Single-ion transfer properties and solvent parameters

Studies on the temperature dependences of polarographic half-wave potentials and electrode potentials in nonisothermal cells allowed the estimation of entropies of transfer of cations from acetonitrile in up to 22 solvents. Gibbs energies of transfer were obtained from electrochemical measurements employing bis(biphenyl)chromium(I)/(0) as a reference redox system. Combining the Gibbs energies of transfer with the 298K $ \Delta \ _t$ S°-values resulted in enthalpies of transfer for cations. Transfer properties for anions are available from the tetraphenylarsonium tetraphenylborate assumption. Gibbs energies of transfer for cations and also for anions are accounted for in a donor-acceptor (coordination) model including the principle of hard and soft acids and bases. These values are also a suitable data base to abtain and to evaluate solvent parameters, which either reflect tha hard or soft donor properties or the acceptor properties of solvents. Since no solvent parameter for the transfer entropies of cations could be found, parameters for the transfer entropies are proposed.