Solvent effects on the solid-state electrochemistry of samarium (III) hexacyanoferrate (II)

An electroactive polynuclear inorganic compound of a rare earth metal hexacyanoferrate, samarium (III) hexacyanoferrate (II) (SmHCF), was prepared chemically. The electrochemical characteristics of SmHCF mechanically attached to the surface of a graphite electrode were studied in organic solvents, such as tetrahydrofuran, acetone and N,N-dimethylformamide, etc., using cyclic voltammetry and ac impedance. The cyclic voltammograms of SmHCF in organic solvent were well defined and exhibited a pair of redox peaks, which corresponded to the redox reaction of the Fe(II)/Fe(III) couple in SmHCF, and the redox reaction was accompanied by insertion of a counter-cation into the SmHCF during the reduction and its exclusion upon oxidation. The redox potentials increased linearly with the increase of the dielectric constant of solvents. The transport behavior of K+, Na+ and Li+ counter-cations through the ion channel of SmHCF were also studied by voltammetry.