A new calix[4]arene derivative and its ionic recognition for silver(i) and mercury(ii): the solvent effect

Abstract

A new lower rim partially functionalized calix[4]arene, namely, 5,11,17,23-tetra-tert-butyl[25,27-bis(diethylthiocarbamoyl)oxy]calix[4]arene, 1 was synthesized and characterized by ¹H NMR in different deuterated solvents to assess the degree of solvent–ligand interactions and the conformation of 1 in solution. ¹H NMR, conductometric and thermodynamic investigations reveal that this receptor interacts only with silver(I) and mercury(II) in dipolar aprotic media. The complexation process has been thermodynamically characterized and the results are compared with the corresponding data (when available) involving analogous ligands and these metal cations in the appropriate solvent. Emphasis is made on the difference between ‘selective extraction’ and ‘selective ionic recognition’ by receptors. Final conclusions are given.