Diaminomaleonitrile-based Fluorophores as Highly Selective Sensing Platform for Cu.

A colorimetric and turn-on fluorescent chemodosimeter 1 based on diaminomaleonitrile was synthesized for Cu detection. It showed high selectivity and sensitivity towards Cu over the other tested metal ions. Probe 1 in acetonitrile exhibited a strong absorption band at 530 nm and weak fluorescence emission when excited at 480 nm, while the addition of Cu could lead to a 30-nm blue shift of the absorption band and a remarkable fluorescence enhancement. Moreover, the detection limit of probe 1 for Cu was calculated to be 28 nM. Quite different from the reported mechanism based on a metal-complexation induced fluorescence enhancement, the sensing mechanism was proved to be based on the Cu-promoted hydrolysis reaction, which was confirmed by H NMR, C NMR and mass spectrum analysis. Studies on probe 2 were carried out to verify the universality of this sensing mechanism.