Statistical evaluations of single-ion Gibbs energies of transfer

A statistical approach for the evaluation of single-ion Gibbs energies of transfer of the cations Li+, Na+, K+, Rb+, Cs+, Ba2+, Ag+, Tl+, Cu+, Zn2+, Cu2+, Cd2+, Hg2+ and Pb2+ into 40 solvents based on the principal component analysis is presented. It is shown that the Gibbs energies of transfer depend both on the nature of the cation and on the donor site of the respective solvent molecule. Correlation of the data for the investigated cations required separating the solvents into subgroups according to their donor atoms in the solvent molecule. Gibbs energies of transfer into oxygen donor solvents could be correlated with the Born term [N-L(z(i)e(0))(2)/(8 pi epsilon(0)r(i))]. Several cation parameters were investigated with respect to the transfer data into nitrogen and sulfur donor solvents. No correlations were found. Thus the use of cation parameters derived from the statistical analysis are proposed to account for the Gibbs energies of transfer into nitrogen and sulfur donor solvents.