Perarylation as a strategy toward aggregation-induced emitters: Will they ever be stable?

Abstract

The periphery of most AIEgens is decorated with aryl substituents, which, according to the principle of restricted intramolecular motion, play a key role for fluorescence behavior of AIEgens. However, these peripheral aryl substituents create structural motifs, which undergo photoreactions (stilbenes, ortho-terphenyls, etc.). The sterically overcrowded molecules thus seek to relax their geometry by photoisomerization reactions, leading to energetically favored species. In this chapter, we will first give a brief overview of examples of perarylated AIE emitters vs. their non-AIE counterparts, then have a look at the photochemistry of stilbenes and ortho-terphenyls, dealing with their excited states and photochemistry, and discuss examples of photolabile AIEgens and the extent of their lability (hexaarylbutadienes, distyrylbenzene derivatives). Finally, we will have a look at strategies to stabilize these structural motifs, suppress the photocyclization, and look at the applicability to AIE active molecules.