Synthesis and metal ion extraction of partial-cone di-ionizable p-tert-butylcalix[4]arene-1,2-crown-5 ligands with elongated acidic side arms

Abstract

Proton di-ionizable calix[4]arene-1,2-crown-5 ligands with elongated pendant side arms are synthesized in the partial-cone conformation. Solvent extraction studies probed the influence of elongated side arms and conformation toward various metal cations. Results of the solvent extraction experiments show that these compounds are poor extractants from aqueous solutions into chloroform for hard alkali metal cations and alkaline earth metal cations and intermediate Pb2+. For soft Hg2+, the ligands with N-(X)sulfonyl carbamoyl ionizable groups exhibit very good to excellent extraction efficiency. In general, the metal ion extraction behavior for the new partial-cone conformers is quite similar to that reported recently for their cone conformational isomers.