A simple coumarin-based colorimetric and ratiometric chemosensor for acetate and a selective fluorescence turn-on probe for iodide

► Colorimetric and ratiometric anion chemosensor of phenylhydrazone-coumarin moiety. ► Red shifted peak resulting from the π−π⁎ transition. ► Redox reaction between iodide and Cu2+. ► Fluorescence turn-on sensing of iodide.