A thallium-205 NMR study of thallium acetate ion association in 2,2,2-trifluoroethanol and dimethylsulfoxide

The association of thallium acetate ion in 2,2,2-trifluoroethanol and dimethyl-sulfoxide has been investigated by thallium-205 NMR spectroscopy. Analysis of the association constants as a function of temperature indicates that in trifluoroethanol the association enthalpy and entropy are, respectively, 1.6 kcal-mol^–1 and 19.3 cal-mol^–1-K^–1 and in dimethylsulfoxide they are-0.99 kcal-mol^–1 and 18.0 cal-mol^–1-K^–1. Examination of the temperature dependence of the chemical shift of the ion-pair reveals that in dimethylsulfoxide the ion-pair exists as a contact species, while in trifluoroethanol the solvent-separated ion-pair is more likely.