Diastereoisomerically Pure Fulleropyrrolidines as Chiral Platforms for the Design of Optically Active Liquid Crystals

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• 作者：Stphane Campidelli ; Philippe Bourgun ; Boris Guintchin ; Julien Furrer ; Helen Stoeckli-Evans ; Isabel M. Saez ; John W. Goodby ; Robert Deschenaux
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：March 17, 2010
• 年：2010
• 卷：132
• 期：10
• 页码：3574-3581
• 全文大小：390K
• 年卷期：v.132,no.10(March 17, 2010)
• ISSN：1520-5126

文摘

Incorporation of [60]fullerene (C₆₀) within self-organizing systems is conceptually challenging but allows us to obtain materials which combine the characteristics (anisotropy, organization) of condensed mesophases with the properties of C₆₀ (photo- and electrochemical activity). Here, we report on the synthesis, characterization, and liquid-crystalline properties of four optically active fullerodendrimers, which are chiral at the point of conjunction between the fullerene scaffold and the mesogenic moieties. Thus, the novelty of this study is to take advantage of the asymmetric carbon atom created during the 1,3-dipolar cycloaddition reaction on C₆₀ in order to induce mesoscopic chirality in the materials. Four diastereoisomeric fulleropyrrolidines ((R,S)-1, (R,R)-1, (S,R)-1, and (S,S)-1) were synthesized and associated with a second-generation nematic (N) dendron to give fullerodendrimers ((R,S)-2, (R,R)-2, (S,R)-2, and (S,S)-2) which display chiral nematic (N*) phases. The absolute configurations of the stereogenic centers were determined by X-ray crystallography, 1D and 2D NMR experiments, and circular dichroism (CD) spectroscopy. The liquid-crystalline properties of the fullerodendrimers were studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The fulleropyrrolidine derivatives 2 exhibit supramolecular helicoidal organizations with a right-handed helix for the (R,S)-2 and (R,R)-2 diastereoisomers and a left-handed helix for the (S,R)-2 and (S,S)-2 diastereoisomers. This result suggests that the self-organization of such supermolecular materials can be controlled at the molecular level by the introduction of only one chiral center.