Novel styrylbenzothiazolium dye-based sensor for mercury, cyanide and hydroxide ions

We report the design and synthesis of a novel styrylbenzothiazolium (3) derivative developed as a fluorescent and colorimetric chemodosimeter with high selectivity toward Hg(2+), CN(-) and OH(-) ions. An obvious loss of pink color in the presence of Hg(2+) and CN(-) ions could make it a suitable "naked eye" indicator. We propose a sensing mechanism whereby the benzenoid form is changed to a quinoid form upon Hg(2+) binding in a 1:1 stoichiometric ratio. More significantly, the styrylbenzothiazolium-Hg(2+) and styrylbenzothiazolium-CN(-) complexes exhibited a dual-channel chromo-fluorogenic response. The sensors exhibit remarkable Hg(2+)-, CN(-)-, and OH(-)-selective red fluorescence but remain dark-green in the presence of a wide range of tested metal ions and anions.