Asymmetric Cyclophanes Permit Access to Supercooled Nematic Liquid Crystals with Stimulus-Responsive Luminescence

A novel material with stimulus-responsive luminescence was created by integrating a chromophore with assembly-dependent emission properties into a liquid crystalline compound that can be kinetically trapped in a supercooled liquid crystalline state. This was achieved by synthesizing an asymmetric cyclophane containing one 1,6-bis(phenylethynyl)pyrene group. The new compound displays a broad nematic phase above ∼110 °C upon being heated. Quenching to room temperature allows one to avoid crystallization, and the supercooled nematic phase is stable for at least 1 h. When the compound is heated, a phase transition from the kinetically trapped state to a crystalline state occurs, concomitant with a pronounced change in photoluminescence. The crystalline phase thus accessed shows mechanoresponsive luminescence behavior.