Tetradiazo(o-carboxy)phenylcalix[4]arene for determination of Pb 2+ ion

Abstract

A new azocalix[4]arene, 5,14,17,23-tetra[(2-benzoic acid)(azo)phenyl] calix[4]arene (2), has been prepared by hydrolysis of its ester derivative and characterized by 1H NMR, IR, UV-Vis spectroscopy and elemental analysis. Based on UV spectral changes, we found that 2 exhibits Pb2+ ion selectivity. In basic media, Pb2+ forms a 1:1 complex with the ligand. Beer's law is obeyed in the range of 2.0 x 10-6 - 2.4 x 10-5 mol L-1 of Pb2+. The molar absorptivity (ε) of 2-Pb2+ complex is 1.89 x 104 L mol -1 cm-1 at 440 nm, and the detection limit is 1.6 x 10-6 mol L-1.