Fluorescence quenching of versatile fluorescent probes based on strongly electron-donating distyrylbenzenes responsive to aromatic chlorinated and nitro compounds, boronic acid and Ca2+

The fluorescence quenching behavior of two distyrylbenzenes (DSBs) newly prepared bearing strongly electron-donating groups was investigated. Several chlorinated and nitro compounds quench the fluorescence of both DSBs with various efficiencies depending on the electron-withdrawing properties; the strongly electron-withdrawing compound, such as 2,4,5-trichlorophenol and 2,4-dinitrofluorobenzene, effectively diminish the fluorescence intensities of the DSBs. The fluorescence quenching was also detected in the interaction between the azacrown DSB and phenylboronic acid, while the fluorescence recovers by adding triethylamine. These quenching phenomena are attributed to the photo-induced electron transfer (PET) process. On the other hand, the azacrown DSB selectively interacts with Ca2+ to decrease its fluorescence intensity, but the DSB with the dimethylamino groups did not. These results suggest a potential use of these types of compounds as sensors for strongly electron-withdrawing substances and a suitable metal cation.