Manipulating the Position of Triplet Chromophores To Achieve a Dynamic Photoactivated Ultralong Organic Phosphorescence Effect

Pure
organic materials with room-temperature phosphorescence (RTP)
have promising applications in bioimaging, information storage, and
encryption. However, these materials are still very scarce due to
a lack of design guidelines. Herein, a series of commercial/lab-synthesized
carbazole-based derivatives is prepared by manipulating the positions
of the chlorine substituents on the phenyl ring. The results show
that 4CDCzB-Cm and 5CDCzB-Cm have ultralong phosphorescence lifetimes
of 699.13 and 710.96 ms with good conjugation, longer than lab-synthesized
ones due to the existence of isomers in the commercial samples. Remarkably,
2CDCzB-Cm shows photoactivated ultralong RTP with increased lifetimes
from 51.24 to 631.83 ms by manipulating intermolecular interactions
upon UV irradiation. The phosphor can also be deactivated back to
its original state after standing in the dark for 5 h. The extraordinary
photoresponsive and highly reversible properties of 2CDCzB-Cm provide
a significant step forward in expanding the scope of organic phosphorescence
applications.