Synthesis and mechanism study of two similar colorimetric fluorescent probes for specific detection of bisulfite and hypochlorite

Based on coumarin structure, two fluorescent probes (L1 and L2) were constructed for specific detection of bisulfite (HSO3-) and hypochlorite (ClO-). Electron deficient carbon-carbon double bond and acidic proton were introduced to regulate the performance of two fluorescent molecules. Both L1 and L2 displayed high selectivity and sensitivity, low detection limit (28.2, 52.0 nM), fast response time and visible color change after addition of HSO3- or ClO-. Different techniques including H-1 NMR analysis, high-resolution mass spectrometry and density functional theory calculations were used to confirm our conception and to get insight into the interaction of receptors with anions. Furthermore, probe L1 was successfully applied to monitor the level of HSO3- in sugar samples and real water samples.