State-crossing from a Locally Excited to an Electron Transfer State(SLEET) Model Rationalizing the Aggregation-induced Emission Mechanism of (Bi)piperidylanthracenes

Luminogens with aggregation-induced emission(AIE) characte-ristics(or AIEgens) have been widely used in various applications due to their excellent luminescent properties in molecular aggregates and the solid state. A deep understanding of the AIE mechanism is critical for the rational development of AIEgens. In this work, the "state-crossing from a locally excited to an electron transfer state"(SLEET) model is employed to rationalize the AIE phenomenon of two (bi)piperidylanthracenes. According to the SLEET model, an electron transfer(ET) state is formed along with the rotation of the piperidyl group in the excited state of (bi)piperidylan-thracene monomers, leading to fluorescence quenching. In contrast, a bright state exists in the crystal and molecular aggregates of these compounds, as the intermolecular interactions restrict the formation of the dark ET state. This mechanistic understanding could inspire the deployment of the SLEET model in the rational designs of various functional AIEgens.