Synthesis of alkyl nitrile and alkyl benzonitrile derivatives of calix[4]arene and their polymer supported analogues: A comparative study in two-phase extraction systems

The article describes the synthesis and extraction properties of new alkylnitrile and alkylbenzonitrile substituted calix[4]arene based polymers. These compounds have been synthesized via nucleophilic substitution reactions involving 5,11,17,23-tetra-tert-butyl-25,27-bis-(cyanomethoxy)-26,28-dihydroxycalix[4]arene (2a), 5,11,17,23-tetra-tert-butyl-25-(2-cyanobenzyloxy)-26,27,28-trihydroxycalix[4]arene (3a), or 5,11,17,23-tetra-tert-butyl-25,27-bis-(2-cyanobenzyloxy)-26,28-dihydroxycalix[4]arene (4a), with Merrifield's resin (0.8 mM Cl/1.0 g resin). The two-phase extraction properties of ligands 2a-4a along with their polymers 2b-4b toward the selected metal cations and dichromate (HCr2O7-/Cr2O72-) anions are reported. Extraction studies with monomer 2a show selectivity for Hg2+, where as monomers 3a and 4a are selective for Cd2+ and Hg2+ cations. Nevertheless, due to the higher oxidative stability of nitrile groups, polymers 2b-4b have been developed as good extractants for transferring the selected metal cations and dichromate (HCr2O7-/Cr2O72-) anions from an aqueous into a dichloromethane phase.