Bis-pyrene-based supramolecular aggregates with reversibly mechanochromic and vapochromic responsiveness

We have designed and synthesized bis-pyrene derivatives, where the two pyrene units are connected by para-phthaloyl (p-BP) and meta-phthaloyl (m-BP) linkers. The compound p-BP in the condensed state does not respond to mechanical shearing. The fluorescence emission of supramolecular aggregates of compound m-BP in the condensed state shows reversibly mechanochromic and vapochromic behavior. The dual-responsive phenomena were characterized by UV-vis and fluorescence spectroscopy. Furthermore, the changes of the supramolecular structures of p-BP and m-BP were analyzed by powder X-ray diffraction (XRD) and time-resolved fluorescence spectroscopy, which indicated that the dual-responsive mechanism is related to their intermolecular interactions and packing modes. Scanning electron microscopy (SEM) was utilized to study the morphology of m-BP in the different emission states. Finally, the multi-cycled information recording and erasing on m-BP-based film was demonstrated.