Chalcogen Atoms as Electron Donors in Proton-Coupled Electron Transfer Reactions

Mena, Leandro Daniel; Baumgartner, María T.

doi:10.1021/jacs.2c05602

Cited by 10 publications

(6 citation statements)

References 33 publications

(63 reference statements)

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“…Also, the change in IBO ϕ4 indicates the transformation from an aromatic π-orbital into the lone pair of the N1 atom, indicating that this CPET mechanism contains PT and ET from the aromatic π-cloud. This is in good agreement with previous studies on the CPET mechanism related to phenol derivatives. – This result indicates that the reaction from RC O to PC O via TS O includes five elementary events, which proceed concertedly; furthermore, it indicates that they start with a timing gap for each other.…”

Section: Resultssupporting

confidence: 92%

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

Kametani,

Ikeda,

Yoshizawa

et al. 2023

Inorg. Chem.

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The literature contains numerous reports of copper complexes for nitrite (NO 2 − ) reduction. However, details of how protons and electrons arrive and how nitric oxide (NO) is released remain unknown. The influence of the coordination mode of nitrite on reactivity is also under debate. Kundu and co-workers have reported nitrite reduction by a copper(II) complex [J. Am. Chem. Soc. 2020, 142, 1726−1730. In their report, the copper(II) complex reduced nitrite using a phenol derivative as a reductant, resulting in NO, a hydroxyl copper(II) complex, and the corresponding biphenol. Also, the involvement of proton-coupled electron transfer was proposed by mechanistic studies. Herein, density functional theory calculations were performed to determine a mechanism for reduction of nitrite by a copper(II) complex. As a result of geometry optimization of an initial complex, two possible structures were obtained: Cu−ONO and Cu−NO 2 . Two possible reaction pathways initiated from Cu−ONO or Cu−NO 2 were then considered. The calculation results indicated that the Cu−ONO pathway is energetically favorable. When changes in the electronic structure were considered, both pathways were found to involve concerted proton−electron transfer (CPET). In addition, an intrinsic reaction coordinate analysis revealed that the two pathways were achieved by different types of CPET. Furthermore, an intrinsic bond orbital analysis clearly indicated that, in the Cu−ONO pathway, the chemical events involved proceeded concertedly yet asynchronously.

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Section: Resultssupporting

confidence: 92%

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

Kametani,

Ikeda,

Yoshizawa

et al. 2023

Inorg. Chem.

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“…To determine the nature of this transfer, we localized the canonical molecular orbitals using the intrinsic bond orbital (IBO) scheme for each point along the intrinsic reaction coordinate (IRC). This procedure allows us to track the evolution of each localized IBO orbital. − …”

Section: Resultsmentioning

confidence: 99%

Methane to Methanol Conversion over N-Doped Graphene Facilitated by Electrochemical Oxygen Evolution: A First-Principles Study

Hsieh

Tang

et al. 2022

J. Phys. Chem. C

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Direct methane oxidation to methanol is ideal for replacing the oxygen evolution reaction (OER) in artificial photosynthesis. This reaction requires less electricity and generates more valuable products than the OER. Moreover, it provides a better way to utilize abundant but inert methane. In this study, we have used density functional theory combined with a constant electrode potential model to evaluate the possibility of using abundant and low-cost N-doped graphene to catalyze this reaction. The active oxygen (*O) for rate-determining C−H activation is generated during the OER process. The results from our calculations show that this catalysis could be realized when graphene is doped with two nitrogen atoms in the vicinity of the reaction center so that long-lived *O is present and reacts to break strong methane C−H bonds. The minimum overall kinetic barrier is 0.91 eV at a potential of U = 1.10 V SHE , which is 0.82 eV lower than that in the absence of Us. The significant barrier reduction indicates that anodic potentials play essential roles in increasing the reactivity of N-doped graphene. During C−H activation, hydrogen is transferred from methane to *O. Analyzing this step using the Intrinsic Atomic Orbitals approach, we find that it follows a hydrogen atom transfer mechanism where the proton and electron travel together. Importantly, our analysis reveals that this transfer starts with the excitation of one electron from the *O lone pair to a surface π-orbital. This excitation increases the radical character on *O, rendering it reactive to couple with the transferred hydrogen atom. Easing this excitation is expected to further improve the reactivity of *O, as demonstrated by our calculations.

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“…They also investigated that Se–N heterocycles could not quench ROO· in the presence of N -acetylcysteine as thiol co-antioxidant. Not long ago, this hypothesized unconventional mechanism was supported by theoretical investigation . The most notable advancement of EDGs at ortho / para position in the aromatic ring of isoselenazolones caused a dramatic increase in the rate constant for quenching of ROO· and regenerability. , The bond dissociation energy (BDE O–H ) of the phenolic O–H bond is sensitive to the electronic contribution of EDGs from the aromatic ring and, thus, increases the rate of formal HAT to quench ROO· in an unconventional mechanism .…”

Section: Introductionmentioning

confidence: 94%

Introduction of Methyl Group in Substituted Isoselenazolones: Catalytic and Mechanistic Study

et al. 2023

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Copper-catalyzed direct selenation of substituted 2-bromo-N-phenylbenzamide substrates with elemental selenium powder provided a series of methoxysubstituted isoselenazolones via the C−Se and Se−N bond formations. Phenolic substituted isoselenazolones have been obtained by O-demethylation of the corresponding methoxy-substituted analogues using boron tribromide. Some isoselenazolones have been structurally characterized by X-ray single-crystal analysis. The glutathione peroxidase (GPx)-like antioxidant activity of isoselenazolones has been evaluated both in thiophenol and coupled-reductase assays. All isoselenazolones showed good GPx-like activities in the coupled-reductase assay. The ferric-reducing antioxidant power of phenolic antioxidants has also been evaluated. The best phenolic antioxidants were found to be good ferric-reducing antioxidant power agents. The single electron transfer, hydrogen atom transfer, and proton-coupled electron transfer mechanisms for the antioxidant properties of all catalysts have been supported by density functional theory calculations. The catalytic cycle was proposed for one of the phenolic isoselenazolones involving diselenide, selenenyl sulfide, selenol, and selenenic acid as intermediates using 77 Se{ 1 H} NMR spectroscopy.

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Chalcogen Atoms as Electron Donors in Proton-Coupled Electron Transfer Reactions

Cited by 10 publications

References 33 publications

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

Methane to Methanol Conversion over N-Doped Graphene Facilitated by Electrochemical Oxygen Evolution: A First-Principles Study

Introduction of Methyl Group in Substituted Isoselenazolones: Catalytic and Mechanistic Study

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