A multi-responsive crown ether-based colorimetric/fluorescent chemosensor for highly selective detection of Al3+, Cu2+ and Mg2.

ABSTRACT

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 Al3+ and Cu2+ and fluorescent recognizing Al3+ and Mg2+ in ethanol. L can monitor Al3+ and Cu2+ via distinct color changes from a slight yellow to pink and to orange, respectively. The sensor L can also monitor Al3+ and Mg2+ 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 Al3+, Cu2+ and Mg2+ 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, 1H NMR titration and IR spectroscopy analysis, it was unanimously confirmed that the sensor L had a stoichiometric ratio of 11 with Cu2+ and Mg2+, and 12 with Al3+. The order of the stability of the complexes formed by L and Al3+, Cu2+, Mg2+ was as follows L-Al3+ > L-Cu2+ > L-Mg2+. 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 Al3+, Cu2+ and Mg2+ were confirmed by the calculations of DFT/B3LYP and TD-DFT methods in a suite of Gaussian 09 programs.