Oxidation-enhanced emission: exploring novel AIEgens from thieno[3,2-b] thiophene S,S-dioxide

Luminescent materials with high thiophene contents generally suffer from severe emission quenching in the aggregated state, owing to various active nonradiative decay channels. Herein, we report that a series of novel propeller-like luminogens consisting of a thieno[3,2-b] thiophene S, S-dioxide core and different phenyl rotors can behave oppositely. They show faint emission in solutions, but can fluoresce strongly in solid films, displaying prominent aggregation-induced emission ( AIE) nature. Crystallographic, computational, and spectroscopic results reveal the synergistic effect of a propeller-like conformation and the oxidation of thieno[3,2-b] thiophene to thieno[3,2-b] thiophene S, S-dioxide greatly enhances emission efficiency of the luminogen in solid film. Calculation and electrochemical experiments reveal that they have much lower LUMO energy levels than the unoxidized counterparts. This work not only presents a feasible approach to create robust luminescent materials from thiophene by oxidation but also provides a new AIE platform with advantages of structural variety, high solid-state emission efficiency, and strong electron affinity for optoelectronic and biological applications.