Linearities in Gibbs energies of transfer of alkali metal cations between two solvents and a new aspect of resolvation related to gas phase data

A reported set of data on Gibbs energies of transfer of alkali metal cations between pure solvents Delta(t)G degrees(i) was analyzed in terms of linearities Delta(t)G degrees = a(S) + b(S) Delta G(hydr)(0)(i). Propylene carbonate was chosen as a reference solvent. After reasonable correction of a numerical value of Delta G(solv)(0)(Rb+) in propylene carbonate and adding data from other literature source for the transfers between propylene carbonate and nitromethane, good straight line correlations with r = 0.98-0.99 were obtained for 15 solvents. Straight lines mostly intersect near the region of Delta(t)G degrees(i) = 0 and Delta G(hydr)(0)(i) = -200 KJ/mol and b(S) coefficients correlate roughly with donor numbers of solvents. Gibbs energies of formation of small clusters in gas phase in water and acetonitrile show the same linear pattern as transfer values when plotted against Delta G(hydr)(0)(i) values. The pronounced tendency of the first two to three clusters to form a "future" 1:4 ion/solvent solvate of a saturation type is apparent. New scale of softness, proposed in the paper, is compared with previously proposed scale.