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

•The dual mode chemosensor 3 for Hg2+, CN− and OH− has developed based on styrylbenzothiazolium.•The selective binding of Hg2+ leads to a visible color change in pink to colorless.•The selective binding of CN− and OH− leads to color change in red to colorless under 365-nm UV lamp.•Selective binding of Hg2+ pointers to ∼133 nm hypochromic (blue) shifts (λmax 516–383 nm).•Mode of binding site with anions were confirmed by the 1H NMR titration studies.

We report the design and synthesis of a novel styrylbenzothiazolium (3) derivative developed as a fluorescent and colorimetric chemodosimeter with high selectivity toward Hg2+, CN− and OH− ions. An obvious loss of pink color in the presence of Hg2+ 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 Hg2+ binding in a 1:1 stoichiometric ratio. More significantly, the styrylbenzothiazolium-Hg2+ and styrylbenzothiazolium-CN− complexes exhibited a dual-channel chromo-fluorogenic response. The sensors exhibit remarkable Hg2+-, CN−-, and OH−-selective red fluorescence but remain dark-green in the presence of a wide range of tested metal ions and anions.

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