Cyclic voltammetric studies of copper(II) complexes with N,N,N′,N′-tetramethylethylenediamine in dimethylsulfoxide

The electrochemical behaviour of [Cu(tmen)X-2] (where tmen = N,N,N',N'-tetramethylethylenediamine and X = Cl or Br) has been studied in dimethylsulfoxide (DMSO) solution containing 0.1 M tetrabutylammoniumperchlorate (TBAP) as supporting electrolyte at a platinum working electrode. The diffusion-controlled reduction of both the complexes occurred in two stages; the first one at E0' = 342 to 352 and second at E0' = 16 to 24 mV vs Ag/AgCl. The anodic to cathodic peak current ratio is greater than unity for the first redox couple while it is less than 1.0 for the second couple, suggesting that the electrogenerated Cu-I-complex species is weakly adsorbed in the former case while the second step involves electron transfer followed by a chemical reaction (EC mechanism). The two redox processes observed may be because of chemical equilibrium between the two complex species in DMSO medium.