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Guerra, Sebastiano
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Guerra, Sebastiano
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Voici les éléments 1 - 10 sur 12
- PublicationMétadonnées seulementMacrocyclic Effects in the Mesomorphic Properties of Liquid-Crystalline Pillar[5]- and Pillar[6]arenes(2013)
; ; Nierengarten, Jean-FrancoisWhereas 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)] - PublicationAccès libreLa chimie click au service des cristaux liquides: du concept à l'application(2012)
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Ce travail de thèse traite de la mise en place ainsi que de l’application d’une nouvelle méthodologie de synthèse basée sur la cycloaddition 1,3-dipolaire de Huisgen connue sous le nom de chimie click. Tout au long de ce travail, cette méthode sera appliquée dans la synthèse de nouveaux composés mésomorphes dont la complexité structurale augmentera au fur et à mesure des chapitres. Différents dendrimères, dendromésogènes et mésogènes ont été synthétisés dans le but d’évaluer la viabilité de cette nouvelle réaction ainsi que son influence sur les propriétés mésomorphes.
Une fois les conditions déterminées, cette méthodologie a été appliquée au greffage de différents cœurs par des composés mésomorphes dans l’intention d’obtenir de nouveaux matériaux combinant les propriétés d’organisation des cristaux liquides aux propriétés physico-chimiques des cœurs choisis. Dans cette optique, des nanoparticule d’or mésomorphes, ainsi que différents hexaadduits colonnaires du fullerène ont été obtenus.
Finallement, une nouvelle famille de synthons, basée sur le motif méthanofulléro-hémidendrimère, a été synthétisée dans le but de les greffer sur des cœurs afin d’obtenir des matériaux hybrides comme des fulléro-nanoparticules d’or mésomorphes.,
Our research project deals with the design of liquid-crystalline materials based on the 1,3-dipolar cycloaddition reaction, i.e. the click chemistry. This reaction was found to be effective and versatile, and a great variety of new complex structures could be synthesized, including dendrimers, dendromesogens, gold nanoparticles and polyadducts of fullerenes. In the area of mesomorphic materials, this reaction is of particular interest to prepare liquid-crystals, the self-organization behavior of which can be controled at the molecular level. Our results are of general interest, and our concept can be used in other fields of supramolecular chemistry to assemble various subunits. - PublicationMétadonnées seulementDesign of liquid-crystalline gold nanoparticles by click chemistryMesomorphic 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)]
- PublicationMétadonnées seulementBuilding liquid crystals from the 5-fold symmetrical pillar[5]arene core(2012)
; - PublicationAccès libreAccordion-optimized DEPT experiments(2011)
; 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. - PublicationMétadonnées seulementAccordion-optimized DEPT experiments(2010)
; 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 (1)J(CH) coupling constants associated with the various structural elements. The ACCORDEPT experiment afforded significant enhancements for the resonances with the larger (1)J(CH) 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. Copyright © 2010 John Wiley & Sons, Ltd.[on SciFinder (R)] - PublicationAccès librePiling Up Pillar[5]arenes To Self-Assemble Nanotubes
; ; Nierengarten, Jean-FrançoisNew 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. - PublicationAccès libreBuilding liquid crystals from the 5-fold symmetrical pillar[5]arene core
; - PublicationAccès libreDesign of liquid-crystalline gold nanoparticles by click chemistryMesomorphic alkyne-based first- and second-generation dendrons were grafted onto gold nanoparticles carrying azide groups under click reaction conditions. The nanoparticles decorated with the dendrons displayed liquid-crystalline properties and good thermal stability.
- PublicationAccès libreSelf-organisation of dodeca-dendronized fullerene into supramolecular discs and helical columns containing a nanowire-like core
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