Constructing Aggregation‐Induced Emission Luminogens With Significantly Improved Performance Through Local Chemical Modification From Thiophene to Thiophene Sulfone

A novel aggregation‐induced emission (AIE) system with superior performance was successfully developed through local chemical modification from thiophene to thiophene sulfone. This approach, leveraging easily accessible tetraphenylthiophene precursors, dramatically enhances the photophysical properties in a simple oxidation step. Notably, the representative 2,3,4,5‐tetraphenylthiophene sulfone ( 3c ) demonstrates remarkable solid‐state emission characteristics with a fluorescence quantum yield of 72% and an AIE factor of 240, substantially outperforming its thiophene analog. Mechanistic investigations elucidate that while restriction of intramolecular motion in the aggregate state accounts for the AIE effects of both fluorophores, the exceptional enhancement in optical performance originates from the suppression of the sulfur's heavy‐atom effect. Theoretical calculations confirm that this is achieved upon oxidation to the thiophene sulfone, which effectively blocks the nonradiative decay pathway via intersystem crossing. Furthermore, the thiophene sulfone‐cored AIE luminogens (AIEgens) possess outstanding photo‐, thermal, and chemical stability, ensuring their robustness for applications under demanding conditions. Consequently, these merits enabled their successful application as a sensitive fluorescent probe for sensing the glass transition temperature of polymers. This work not only provides a new paradigm for the rational design of high‐performance AIEgens but also highlights the significant potential of thiophene sulfone‐based AIEgens in advanced materials.