A benzoxadiazole–thiourea conjugate as a fluorescent chemodosimeter for Hg(II) in aqueous media

A benzoxadiazole–thiourea conjugate (1) was synthesized and used for chemodosimetric detection of Hg2+ in aqueous media. The compound 1 shows a selective and quantitative fluorescence quenching upon addition of Hg2+. This is promoted via a Hg2+-induced desulfurization of the thiourea moiety, leading to a formation of an imidazoline derivative, 2. Ab initio molecular orbital calculation reveals that the formation of imidazoline moiety by the reaction of 1 with Hg2+ promotes a photoinduced electron transfer from the aniline moiety to the excited state benzoxadiazole moiety and results in fluorescence quenching.

Graphical abstractA benzoxadiazole–thiourea conjugate (1) shows selective and quantitative fluorescence decrease upon Hg2+ addition in aqueous media. The fluorescence decrease is promoted by a Hg2+-induced desulfurization of the thiourea moiety, leading to a promotion of intramolecular photoinduced electron transfer from the aniline moiety to the excited state benzoxadiazole moiety.Figure optionsDownload full-size imageDownload as PowerPoint slide