalline fullerene derivative and (2) a reference compound (compound 2) was synthesized by attachment of nonamethyl ferrocene to a fulleropyrrolidine. The liquid-crystalline dyad displayed an enantiotropic smectic A phase from 57 to 155 °C. Oxidation and reduction processes were investigated by cyclic voltammetry, and were in agreement with the electrochemical characteristics of the redox-active units (peralkylated ferrocene, fullerene, dendrimer). Photoinduced electron transfer from ferrocene derivative to fullerene was identified.
  • Publication
    Métadonnées seulement
    A dendritic fullerene-porphyrin dyad
    (2006)
    Campidelli, Stephane
    ;
    Deschenaux, Robert 
    ;
    Swartz, Angela
    ;
    Rahman, G. M. Aminur
    ;
    Guldi, Dirk M.
    ;
    Milic, Dragana
    ;
    Vazquez, Ester
    ;
    Prato, Maurizio
    We describe the synthesis, characterization and photophys. properties of a fullerene deriv. whose structure includes a Zn-porphyrin and a second generation liq.-cryst. (LC) dendrimer. The size of the fullerene and porphyrin units with respect to the size of the LC dendrimer prevents the formation of liq.-cryst. phases. However, this system gives interesting photoinduced electron transfer phenomena. Compd. 1 has been investigated by steady state and time resolved fluorescence as well as transient absorption spectroscopy in polar and apolar solvents. We demonstrate that the fluorescence of the porphyrin unit in 1 is quenched compared to the Zn-tetraphenylporphyrin used as ref. Femto- and picosecond transient absorption permit to identify the formation of a radical ion pair while nanosecond expts. allowed the detn. of the charge recombination lifetimes. [on SciFinder(R)]
  • Publication
    Accès libre
    Liquid-Crystalline Bisadducts of [60]Fullerene
    (2006)
    Campidelli, Stéphane
    ;
    Vázquez, Ester
    ;
    Milic, Dragana
    ;
    Lenoble, Julie
    ;
    Atienza Castellanos, Carmen
    ;
    Sarova, Ginka
    ;
    Guldi, Dirk M.
    ;
    Deschenaux, Robert 
    ;
    Prato, Maurizio
    A second-generation cyanobiphenyl-based dendrimer was used as a liquid-crystalline promoter to synthesize mesomorphic bisadducts of [60]fullerene. Liquid-crystalline trans-2, trans-3, and equatorial bisadducts were obtained by condensation of the liquid-crystalline promoter, which carries a carboxylic acid function, with the corresponding bisaminofullerene derivatives. A monoadduct of fullerene was also prepared for comparative purposes. All the compounds gave rise to smectic A phases. An additional mesophase, which could not be identified, was observed for the trans-2 derivative. The supramolecular organization of the monoadduct derivative is governed by steric constraints. Indeed, for efficient space filling, adequacy between the cross-sectional areas of fullerene (∼100 Å2) and of the mesogenic groups (∼22−25 Å2 per mesogenic group) is required. As a consequence, the monoadduct forms a bilayered smectic A phase. The supramolecular organization of the bisadducts is essentially governed by the nature and structure of the mesogenic groups and dendritic core. Therefore, the bisadducts form monolayered smectic A phases. The title compounds are promising supramolecular materials as they combine the self-organizing behavior of liquid crystals with the properties of fullerene.
  • Publication
    Accès libre
    A dendritic fullerene–porphyrin dyad
    (2006)
    Campidelli, Stéphane
    ;
    Deschenaux, Robert 
    ;
    Swartz, Angela
    ;
    Rahman, G. M. Aminur
    ;
    Guldi, Dirk M.
    ;
    Milic, Dragana
    ;
    Vázquez, Ester
    ;
    Prato, Maurizio
    We describe the synthesis, characterization and photophysical properties of a fullerene derivative whose structure includes a Zn-porphyrin and a second generation liquid-crystalline (LC) dendrimer. The size of the fullerene and porphyrin units with respect to the size of the LC dendrimer prevents the formation of liquid-crystalline phases. However, this system gives interesting photoinduced electron transfer phenomena. Compound 1 has been investigated by steady state and time resolved fluorescence as well as transient absorption spectroscopy in polar and apolar solvents. We demonstrate that the fluorescence of the porphyrin unit in 1 is quenched compared to the Zn-tetraphenylporphyrin used as reference. Femto- and picosecond transient absorption permit to identify the formation of a radical ion pair while nanosecond experiments allowed the determination of the charge recombination lifetimes.
  • Publication
    Métadonnées seulement
    Liquid-crystalline fullerene-ferrocene dyads
    (2004)
    Campidelli, Stephane
    ;
    Vazquez, Ester
    ;
    Milic, Dragana
    ;
    Prato, Maurizio
    ;
    Barbera, Joaquin
    ;
    Guldi, Dirk M.
    ;
    Marcaccio, Massimo
    ;
    Paolucci, Demis
    ;
    Paolucci, Francesco
    ;
    Deschenaux, Robert 
    The 1,3-dipolar cycloaddn. reaction was used to assemble fullerene, ferrocene and a 2nd-generation liq.-cryst. cyanobiphenyl-based dendrimer. The targeted compd. displayed an enantiotropic smectic A phase from 40 to 135°. The d-layer spacing was detd. by x-ray diffraction, and is independent of temp. with a value of 95 Å. Mol. modeling and structural considerations suggested partial bilayer organization of the mesogenic mol. units within the smectic layers. Oxidn. or redn. processes of the basic components (ferrocene, fullerene, dendrimer) were studied by electrochem. techniques, and were in agreement with the structure. Photoinduced electron transfer from ferrocene to fullerene was identified, most likely with a through space mechanism. [on SciFinder(R)]
  • Publication
    Accès libre
    Liquid-crystalline fullerene–ferrocene dyads
    (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.
  • Publication
    Métadonnées seulement
    A mixed fullerene-ferrocene thermotropic liquid crystal: synthesis, liquid-crystalline properties, supramolecular organization and photoinduced electron transfer
    (2001)
    Even, Michael
    ;
    Heinrich, Benoit
    ;
    Guillon, Daniel
    ;
    Guldi, Dirk M.
    ;
    Prato, Maurizio
    ;
    Deschenaux, Robert 
    Grafting of a ferrocene-contg. liq.-cryst. malonate deriv. to C60 led to the mixed fullerene - ferrocene material 1 which gave rise to a smectic A phase. Cholesterol was used as liq.-cryst. promoter. X-ray diffraction expts. and volumetric measurements indicated that 1 is organized in double layered structures. The corresponding supramol. organization within the mesomorphic lamellar phase was characterized by a microsegregation of the different units (ferrocene, fullerene, and cholesterol) in distinct sublayers. In such a smectic A phase, C60 imposes the arrangement of the other mol. moieties. Photophys. studies revealed that electron transfer occurs from the donor ferrocene to the electron accepting fullerene. The formation of a long-lived radical pair, with lifetimes of the order of several hundred nanoseconds, was confirmed by time-resolved spectrometry, esp. in the near IR region, in which the radical anion of the fullerene moiety displays its characteristic fingerprint absorption. [on SciFinder(R)]
  • Publication
    Accès libre
    A Mixed Fullerene-Ferrocene Thermotropic Liquid Crystal: Synthesis, Liquid-Crystalline Properties, Supramolecular Organization and Photoinduced Electron Transfer
    (2001)
    Even, Michaël
    ;
    Heinrich, Benoît
    ;
    Guillon, Daniel
    ;
    Guldi, Dirk M.
    ;
    Prato, Maurizio
    ;
    Deschenaux, Robert 
    Grafting of a ferrocene-containing liquid-crystalline malonate derivative to C60 led to the mixed fullerene-ferrocene material 1 which gave rise to a smectic A phase. Cholesterol was used as liquid-crystalline promoter. X-ray diffraction experiments and volumetric measurements indicated that 1 is organized in double layered structures. The corresponding supramolecular organization within the mesomorphic lamellar phase is characterized by a microsegregation of the different units (ferrocene, fullerene, and cholesterol) in distinct sublayers. In such a smectic A phase, C60 imposes the arrangement of the other molecular moieties. Photophysical studies revealed that electron transfer occurs from the donor ferrocene to the electron accepting fullerene. The formation of a long-lived radical pair, with lifetimes of the order of several hundred nanoseconds, was confirmed by time-resolved spectrometry, especially in the near infrared region, in which the radical anion of the fullerene moiety displays its characteristic fingerprint absorption.