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Issue 30, 2012
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Helical self-assembly and co-assembly of fluorinated, preorganized discotics

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The synthesis and self-assembly properties of a fluorinated C3-symmetrical 3,3′-bis(acylamino)-2,2′-bipyridine discotic (1) in the mesophase and in solution are described. First, 3,4,5-tris-(1H,1H,2H,2H,3H,3H-perfluoroundecyl-1-oxy)benzoyl chloride was coupled to mono-t-BOC protected 2,2′-bipyridine-3,3′-diamine to afford after deprotection the corresponding fluorinated aromatic amine on a multigram scale. Then, three-fold reaction of this amine with trimesyl chloride yielded the target C3-symmetrical fluorinated disc. The latter displayed columnar liquid crystallinity over a temperature range of more than 350 K in which helical rectangular and hexagonal columnar mesophases were detected by X-ray diffraction measurements. 1H-NMR spectroscopy showed a preorganized structure due to strong intramolecular hydrogen bonding between the amide N–H's and bipyridine nitrogen atoms, even in the presence of a large excess of hexafluoroisopropanol. This preorganized structure allows the formation of helical self-assemblies in fluorinated solvents, as was established using UV-Vis spectroscopy. The fluorinated disc and two chiral hydrocarbon analogues (a C3-symmetrical and a desymmetrized disc) were mixed in a 1 : 10 v : v mixture of methoxynonafluorobutane (MNFB) and 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113). Importantly, the C3-symmetrical hydrocarbon disc dissolves only in the presence of fluorinated disc in the latter solvent mixture, proving a mutual interaction. CD spectroscopy performed on these mixtures points to a preference for alternating self-assemblies of fluorinated and chiral hydrocarbon discotics.

Graphical abstract: Helical self-assembly and co-assembly of fluorinated, preorganized discotics

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The article was received on 22 Feb 2012, accepted on 16 Apr 2012 and first published on 17 May 2012

Article type: Paper
DOI: 10.1039/C2OB25385B
Org. Biomol. Chem., 2012,10, 5898-5908

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    Helical self-assembly and co-assembly of fluorinated, preorganized discotics

    M. H. C. J. van Houtem, F. Benaskar, C. F. C. Fitié, R. Martín-Rapún, J. A. J. M. Vekemans and E. W. Meijer, Org. Biomol. Chem., 2012, 10, 5898
    DOI: 10.1039/C2OB25385B

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