Synthesis and Properties of a Water-soluble Fluorescent Probe Based on ICT System for Detection of Ultra-trace SO₂ Derivatives

SO₂ and its derivatives are widely present in the environment and living organisms, endangering the environment and human health. Therefore, it is of great significance for the effective detection of sulfur dioxide (SO₂) and its hydrated derivatives (HSO₃^- /SO₃^2-). In this study, based on the mechanism of intramolecular charge transfer (ICT), a water-soluble colorimetric fluorescent probe (E)-2-(4-acetamidostyryl)-3-(5-carboxypentyl)-1, 1-dimethyl-1H-benzo[e]indol-3-ium (ABI) for the detection of SO₂ derivatives was successfully synthesized from p-acetaminobenzaldehyde by connecting the benzo[e]indoles cationic fluorophore containing highly activated methyl via C = C double bond, and the ABI structure was characterized by HRMS and ¹H NMR, ¹³ C NMR. Studies have shown that the ABI probe has some advantages such as good selectivity for SO₂ derivatives, high sensitivity (detection limit LOD = 14.9 nM), and fast reaction rate. After adding HSO₃^-, the color of the probe solution changed from light yellow to colorless within 10 s, which provides a simple way to identify bisulfite with the naked eye. Studies on the effect of pH on the fluorescence performance of ABI showed that fluorescence performance of ABI was stable in the range of pH (7.0-10.26). Therefore, ABI is expected to become an effective tool for detecting SO₂ derivatives in cells and organisms in the future.