A novel simple red emitter characterized with AIE plus intramolecular charge transfer effects and its application for thiol-containing amino acids detection

Developing red fluorescence emitters with simple structures via convenient synthetic routes is highly desirable yet challenging. A novel simple AIE-active red emitter featured with intramolecular charge transfer (ICT) effect was designed by simply integrating common electron donor (D) and acceptors (A) through pi bridges, and facilely synthesized via stepwise asymmetric Knoevenagel condensations. Its AIE property comes out from the non planar 3D configuration and multiple rotors, and the ICT effect is originated from its D A electronic structure. This aldehyde group-functionalized AIEgen holds the capability to specifically detect thiol-containing amino acids in a light-up fashion with notable blue-shift in fluorescence in 2 min. Dramatic difference in the kinetics enabled this probe to differentiate cysteine (Cys) and homocysteine (Hcy) from glutathione (GSH). More interestingly, it generally shows a higher sensitivity to Hcy over Cys. Moreover, the remarkable fluorescence enhancement when the Cys concentration is above 250 mu M and the obvious blue-shift in the UV-Vis absorption spectrum at 15 mu M for Hcy reveal the potential of this AIEgen to be applied as an indicator of Cys/Hcy-related diseases.