Thermodynamics of metal-ion cryptates and cryptand 222 in N,N-dimethylformamide and dimethyl sulphoxide

Abstract

Enthalpies of complexing of alkali-metal and silver cations with cryptand 222 in N,N-dimethylformamide and dimethyl sulphoxide have been determined using a calorimetric technique. A new set of data is reported for the enthalpy of complexing of Ag⁺ and Li⁺ cations with cryptand 222 in methanol.

Combination of the data with the free energy of complexing yields entropies of complexing for these cations with cryptand 222 in the solvents. Entropies of transfer of the gaseous metal ions to the solvated cryptand 222 to form the solvated cryptates in N,N-dimethylformamide and dimethyl sulphoxide are reported and compared with results obtained in methanol. Enthalpies, free energies and entropies of complexing for metal-ion cryptates in DMF and Me₂SO and for lithium and silver cryptates in methanol are combined with the corresponding parameters for complexing in water and with ΔH^⊖_t, ΔG^⊖_t and ΔS^⊖_t for the transfer of cryptand 222 and single ions from water to the respective solvents in order to obtain the thermodynamic parameters for the transfer of the metal-ion cryptates from water. Also reported are thermodynamic data for the transfer of cryptates from solvents other than water. The results indicate that for the transfer of metal-ion cryptates ΔG^⊖_t, ΔH^⊖_t and ΔS^⊖_t do not vary appreciably with the cation for transfer from Me₂SO to DMF.