Robust White‐Light Emitting and Multi‐Responsive Luminescence of a Dual‐Mode Phosphorescence Molecule

Abstract Developing a single emitter with dual emission or multi‐emission, termed as single‐molecule white‐light emission (SMWLE), has attracted more and more attention. However, the exploration of fluorescence‐RTP SMWLE is very challenging because purely organic RTP molecule is still at the preliminary stage. Here, a robust white‐light emitting is successfully achieved through dual‐mode phosphorescence by incorporating intramolecular electron coupling. A series of carbazole–nicotinamide isomers are designed and synthesized. Dyads 2–4 show efficient room‐temperature persistent phosphorescence with the highest quantum yield of 21.3% and the longest lifetime of 846 ms. In particular, dyad 4 manifests robust white‐light emitting property with a rather high phosphorescence quantum yield of 11.2%. The calculated CIEx,y chromaticity coordinate is (0.26, 0.28) in the white‐light zone. Interestingly, dyad 4 is sensitive to mechanical force and acid, demonstrating the multi‐state stimuli‐responsive properties. It is found that the force‐induced phase transition from crystalline to amorphous drives the dual‐mode mechanochromism (fluorescence shift and phosphorescence on–off), and the protonation of pyridine units results in acidichromism. Moreover, a RTP self‐enhancement process is observed. Dyad 4 is a considerably rare white‐light‐emitting purely organic RTP molecule with multi‐responsive luminescence via dual‐mode phosphorescence.