Luminescent columnar liquid crystals generated by self-assembly of 1,3,4-oxadiazole derivatives

Abstract

Five new V-shaped acids derived from 1,3,4-oxadiazole are described. These compounds were used to prepare supramolecular complexes via hydrogen bonding interactions with 2,4-diamino-6-dodecylamino-1,3,5-triazine in a 3 : 1 ratio. The formation of the complexes was evidenced by infrared and NMR techniques. All the complexes were studied by polarizing optical microscopy, differential scanning calorimetry and small-angle X-ray diffraction. Rectangular and hexagonal columnar mesophases were observed for the complexes at room temperature, without signs of crystallization. Circular dichroism studies demonstrated that, in the liquid crystalline state, these materials show supramolecular optical activity. It is proposed that this phenomenon arises due to a helical columnar organization. Furthermore, the complexes display strong blue light emission in solution, with good photoluminescence quantum yields, and in the mesophase. These materials could therefore be promising candidates for optoelectronic applications.