Supramolecular Liquid Crystals

Significance

The authors report the self-organization of the cyclo[8]pyrrole mesophase, which is induced by vapors of polynitroaromatic compounds. Three new cyclo[8]pyrroles, each possessing eight large substituents, namely undecyl, 4-dodecyloxyphenyl, or 3,4-bis(decyloxy)phenyl chains were isolated as the dihydrogen sulfate salts starting from the appropriately substituted bipyrroles and reacting with FeCl₃·H₂O and 1 M H₂SO₄ in dichloromethane. The sulfate anion is firmly bound within the cavity of the diprotonated macrocycle and the resulting ion pair persists both in the solid state and in solution. An equimolar mixture of 1a and 2,4,7-trinitrofluorenone (TNF) formed a mesophase that is stable from room temperature to 74 °C. The texture obtained on slow cooling of the isotropic melt shows well-developed cylindrical domains and large homeotropic zones, characteristic of a columnar hexagonal phase (Col_h).