Full-color emission of fluorinated benzothiadiazole-based D–A–D fluorophores and their bioimaging applications

There is an active demand for full-color fluorophores in the field of fluorescent dyes. However, a core skeleton with a simple structure and easy modification is currently insufficient. Herein, we develop a range of full-color-tunable fluorophores 3a–3m based on the fluorinated benzothiadiazole skeleton and their control compounds 3n–3p. By regulating the charge transfer strength between donors and acceptors, the emission colors of 3a–3p spanning from blue to red (λem = 445–672 nm) are achieved. Interestingly, compounds 3a–3p with a fluorinated core skeleton exhibit sensitive solvatochromism effects, large Stokes shifts and excellent dual-state emission (especially 3c–3k). Meanwhile, with the control of different substituents in the donor structure, ACQgens (3a–3i and 3n–3p) can be facilely tuned to AIEEgens (3j–3m). Notably, red AIEEgen 3m shows great potential for bioimaging in live cells with low cytotoxicity.