Novel, triphenylamino benzothiazole-based excited-state intramolecular proton transfer (ESIPT) and non-ESIPT fluorophores were prepared by Suzuki coupling reactions. Their photophysical properties in solution, aqueous suspension, and in the solid state were systematically investigated. High fluorescence quantum efficiencies (Φsol≈95 %; Φsolid≈88 %), moderate Stokes shifts (≈8000 cm−1), microenvironment-sensitive and molecular-framework-dependent emission are the striking features of the protocol described here. Solid-state emission was modulated and interpreted as a crossover effect of π–π interactions using single-crystal X-ray analyses. The nonplanar/twisted framework of the system helps to avoid noncovalent interactions, facilitating the suppression of fluorescence quenching in the solid state with high quantum efficiency over 88 %.
- aggregation-induced emission
- excited-state intramolecular proton transfer
- molecular packing