The electrochemistry of [Re-III(DIARS)(2)Cl-2]Cl in aqueous and aqueous/ethanol solvents at bare and Nafion-modified electrodes has been studied by cyclic voltammetry, differential pulse voltammetry, and chronocoulometry. Cyclic voltammetry of [Re-III(DIARS)(2)Cl-2](+) reduction to [Re-II(DIARS)(2)Cl-2](0) at gold in acetonitrile, ethanol, 33 % ethanol/aqueous pH 6.93 phosphate buffer, and aqueous pH 6.93 phosphate buffer solutions gave formal reduction potentials that fall within the range of -0.319 V to -0.263 V (vs. Ag/AgCl) and increase with the dielectric constant of the solvent. In 33 % ethanol/aqueous pH 6.93 phosphate buffer and aqueous pH 6.93 phosphate buffer, both the oxidized and reduced forms of the complex exhibited adsorption at the surface of gold electrodes as shown by cyclic voltammetry and chronocoulometry. An especially sharp reduction wave, which is more negative than the reduction wave in subsequent cycles, was obtained on the first scan in cyclic voltammetry. By comparison, well-defined voltammograms were obtained at Nafion-modified glassy carbon. Substantial partitioning into Nafion occurred and a detectable signal was measured for Nafion coated glassy electrodes at concentrations as low as 4.0 x 10(-10) M by differential pulse voltammetry. Nafion also prevented uric acid dopamine, DOPAC, and ascorbic acid from interfering with the electrochemical detection of [Re-III(DIARS)(2)Cl-2](+). Nafion modified carbon shows good potential For development into an electrochemical sensor for in vivo monitoring of [Re-III(DIARS)(2)Cl-2](+), which is potentially useful for the study of its imaging properties in nuclear medicine.
