Lutetium bis(tetra-tert-butylphthalocyaninato): a superior redox probe to study the transfer of anions and cations across the water/nitrobenzene interface by means of square-wave voltammetry at the three-phase electrode

The redox properties of lutetium bis(tetra-tert-butylphthalocyaninato) (LBPC) have been studied in nitrobenzene that is deposited as a microfilm on the surface of highly oriented pyrolytic graphite electrodes. The behavior of the modified electrode, which is immersed in an aqueous electrolyte solution, is typical for the three-phase electrode (Scholz, F.; Komorsky-Lovri?, S.; Lovri?, M. Electrochem. Comm. 2000, 2, 112-118). LBPC can be both oxidized and reduced in one electron reversible processes. The oxidation and the reduction of LBPC at the graphite/nitrobenzene interface is accompanied by the transfer of anion or cation, respectively, from the aqueous phase into the organic layer. Thus, using LBPC as a redox probe for the three-phase electrode, the transfer of both anions and cations across the water/nitrobenzene interface can be studied in a single experiment. The hydrophobicity of LBPC is so high that it enables inspection of cations and anions with Delta (nb)(w) (G)(theta)(Cat+) < or = 43 kJ/mol and Delta (nb)(w) (G)(theta)(X-) < or = 50 kJ/mol, respectively. The direct transfer of Na(+) and Li(+) from water to nitrobenzene, mutually saturated, is achieved for the first time at a macroscopic water/nitrobenzene interface.