Measurement of the diffusion coefficients of [Ru(NH3)6]3+ and [Ru(NH3)6]2+ in aqueous solution using microelectrode double potential step chronoamperometry

Abstract Microelectrode double potential step chronoamperometry is reported which allows the measurement of the diffusion coefficients of [Ru(NH3)6]3+ and [Ru(NH3)6]2+ in aqueous solutions containing various concentrations of the supporting electrolyte, KCl, KNO3 or K2SO4. In the case of K2SO4, ion-pairing of hexaammineruthenium cations is inferred where for KCl and KNO3 no such effects were noted. The triply charged ion was found to have a significantly lower diffusion coefficient than the doubly charged ion with a ratio of ∼0.71 in the KCl and KNO3 media.

[1]  C. Banks,et al.  The transport limited currents at insonated electrodes , 2004 .

[2]  R. G. Evans,et al.  Double potential step chronoamperometry at microdisk electrodes: simulating the case of unequal diffusion coefficients , 2004 .

[3]  A. Yamagishi,et al.  Clay-modified electrodes as studied by the quartz crystal microbalance: adsorption of ruthenium complexes , 1998 .

[4]  Allen J. Bard,et al.  Electrochemical Methods: Fundamentals and Applications , 1980 .

[5]  R. G. Evans,et al.  Oxidation of N,N,N ’,N ’-tetraalkyl-para-phenylenediamines in a series of room temperature ionic liquids incorporating the bis(trifluoromethylsulfonyl)imide anion , 2003 .

[6]  J. Georges,et al.  Electrochemistry of ferrocene in anionic, cationic and nonionic micellar solutions. Effet of the micelle solubilization of the half-wave potentials , 1984 .

[7]  K. Uosaki,et al.  Anion effect on the electrochemical characteristics of a gold electrode modified with a self-assembled monolayer of ferrocenylhexanethiol in aqueous and dichloromethane solutions , 2001 .

[8]  Mauro Bertotti,et al.  Use of microdevices to determine the diffusion coefficient of electrochemically generated species: application to binary solvent mixtures and micellar solutions. , 2007, The journal of physical chemistry. B.

[9]  S. Rizzato,et al.  Ion pairing and salt structure in organic salts through diffusion, Overhauser, DFT and X-ray methods. , 2009, Chemistry.

[10]  R. Compton,et al.  The measurement of the diffusion coefficients of ferrocene and ferrocenium and their temperature dependence in acetonitrile using double potential step microdisk electrode chronoamperometry , 2010 .

[11]  Darren L. Poole,et al.  Voltammetric Characterization of the Ferrocene|Ferrocenium and Cobaltocenium|Cobaltocene Redox Couples in RTILs , 2008 .

[12]  Jeongmin T. Han,et al.  Quantitative Voltammetry in Weakly Supported Media. Chronoamperometric Studies on Diverse One Electron Redox Couples Containing Various Charged Species: Dissecting Diffusional and Migrational Contributions and Assessing the Breakdown of Electroneutrality , 2010 .

[13]  Á. Molina,et al.  Theoretical and experimental study of Differential Pulse Voltammetry at spherical electrodes: Measuring diffusion coefficients and formal potentials , 2009 .

[14]  J. Wadhawan,et al.  Voltammetry of oxygen in the room-temperature ionic liquids 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide and hexyltriethylammonium bis((trifluoromethyl)sulfonyl)imide: One-electron reduction to form superoxide. Steady-state and transient behavior in the same cyclic voltammogram re , 2003 .

[15]  Xiaobo Ji,et al.  Electrode Kinetic Studies of the Hydroquinone−Benzoquinone System and the Reaction between Hydroquinone and Ammonia in Propylene Carbonate: Application to the Indirect Electroanalytical Sensing of Ammonia , 2007 .

[16]  R. Compton,et al.  The electrochemical reduction of 1,4-benzoquinone in 1-ethyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)-imide, [C2mim][NTf2]: A voltammetric study of the comproportionation between benzoquinone and the benzoquinone dianion , 2010 .

[17]  A. Baticle,et al.  Sur trois méthodes de détermination des coefficients de diffusion d'ions en solutions de forces ioniques constantes , 1971 .

[18]  R. Compton,et al.  Chronoamperometry at channel electrodes: a general computational approach , 1991 .

[19]  K. B. Oldham,et al.  Use of the ferrocene oxidation process to provide both reference electrode potential calibration and a simple measurement (via semiintegration) of the uncompensated resistance in cyclic voltammetric studies in high-resistance organic solvents , 2000, Analytical chemistry.

[20]  A. Szabó,et al.  Chronoamperometric current at finite disk electrodes , 1982 .

[21]  Richard G. Compton,et al.  How Much Supporting Electrolyte Is Required to Make a Cyclic Voltammetry Experiment Quantitatively “Diffusional”? A Theoretical and Experimental Investigation , 2009 .

[22]  Makoto Sato,et al.  Diffusion Coefficients of Tris(β-diketonato)ruthenium Complexes of Different Charge Numbers in Acetonitrile Solutions, Measured by Chronoamperometry , 2007 .

[23]  E. Yang,et al.  Electron exchange between ferrocene and ferrocenium ion. Effects of solvent and of ring substitution on the rate , 1980 .

[24]  C. Banks,et al.  Sonoelectrochemistry in acoustically emulsified media , 2002 .

[25]  R. Compton,et al.  Modeling Diffusion Effects for a Stepwise Two-Electron Reduction Process at a Microelectrode: Study of the Reduction of para-Quaterphenyl in Tetrahydrofuran and Inference of Fast Comproportionation of the Dianion with the Neutral Parent Molecule , 2009 .

[26]  F. Marken,et al.  Voltammetry in the presence of ultrasound: Can ultrasound modify heterogeneous electron transfer kinetics? , 1995 .

[27]  J. Redepenning,et al.  Influence of supporting electrolyte activity on formal potentials measured for dissolved internal standards in acetonitrile , 2001 .

[28]  Á. Molina,et al.  Potential step chronoamperometry at hemispherical mercury electrodes: The formation of thallium amalgams and the measurement of the diffusion coefficient of thallium in mercury , 2008 .

[29]  S. Creager,et al.  INTERFACIAL SOLVATION AND DOUBLE-LAYER EFFECTS ON REDOX REACTIONS IN ORGANIZED ASSEMBLIES , 1994 .

[30]  A. Nowicka,et al.  Direct determination of diffusion coefficients of substrate and product by chronoamperometric techniques at microelectrodes for any level of ionic support. , 2002, Analytical chemistry.

[31]  R. Compton,et al.  Applications of the channel flow cell for UV-visible spectroelectrochemical studies Part 3. Do radical cations and anions have similar diffusion coefficients to their neutral parent molecules? , 1997 .

[32]  I. Furó,et al.  Ion pairing in ethanol/water solution probed by electrophoretic and diffusion NMR. , 2009, Journal of the American Chemical Society.

[33]  R. Compton,et al.  Kinetics and Thermodynamics of Redox Processes in Room Temperature Ionic Liquids: The Use of Voltammetry and the Disproportionation of Radical Cations of N,N-Dimethyl-p-phenylenediamine in 1-Butyl-3-methylimidazolium Tetrafluoroborate , 2010 .

[34]  P. Unwin,et al.  Scanning electrochemical microscopy: theory and experiment for the positive feedback mode with unequal diffusion coefficients of the redox mediator couple , 1997 .