A Novel Calix[4]Crown-Based 1,3,4-Oxadiazole as a Fluorescent Chemosensor for Copper(II) Ion Detection.

The synthesis and characterization of a novel florescent chemosensor with two different types of cationic binding sites have been reported in this work, which is a calix[4]crown derivative in 1,3-alternate conformation bearing two 2-phenyl-5-(4-dimethylaminopyenyl)-1,3,4-oxadiazole units. The recognition behaviors of in dichloromethane/acetonitrile solution to alkali metal ions (Na and K), alkaline earth metal ions (Mg and Ca), and transition metal ions (Co, Ni, Zn, Cd, Cu, Mn, and Ag) have been investigated by UV-Vis and fluorescence spectra. The fluorescence of might be quenched selectively by Cu due to the photo-induced electron transfer mechanism, and the quenched emission from could be partly revived by the addition of Ca or Mg; thus, the receptor might be worked as an on-off switchable fluorescent chemosensor triggered by metal ion exchange.