Stimuli-responsive Enaminitrile Molecular Switches As Tunable AIEgens Covering the Chromaticity Space, Operating Out-of-equilibrium, and Acting As Vapor Sensors

A family of responsive enaminitrile molecular switches showing tunable turn-on fluorescence upon switching and aggregation is reported. When activated by the addition of acid/base, isomerization around the C & boxH;C bond could be effectuated, resulting in complete and reversible switching to the E- or Z-isomers. Typical aggregation-induced emission (AIE) could be recorded for one specific state of the different switches. By subtle tailoring of the parent structure, a series of compounds with emissions covering almost the full visible color range were obtained. The switchable AIE features of the enaminitrile structures enabled their demonstration as solid-state chemosensors to detect acidic and basic vapors, where the emission displayed an "off-on-off" effect. Furthermore, switching to the Z-configuration could be driven out-of-equilibrium through transient changes in acidity while giving rise to fluorescence. Single-crystal X-ray diffraction measurements suggested a luminescence mechanism based on restriction of intramolecular rotation and an intramolecular charge transfer effect in the AIE luminogens. Responsive enaminitrile molecular switches showing tunable turn-on fluorescence upon switching and aggregation are presented. The switches were emissive over the visible color range and responsive aggregation-induced emission could be recorded. When applied as solid-state chemosensors, the switches could be used to detect acidic and basic vapors while displaying "off-on-off". image