Controlling Aggregation and Excited-State Intramolecular Proton Transfer in BODIPYs by Incorporation of 2-(2-Hydroxyphenyl)quinazoline and Variation of Substituents

Abstract

A series of BODIPY-based AIEgens (QB1-QB5 and Bis-QB) containing 2-(2-hydroxyphenyl)quinazoline have been synthesized and thoroughly characterized. Photophysical properties of these compounds in solution and the aggregated state have been meticulously investigated and fine-tuned via structural modifications. These display green emission (∼530 nm) in solution and bright red emission (600-655 nm) in the aggregated/solid state with increased quantum yield. Crystal structure analyses and spectral studies revealed efficient J-type aggregation in these derivatives. Significant impact of 2-(2-hydroxyphenyl)quinazoline toward modulating intermolecular interactions and facilitating J-type stacking between BODIPY units has also been established. Moreover, the essential role of excited-state intramolecular proton transfer (ESIPT) in inducing emission in the aggregated state and tuning of ESIPT emission by variation of substituents have been supported by various studies. Copyright © 2020 American Chemical Society.