Aggregation Induced Transition by Modulation of Substituent Groups on Rofecoxib Analogues and Multi-Stimulus Response Properties

Aggregation-induced emission luminogens (AIEgens) have been widely investigated due to their promising applications in data storage, organic light-emitting diodes, and deep tissue bioimaging as compared to conventional fluorophores. In this work, we have designed and synthesized two novel rofecoxib analogues functionalized with different terminal groups (-NH2, -Br) on the benzene ring B. Interestingly, the compound 2 a-3 with -NH2 substituent shows aggregation-caused quenching effect whereas the compound 1 b-3 with -Br group displays aggregation-induced emission (AIE) property which may be caused by the twisted conformation and restricted - stacking of 1 b-3 according to the X-ray single crystal diffraction analysis. These opposite results indicated that the terminal groups could have great influence on the photophysical properties of targets. Moreover, the compound 1 b-3 exhibited multi-stimuli response luminescence behaviors under various external stimuli including solvatochromism, mechanochromism and acidochromism. Furthermore, lipid droplets imaging investigation proved the compound 1 b-3 was capable of achieving specific lipid droplets bioimaging. This work not only presents a better understanding of the structure-fluorescent property relationship based on the scaffold of rofecoxib, but also provides a new avenue for spectral modulation and the development of new MSR materials.