Aggregation-Induced Emission from Fluorophore–Quencher Dyads with Long-Lived Luminescence

Aggregation-induced emission (AIE)
is an important photophysical
phenomenon in molecular materials and has found broad applications
in optoelectronics, bioimaging, and chemosensing. Currently, the majority
of reported AIE-active molecules are based on either propeller-shaped
rotamers or donor–acceptor molecules with strong intramolecular
charge-transfer states. Here, we report a new design motif, where
a fluorophore is covalently tethered to a quencher, to expand the
scope of AIE-active materials. The fluorophore–quencher dyad
(FQD) is nonemissive in solutions due to photoinduced electron-transfer
quenching but becomes luminescent in the solid state. The intrinsic
emission lifetimes are found to be within the microseconds domain
at both room and low temperatures. We performed single-crystal X-ray
diffraction measurement for each of the FQDs as well as theoretical
calculations to account for the possible origin of the long-lived
AIE. These FQDs represent a new class of AIE-active molecules with
potential applications in organic optoelectronics.

聚集诱导发光（Aggregation-induced emission, AIE）是分子材料领域中一类重要的光物理现象，目前已在光电子学、生物成像与化学传感等领域获得广泛应用。当前，已报道的多数具有AIE活性的分子主要基于螺旋桨状旋转异构体，或是带有强分子内电荷转移态的给体-受体型分子。本研究报道了一种全新的设计策略：将荧光团通过共价键合连接至猝灭剂，以此拓展AIE活性材料的研究范畴。该荧光团-猝灭剂二元体（fluorophore–quencher dyad, FQD）在溶液中因光诱导电子转移猝灭效应而无荧光发射，但在固态时则会产生发光现象。研究发现，该类材料在室温与低温条件下的本征发射寿命均处于微秒量级。我们对所有FQD进行了单晶X射线衍射测试，并结合理论计算，以阐明该长寿命AIE现象的潜在成因。此类FQD代表了一类全新的AIE活性分子，在有机光电子学领域具备潜在应用价值。