Molecular Engineering of α-Substituted Acrylate Ester Template for Efficient Fluorescence Probe of Hydrogen Polysulfides.

In this article, hydrogen polysulfide (H2Sn)-mediated Michael addition/cyclization cascade reactions toward acrylate ester analogues were exploited and utilized to construct novel and robust H2Sn-specific fluorescence probe for the first time. Through rational molecular engineering of the α-substituted acrylate ester template, the optimal candidate probe FP-CF3 containing trifluoromethyl-substituted acrylate ester group as recognition unit and 3-benzothiazol-7-hydroxycoumarin dye BHC as signal reporter can highly selectively detect H2Sn over other reactive sulfur species, especially biothiols including cysteine (Cys) and homocysteine (Hcy)/glutathione (GSH), with a rapid and significant turn-on fluorescence response (less than 60 s for response time and over 44-fold for signal-to-background ratio). The fast response and high selectivity of FP-CF3 for H2Sn could be attributed to a kinetically and spatially favored pentacyclic addition produced by the dual nucleophilic reaction of H2Sn with the CF3-substituted acrylate group. The big off-on fluorescence response is due to the pentacyclic intermediate results in the release of the highly fluorescent BHC. Moreover, it has been successfully applied in imaging of endogenous H2Sn fluctuation in living cells.