A turn-on AIE active fluorescent sensor for Hg2+ by combination of 1,1-bis(2-pyridyl)ethylene and thiophene/bithiophene fragments

Abstract

Fluorescent sensors for Hg2+ that combine aggregation-induced emission (AIE) activity of tetraarylethylenes with metal chelating 1,1-bis(2-pyridylethylene) fragments and thiophene/bithiophene substituents have been prepared and characterized. The sensors exhibit red-shifted and enhanced emission in the presence of Hg2+ in aqueous solution while exhibiting little to no change in fluorescence in the presence of other metal ions. Job plot analyses indicate 2:1 sensor:Hg2+ binding stoichiometries in solution. 1H-NMR spectroscopy was also employed to investigate solution phase binding interactions between the sensors and Hg(ClO4)2, and a chelated HgI2-bis(pyridyl) complex has been characterized by X-ray crystallography. The limit of detection for Hg2+ was determined to be 48 nM. In contrast, the fluorescence of structurally analogous materials possessing quinoline rings in place of pyridine groups is completely quenched in the presence of Hg(ClO4)2. The high sensitivity and selectivity displayed by these sensors for Hg2+ over other metal ions may enable monitoring of mercury in aqueous environments.