Columnar mesophase formation of cyclohexa-m-phenylene-based macrocycles
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- Columnar mesophase formation of cyclohexa-m-phenylene-based macrocycles
- Pisula, Wojciech; Kastler, Marcel; Yang, Changduk; Enkelmann, Volker; Muellen, Klaus
- Cross-coupling; Macrocycles; Mesophases; Phase transitions; Self-assembly
- Issue Date
- WILEY-V C H VERLAG GMBH
- CHEMISTRY-AN ASIAN JOURNAL, v.48, no.9, pp.1592 - 1595
- Two novel discotic macrocycles, substituted cyclohexa-m-phenylene (CHP) and cyclo-3,6-trisphenanthrylene (CTP), and the linear oligomer 3,3′:6′,3″-terphenanthrene (TP) as a model substance have been synthesized by repetitive cross-coupling reactions. To correlate the molecular design with the supramolecular architecture and the established macroscopic order, 2D wide-angle X-ray scattering experiments were performed on mechanically extruded filaments. At room temperature in their crystalline phases, all three compounds revealed columnar assemblies in which the macrocycles self-organized by π-stacking interactions. The degree of macroscopic order was found to depend upon the planarity and stiffness of the aromatic core. The flexible CHP ring showed a poor macroscopic order of the columnar structures and a low isotropization temperature, whereas the more-planar, less-flexible CTP self-assembled into well-defined superstructures. The larger π-stacking area and the more-pronounced intermolecular interactions for CTP led to the formation of a mesophase over a very large temperature range. The surprising columnar organization of the "open" TP system was explained by back-folding of the molecule into a ringlike structure.
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