Topology Switch between AIE and ACQ: A Balance of Substituents

Herein, we describe a novel strategy developed for aggregation-induced emission (AIE)/aggregation-caused quenching (ACQ) based on the subtle balance of mild electron-donating/-accepting substituents. The new approach eliminates the need to use bulky and flexible groups that are usually responsible for AIE and ACQ. The obtained regioisomers exhibit the same crystal packing but extremely different behavior upon aggregation, leading to the extremely bright aggregates of the compounds being dark in solution and vice versa. Such an approach opens a way to explore a new method of controlling small molecules' AIE/ACQ behavior.