Selective detection of Hg(II) with benzothiazole-based fluorescent organic cation and the resultant complex as a ratiometric sensor for bromide in water

A benzothiazole-based receptor conjugated with an imidazolium cation, receptor N1, was synthesized. Receptor N1 is capable of selectively binding Hg(II) in the presence of other metal ions in water, with a large enhancement in fluorescence intensity at 380 nm via a PET mechanism. The resulting Hg(II) complex of receptor N1 showed a selective ratiometric response upon addition of Br^- ions. The Hg(II) complex of receptor N1 was used to determine the concentration of Br^- ions in the presence of other anions, with a detection limit of 22 nM. ¹H NMR studies showed that the imidazolium hydrogen in the Hg(II) complex of receptor N1 participates in the recognition of Br^- ions. In the absence of Hg(II), receptor N1 did not recognize Br^- ions.