Lower rim calix[4]arene derivatives: complexation with silver in non-aqueous media and extraction of this cation in the water–nitrobenzene solvent system

Abstract

The interaction of lower rim calix[4]arene containing aliphatic and alicyclic amines as pendant arms and the silver cation in a variety of solvents has been investigated. Conductance measurements indicate that the stoichiometry of the metal-ion complexes is 1:1 (ligand:metal cation) in these solvents. Using silver electrodes, direct potentiometric titrations were carried out at 298.15 K to derive the stability constants of these ligands and the silver cation in these solvents. The results are compared with previously reported data for this cation and a calix[4]arene derivative containing two different pendant arms alternately arranged, one of which contains an aliphatic amine substituent while the remaining one is a methylsulfanyl substituent. The extraction properties of calix[4]arene amine derivatives for the silver cation was investigated, from distribution data for silver(I) in the water–nitrobenzene solvent system at 298.15 K in the absence and in the presence of the ligand. Distribution data in the absence of the ligand were used to derive the partition, K_p, and the distribution, K_d, equilibrium constants for the silver(I) perchlorate in the mutually saturated solvents as well as the ion-pair formation constant, K_a, for this salt in nitrobenzene (saturated with water). K_d values were also obtained from distribution data for the silver salt in the presence of five different ligands. Equilibrium extraction constants, K_ex, for the various ligands also derived from these data are reported. Good agreement is found between the K_d values derived from experimental work carried out in the presence of the various ligands as well as in their absence.