Electrode Modification from the Electrolysis of [M(Bipyridine)3](ClO4)2 (M = CoII, FeII, and RuII) in Media of Low Dielectric Constant. Electrocatalytic Behavior and an Amperometric C60 Sensor

The voltammetric behavior of transition metal complexes of 2,2‘-bipyridine, [M II (bpy) 3 ](ClO 4 ) 2 (M II = Co II, Fe II, or Ru II ), in toluene/acetonitrile mixtures has been studied by cyclic voltammetry. In solutions with a low acetonitrile-to-toluene ratio and tetra( n -butyl)ammonium perchlorate as supporting electrolyte, oxidation of [M II (bpy) 3 ](ClO 4 ) 2 leads to the precipitation of a solid, electrochemically inactive phase of [M III (bpy) 3 ](ClO 4 ) 3 (M = Co or Fe) on the electrode. Electrodes modified by this solid phase are shown to display catalytic waves that result from chemical reduction of the film by soluble species: [M(bpy) 3 ] + when no other electroactive species is present or [C 60 ] - when C 60 is also present in the solution. The redox behavior of C 60 on an electrode covered by a [Co III (bpy) 3 ](ClO 4 ) 3 layer was extensively investigated. The catalytic current associated with the reduction of C 60 at a [Co III (bpy) 3 ](ClO 4 ) 3 modified electrode can be used for the quantitative determination of fullerene concentration in solution. The reduction current associated with square wave voltammetric experiments increased linearly with the concentration of C 60 in the range of 0.25−20 μM. The detection limit is 0.1 μM. This method of fullerene quantitative determination exhibits good reproducibility, simplicity, and is relatively fast. Electrochemical oxidation of [Ru II (bpy) 3 ](ClO 4 ) 2 does not produce an analogous redox inactive layer of [Ru III (bpy) 3 ](ClO 4 ) 3 .