A multi-responsive crown ether-based colorimetric/fluorescent chemosensor for highly selective detection of Al, Cu and Mg.

A novel multi-response chemosensor L based on coumarin-chalcone-crown ether was designed and synthesized, which exhibited a high selectivity for the colorimetric detecting Al and Cu and fluorescent recognizing Al and Mg in ethanol. L can monitor Al and Cu via distinct color changes from a slight yellow to pink and to orange, respectively. The sensor L can also monitor Al and Mg by fluorescence emission responses at 592 nm and 547 nm with low detection limits of 0.31 μM and 0.23 μM, respectively. The selectivity of L toward Al, Cu and Mg was not interfered by a large number of coexisting ions and was found to be reversible. By means of spectrometric titration, Job's plot, mass spectrometry, H NMR titration and IR spectroscopy analysis, it was unanimously confirmed that the sensor L had a stoichiometric ratio of 1:1 with Cu and Mg, and 1:2 with Al. The order of the stability of the complexes formed by L and Al, Cu, Mg was as follows: L-Al > L-Cu > L-Mg. At the same time, some possible bonding modes and sensing mechanisms were further proposed, and the optimized structure of the sensor L and its sensing mechanism for Al, Cu and Mg were confirmed by the calculations of DFT/B3LYP and TD-DFT methods in a suite of Gaussian 09 programs.