Enthalpies and entropies of complexation of cryptand 222 and metal ions in propylene carbonate and acetonitrile. Derived thermodynamic parameters for the transfer of metal-ion cryptates

Abstract

Enthalpies of complexing of alkali-metal and silver cations in propylene carbonate (PC) and acetonitrile (AN) have been obtained and are compared with corresponding data in N,N-dimethylformamide and dimethylsulphoxide.A correlation is found between the single-ion enthalpy for the transfer of a given cation between two dipolar aprotic solvents and the differences between the heats of complexing of the same cation with cryptand 222 in these solvents.The free energy and entropy of complexing in PC and AN have been obtained and the relevant data are used for the calculation of the thermodynamic parameters of transfer of metal-ion cryptates from water to PC and AN and from PC to a number of dipolar aprotic solvents. The results indicate that no appreciable variation is observed in the ΔG⊖t, ΔH⊖t and ΔS⊖t values for the different metal-ion cryptates in their transfer among dipolar aprotic solvents.