Utilizing the aggregation-induced emission phenomenon to visualize spontaneous molecular directed motion in the solid state

The real-time monitoring of spontaneous molecular directed motion is a highly important but very challenging task. In this work, a rod-like aggregation-induced emission (AIE) molecule was carefully designed and facilely synthesized. The AIE molecule, the salicylaldehyde 4-butoxyaniline Schiff base (SBA), exhibited a unique self-recovery property from a semi-ordered structure to an ordered structure along with significant fluorescence changes after grinding. The fluorescence changes were monitored to obtain important kinetic information regarding the spontaneous molecular directed motion process, including the kinetic order, rate constants, half-life, and apparent activation energy. Unlike instrumental analytical methods such as PXRD and AFM, which only give information on a stable state of samples, the proposed fluorescence method provides a new perspective for real-time visualization of spontaneous molecular directed motion in situ in the solid state.