Design, synthesis and DFT analysis of a highly selective chromenylium based fluorescent probe for cellular imaging...

Sulfite (SO₃ ^2-) is a significant analyte that is frequently employed as a food and beverage sector preservative but its excessive consumption might lead to negative health effects. Therefore, it is important to develop ultra-sensitive and ultra-selective sulfite detection methods. Herein, we demonstrate the design, synthesis and application of a highly selective fluorescent probe for fast and sensitive detection of sulfite ions. The interaction between this probe and SO₃ ^2- ions induced a fluorescence signal (quenching) which made it possible to monitor the ions in a highly selective manner amongst various competing anions. Furthermore, the probe exhibited an excellent detection capability within a wide linear range and a high sensitivity with low detection limit (1.44 µM). Besides, the probe was applied for the analysis of sulfite ions in real samples as well as for cell imaging. Further validation of the suggested sensing mechanism was obtained from density functional theory (DFT) calculations, which showed substantial variation in the energy gaps between HOMO-LUMO, charge distribution, and intramolecular charge transfer (ICT). DFT calculations confirmed that the nucleophilic attack of SO₃ ^2- on the π-conjugated system of the probe causes inhibition of ICT and fluorescence quenching behavior. The above findings clearly highlight the efficiency of the designed probe as an analytical tool for detecting sulfite ions in the environment and food safety applications.