Relationship between structural change and heterogeneous electron-transfer rate constant in iron-tetraphenylporphyrin complexes

Feng, Diwei; Schultz, Franklin A.

doi:10.1021/ic00285a027

Cited by 20 publications

(9 citation statements)

References 1 publication

(1 reference statement)

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“…It is assumed that a = 0.5 and Do = D,. The result is in excellent agreement with the value of 2.4 X cm s-' reported earlier in 0.1 TBAC104/CH,C12 [16]. The reliability of the k,, measurement is supported by the fact that a fully reversible, sweep-rate-independent response is obtained concurrently for ferrocene oxidation in the same solution at the same electrode surface.…”

Section: Measurement Of Electron Transfer Kineticssupporting

confidence: 90%

“…Our laboratory is interested in studying the kinetics of electrode reactions that are characterized by large changes in the structure o f the reactant [15][16][17]. One goal of these investigations is to determine if the Marcus-Hush theory [ 181 correctly predicts the extent to which electron transfer is slowed by changes in nuclear coordinates.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical cell design and experimental procedures for measuring electrode reaction kinetics at low and variable temperatures

Schultz

1990

Electroanalysis

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An electrochemical cell is described for measuring electrode reaction kinetics at low and variable temperatures in nonaqueous solvents. The cell contains a working electrode of conventional size (at which the standard heterogeneous electron transfer rate constant is determined by cyclic voltammetry) and a microelectrode (at which the diffusion coefficient is measured by steady-state microelectrode voltammetry). I Jncompensated solution resistance is minimized by a combination o f close placement o f the reference electrode salt bridge tip and the working electrode surface and instrumental positive feeclback. Cell performance is evaluated by an examination o f ferrocene oxidation and manganese( 111) (tetra~~henylporpliyrin ) chloride reduction at temperatures between 229 and 298 K. Comparison of the rcsponses from these reversible and quasi-reversible redox couples in the sane solution demonstrates that the effects of uncompensated solution resistance are absent from the experimental measurements and that increases in the cyclic voltammetric peak potential separation with sweep rate are due entirely to the kinetics o f the Mn(IlI)/Mn( 11) electrode reaction.1040-0397/90/$3 50 + .L5

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Section: Measurement Of Electron Transfer Kineticssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Electrochemical cell design and experimental procedures for measuring electrode reaction kinetics at low and variable temperatures

Schultz

1990

Electroanalysis

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“…Since both 1,2,4-triazole and benzotriazole form iron complexes [31,32] their inhibition performance might be related to slowing the rate of Fe re-plating. With no intention to question in any way the correctness of the inhibiting mechanism proposed for 5,10,15,20-tetraphenylporphyrin in [18] (formation of chelate complexes with Mg that precipitate on Mg surface) we would like to note that this complexing agent also forms stable complexes with iron [33] and high inhibiting efficiency of tetraphenylporphyrin well could be a synergistic effect of both mechanisms.…”

Section: Resultsmentioning

confidence: 99%

A new concept for corrosion inhibition of magnesium: Suppression of iron re-deposition

Lamaka

Höche

Petrauskas

et al. 2016

Electrochemistry Communications

105

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In our recent work (Höche et al. 2015) we proposed that non-faradaic dissolution of Fe impurities and subsequent re-deposition of thin film of pure ("in statu nascendi") iron enlarges cathodically active sites at Mg surface. The effect drastically accelerates corrosion of impurity containing Mg. In this work we assumed that if Fe re-deposition is prevented, the area of cathodic sites can be drastically decreased and hence corrosion of Mg can be suppressed. In this prove of concept work we used strong Fe 3+ complexing agents in order to remove dissolved iron from corrosion sites and prevent iron re-deposition. All used iron complexing agents efficiently lowered the corrosion rate of Mg. Direct correlation of complex stability with its inhibiting efficiency was established. It was shown that cyanide, salicylate, oxalate, methylsalicylate and thiocyanate efficiently reduce hydrogen evolution and suppress critical dark area formation.

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“…71 They explained that the reduction of high spin heme complexes involves greater activation energy than the reduction of low spin heme complexes. They also showed that the electron self-exchange rate is several-fold larger for low spin hemes compared to high spin.…”

Section: Discussionmentioning

confidence: 99%

“…They also showed that the electron self-exchange rate is several-fold larger for low spin hemes compared to high spin. 71 Unlike the natural reductase–P450 electron transfer involving a prior protein–protein interaction on a membrane, in thin film voltammetry an electron is transferred from the solid electrode to heme irons of the cyt P450 near the surface, and self-exchange within the film propagates charge transfer. 20,21 Thus, correlation of hET rate constants to spin state the same as in model heme iron complexes is reasonable.…”

Section: Discussionmentioning

confidence: 99%

Control of Electrochemical and Ferryloxy Formation Kinetics of Cyt P450s in Polyion Films by Heme Iron Spin State and Secondary Structure

et al. 2009

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Voltammetry of cytochrome P450 (cyt P450) enzymes in ultrathin films with polyions was related for the first time to electronic and secondary structure. Heterogeneous electron transfer (hET) rate constants for reduction of the cyt P450s depended on heme iron spin state, with low spin cyt P450cam giving a value 40-fold larger than high spin human cyt P450 1A2, with mixed spin human P450 cyt 2E1 at an intermediate value. Asymmetric reduction–oxidation peak separations with increasing scan rates were explained by simulations featuring faster oxidation than reduction. Results are consistent with a square scheme in which oxidized and reduced forms of cyt P450s each participate in rapid conformational equilibria. Rate constants for oxidation of ferric cyt P450s in films by t-butyl hydroperoxide to active ferryloxy cyt P450s from rotating disk voltammetry suggested a weaker dependence on spin state, but in the reverse order of the observed hET reduction rates. Oxidation and reduction rates of cyt P450s in the films are also likely to depend on protein secondary structure around the heme iron.

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Relationship between structural change and heterogeneous electron-transfer rate constant in iron-tetraphenylporphyrin complexes

Cited by 20 publications

References 1 publication

Electrochemical cell design and experimental procedures for measuring electrode reaction kinetics at low and variable temperatures

Electrochemical cell design and experimental procedures for measuring electrode reaction kinetics at low and variable temperatures

A new concept for corrosion inhibition of magnesium: Suppression of iron re-deposition

Control of Electrochemical and Ferryloxy Formation Kinetics of Cyt P450s in Polyion Films by Heme Iron Spin State and Secondary Structure

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