Electrochemistry of [Re-III(DIARS)(2)Cl-2]Cl, where DIARS = o-phenylenebis(dimethylarsine), in aqueous and aqueous ethanol solvents at bare and Nafion-modified electrodes

The electrochemistry of [Re-III(DIARS)(2)Cl-2]Cl in aqueous and aqueous/eth anol solvents at bare and Nafion-modified electrodes has been studied by cy clic voltammetry, differential pulse voltammetry, and chronocoulometry. Cyc lic voltammetry of [Re-III(DIARS)(2)Cl-2](+) reduction to [Re-II(DIARS)(2)C l-2](0) at gold in acetonitrile, ethanol, 33 % ethanol/aqueous pH 6.93 phos phate buffer, and aqueous pH 6.93 phosphate buffer solutions gave formal re duction 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 buff er, both the oxidized and reduced forms of the complex exhibited adsorption at the surface of gold electrodes as shown by cyclic voltammetry and chron ocoulometry. An especially sharp reduction wave, which is more negative tha n the reduction wave in subsequent cycles, was obtained on the first scan i n cyclic voltammetry. By comparison, well-defined voltammograms were obtain ed at Nafion-modified glassy carbon. Substantial partitioning into Nafion o ccurred and a detectable signal was measured for Nafion coated glassy elect rodes at concentrations as low as 4.0 x 10(-10) M by differential pulse vol tammetry. Nafion also prevented uric acid dopamine, DOPAC, and ascorbic aci d from interfering with the electrochemical detection of [Re-III(DIARS)(2)C l-2](+). Nafion modified carbon shows good potential For development into a n 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 n uclear medicine.