Aggregation-induced emission in fluorophores containing a hydrazone structure and a central sulfone: restricted molecular rotation

Abstract

Four D–π–A–π–D structured 4,4′-di(E)-2-(4-4-alkoxyaniline)hydrazinyldiphenyl sulfones were synthesized and their structures were characterized using NMR, IR, and element analysis. These compounds displayed weak fluorescence emission in THF while their fluorescence was enhanced in a THF/water mixture solvent. Fluorescence microscope imaging showed the formation of the aggregate state. The mechanism of aggregation-induced emission (AIE) was supported by molecular dynamics calculations. The intermolecular hydrogen bonds between adjacent molecules inhibited the intramolecular rotations, preventing π–π stacking and causing AIE enhancement. Living cell imaging experiments opened up a new method for cell fluorescence staining.