Fluorescence Regulation and Photoresponsivity in AIEE Supramolecular Gels Based on a Cyanostilbene Modified Benzene-1,3,5-Tricarboxamide Derivative.

Supramolecular interactions play an important role in regulating the optical properties of molecular materials. Different arrangements of identical molecules can afford a more straightforward insight into the contributions of supramolecular interactions. Herein, a novel gelator, BTTPA, composed of a benzene-1,3,5-tricarboxamide (BTA) central unit functionalized with three cyanostilbenes is designed, which forms two kinds of gels in DMSO/water mixtures. Depending on the water volume content, the gels exhibit quite different aggregation-induced emission enhancement (AIEE) properties, with one emitting a green emission (G-gel), and the second emitting a blue emission (B-gel). The main reason for this difference is that water affects H-bonding and π-π interactions, further resulting in disparate packing modes of gelators. In addition, only the G-gel displays gel-to-sol transition accompanied with fluorescence switching according to the trans-cis photoisomerization of cyanostilbene under UV light irradiation. The B-gel does not exhibit any change because of its tight hexagonal packing arrangement. Such packing modes restricted the space in which molecules were located and inhibited the transformation of configuration of cyanostilbene. These phenomena underline the incomparable status of packing modes and molecular configuration in regulating fluorescence properties and photoresponse behavior in organic solid-state luminescent materials.