Aggregation-enhanced emission enables phenothiazine coumarin as a robust ratiometric fluorescent for rapid and selective detection of HClO.

By taking advantage of phenothiazine moiety as an electron-donating group, a novel donor-acceptor (D-A) type coumarin dye, PTZ-Et, was developed. The introduction of phenothiazine moiety not only caused emission red-shifting and Stokes shift enlarging, but also endowed PTZ-Et with significant aggregation-enhanced emission (AEE) features, thereby enabled PTZ-Et as a robust ratiometric fluorescent probe for HClO detection. Upon oxidation of the sulfur atom on phenothiazine into sulfoxide, PTZ-Et displayed remarkable ratiometric fluorescence response (over 150 folds variations of F 534 /F 626) toward HClO with rapid response time (<30 s) and ultra-sensitivity (LOD = 15 nM). Additionally, the corresponding sensing mechanism of PTZ-Et for HClO was fully elucidated through the successful purification and well characterization (1H NMR, 13C NMR, HRMS, and single crystal data) of the corresponding reaction product between PTZ-Et and HClO. Significantly, PTZ-Et was capable of monitoring both exogenous and endogenous HClO in living RAW 264.7 cells by ratiometric fluorescence imaging. A novel fast responsive ratiometric fluorescent probe for HClO based on phenothiazine coumarin scaffold was developed. Image 1 • A novel AEE active phenothiazine coumarin, PTZ-Et, was developed as a robust ratiometric fluorescent probe for HClO. • PTZ-Et exhibited well ratiometric fluorescence variations with rapid response time and sensitivity in response to HClO • The sensing mechanism of PTZ-Et for HClO was investigated, and the single crystal of the reaction product was obtained. • The application of PTZ-Et to visualize both exogenous and endogenous HClO in RAW 264.7 cells was successfully achieved. [ABSTRACT FROM AUTHOR]