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

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.