An effective Hg2+-Selective fluorescent chemosensor based on a calix[4]arene bearing four dansyl amides

A new calix[4]arene-based fluorescent chemosensor bearing- four dansyl amides on the upper rim (1) was conveniently synthesized. which showed hi-h sensitivity and selectivity toward Hg2+ over a wide range of metal ions in 50% aqueous acetonitrile. The complexation of Hg2+ ion induced a strong fluorescence quenching of 1 due to a well-defined electron transfer process from the dansyl group(s) to the metal center. Compared with compounds 2 and 3. tetradansyl amide substituted calix[4]arene 1 showed a preorganized and coordinated complexing site for metal ions. Moreover, the detection limit for Hg2+ was found to be 3.41 X 10(-6) mol center dot L-1, which might make 1 a potentially practical Hg2+-selective fluorescent sensor in aqueous system.