Abnormal salt effects on a cation/anion reaction. An interpretation based on the analysis of the components of the experimental rate constant

2009 ◽  
Vol 74 (4) ◽  
pp. 627-641
Author(s):  
Francisco Sánchez ◽  
Pilar Perez-Tejeda ◽  
Rafael Jimenez ◽  
Isaac Villa
Keyword(s):  
Electron Transfer ◽  
Salt Effect ◽  
Transfer Reactions ◽  
Forward Reaction ◽  
Salt Effects ◽  
Experimental Rate ◽  
Asymmetric Behavior ◽  
Negative Effect ◽  
Kinetics Of ◽  
Charge Sign

Salt effects (NaNO3) on the kinetics of the reactions [Fe(CN)6]3– + [Ru(NH3)5(pyz)]2+ = [Fe(CN)6]4– + [Ru(NH3)5(pyz)]3+ (pyz = pyrazine) were studied through T-jump measurements. An abnormal (positive) salt effect on the forward reaction was observed and a normal (negative) effect on the reverse one. These facts imply an asymmetric behavior of anion/cation reactions depending on the charge sign of the oxidant and reductant. The results can be rationalized by using the Marcus–Hush treatment for electron-transfer reactions after decomposition of the experimental rate constants into their components.

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.

Kinetics of intra-polymer electron-transfer reactions in macromolecule–metal complexes

1995 ◽  
Vol 91 (17) ◽  
pp. 2877-2880 ◽  
Author(s):  
Masahiro Suzuki ◽  
Satoshi Kobayashi ◽  
Toshiki Koyama ◽  
Kenji Hanabusa ◽  
Hirofusa Shirai ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Metal Complexes ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
Kinetics Of

Substituent Effects in Electron Transfer Reactions: The Preparation and Chromium(II) Reduction of 3-Formylpentane-2,4-dionatobis(ethylenediamine)cobalt(III). Preparation of the Linkage Isomer 2-Acetylbutane-1,3-dionatobis(ethylenediamine)cobalt(III)

1975 ◽  
Vol 53 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Robert J. Balahura ◽  
N. A. Lewis
Keyword(s):  
Electron Transfer ◽  
Acidic Solution ◽  
Substituent Effects ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Linkage Isomers ◽  
A Value ◽  
Parent Complex ◽  
Kinetics Of ◽  
Sphere Mechanism

The preparation of the linkage isomers, 3-formylpentane-2,4-dionatobis(ethylenediamine)cobalt(III), (1), and 2-acetylbutane-1,3-dionatobis(ethylenediamine)cobalt(III), (2), are described. The kinetics of the reaction of Cr(OH2)62+ with 1 and the parent complex, 2,4-pentanedionatobis(ethylenediamine)cobalt(III), (3), have been studied spectrophotometrically in acidic solution. For 1, the reduction is described by the rate law −d ln [Co(III)complex]/dt = k[Cr2+], and k = 0.0863 M−1 s−1 at 25 °C, μ = 1.0 M (LiClO4). The activation parameters for this reaction were found to be ΔH≠ = 9.9 ± 0.5 kcal mol−1 and ΔS≠ = −30 ± 3 e.u. The reaction proceeded by an inner-sphere mechanism and the product of this reaction was isolated and characterized as 2-acetylbutane-1,3-dionatotetraaquochromium(III). The linkage isomer of this complex was also prepared. The parent complex (3) was not reduced by Cr(OH2)62+ at an observable rate and an upper limit for the rate constant of this reaction was assigned a value of 10−4–10−6M−1s−1 at 25 °C. The ability of the formyl group to enhance the rate of electron transfer is discussed, and the chromium(II) reduction studies of related chelated systems are compared with the results obtained in this investigation.

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