The HOMO, LUMO (Figure In addition to describing the adsorption on the electrode, the energy level of the HOMO and LUMO is an excellent descriptor of the energy of binding into a complex (R 2 =0.70-0.95) and the distance between the solvent molecule and the ions (R 2 =0.36-0.98). In almost all the cases, the correlation coefficients are much better for the complexes than for the electrodes. Reducing the number of orbitals involved in the binding makes the complex formation easier and closer to theoretical models (paragraph 1).