A reversible room temperature phosphorescence/delayed fluorescence switch trigged by solvent exchange in a Ca-based coordination polymer

Abstract

Stimulus-responsive luminescent materials have attracted considerable attention owing to their intensive applications in diverse fields. However, most of the reported materials are based on short-lived luminescence, while those based on the switch between two different types of afterglows are still very rare. Herein, we report a one dimensional coordination polymer (1) as the first switch compound with reversible conversion between room temperature phosphorescence (RTP) and delayed fluorescence (DF) trigged by solvent exchange. The as-synthesized 1 shows a blue DF (463 nm) emission with a lifetime of 55.6 ms, which can be converted to a RTP emission (503 nm, 3.2 ms) via water vapor fumigation or exposing to wet air. Detailed studies reveal that fumigation can make part of the DMSO molecules of 1 be exchanged by H₂O molecules, which changes the singlet–triplet energy difference (ΔE_st), thereby realizing the conversion from DF to RTP. Remarkably, the initial luminescence can be restored by DMSO vapor fumigation and this reversible switch property can be used for advanced data encryption and decryption. The work provides fresh opportunities for the development of long-lived luminescence switches.