Organic emitter integrating aggregation-induced delayed fluorescence and room-temperature phosphorescence characteristics and its application in time-resolved luminescence imaging

摘要

Thermally activated delayed fluorescence (TADF) with a substantially long lifetime furnishes a new paradigm in developing probes for time-resolved imaging. Herein, a novel TADF fluorophore, namely, >PXZT, with terpyridine as the acceptor and phenoxazine (PXZ) as the donor, was rationally designed and synthesized. The new compound shows typical thermally activated delayed fluorescence, aggregation-induced emission and crystallization-induced room-temperature phosphorescence (RTP). The coordination of >PXZT with a zinc ion causes the quenching of the fluorescence of >PXZT due to the enhanced intramolecular charge transfer of the resulting complex >ZnPXZT1. With the dissociation of the >ZnPXZT1 to release >PXZT and the subsequent in situ hydrophobic aggregation of the free >PXZT to resist the influence of oxygen, the TADF emission of >PXZT is recovered. This zinc-assisted process is successfully used for time-resolved imaging of HeLa and 3T3 cells. This work presents a simple and effective strategy for time-resolved imaging by in situ forming TADF aggregates to turn on the TADF emission.