Solvent Dynamics and Pressure Effects in the Kinetics of the Tris(bipyridine)cobalt(III/II) Electrode Reaction in Various Solvents

1999 ◽  
Vol 121 (44) ◽  
pp. 10410-10415 ◽  
Author(s):  
Yansong Fu ◽  
Amanda S. Cole ◽  
Thomas W. Swaddle
Keyword(s):  
Electrode Reaction ◽  
Pressure Effects ◽  
Solvent Dynamics ◽  
Kinetics Of

Pressure effects and solvent dynamics in the electrochemical kinetics of the tris(hexafluoroacetylacetonato)ruthenium(III)/(II) couple in nonaqueous solvents

2001 ◽  
Vol 79 (5-6) ◽  
pp. 841-847 ◽  
Author(s):  
Jinkui Zhou ◽  
Thomas W Swaddle
Keyword(s):  
Free Energy ◽  
Activation Barrier ◽  
Electrode Reaction ◽  
Pressure Effects ◽  
Electrochemical Kinetics ◽  
Free Energy Barrier ◽  
Exchange Reactions ◽  
Electrode Processes ◽  
Solvent Dynamics ◽  
Kinetics Of

Rate constants and reactant diffusion coefficients for the Ru(hfac)30/– electrode reaction have been measured at 25°C as functions of pressure (0-200 MPa) in acetone, acetonitrile, methanol, and propylene carbonate. In sharp contrast to the negative volumes of activation ΔVex‡ found for the corresponding bimolecular self-exchange reaction in organic solvents, the volumes of activation ΔVel‡ for the electrode reaction are markedly positive, ranging from 8 to 12 cm3 mol–1. The volumes of activation ΔVdiff‡ for reactant diffusion (which can be equated to the volume of activation ΔVvisc‡ for viscous flow) range from 12 to 19 cm3 mol–1. For the Debye solvents acetonitrile and acetone at least, ΔVel‡ is given within the experimental uncertainty by ΔVdiff‡ + (ΔVex‡/2). In this relation, the numerical value of ΔVdiff‡ represents indirectly the dominant contribution of solvent dynamics (solvent friction) to ΔVel‡, and ΔVex‡/2 represents the pressure dependence of the free-energy barrier height for the electrode reaction. It is proposed that solvent friction is important in nonaqueous electrode processes but not in the corresponding bimolecular self-exchange reactions because the free-energy activation barrier is twice as high in the latter.Key words: electrode reaction kinetics, solvent dynamics, electron transfer mechanisms, pressure effects, volume of activation.

Volumes of activation for electrode processes of various charge-types in nonaqueous solvents

2001 ◽  
Vol 79 (12) ◽  
pp. 1864-1869 ◽  
Author(s):  
Mitsuru Matsumoto ◽  
Delanie Lamprecht ◽  
Michael R North ◽  
Thomas W Swaddle
Keyword(s):  
Electron Transfer ◽  
Reaction Rate ◽  
Electrode Reaction ◽  
State Theory ◽  
Exchange Reactions ◽  
Pt Electrode ◽  
Electrode Processes ◽  
Solvent Dynamics ◽  
The Mean ◽  
Dynamical Control

Volumes of activation (ΔV‡el) are reported for electron transfer at a Pt electrode of Mn(CN-cyclo-C6H11)62+/+ in acetonitrile, acetone, methanol, and propylene carbonate, and of Fe(phen)33+/2+ in acetonitrile. In all cases, ΔV‡el is markedly positive, whereas for the homogeneous self-exchange reactions of these couples in the same solvents the corresponding parameter is known to be strongly negative. The rate constants for the electrode reactions correlate loosely with the mean reactant diffusion coefficients (i.e., with solvent fluidity) and the ΔV‡el values with the volumes of activation for diffusion (i.e., for viscous flow), consistent with solvent dynamical control of the electrode reaction rate in organic solvents. A detailed analysis of ΔV‡el values of the kind presented for a couple with an uncharged member (Zhou and Swaddle, Can. J. Chem. 79, 841 (2001)) fails, however, either because of ion-pairing effects with these more highly charged couples or because of breakdown of transition-state theory in predicting the contribution of the activational barrier. Attempts to measure ΔV‡el for the oxidation of the uncharged molecule ferrocene at various electrodes in acetonitrile were unsuccessful, although ΔV‡el was again seen to be clearly positive.Key words: electrode kinetics, volumes of activation, nonaqueous electron transfer, solvent dynamics.

Electrode kinetics of Eu3+/Eu2+ reaction by cyclic voltammetry

1982 ◽  
Vol 47 (7) ◽  
pp. 1773-1779 ◽  
Author(s):  
T. P. Radhakrishnan ◽  
A. K. Sundaram
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Outer Sphere ◽  
Electrode Reaction ◽  
Transfer Reactions ◽  
Cyclic Voltammetric ◽  
Edta Solution ◽  
Kinetics Of ◽  
Activated Complex ◽  
Good Agreement

The paper is a detailed study of the cyclic voltammetric behaviour of Eu3+ at HMDE in molar solutions of KCl, KBr, KI, KSCN and in 0.1M-EDTA solution with an indigenously built equipment. The computed values of the rate constants at various scan rates show good agreement with those reported by other electrochemical methods. In addition, the results indicate participation of a bridged activated complex in the electron-transfer step, the rate constants showing the trend SCN- > I- > Br- > Cl- usually observed for bridging order of these anions in homogeneous electron-transfer reactions. The results for Eu-EDTA system, however, indicate involvement of an outer sphere activated complex in the electrode reaction.

Voltammetric investigation of the kinetics of alkali metal cation reduction in N,N-dimethylformamide

1975 ◽  
Vol 28 (2) ◽  
pp. 237 ◽  
Author(s):  
JW Diggle ◽  
AJ Parker ◽  
DA Owensby
Keyword(s):  
Electron Transfer ◽  
Alkali Metal ◽  
Propylene Carbonate ◽  
Rate Constant ◽  
Alkali Metal Cation ◽  
Electrode Reaction ◽  
Amalgam Electrode ◽  
Kinetics Of ◽  
Dipolar Aprotic Solvents

The standard electron-transfer heterogeneous rate constant of lithium, potassium, sodium and caesium amalgams in N,N-dimethylformamide was ascertained employing cyclic voltammetry in an effort to relate the presence of a non-equilibrium electrode reaction at the dropping lithium amalgam electrode to the variation of the lithium amalgam electrode potential with amalgam electrode con- figuration, i.e. whether streaming, dropping or stationary. Such variations are not observed at other alkali metal amalgam electrodes. ��� In the dipolar aprotic solvents the standard electron-transfer heterogeneous rate constant for the Li(Hg) electrode increases as the solvating power for Li+ decreases, i.e. dimethyl sulphoxide < di- methylformamide < propylene carbonate. Water is a much stronger solvator of Li+ than is propylene carbonate, but the electron transfer is faster in water than in propylene carbonate; the important role of entropic contributions in ion solvation is discussed as an explanation.

Sign in / Sign up

Export Citation Format

Share Document