Solvents Influence On Thermodynamics Of Complexation Between Dibenzo 18-Crown-6 With Tl+, Cs+ And Uo22+ Cations In Pure Acetonitrile, Pure Dimethylesulfoxide And Acetonitrile-Dimethylesulfoxide Binary Mixtures By Conductometric Method

Abstract

The stability constants of 1:1 (M-L) complexes of Dibenzo-18-crown-6 (DB18C6) with Tl+, Cs+ and UO22+ cations have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and Tl+, Cs+ and UO22+ cations is 1:1 (M:L). GENPLOT computer program used to find the stability constants of the complexes were obtained from fitting of molar conductivity curves. The selectivity order of DB18C6 for the metal cations changes with the nature and composition of the binary mixed solvent. We also determined the Gibbs standard free energies (∆G0), the standard enthalpy changes (∆H0) and standard entropy changes (∆S0) for formation of these complexes in acetonitrile – dimethylesulfoxide (AN-DMSO) binary mixtures for the complexation. The values of standard enthalpy changes (∆H0 ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy (∆S0) were calculated from the relationship ∆G0298.15 = ∆H0 - 298.15 ∆S0.