Coumarin based colorimetric and fluorescence on-off chemosensor for F, CN and Cu ions.

(E)-4-Chloro-3-[{2-(4-nitrophenyl)hydrazono}methyl]-2H-chromen-2-one (C), a coumarin derivative has been studied toward its ion sensing properties for F, CN and Cu. A proton-transfer mechanism for F sensing has been deduced with the help of H NMR titration alongwith from the changes in the absorption and emission spectra of C in the presence of F. C formed 1:1 stoichiometric complex with each of these analytes. Sensing of C toward Cu is poor, but interestingly in the presence of For CN the sensing ability of Cu gets enhanced many folds, and C can act as For CN mediated off-on sensor for Cu. Moreover, colorimetric strip (pre-coated with the coumarin derived compound) tests for Fand CN from their DMSO solution at high temperature (100°C) opens up the door for easiest naked eye recognition and distinction of these ions, and also for naked-eye detection of F and CN from its aqueous solution at high temperature (100°C).