An off-on chemosensor for Hg2+ based on the excimer emission of anthracene

A quinazoline derivative 6-anthracenyl-5,6-2H-benzimidazo[1,2-c]quinazoline (L) was obtained and characterized by elemental analysis, IR spectroscopy, H-1 NMR and single-crystal X-ray diffraction. L shows very weak emission in DMSO, but can respond to Hg2+ ion intensively in off-on mode. Job's plot and titration experiments show that Hg2+ ion binds L in 1:1 stoichiometry. The detection limit for Hg2+ is 6.34 mu M. H-1 NMR titration experiments indicate that only one benzimidazo nitrogen atom coordinates with Hg2+. And the fluorescence emission spectra imply that an excimer formed in the Hg2+-L system, and the detection of Hg2+ was realized by excimer emission of anthracene moiety.