Multichannel Delayed Emission Based on Anti-Kasha Excited State Intramolecular Proton Transfer

Multichannel luminescence has gained significant traction across diverse fields such as optics, electronics, biology, etc. However, achieving the selective manifestation of multichannel emissions, particularly those involving delayed emission like thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP), from a solitary molecule remains a formidable challenge. Herein, an innovative strategy based on excited-state intramolecular proton transfer (ESIPT) facilitates the transition between TADF and RTP. The intermolecular hydrogen bonds between 2-(2′-hydroxyphenyl)benzothiazole (HBT) derivatives and polyvinyl alcohol (PVA) are utilized to modulate the ESIPT potential barrier. Only under excitation <370 nm, higher excited states are allowed to proceed to luminescence through ESIPT prior to transitioning to the lowest singlet states, defying Kasha's rule. Thus, the adjustment of the excitation wavelength allows for precise control over both the RTP of the enol configuration and the TADF of the keto configuration. Further addition of a third component, sulforhodamine B, achieves a red-shifted afterglow via energy transfer.