Turning Non-Emissive Schiff Bases Into Aggregate Emitters.

Schiff bases are a crucial component in various functional materials but often exhibit non-emissive behavior which significantly limits their potential applications as luminescent materials. However, traditional approaches to convert them into aggregate emitters often require intricate molecular design, tedious synthesis, and significant time and resource consumption. Herein, we present a cocrystallization-induced emission strategy that can transform non-emissive (hetero)aryl-substituted Schiff bases into green-yellow to yellow aggregate emitters via even simple grinding of a mixture of Schiff bases and 1,2,4,5-tetracyanobenzene (TCB) mixtures. The combined experimental and theoretical analysis revealed that the cocrystallization inhibits the C=N isomerization and promotes face-to-face π-π interaction, which restricts access to both the dark state and canonical intersection to ultimately induce emission. Furthermore, the induced emission enables the observation of solid-state molecular diffusion through fluorescence signals, advancing white light emission diodes, and notably, solution-processed organic light-emitting diodes based on cocrystal for the first time. This study not only highlights the potential of developing new C=N structural motifs for AIEgens but also could boost advancements in related structure motifs like C=C and N=N.