Liquid-Crystalline Bisadducts of Fullerene
journal contributionposted on 29.09.2006 by Stéphane Campidelli, Ester Vázquez, Dragana Milic, Julie Lenoble, Carmen Atienza Castellanos, Ginka Sarova, Dirk M. Guldi, Robert Deschenaux, Maurizio Prato
Any type of content formally published in an academic journal, usually following a peer-review process.
A second-generation cyanobiphenyl-based dendrimer was used as a liquid-crystalline promoter to synthesize mesomorphic bisadducts of 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.