Diaminomaleonitrile-based Fluorophores as Highly Selective Sensing Platform for Cu 2+

A colorimetric and turn-on fluorescent chemodosimeter 1 based on diaminomaleonitrile was synthesized for Cu 2+ detection. It showed high selectivity and sensitivity towards Cu 2+ 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 2+ 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 2+ 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 2+ -promoted hydrolysis reaction, which was confirmed by 1 H NMR, 13 C NMR and mass spectrum analysis. Studies on probe 2 were carried out to verify the universality of this sensing mechanism.