Thermodynamic study of the complexation of p-isopropylcalix[6]arene with Cs + cation in dimethylsulfoxide-acetonitrile binary media

Abstract

The complexation reactions between the macrocyclic ionophore, p-isopropylcalix[6]arene and Cs + cation were studied in dimethylsulfoxide-acetonitrile (DMSO-AN) binary non-aqueous solvents at different temperatures using a conductometry method. The conductance data show that the stoichiometry of the (p-isopropylcalix[6]-arene•Cs) + complex in all binary mixed solvents is 1:1. The stability of the complexes is affected by the composition of the binary solvent media and a nonlinear behavior was observed for changes of log Kf of the complex versus the composition of the binary mixed solvents. The thermodynamic parameters (ΔH° c and ΔS° c) for formation of (p-isopropyl-calix[6] arene•Cs) + complex were obtained from temperature dependence of the stability constant and the obtained results show that the (p-isopropylcalix[6]arene•Cs)+ complex is enthalpy destabilized, but entropy stabilized, and the values of the mentioned parameters are affected strongly by the nature and composition of the binary mixed solvents. © 2011 by The Authors.