Synthesis of tetra-substituted calix[4]arene ionophores and their recognition studies toward toxic arsenate anions

The article displays the synthesis of a family of novel tetra-substituted calix[4]arene ionophores bearing furyl, phenyl, and pyridyl units in the cone conformation. In the synthesis, the lower rims of calix[4]arene scaffold were modified in order to establish the influence of the molecular structure of calixarene on recognition of toxic anions as arsenate by liquid–liquid extraction process. In addition, the effects of solvent, solution conditions (mainly pH), and counter ions (Cl−, −NO3NO3−, and SO42−SO42−) on the extraction abilities of the ionophores were studied. From the liquid–liquid phase extraction studies, it was observed that the structures of the tetra-substituted calix[4]arenes influenced the extraction percentage of selected toxic anion. Also, thermodynamic parameters, such as the free energy (ΔG°) and enthalpy (ΔH°) indicated an exothermic nature of extraction and a spontaneous and favorable process.

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