Technetium electrochemistry. 6. Electrochemical behavior of cationic rhenium and technetium complexes in aqueous and aqueous micellar solutions
The behavior of the M(III/II) redox couple of a number of technetium(III) and rhenium(III) complexes of the general formula trans-(MD/sub 2/X/sub 2/)/sup +/, where D is 1,2-bis(diethylphosphino)ethane (depe) or 1,2-bis(dimethylphosphino)ethane (dmpe) and X is Cl or Br, has been investigated by cyclic voltammetry, chronocoulometry, and square-wave voltammetry in aqueous solution and in aqueous media that contain anionic (SDS), cationic (CTAB), or nonionic (Triton X-100) surfactants. In aqueous solution, insolubility of the electrogenerated trans-(M/sup II/D/sub 2/X/sub 2/)/sup 0/ complex results in adsorption at a glassy-carbon electrode for all complexes. However, ionic surfactants effectively solubilize the (M(dmpe)/sub 2/X/sub 2/)/sup 0/ species such that diffusion-controlled reversible cyclic voltammograms are observed in these media. In contrast, the more lipophilic (M(depe)/sub 2/Cl/sub 2/)/sup +/ complexes behave differently in that while the solubility of the cationic M(III) complexes is enhanced in the surfactant media, the electrogenerated neutral M(II) complexes are adsorbed on the electrode surface. These observations are qualitatively discussed in terms of the net stabilization of the components of the M(III/II) redox pair in the various surfactant media. This stabilization is primarily dependent on (i) the formal charge on the electroactive complex (cationic vs neutral), (ii) the formal charge on the surfactant molecule that forms the micelle (anionic, cationic, or neutral), and (iii) the lipophilicity of the components of the redox couple (dmpe or depe) and somewhat dependent on the chemical nature of the ions from the supporting electrolyte. 36 references, 7 figures, 5 tables.
- Research Organization:
- Univ. of Cincinnati, OH (USA)
- DOE Contract Number:
- FG02-86ER60487
- OSTI ID:
- 6180589
- Journal Information:
- Inorg. Chem.; (United States), Vol. 27:20
- Country of Publication:
- United States
- Language:
- English
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400400* - Electrochemistry