Standard electrode potentials involving radicals in aqueous solution: inorganic radicals (IUPAC Technical Report)

Armstrong, David A.; Huie, Robert E.; Koppenol, Willem H.; Lymar, Sergei V.; Merényi, Gábor; Neta, P.; Ruščić, Branko; Stanbury, David M.; Steenken, S.; Wardman, Peter

doi:10.1515/pac-2014-0502

Cited by 429 publications

(397 citation statements)

References 11 publications

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“…The carbonate radical anion is a strong single‐electron oxidant with a redox potential of 1.76 V versus NHE at pH 7.0 and 1.57 V versus NHE at pH 12.0 . When N 2 O saturated solutions containing {Cu II (HCO 3 ) m (CO 3 ) n 2−2 n − m } aq (for simplicity in the following the equations will be written, {Cu II (CO 3 ) n 2−2 n } aq without the ligated bicarbonate) are irradiated, three consecutive reactions are observed.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Studies on the Role of [Cu^II(CO₃)_n]²⁻²ⁿ as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Mizrahi¹,

Maimon

Cohen

et al. 2017

Chemistry A European J

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Recently it was reported that copper bicarbonate/carbonate complexes are good electro-catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a Cu or a Cu complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that Cu (CO ) complexes are the active intermediates in the electrolysis of Cu (CO ) solution. The results enable the evaluation of E°[(Cu (CO ) ) ]≈1.42 V versus NHE at pH 8.4. This redox potential is in accord with the electrochemical report. As opposed to literature suggestions for water oxidation, the present results rule out single-electron transfer from Cu (CO ) to yield hydroxyl radicals. Significant charge transfer from the coordinated carbonate to Cu results in the formation of C O by means of a second-order reaction of Cu (CO ) . The results point out that carbonate stabilizes transition-metal cations at high oxidation states, not only as a good sigma donor, but also as a non-innocent ligand.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Studies on the Role of [Cu^II(CO₃)_n]²⁻²ⁿ as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Mizrahi¹,

Maimon

Cohen

et al. 2017

Chemistry A European J

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“…Additionally, some of the reference potentials used in the older literature were not as well-determined as they are today. 56 Aqueous Y gives rise to irreversible voltammograms since Y–O• dimerization is fast ( k dim 2–7 × 10 8 M −1 s −1 ) 29,57 relative to the experimental time scale. These voltammograms, which display only an anodic wave, may reflect a reversible, quasi-reversible or irreversible electrode reaction.…”

Section: Discussionmentioning

confidence: 99%

“…58,59 Harriman 53 and DeFelippis et al 54 applied this approach but unfortunately used an incorrect equation to compensate for k dim . 46 Recently reported (or recommended) pH 7.0 potentials for aqueous Y are 0.93 ± 0.02 V, 52 0.91 ± 0.02 V, 56 and 0.96 V. 46 We therefore take a consensus value of 920–940 ± 20 mV for the aqueous Y(O•/OH) redox couple at pH 7.0. E °′ of Y 32 (O•/OH) is 986 ± 3 mV at pH 7.0 (Figure 5; Table S2).…”

Section: Discussionmentioning

confidence: 99%

Formal Reduction Potentials of Difluorotyrosine and Trifluorotyrosine Protein Residues: Defining the Thermodynamics of Multistep Radical Transfer

Ravichandran¹,

Zong

Taguchi³

et al. 2017

J. Am. Chem. Soc.

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Redox-active tyrosines (Ys) play essential roles in enzymes involved in primary metabolism including energy transduction and deoxynucleotide production catalyzed by ribonucleotide reductases (RNRs). Thermodynamic characterization of Ys in solution and in proteins remains a challenge due to the high reduction potentials involved and the reactive nature of the radical state. The structurally characterized α3Y model protein has allowed the first determination of formal reduction potentials (E°′) for a Y residing within a protein (Berry, B. W.; Martínez-Rivera, M. C.; Tommos, C. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 9739–9743). Using Schultz’s technology, a series of fluorotyrosines (FnY, n = 2 or 3) was site-specifically incorporated into α3Y. The global protein properties of the resulting α3(3,5)F2Y, α3(2,3,5)F3Y, α3(2,3)F2Y and α3(2,3,6)F3Y variants are essentially identical to those of α3Y. A protein film square-wave voltammetry approach was developed to successfully obtain reversible voltammograms and E°’s of the very high-potential α3FnY proteins. E°′(pH 5.5; α3FnY(O•/OH)) spans a range of 1040 ± 3 mV to 1200 ± 3 mV versus the normal hydrogen electrode. This is comparable to the potentials of the most oxidizing redox cofactors in Nature. The FnY analogs, and the ability to site-specifically incorporate them into any protein of interest, provide new tools for mechanistic studies on redox-active Ys in proteins and on functional and aberrant hole-transfer reactions in metallo-enzymes. The former application is illustrated here by using the determined α3FnY ΔE°’s to model the thermodynamics of radical-transfer reactions in FnY-RNRs and to experimentally test and support the key prediction made.

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“…Reduction potentials can be found in Ref. [7]. Copper-containing enzymes that perform parts of this reduction are shown…”

Section: Figmentioning

confidence: 99%

“…This process is well known in aqueous systems and proceeds through various intermediates including superoxide (

{normalO}_{2}^{\cdot -}

), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical ( · OH); two equivalents of water are produced from this reaction (Scheme 1) [4–7]. However, it is also important to know how these processes occur in the presence of metal ions, as many important oxidative transformations have been attributed to various reactive metal–oxygen species [3, 8–11].…”

Section: Introductionmentioning

confidence: 99%

Activation of dioxygen by copper metalloproteins and insights from model complexes

et al. 2016

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Nature uses dioxygen as a key oxidant in the transformation of biomolecules. Among the enzymes that are utilized for these reactions are copper-containing met-alloenzymes, which are responsible for important biological functions such as the regulation of neurotransmitters, dioxygen transport, and cellular respiration. Enzymatic and model system studies work in tandem in order to gain an understanding of the fundamental reductive activation of dioxygen by copper complexes. This review covers the most recent advancements in the structures, spectroscopy, and reaction mechanisms for dioxygen-activating copper proteins and relevant synthetic models thereof. An emphasis has also been placed on cofactor biogenesis, a fundamentally important process whereby biomolecules are post-translationally modified by the pro-enzyme active site to generate cofactors which are essential for the catalytic enzymatic reaction. Significant questions remaining in copper-ion-mediated O2-activation in copper proteins are addressed.

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Standard electrode potentials involving radicals in aqueous solution: inorganic radicals (IUPAC Technical Report)

Cited by 429 publications

References 11 publications

Mechanistic Studies on the Role of [Cu^II(CO₃)_n]²⁻²ⁿ as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Mechanistic Studies on the Role of [Cu^II(CO₃)_n]²⁻²ⁿ as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Formal Reduction Potentials of Difluorotyrosine and Trifluorotyrosine Protein Residues: Defining the Thermodynamics of Multistep Radical Transfer

Activation of dioxygen by copper metalloproteins and insights from model complexes

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Standard electrode potentials involving radicals in aqueous solution: inorganic radicals (IUPAC Technical Report)

Cited by 429 publications

References 11 publications

Mechanistic Studies on the Role of [CuII(CO3)n]2−2n as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Mechanistic Studies on the Role of [CuII(CO3)n]2−2n as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Formal Reduction Potentials of Difluorotyrosine and Trifluorotyrosine Protein Residues: Defining the Thermodynamics of Multistep Radical Transfer

Activation of dioxygen by copper metalloproteins and insights from model complexes

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Mechanistic Studies on the Role of [Cu^II(CO₃)_n]²⁻²ⁿ as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand

Mechanistic Studies on the Role of [Cu^II(CO₃)_n]²⁻²ⁿ as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand