Reversible “off–on” fluorescent chemosensor for Hg2+ based on rhodamine derivative

A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg2+ with high selectivity. The structure of chemosensor 1 was characterized by IR, 1H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg2+ in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg2+ complex with the Hg2+-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg2+ ions and TBAI (tetrabutylammonium iodide) titration experiments.

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► We report a novel and simple fluorescent chemosensor 1 based on rhodamine.
► Chemosensor 1 shows unique selectivity for Hg2+ over other cations.
► The reversibility of 1 is demonstrated by the alternate addition of Hg2+ and TBAI.