Calix[4arene 3, which contains two distal triazole groups on the lower rim and two distal o-methoxyphenylazo groups on the upper rim, was synthesized and found to be a specific and ratiometric sensor for Hg2+ in a polar protic solvent. A series of o-methoxyphenylazo derivatives (3, 4, 5, 7, and 9) were synthesized, which proved that the lower-rim triazoles and the hydroxyl azophenol(s) were the major ligands for metal ion binding. Though analogues 4 and 10 showed some sensitivity for Hg2+, compound 3 was the only ratiometric chemosensor for Hg2+ among the series of azocalix[4arenes synthesized in this work. The formation of 3·Hg2+ complex was supported by UV/vis and NMR titration studies and Mass spectrometry. Based on the symmetrical features of NMR spectra of 3·Hg2+, the complex is believed to be symmetrical with respect to the calix[4arene cavity. Furthermore, the complex was determined to be 1:1 binding stoichiometry by Job's plot, and the association constant was determined to be 4.02×10 3 M-1 using Benesi-Hildebrand plot.
- Click reaction
- Mercury ion