ELECTROCHEMICAL-BEHAVIOR OF CERTAIN BIOMIMETIC COPPER(II) COMPLEXES IN AQUEOUS AND AQUEOUS MICELLAR SOLUTIONS

Voltammetric studies of biomimetic Cu(II) complexes of bis(pyrid-2-yl) dithia (N2S2) and -trithia (N2S3) and bis(benzimidazol-2-yl)dithia lig ands in aqueous and sodium dodecylsulphate (SDS, anionic), cetyltrimet hylammonium bromide (CTAB, cationic) and Triton X-100 methylbutyl)phen yl]-w-hydroxypolyoxyethylene(9.5), nonionic] micellar solutions have b een carried out on a glassy carbon electrode. The electronic spectral properties of Cu(II) complexes in micellar solutions are consistent wi th their incorporation into hydrophobic microenvironments. For most of the complexes, the adsorption of Cu(I) species observed in aqueous so lution is absent and the reversibility of the Cu(II)/Cu(I) couple is i ncreased in SDS and Triton X-100 micellar solutions. From the dependen ce of I-pc values on SDS concentration, the micellar binding constant K-M has been estimated, Ligand enlargement and the structure of the Cu (II) complexes and Cu(I) forms of complexes enhance the binding with m icelles. Compared with aqueous isotropic solutions, the E(1/2) values in micellar solutions either decrease or increase depending upon the n ature of the surfactant and the hydrophobicity and structure of the co mplexes. The ratio of equilibrium binding constants K-+/K-2+ of Cu(I) and Cu(II) species does not follow the same trend in SDS, CTAB and Tri ton X-100 solutions, indicating that the interaction of the cationic c omplexes depends on a delicate balance between hydrophobic and electro static interactions. Interestingly, for complexes with the CuN2S2 chro mophore the Cu(I)/Cu(0) couple is also observed in Triton X-100 micell es.