Proton-Coupled Electron Transfer Guidelines, Fair and Square

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(2), P. 560 - 576

Published: Jan. 6, 2021

Proton-coupled electron transfer (PCET) reactions are fundamental to energy transformation in natural and artificial systems increasingly recognized areas such as catalysis synthetic chemistry. The interdependence of proton brings a mechanistic richness reactivity, including various sequential concerted mechanisms. Delineating between different PCET mechanisms understanding why particular mechanism dominates crucial for the design optimization that use PCET. This Perspective provides practical guidelines how discern based on interpretations thermodynamic data with temperature-, pressure-, isotope-dependent kinetics. We present new PCET-zone diagrams show can switch or even be eliminated by varying (ΔGPT° ΔGET°) coupling strengths system. discuss appropriateness asynchronous rationalize observations organic reactions, distinction hydrogen atom other reactions. Contemporary issues future prospects research discussed.

Language: Английский

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Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2017 - 2291

Published: Nov. 23, 2021

We present here a review of the photochemical and electrochemical applications multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms which both an proton exchanged together, often concerted elementary step. As such, MS-PCET can function as non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from wide variety common functional groups. introduction practitioner’s guide reaction design, with emphasis on unique energetic selectivity features that characteristic this class. then chapters oxidative N–H, O–H, S–H, C–H homolysis methods, generation corresponding neutral species. Then, reductive PCET activations involving carbonyl, imine, other X═Y π-systems, heteroarenes, where ketyl, α-amino, heteroarene-derived radicals be generated. Finally, we asymmetric catalysis materials device applications. Within each chapter, subdivide by group undergoing homolysis, thereafter type transformation being promoted. Methods published prior end December 2020 presented.

Language: Английский

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An Unconventional Iron Nickel Catalyst for the Oxygen Evolution Reaction

ACS Central Science, Journal Year: 2019, Volume and Issue: 5(3), P. 558 - 568

Published: Feb. 26, 2019

The oxygen evolution reaction (OER) is a key process that enables the storage of renewable energies in form chemical fuels. Here, we describe catalyst exhibits turnover frequencies higher than state-of-the-art catalysts operate alkaline solutions, including benchmark nickel iron oxide. This new easily prepared from readily available and industrially relevant foam, it stable for many hours. Operando X-ray absorption spectroscopic data reveal made nanoclusters γ-FeOOH covalently linked to γ-NiOOH support. According density functional theory (DFT) computations, this structure may allow path involving as evolving center nearby terrace O site on support oxide hydrogen acceptor.

Language: Английский

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Photoinduced intermolecular hydrogen atom transfer reactions in organic synthesis

Chem Catalysis, Journal Year: 2021, Volume and Issue: 1(3), P. 523 - 598

Published: May 24, 2021

Language: Английский

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Free Energies of Proton-Coupled Electron Transfer Reagents and Their Applications

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(1), P. 1 - 49

Published: Dec. 20, 2021

We present an update and revision to our 2010 review on the topic of proton-coupled electron transfer (PCET) reagent thermochemistry. Over past decade, data thermochemical formalisms presented in that have been value multiple fields. Concurrently, there advances cycles experimental methods used measure these values. This Review (i) summarizes those advancements, (ii) corrects systematic errors prior shifted many absolute values tabulated data, (iii) provides updated tables values, (iv) discusses new conclusions opportunities from assembled associated techniques. advocate for provide greater clarity reduce barriers calculation measurement Gibbs free energies conversion X XHn PCET reactions. In particular, we demonstrate utility generality reporting potentials hydrogenation, E°(V vs H2), almost any solvent how are connected more widely reported bond dissociation (BDFEs). The H2) BDFEs generally insensitive nature and, some cases, even phase (gas versus solution). also presents introductions several emerging fields thermochemistry give readers windows into diversity research being performed. Some next frontiers this rapidly growing field coordination-induced weakening, novel environments, reactions at material interfaces.

Language: Английский

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Recognition of Surface Oxygen Intermediates on NiFe Oxyhydroxide Oxygen-Evolving Catalysts by Homogeneous Oxidation Reactivity

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(3), P. 1493 - 1502

Published: Jan. 13, 2021

NiFe oxyhydroxide is one of the most promising oxygen evolution reaction (OER) catalysts for renewable hydrogen production, and deciphering identity reactivity intermediates on its surface a key challenge but critical to catalyst design improving energy efficiency. Here, we screened utilized in situ reactive probes that can selectively target specific with high rates investigate OER pathway oxyhydroxide. Most importantly, atom transfer (OAT) (e.g., 4-(diphenylphosphino) benzoic acid) could efficiently inhibit kinetics by scavenging intermediates, exhibiting lower currents, larger Tafel slopes, kinetic isotope effect (KIE) values, while other reactivities demonstrated much smaller effects. Combining OAT electrochemical operando Raman spectroscopic techniques, identified resting Fe═O intermediate Ni–O scaffold rate-limiting O–O chemical coupling step between moiety vicinal bridging O. DFT calculation further revealed longer bond formed large barrier step, corroborating experimental results. These results point new direction liberating lattice O expediting optimizing NiFe-based electrocatalyst.

Language: Английский

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Mechanistic Characterization of (Xantphos)Ni(I)-Mediated Alkyl Bromide Activation: Oxidative Addition, Electron Transfer, or Halogen-Atom Abstraction

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(4), P. 1788 - 1796

Published: Jan. 6, 2019

Ni(I)-mediated single-electron oxidative activation of alkyl halides has been extensively proposed as a key step in Ni-catalyzed cross-coupling reactions to generate radical intermediates. There are four mechanisms through which this could take place: addition, outer-sphere electron transfer, inner-sphere and concerted halogen-atom abstraction. Despite considerable computational studies, there is no experimental study evaluate all pathways for formation. Herein, we report the isolation series (Xantphos)Ni(I)–Ar complexes that selectively activate over aryl eject radicals form Ni(II) complexes. This observation allows application kinetic studies on steric, electronic, solvent effects, combination with DFT calculations, systematically assess possible pathways. Our data reveal (Xantphos)Ni(I)-mediated halide proceeds via abstraction mechanism. result corroborates previous (terpy)Ni(I)- (py)Ni(I)-mediated formation, contrasts transfer pathway observed (PPh3)4Ni(0)-mediated activation. model system provides insight into overall mechanism offers basis differentiating electrophiles cross-electrophile coupling reactions.

Language: Английский

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Anti-Markovnikov alcohols via epoxide hydrogenation through cooperative catalysis

Science, Journal Year: 2019, Volume and Issue: 364(6442), P. 764 - 767

Published: May 23, 2019

Markovnikov falls to chromium and titanium Ring opening of strained triangular epoxides is a versatile method for making alcohols. However, these reactions are limited by their tendency leave the oxygen on more heavily substituted carbon, in accord with rule. Yao et al. now show that pair catalysts working cooperatively can invert this selectivity pattern. A catalyst pries ring open while activates delivers hydrogen. In an unusual mechanistic twist, complex appears deliver hydrogen atom, proton, electron at different stages cycle. Science , issue p. 764

Language: Английский

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Proton-Coupled Electron Transfer: The Engine of Energy Conversion and Storage

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(3), P. 1069 - 1081

Published: Jan. 13, 2022

Proton-coupled electron transfer (PCET) underpins energy conversion in chemistry and biology. Four systems are described whose discoveries based on PCET: the water splitting of Artificial Leaf, carbon fixation Bionic Leaf-C, nitrogen Leaf-N Coordination Chemistry Flow Battery (CCFB). Whereas require strong coupling between proton to reduce energetic barriers enable high efficiencies, CCFB requires complete decoupling so as avoid parasitic energy-wasting reactions. The proper design PCET these facilitates their implementation areas (i) centralized large scale grid storage electricity (ii) decentralized storage/conversion using only sunlight, air any source produce fuel food within a sustainable cycle for biogenic elements C, N P.

Language: Английский

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Surface Sulfate Ion on CdS Catalyst Enhances Syngas Generation from Biopolyols

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(17), P. 6533 - 6541

Published: April 27, 2021

Photocatalytic biomass conversion represents an ideal way of generating syngas because the sustainable use carbon and solar energy. However, lack efficient electron–proton transfer limits its efficiency. We here report unprecedented method to simultaneously increase both electron proton by creating surface sulfate ions on CdS catalyst ([SO4]/CdS). Surface ion [SO4] is bifunctional, serving as acceptor promote transfer, increasing oxidation potential valence band enhance transfer. [SO4]/CdS produces a mixture from glycerol without CO2. Compared with pristine CdS, exhibits 9-fold higher CO generation rate (0.31 mmol g–1 h–1) 4-fold H2 (0.05 h–1). A wide range sugars, such glucose, fructose, maltose, sucrose, xylose, lactose, insulin, starch, were facilely converted into syngas. This study reports pivotal effect in photocatalysis provides facile for photocatalytic

Language: Английский

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