Syntheses and photophysical properties of axially chiral thiazolothiazoles: Multi-stimuli-responsive fluorescence and circularly polarized luminescence

The synthesis, characterization, single crystal X-ray diffraction structures and photophysical and chiroptical properties of a novel series of binaphthol-substituted thiazolothiazoles are reported. The introduction of two binaphthol groups can help to achieve not only axial chirality but also helical molecule arrangements. Their charge contributions, transition processes (π−π* transition and/or donor-acceptor charge transfer) and excited-state intramolecular proton transfer properties are highly depend on alkyl-protecting groups at naphthol units. They exhibit good thermal and anti-photobleaching stabilities and strong blue fluorescence with quantum yields up to 0.40 in solution and polymer film and can be potentially used in the circularly polarized luminescence (CPL), ion sensing, vapochromism (HCl and NH vapor; pH-triggered chiroptical switch with CPL sign reversal) and thermochromism (fluorescence at 298 K and phosphorescence at 77 K) applications. Therefore, the present work affords a new platform in designing multi-stimuli-responsive chiral organic dyes.