Bimolecular fluorescence quenching of benzoxazole/benzothiazole-based functional dyes

Four dyes that belong to the group of hemicyanines and possess benzoxazole and benzothiazole moieties are synthesised and described. The spectroscopic properties of these compounds in 1-methyl-2-pyrrolidinone (MP) were studied. Synthesised dyes absorb in the UV–Vis region. The emission spectra are broad with a maximum located at approximately 500–520 nm. The deactivation of excited states of the synthesised molecules by various quenchers is also presented. The fluorescence quenching parameters were calculated using the Stern-Volmer equation. It was found, that the fluorescence quenching of the excited dye by quencher molecules occurs. The fluorescence quenching rates (kq) are about 1010 M−1 × s−1.