Oxidation-state-controlled switching between AIE and ACQ in pyrene luminophores.

Stepwise oxidation of sulphide to sulfoxide and sulfone modulates aggregation-induced emission (AIE) in pyrene luminophores by tuning excited-state character and molecular packing. The flexible sulphide exhibits weak emission, partial conformational locking in the sulfoxide enables strong AIE through suppression of non-radiative decay, whereas the rigid sulfone undergoes aggregation-caused quenching (ACQ). These results reveal that AIE arises from a delicate interplay between conformational restriction and excited-state nature, extending beyond conventional restriction of intramolecular rotation mechanisms.