ION-EXCHANGE VOLTAMMETRY OF TRIS(2,2'-BIPYRIDYL) RUTHENIUM(II), IRON(II), OSMIUM(II) AND TRIS(2,2'-BIPYRAZYL) RUTHENIUM(II) IN ACETONITRILESOLUTIONS AT POLY(ESTER-SULFONATE) COATED ELECTRODES

Glassy carbon electrodes modified with the poly(ester-sulphonate) iono mer Kodak AQ 55 D are used and characterized in acetonitrile solutions . The potential window accessible in acetonitrile + tetrabutylammonium hexafluorophosphate extends from - 1.750 V to + 1.900 V vs, an aqueou s KCl saturated Ag\AgCl reference electrode. The electrochemical behav iour of [Ru(bpy)(3)](2+), [Fe(bpy)(3)](2+), [Os(bpy)(3)](2+) and [Ru(b pz)(3)](2+) (where bpy = 2,2'bipyridyl and bpz = 2,2'bipyrazyl) is stu died at the modified electrode. All the electroactive cations are prec oncentrated efficiently in the polymeric coating. In the case of bpy c omplexes both a one-electron oxidation as well as two one-electron ste ps of the stepwise reduction of the starting complex are detected at t he modified electrode. In the case of [Ru(bpz)(3)](2+), three consecut ive reduction steps can be observed, while no oxidation process is obs erved in the direct positive scan before reaching the upper limit of t he potential range accessible at the modified electrode. The relative order in the ion-exchange selectivity coefficients in acetonitrile sol utions for the cations studied is evaluated by comparison with the ele ctrochemical behaviour observed at unmodified electrodes, The possibil ity of gaining information on preconcentration effects for ion-exchang e voltammetry in non-aqueous solvents from the Gibbs energies of trans fer from water to hydrophobic media is also discussed.