Multi-stimuli fluorescence responsiveness of α-cyanostilbene derivative: AIEE, stimuli response to polarity, acid, force and light, applications in anti-counterfeiting and single phosphor w-OLED

Recently, the small molecule functional materials with a simple synthesis have attracted more and more attention. A multi-stimuli-responsive aggregation-induced emission (AIE) molecule is expected to have great applications in the near future. Identically, the single-component white organic light diode (w-OLED) has a good application field. Herein, a cyanostilbene derivative (TSC) was efficiently synthesized by Vilsmeier and Knoevenagel reactions with only 2 steps under mild conditions. TSC was characterized by NMR (1H, 13C), FT-IR, HRMS and elemental analysis. TSC has aggregation-induced enhanced emission (AIEE) effect, and significant polar-, acid-, force- and light-stimuli fluorescence responsiveness properties. The AIE effect and four different stimulus responses are all simultaneously presented in TSC. This phenomenon is relatively rare in small molecule fluorescent compounds. The results of SEM and DLS reveal the AIEE of TSC is mainly due to the fact that molecular self-assembly into nanofiber networks in the aggregated state limiting the distortion of molecules. DFT calculations show that the polarity stimuli-response (fluorescence from green to orange) is closely related to intramolecular charge transfer (ICT). Acid/base 1H NMR titration proves that the acidochromism results from reversible protonation/deprotonation. The results of DSC, SEM, PXRD and POM prove that the essence of mechanical force stimuli-response is the change of crystallinity. The results of 1H NMR, UV–vis and fluorescence spectra, DFT calculations and SEM reveal that the light stimuli-response is attributed to the Z/E configuration transformation. Based on multi-stimuli responsive properties, TSC can be used for recognition of solvents polarity by naked eyes or fluorophotometer, used as an acid indicator and also used to quantitatively test the concentration of trace acids, used in anti-counterfeiting including safty ink, data rewriting, even can be used to construct supramolecular liquid crystals materials. In addition, TSC can be used to fabricate single phosphor w-OLED, avoiding using multicomponent composite materials.