Synthesis and application of methylthio-substituted BODIPYs/aza-BODIPYs

A series of new BODIPYs/aza-BODIPYs with a methylthio group were Herein prepared. Introduction of the electron-donating methylthio substituent into such dyes could reduce the fluorescence quantum yield, red-shift its emission spectra, provide higher extinction coefficients and larger Stokes' shift. Oxidation of the thioether of BODIPY 4 into the corresponding electron-withdrawing sulfoxide by HClO can restore the quantum yield and blue-shift its emission spectra, and dye 4 was highly sensitive and selective to HClO.