ACQ-to-AIE modulation through delicate donor-acceptor switch strategy for multi-functional AIEgens applications

The development of novel aggregation-induced emission luminogens (AIEgens) has been a hot research topic due to their promising applications in biosensors, organic light-emitting diodes (OLEDs) and data storage, etc. In this study, two new rofecoxib derivatives, QE-DA and QE-D were successfully developed as novel AIEgens by exchanging the donor-acceptor (D-A) position or migrating the position of electron donor (D) group based on the fluorescent aggregation-caused quenching (ACQ) structure of (Z)-5-benzylidene-3-(4-isocyanophenyl)-4-phenylfuran-2(5H)-one (QE). Next, single crystal X-ray analysis of QE, QE-DA and QE-D revealed that their molecular conformations and packing modes were mainly responsible for the AIE or ACQ behavior. Specifically, QE exhibits ACQ behavior, while QE-DA and QE-D display AIE behavior. These differences are determined based on key parameters such as the displacement angle (θ₁) and vertical distance (d). In addition, QE-DA and QE-D also showed solvatochromic effects as well as acidochromic properties with good reversible multi-stimulus behaviors. Moreover, their potential applications such as pH and water sensors as well as specific probes targeting lipid droplets (R = 0.98) were fully investigated. Taken together, this study provides two new design philosophies for achieving ACQ-to-AIE conversion by migrating the position of the D group or switching the position of D and A groups, and further presents the potential of these targets to be developed as water sensors, security ink and LDs-targeting probes.