Construction and evaluation of ratiometric fluorescent probes based on a 7-aminocoumarin scaffold for the detection of SO₂ derivatives

As a signal molecule, SO₂ participates in many complex physiological processes. Therefore, in view of the addition properties of SO₂ derivatives to unsaturated olefins, we reasonably designed a set of ratiometric fluorescent probes (NB1, NB2, NB3), and evaluated the influence of the coumarin moiety on the optical properties of the probes. Amongst the probes when the 7-position is substituted by a fused quinolizine (julolidine) unit, the probe NB2 shows a change from red to green fluorescence upon reaction with SO₂, and has excellent optical properties: 136 nm emission band gap, 230 s response time, high selectivity, and excellent sensitivity. More valuable is the fact that NB2 can be used in cell imaging experiments, real sample detection, and employed to prepare fluorescent test paper for the qualitative test of SO₂ gas, indicating that NB2 can be used as a powerful tool for the detection of SO₂ derivatives.