Recognition of specific monosaccharides by fluorescence change through the suppression effect on excited-state intermolecular proton transfer reactions†

Pyrene–urea derivatives and acetate anions were used to investigate the excited-state intermolecular proton transfer (ESPT) reaction, where a molecule undergoes intermolecular proton transfer to form a tautomer species in the excited state. Since ESPT occurs when intermolecular hydrogen bonds exist between urea compounds and acetate species, we hypothesize that this reaction might be influenced by compounds with hydroxy groups. In this study, cyclodextrins, saccharides, and ethanol were examined to assess the effects of hydroxy groups on the ESPT reaction. After introducing various hydroxy compounds into the urea–acetate system in dimethylformamide, we observed differences in the fluorescence spectra and fluorescence decay curves. These differences indicate varying interactions between the hydroxy compounds and complexes, leading to distinct fluorescence lifetime behaviors, which makes fluorescence lifetime imaging technology particularly suitable.