A versatile approach toward chemosensor for Hg2+ based on para-substituted phenylazocalix[4]arene containing mono ethyl ester unit

•In this study, azocalix[4]arene mono ethyl ester derivatives were synthesized.•Azocalix[4]arene derivatives have showed a good selectivity toward Hg2+ and Hg+ ions.•These compounds could be applied for the selective extraction of Hg2+ ions from environmental waters.

In the present study, six new azocalix[4]arenes have been synthesized by reacting calix[4]arene with p-substituted aniline and ethyl bromoacetate. Characterization of these compounds has been used by elemental analyses, UV–Vis, FT-IR and 1H NMR spectroscopic studies. Their phase transfer studies have been performed by using liquid–liquid extraction procedure. With respect to the chromogenic behavior of hosts upon metal ion complexation, mono ethyl ester azocalix[4]arene derivatives have shown a significant selectivity toward Hg2+ and Hg+ over many other cations. It has been deduced that these new compounds are selective ionophores toward metal cations (Na+, K+, Sr2+, Ag+, Hg+, Hg2+, Co2+, Ni2+, Cu2+, Zn2+, Cr3+, Al3+ and La3+).

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