A new chromogenic and fluorogenic chemosensor for Hg(II) with high selectivity based on the Hg2+-promoted deprotection of thioacetals

In this paper, a thioacetal chemosensor 1 incorporating simultaneously a carbazole moiety and an azobenzene moiety was synthesized. Among other metal ions , Hg 2+ proved to be able to selectively induce both color and fluorescence changes of 1 . The mechanism of Hg 2+ -promoted cleavage of thioacetal was confirmed by 1 H NMR experiments. Upon the addition of Hg 2+ into the yellow CH 3 CN/H 2 O solution of 1 , the resultant azobenzene-containing thioglycolamide was precipitated from the solution as a mercuric salt, leading to a colorless solution. Therefore, a novel color change pattern was developed.