Acridine-derivated receptor for selective mercury binding based on chelation-enhanced fluorescence effect

In this study, 9-acrylamidoacridine (VAc) was synthesized by the reaction of 9-aminoacrydine (Ac) and acryloyl chloride and characterized by elemental analysis, FTIR, NMR spectroscopy. The photophysical properties of VAc were elucidated by UV-vis and fluorescence measurements and quantum yield in ethanol was calculated ( ^ΦF=0.15). We have found that VAc exhibited selective fluorescence enhancement upon titration with Hg ²⁺ ion in buffered aqueous-ethanol solution (1:1, v/v) at pH 6.0, whereas the fluorescence emission of VAc was quenched upon addition of other divalent transition-metal ions. Further, pH-dependent change in fluorescent property of VAc was observed and pKa value was determined using data of integrated emission intensity versus pH. This unique property allows the evaluation of both pH of the solution and the selective recognition of Hg ²⁺ ion among the other metal ions. In addition, the stoichiometry of complex between VAc and Hg ²⁺ ion was elucidated as VAc- Hg ²⁺ ₂(1:2) applying by spectrofluorometric titration, and association constant was calculated as to be K=1.42×10 ⁸ M ^-2.