Thermodynamics of ZrO2+ cation complexation with dibenzo-18-crown-6 in mixed non-aqueous solvents

Abstract

The complexation reaction of dibenzo-18-crown-6 (DB18C6) with ZrO2+ cation was studied in some binary solvent solutions of acetonitrile (AN), 1,2 dichloroethane (DCE), nitromethane (NM) and ethylacetate (EtOAc) with methanol (MeOH), at different temperatures by conductometry method. The stability constant of the resulting 1:1 complex at each temperature was determined using a computer fitting conductance-mole ratio data. The results revealed that, the (DB18C6·ZrO)2+ complex is more stable in the EtOAc–MeOH binary mixed solvents compared with the other binary mixed solvent solutions. A non-linear relationship was observed for changes of log Kf of (DB18C6·ZrO)2+ complex versus the composition of the binary mixed solvents. The corresponding standard thermodynamic parameters (ΔH c ° , ΔS c ° ) were obtained from temperature dependence of the stability constant. The results show that the (DB18C6·ZrO)2+ complex is enthalpy destabilized but entropy stabilized and the values along with the sign of these parameters are influenced by the nature and composition of the mixed solvents.