Transfer activity coefficients of crown ethers and their alkali metal ion complexes between water and polar nonaqueous solvents

The stabilities of metal ion complexes with crown ethers in solutions are largely dependent on the solvation of each species involved in the complexation equilibria. The transfer activity coefficients of the solutes express the relative strength of solvation in different solvents, and are important for quantitative evaluation of the solvation. In this paper, the transfer activity coefficients between water and polar nonaqueous solvents (acetonitrile, propylene carbonate, methanol, N,N-dimethylformamide, and dimethyl sulfoxide), which we have so far determined for various neutral crown ethers and their alkali metal ion complexes, are reviewed. The effects of the structures of crown ethers on the solvation properties of the crowns and their complexes are also discussed.