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

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, Kp, and the distribution, Kd, equilibrium constants for the silver(I) perchlorate in the mutually saturated solvents as well as the ion-pair formation constant, Ka, for this salt in nitrobenzene (saturated with water). Kd values were also obtained from distribution data for the silver salt in the presence of five different ligands. Equilibrium extraction constants, Kex, for the various ligands also derived from these data are reported. Good agreement is found between the Kd values derived from experimental work carried out in the presence of the various ligands as well as in their absence.