Multi-stimuli responsive supramolecular gels based on a D-π-A structural cyanostilbene derivative with aggregation induced emission properties.

Developing multi-stimuli responsive fluorescent gel materials in a single system remains challenging. Gelator molecules with classical fluorophores suffer from the aggregation-caused quenching (ACQ) effect, limiting their applications further. Herein, a novel V-shaped cyanostilbene-based molecule (BAPBIA) with aggregation induced emission (AIE) characteristics and great gelation ability was synthesized and was found to exhibit multi-stimuli responsive behaviors. Reversible gel-sol phase transitions together with emission quenching are realized in response to external stimuli including heat, light and fluoride ions. Especially, the introduction of a dimethylaniline group (donor) and a cyano group (acceptor) generates a D-π-A structure, further leading to an intramolecular charge transfer (ICT) effect, which enlarges the emission contrast with the variation of the distribution of charge. Thus, upon trifluoroacetic acid (TFA) triggered protonation of the dimethylaniline group, not only a gel-sol transition but also emission color switching (yellow-to-blue) is achieved due to the loss of the ICT effect. This work paves an easy way to construct fully reversible multi-stimuli responsive fluorescence modulation smart materials.