Oxazine-thione-based Colorimetric Fluorescent OFF-ON Probes for Hg2+ Recognition

Two colorimetric probes based on oxazine-thione 1a and 1b for the detection of Hg2+ were designed and synthesized. The probe 1a exhibits about a 70-fold enhancement in fluorescence and a color change after the addition of Hg2+ in acetonitrile/wate solvent. 1a was also highly selective to Hg2+ over other metal ions. Furthermore, DFT/TDDFT calculations were taken to explain the OFF-ON emission response.