Spectrophotometric and electrochemical behavior of a novel azocalix[4]arene derivative as a highly selective chromogenic chemosensor for Cr+3

Abstract In this study, a novel azocalix[4]arene derivative, 5,11,17-tris[(1-naphtyl)azo]-25,26,27,28-tetrahydroxy-calix[4]arene ( NAC4 ) bearing napthyl groups on the upper rim was synthesized. Its complexation behavior for alkali, alkaline-earth and various heavy metal ions (Li + , Na + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Pb 2+ , Hg 2+ , Ni 2+ , Cd 2+ , Cu 2+ , Zn 2+ , Co 2+ , Fe 2+ , Cr 3+ , Ag + ) was investigated by spectroscopic and voltammetric methods. This chemosensor exhibits decreased absorbance in the presence of Hg 2+ and a unique absorbance quenching effect only for Cr 3+ . In addition, a new absorption band centered at 565 nm with the formation of the 1:1 host–guest complex (Cr 3+ - NAC4 ) was observed in the case of Cr 3+ , leading to an obvious color change from light orange to dark lilac. In voltammetric experiments, Cr 3+ ions decreased voltammetric peaks of NAC4 , whereas no significant changes occurred in the presence of the other metal ions. The Benesi–Hildebrand method was used to determine a logarithmic value of 3.76 for the association constant of the complex between Cr 3+ and NAC4 .