1
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Cui K, Soudackov AV, Kessinger MC, Xu J, Meyer GJ, Hammes-Schiffer S. General Kinetic Model for pH Dependence of Proton-Coupled Electron Transfer: Application to an Electrochemical Water Oxidation System. J Am Chem Soc 2023; 145:19321-19332. [PMID: 37611195 DOI: 10.1021/jacs.3c05535] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
The pH dependence of proton-coupled electron transfer (PCET) reactions, which are critical to many chemical and biological processes, is a powerful probe for elucidating their fundamental mechanisms. Herein, a general, multichannel kinetic model is introduced to describe the pH dependence of both homogeneous and electrochemical PCET reactions. According to this model, a weak pH dependence can arise from the competition among multiple sequential and concerted PCET channels involving different forms of the redox species, such as protonated and deprotonated forms, as well as different proton donors and acceptors. The contribution of each channel is influenced by the relative populations of the reactant species, which often depend strongly on pH, leading to complex pH dependence of PCET apparent rate constants. This model is used to explain the origins of the experimentally observed weak pH dependence of the electrochemical PCET apparent rate constant for a ruthenium-based water oxidation catalyst attached to a tin-doped In2O3 (ITO) surface. The weak pH dependence is found to arise from the intrinsic differences in the rate constants of participating channels and the dependence of their relative contributions on pH. This model predicts that the apparent maximum rate constant will become pH-independent at higher pH, which is confirmed by experimental measurements. Our analysis also suggests that the dominant channels are electron transfer at lower pH and sequential PCET via electron transfer followed by fast proton transfer at higher pH. This work highlights the importance of considering multiple competing channels simultaneously for PCET processes.
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Affiliation(s)
- Kai Cui
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Alexander V Soudackov
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Matthew C Kessinger
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Jeremiah Xu
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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2
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Hammes-Schiffer S. Exploring Proton-Coupled Electron Transfer at Multiple Scales. NATURE COMPUTATIONAL SCIENCE 2023; 3:291-300. [PMID: 37577057 PMCID: PMC10416817 DOI: 10.1038/s43588-023-00422-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 02/23/2023] [Indexed: 08/15/2023]
Abstract
The coupling of electron and proton transfer is critical for chemical and biological processes spanning a wide range of length and time scales and often occurring in complex environments. Thus, diverse modeling strategies, including analytical theories, quantum chemistry, molecular dynamics, and kinetic modeling, are essential for a comprehensive understanding of such proton-coupled electron transfer reactions. Each of these computational methods provides one piece of the puzzle, and all these pieces must be viewed together to produce the full picture.
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3
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Kessinger M, Soudackov AV, Schneider J, Bangle RE, Hammes-Schiffer S, Meyer GJ. Reorganization Energies for Interfacial Proton-Coupled Electron Transfer to a Water Oxidation Catalyst. J Am Chem Soc 2022; 144:20514-20524. [DOI: 10.1021/jacs.2c09672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Matthew Kessinger
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina27599, United States
| | | | - Jenny Schneider
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina27599, United States
| | - Rachel E. Bangle
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina27599, United States
| | | | - Gerald J. Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina27599, United States
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4
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Warburton RE, Soudackov AV, Hammes-Schiffer S. Theoretical Modeling of Electrochemical Proton-Coupled Electron Transfer. Chem Rev 2022; 122:10599-10650. [PMID: 35230812 DOI: 10.1021/acs.chemrev.1c00929] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proton-coupled electron transfer (PCET) plays an essential role in a wide range of electrocatalytic processes. A vast array of theoretical and computational methods have been developed to study electrochemical PCET. These methods can be used to calculate redox potentials and pKa values for molecular electrocatalysts, proton-coupled redox potentials and bond dissociation free energies for PCET at metal and semiconductor interfaces, and reorganization energies associated with electrochemical PCET. Periodic density functional theory can also be used to compute PCET activation energies and perform molecular dynamics simulations of electrochemical interfaces. Various approaches for maintaining a constant electrode potential in electronic structure calculations and modeling complex interactions in the electric double layer (EDL) have been developed. Theoretical formulations for both homogeneous and heterogeneous electrochemical PCET spanning the adiabatic, nonadiabatic, and solvent-controlled regimes have been developed and provide analytical expressions for the rate constants and current densities as functions of applied potential. The quantum mechanical treatment of the proton and inclusion of excited vibronic states have been shown to be critical for describing experimental data, such as Tafel slopes and potential-dependent kinetic isotope effects. The calculated rate constants can be used as input to microkinetic models and voltammogram simulations to elucidate complex electrocatalytic processes.
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Affiliation(s)
- Robert E Warburton
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Alexander V Soudackov
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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5
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Koronkiewicz B, Sayfutyarova ER, Coste SC, Mercado BQ, Hammes-Schiffer S, Mayer JM. Structural and Thermodynamic Effects on the Kinetics of C-H Oxidation by Multisite Proton-Coupled Electron Transfer in Fluorenyl Benzoates. J Org Chem 2022; 87:2997-3006. [PMID: 35113555 DOI: 10.1021/acs.joc.1c02834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Our recent experimental and theoretical investigations have shown that fluorene C-H bonds can be activated through a mechanism in which the proton and electron are transferred from the C-H bond to a separate base and oxidant in a concerted, elementary step. This multisite proton-coupled electron transfer (MS-PCET) mechanism for C-H bond activation was shown to be facilitated by shorter proton donor-acceptor distances. With the goal of intentionally modulating this donor-acceptor distance, we have now studied C-H MS-PCET in the 3-methyl-substituted fluorenyl benzoate (2-Flr-3-Me-BzO-). This derivative was readily oxidized by ferrocenium oxidants by initial C-H MS-PCET, with rate constants that were 6-21 times larger than those for 2-Flr-BzO- with the same oxidants. Structural comparisons by X-ray crystallography and by computations showed that addition of the 3-methyl group caused the expected steric compression; however, the relevant C···O- proton donor-acceptor distance was longer, due to a twist of the carboxylate group. The structural changes induced by the 3-Me group increased the basicity of the carboxylate, weakened the C-H bond, and reduced the reorganization energy for C-H bond cleavage. Thus, the rate enhancement for 2-Flr-3-Me-BzO- was due to effects on the thermochemistry and kinetic barrier, rather than from compression of the C···O- proton donor-acceptor distance. These results highlight both the challenges of controlling molecules on the 0.1 Å length scale and the variety of parameters that affect PCET rate constants.
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Affiliation(s)
- Brian Koronkiewicz
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Elvira R Sayfutyarova
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Scott C Coste
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Brandon Q Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - James M Mayer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, United States
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6
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Salamone M, Galeotti M, Romero-Montalvo E, van Santen JA, Groff BD, Mayer JM, DiLabio GA, Bietti M. Bimodal Evans-Polanyi Relationships in Hydrogen Atom Transfer from C(sp 3)-H Bonds to the Cumyloxyl Radical. A Combined Time-Resolved Kinetic and Computational Study. J Am Chem Soc 2021; 143:11759-11776. [PMID: 34309387 PMCID: PMC8343544 DOI: 10.1021/jacs.1c05566] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Indexed: 12/11/2022]
Abstract
The applicability of the Evans-Polanyi (EP) relationship to HAT reactions from C(sp3)-H bonds to the cumyloxyl radical (CumO•) has been investigated. A consistent set of rate constants, kH, for HAT from the C-H bonds of 56 substrates to CumO•, spanning a range of more than 4 orders of magnitude, has been measured under identical experimental conditions. A corresponding set of consistent gas-phase C-H bond dissociation enthalpies (BDEs) spanning 27 kcal mol-1 has been calculated using the (RO)CBS-QB3 method. The log kH' vs C-H BDE plot shows two distinct EP relationships, one for substrates bearing benzylic and allylic C-H bonds (unsaturated group) and the other one, with a steeper slope, for saturated hydrocarbons, alcohols, ethers, diols, amines, and carbamates (saturated group), in line with the bimodal behavior observed previously in theoretical studies of reactions promoted by other HAT reagents. The parallel use of BDFEs instead of BDEs allows the transformation of this correlation into a linear free energy relationship, analyzed within the framework of the Marcus theory. The ΔG⧧HAT vs ΔG°HAT plot shows again distinct behaviors for the two groups. A good fit to the Marcus equation is observed only for the saturated group, with λ = 58 kcal mol-1, indicating that with the unsaturated group λ must increase with increasing driving force. Taken together these results provide a qualitative connection between Bernasconi's principle of nonperfect synchronization and Marcus theory and suggest that the observed bimodal behavior is a general feature in the reactions of oxygen-based HAT reagents with C(sp3)-H donors.
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Affiliation(s)
- Michela Salamone
- Dipartimento
di Scienze e Tecnologie Chimiche, Università
“Tor Vergata”, Via della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Marco Galeotti
- Dipartimento
di Scienze e Tecnologie Chimiche, Università
“Tor Vergata”, Via della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Eduardo Romero-Montalvo
- Department
of Chemistry, The University of British
Columbia, 3247 University Way, Kelowna, British Columbia, Canada, V1V 1V7
| | - Jeffrey A. van Santen
- Department
of Chemistry, The University of British
Columbia, 3247 University Way, Kelowna, British Columbia, Canada, V1V 1V7
| | - Benjamin D. Groff
- Department
of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - James M. Mayer
- Department
of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Gino A. DiLabio
- Department
of Chemistry, The University of British
Columbia, 3247 University Way, Kelowna, British Columbia, Canada, V1V 1V7
| | - Massimo Bietti
- Dipartimento
di Scienze e Tecnologie Chimiche, Università
“Tor Vergata”, Via della Ricerca Scientifica, 1, I-00133 Rome, Italy
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7
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Zhang J, Borrelli R, Tanimura Y. Probing photoinduced proton coupled electron transfer process by means of two-dimensional resonant electronic–vibrational spectroscopy. J Chem Phys 2021; 154:144104. [DOI: 10.1063/5.0046755] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Jiaji Zhang
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Raffaele Borrelli
- DISAFA, University of Torino, Largo Paolo Braccini 2, I-10095 Grugliasco, Italy
| | - Yoshitaka Tanimura
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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8
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Sakaushi K, Kumeda T, Hammes-Schiffer S, Melander MM, Sugino O. Advances and challenges for experiment and theory for multi-electron multi-proton transfer at electrified solid–liquid interfaces. Phys Chem Chem Phys 2020; 22:19401-19442. [DOI: 10.1039/d0cp02741c] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Understanding microscopic mechanism of multi-electron multi-proton transfer reactions at complexed systems is important for advancing electrochemistry-oriented science in the 21st century.
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Affiliation(s)
- Ken Sakaushi
- Center for Green Research on Energy and Environmental Materials
- National Institute for Materials Science
- Ibaraki 305-0044
- Japan
| | - Tomoaki Kumeda
- Center for Green Research on Energy and Environmental Materials
- National Institute for Materials Science
- Ibaraki 305-0044
- Japan
| | | | - Marko M. Melander
- Nanoscience Center
- Department of Chemistry
- University of Jyväskylä
- Jyväskylä
- Finland
| | - Osamu Sugino
- The Institute of Solid State Physics
- the University of Tokyo
- Chiba 277-8581
- Japan
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9
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Sayfutyarova ER, Lam YC, Hammes-Schiffer S. Strategies for Enhancing the Rate Constant of C-H Bond Cleavage by Concerted Proton-Coupled Electron Transfer. J Am Chem Soc 2019; 141:15183-15189. [PMID: 31464122 DOI: 10.1021/jacs.9b06849] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recently selective C-H bond cleavage under mild conditions with weak oxidants was reported for fluorenyl-benzoates. This mechanism is based on multi-site concerted proton-coupled electron transfer (PCET) involving intermolecular electron transfer to an outer-sphere oxidant coupled to intramolecular proton transfer to a well-positioned proton acceptor. The electron transfer driving force depends predominantly on the oxidant, and the proton transfer driving force depends mainly on the basicity of the carboxylate, which is influenced by the substituent on the benzoate fragment. Experiments showed that the rate constants are much more sensitive to the carboxylate basicity than to the redox potential of the oxidant. Herein a vibronically nonadiabatic PCET theory is used to explain how changing the driving force for the electron and proton transfer components of the reaction through varying the oxidant and the substituent, respectively, impacts the PCET rate constant. In addition to increasing the driving force for proton transfer, enhancing the basicity of the carboxylate also decreases the equilibrium proton donor-acceptor distance, thereby facilitating the sampling of shorter proton donor-acceptor distances. This additional effect arising from the strong dependence of proton transfer on the proton donor-acceptor distance provides an explanation for the greater sensitivity of the rate constant to the carboxylate basicity than to the redox potential of the oxidant. These fundamental insights have broad implications for developing new strategies to activate C-H bonds, specifically by designing systems with shorter equilibrium proton donor-acceptor distances.
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Affiliation(s)
- Elvira R Sayfutyarova
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Yan-Choi Lam
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
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10
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Goldsmith ZK, Soudackov AV, Hammes-Schiffer S. Theoretical analysis of the inverted region in photoinduced proton-coupled electron transfer. Faraday Discuss 2019; 216:363-378. [PMID: 31017599 PMCID: PMC6620152 DOI: 10.1039/c8fd00240a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Photoinduced proton-coupled electron transfer (PCET) plays a key role in a wide range of energy conversion processes, and understanding how to design systems to control the PCET rate constant is a significant challenge. Herein a theoretical formulation of PCET is utilized to identify the conditions under which photoinduced PCET may exhibit inverted region behavior. In the inverted region, the rate constant decreases as the driving force increases even though the reaction becomes more thermodynamically favorable. Photoinduced PCET will exhibit inverted region behavior when the following criteria are satisfied: (1) the overlap integrals corresponding to the ground reactant and the excited product proton vibrational wavefunctions become negligible for a low enough product vibronic state and (2) the reaction free energies associated with the lower excited product proton vibrational wavefunctions contributing significantly to the rate constant are negative with magnitudes greater than the reorganization energy. These criteria are typically not satisfied by harmonic or Morse potentials but are satisfied by more realistic asymmetric double well potentials because the proton vibrational states above the barrier correspond to more delocalized proton vibrational wavefunctions with nodal structures leading to destructive interference effects. Thus, this theoretical analysis predicts that inverted region behavior could be observed for systems with asymmetric double well potentials characteristic of hydrogen-bonded systems and that the hydrogen/deuterium kinetic isotope effect will approach unity and could even become inverse in this region due to the oscillatory nature of the highly excited vibrational wavefunctions. These insights may help guide the design of more effective energy conversion devices.
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Affiliation(s)
- Zachary K Goldsmith
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA.
| | - Alexander V Soudackov
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA.
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA.
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11
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Parada GA, Goldsmith ZK, Kolmar S, Pettersson Rimgard B, Mercado BQ, Hammarström L, Hammes-Schiffer S, Mayer JM. Concerted proton-electron transfer reactions in the Marcus inverted region. Science 2019; 364:471-475. [PMID: 30975771 PMCID: PMC6681808 DOI: 10.1126/science.aaw4675] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/28/2019] [Indexed: 11/02/2022]
Abstract
Electron transfer reactions slow down when they become very thermodynamically favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge-separated state. The rate constants for return charge recombination show an inverted dependence on the driving force upon changing pyridine substituents and the solvent. Calculations using vibronically nonadiabatic PCET theory yield rate constants for simultaneous tunneling of the electron and proton that account for the results.
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Affiliation(s)
| | | | - Scott Kolmar
- Department of Chemistry, Yale University, New Haven, CT, USA
| | | | | | - Leif Hammarström
- Department of Chemistry - Ångström Laboratory, Uppsala University, Uppsala, Sweden.
| | | | - James M Mayer
- Department of Chemistry, Yale University, New Haven, CT, USA.
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12
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Goldsmith ZK, Lam YC, Soudackov AV, Hammes-Schiffer S. Proton Discharge on a Gold Electrode from Triethylammonium in Acetonitrile: Theoretical Modeling of Potential-Dependent Kinetic Isotope Effects. J Am Chem Soc 2019; 141:1084-1090. [PMID: 30570256 DOI: 10.1021/jacs.8b11826] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The discharge of protons on electrode surfaces, known as the Volmer reaction, is a ubiquitous reaction in heterogeneous electrocatalysis and plays an important role in renewable energy technologies. Recent experiments with triethylammonium (TEAH+) donating the proton to a gold electrode in acetonitrile demonstrate significantly different Tafel slopes for TEAH+ and its deuterated counterpart, TEAD+. As a result, the kinetic isotope effect (KIE) for the hydrogen evolution reaction changes considerably as a function of applied potential. Herein a vibronically nonadiabatic approach for proton-coupled electron transfer (PCET) at an electrode interface is extended to heterogeneous electrochemical processes and is applied to this system. This approach accounts for the key effects of the electrical double layer and spans the electronically adiabatic and nonadiabatic regimes, as found to be necessary for this reaction. The experimental Tafel plots for TEAH+ and TEAD+ are reproduced using physically reasonable parameters within this model. The potential-dependent KIE or, equivalently, isotope-dependent Tafel slope is found to be a consequence of contributions from excited electron-proton vibronic states that depend on both isotope and applied potential. Specifically, the contributions from excited reactant vibronic states are greater for TEAD+ than for TEAH+. Thus, the two reactions proceed by the same fundamental mechanism yet exhibit significantly different Tafel slopes. This theoretical approach may be applicable to a wide range of other heterogeneous electrochemical PCET reactions.
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Affiliation(s)
- Zachary K Goldsmith
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Yan Choi Lam
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Alexander V Soudackov
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
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13
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Thammavongsy Z, Mercer IP, Yang JY. Promoting proton coupled electron transfer in redox catalysts through molecular design. Chem Commun (Camb) 2019; 55:10342-10358. [DOI: 10.1039/c9cc05139b] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mini-review on using the secondary coordination sphere to facilitate multi-electron, multi-proton catalysis.
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Affiliation(s)
| | - Ian P. Mercer
- Department of Chemistry
- University of California
- Irvine
- USA
| | - Jenny Y. Yang
- Department of Chemistry
- University of California
- Irvine
- USA
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14
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Lymar SV, Ertem MZ, Polyansky DE. Solvent-dependent transition from concerted electron-proton to proton transfer in photoinduced reactions between phenols and polypyridine Ru complexes with proton-accepting sites. Dalton Trans 2018; 47:15917-15928. [PMID: 30375615 DOI: 10.1039/c8dt03858a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The bimolecular rate coefficients (kobsq) for quenching the metal-to-ligand charge transfer excited states of two Ru polypyridine complexes containing H-bond accepting sites by six p-substituted phenols exhibit abrupt deviations from the expected linear correlations of log kobsq with phenol's Hammett σp constant. This pattern is attributed to a transition of the quenching mechanism from a concerted electron-proton transfer (EPT) to a proton transfer (PT); the latter becomes predominant for the most acidic phenols in acetonitrile, but not in dichloromethane. This assertion is supported by a detailed thermochemical analysis, which also excludes the quenching pathways involving electron transfer from phenols with or without deprotonation of phenols to the solvent, either concerted or sequential. The transition from EPT to PT upon the σp increase is consistent/supported by the magnitudes of the measured and computed PhOH/OD kinetic isotope effects and by the observed reduction of the EPT product yields upon replacing the low σp methoxyphenol by the high σp nitrophenol. In addition to modulating the relative contribution of the EPT and PT quenching pathways, the solvent strongly affects the bimolecular rate coefficients for the EPT quenching proper. Unlike with H-atom transfer reactions, this kinetic solvent effect could not be quantitatively accounted for by the phenol-solvent H-bonding alone, which suggests a solvent effect on the H-bonding constants in the phenol-Ru complex precursor exciplexes and/or on the unimolecular EPT rate coefficients within these exciplexes.
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Affiliation(s)
- Sergei V Lymar
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
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15
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Sayfutyarova ER, Goldsmith ZK, Hammes-Schiffer S. Theoretical Study of C-H Bond Cleavage via Concerted Proton-Coupled Electron Transfer in Fluorenyl-Benzoates. J Am Chem Soc 2018; 140:15641-15645. [PMID: 30383371 DOI: 10.1021/jacs.8b10461] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Developing new strategies to activate and cleave C-H bonds is important for a broad range of applications. Recently a new approach for C-H bond activation using multi-site concerted proton-coupled electron transfer (PCET) involving intermolecular electron transfer to an oxidant coupled to intramolecular proton transfer was reported. For a series of oxidants reacting with 2-(9 H-fluoren-9-yl)benzoate, experimental studies revealed an atypical Brønsted α, defined as the slope of the logarithm of the PCET rate constant versus the logarithm of the equilibrium constant or the scaled driving force. Herein this reaction is modeled with a vibronically nonadiabatic PCET theory. Hydrogen tunneling, thermal sampling of the proton donor-acceptor mode, solute and solvent reorganization, and contributions from excited vibronic states are found to play important roles. The calculations qualitatively reproduce the experimental observation of a Brønsted α significantly less than 0.5 and explain this shallow slope in terms of exoergic processes between pairs of electron-proton vibronic states. These fundamental mechanistic insights may guide the design of more effective strategies for C-H bond activation and cleavage.
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Affiliation(s)
- Elvira R Sayfutyarova
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Zachary K Goldsmith
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
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16
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Xu Y, Bao P, Song K, Shi Q. Theoretical study of proton coupled electron transfer reaction in the light state of the AppA BLUF photoreceptor. J Comput Chem 2018; 40:1005-1014. [PMID: 30341953 DOI: 10.1002/jcc.25561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/01/2018] [Accepted: 07/24/2018] [Indexed: 11/10/2022]
Abstract
The BLUF (blue light sensor using flavin adenine dinucleotide) domain is widely studied as a prototype for proton coupled electron transfer (PCET) reactions in biological systems. In this work, the photo-induced concerted PCET reaction from the light state of the AppA BLUF domain is investigated. To model the simultaneous transfer of two protons in the reaction, two-dimensional potential energy surfaces for the double proton transfer are first calculated for the locally excited and charge transfer states, which are then used to obtain the vibrational wave function overlaps and the vibrational energy levels. Contributions to the PCET rate constant from each pair of vibronic states are then analyzed using the theory based on the Fermi's golden rule. We show that, the recently proposed light state structure of the BLUF domain with a tautomerized Gln63 residue is consistent with the concerted transfer of one electron and two protons. It is also found that, thermal fluctuations of the protein structure, especially the proton donor-acceptor distances, play an important role in determining the PCET reaction rate. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Yang Xu
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Peng Bao
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Kai Song
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Qiang Shi
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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17
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Holmberg N, Laasonen K. Diabatic model for electrochemical hydrogen evolution based on constrained DFT configuration interaction. J Chem Phys 2018; 149:104702. [PMID: 30219020 DOI: 10.1063/1.5038959] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The accuracy of density functional theory (DFT) based kinetic models for electrocatalysis is diminished by spurious electron delocalization effects, which manifest as uncertainties in the predicted values of reaction and activation energies. In this work, we present a constrained DFT (CDFT) approach to alleviate overdelocalization effects in the Volmer-Heyrovsky mechanism of the hydrogen evolution reaction (HER). This method is applied a posteriori to configurations sampled along a reaction path to correct their relative stabilities. Concretely, the first step of this approach involves describing the reaction in terms of a set of diabatic states that are constructed by imposing suitable density constraints on the system. Refined reaction energy profiles are then recovered by performing a configuration interaction (CDFT-CI) calculation within the basis spanned by the diabatic states. After a careful validation of the proposed method, we examined HER catalysis on open-ended carbon nanotubes and discovered that CDFT-CI increased activation energies and decreased reaction energies relative to DFT predictions. We believe that a similar approach could also be adopted to treat overdelocalization effects in other electrocatalytic proton-coupled electron transfer reactions, e.g., in the oxygen reduction reaction.
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Affiliation(s)
- Nico Holmberg
- Department of Chemistry and Materials Science, Aalto University, P.O. Box 16100, 00076 Aalto, Finland
| | - Kari Laasonen
- Department of Chemistry and Materials Science, Aalto University, P.O. Box 16100, 00076 Aalto, Finland
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18
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Soudackov AV, Hammes-Schiffer S. Proton-coupled electron transfer reactions: analytical rate constants and case study of kinetic isotope effects in lipoxygenase. Faraday Discuss 2018; 195:171-189. [PMID: 27735009 DOI: 10.1039/c6fd00122j] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A general theory has been developed for proton-coupled electron transfer (PCET), which is vital to a wide range of chemical and biological processes. This theory describes PCET reactions in terms of nonadiabatic transitions between reactant and product electron-proton vibronic states and includes the effects of thermal fluctuations of the solvent or protein environment, as well as the proton donor-acceptor motion. Within the framework of this general PCET theory, a series of analytical rate constant expressions has been derived for PCET reactions in well-defined regimes. Herein, the application of this theory to PCET in the enzyme soybean lipoxygenase illustrates the regimes of validity for the various rate constant expressions and elucidates the fundamental physical principles dictating PCET reactions. Such theoretical studies provide significant physical insights that guide the interpretation of experimental data and lead to experimentally testable predictions. A combination of theoretical treatments with atomic-level simulations is essential to understanding PCET.
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Affiliation(s)
- Alexander V Soudackov
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
| | - Sharon Hammes-Schiffer
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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19
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Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions. Nat Chem 2018; 10:881-887. [DOI: 10.1038/s41557-018-0076-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 04/27/2018] [Indexed: 12/19/2022]
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20
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Chu KT, Liu YC, Chung MW, Poerwoprajitno AR, Lee GH, Chiang MH. Energy-Efficient Hydrogen Evolution by Fe-S Electrocatalysts: Mechanistic Investigations. Inorg Chem 2018; 57:7620-7630. [PMID: 29893554 DOI: 10.1021/acs.inorgchem.8b00543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The intrinsic catalytic property of a Fe-S complex toward H2 evolution was investigated in a wide range of acids. The title complex exhibited catalytic events at -1.16 and -1.57 V (vs Fc+/Fc) in the presence of trifluoromethanesulfonic acid (HOTf) and trifluoroacetic acid (TFA), respectively. The processes corresponded to the single reduction of the Fe-hydride-S-proton and Fe-hydride species, respectively. When anilinium acid was used, the catalysis occurred at -1.16 V, identical with the working potential of the HOTf catalysis, although the employment of anilinium acid was only capable of achieving the Fe-hydride state on the basis of the spectral and calculated results. The thermodynamics and kinetics of individual steps of the catalysis were analyzed by density functional theory (DFT) calculations and electroanalytical simulations. The stepwise CCE or CE (C, chemical; E, electrochemical) mechanism was operative from the HOTf or TFA source, respectively. In contrast, the involvement of anilinium acid most likely initiated a proton-coupled electron transfer (PCET) pathway that avoided the disfavored intermediate after the initial protonation. Via the PCET pathway, the heterogeneous electron transfer rate was increased and the overpotential was decreased by 0.4 V in comparison with the stepwise pathways. The results showed that the PCET-involved catalysis exhibited substantial kinetic and thermodynamic advantages in comparison to the stepwise pathway; thus, an efficient catalytic system for proton reduction was established.
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Affiliation(s)
- Kai-Ti Chu
- Institute of Chemistry , Academia Sinica , Nankang, Taipei 115 , Taiwan
| | - Yu-Chiao Liu
- Institute of Chemistry , Academia Sinica , Nankang, Taipei 115 , Taiwan
| | - Min-Wen Chung
- Institute of Chemistry , Academia Sinica , Nankang, Taipei 115 , Taiwan
| | | | - Gene-Hsiang Lee
- Instrumentation Center , National Taiwan University , Taipei 106 , Taiwan
| | - Ming-Hsi Chiang
- Institute of Chemistry , Academia Sinica , Nankang, Taipei 115 , Taiwan
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21
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Sutherlin KD, Rivard BS, Böttger LH, Liu LV, Rogers MS, Srnec M, Park K, Yoda Y, Kitao S, Kobayashi Y, Saito M, Seto M, Hu M, Zhao J, Lipscomb JD, Solomon EI. NRVS Studies of the Peroxide Shunt Intermediate in a Rieske Dioxygenase and Its Relation to the Native Fe II O 2 Reaction. J Am Chem Soc 2018; 140:5544-5559. [PMID: 29618204 PMCID: PMC5973823 DOI: 10.1021/jacs.8b01822] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The Rieske dioxygenases are a major subclass of mononuclear nonheme iron enzymes that play an important role in bioremediation. Recently, a high-spin FeIII-(hydro)peroxy intermediate (BZDOp) has been trapped in the peroxide shunt reaction of benzoate 1,2-dioxygenase. Defining the structure of this intermediate is essential to understanding the reactivity of these enzymes. Nuclear resonance vibrational spectroscopy (NRVS) is a recently developed synchrotron technique that is ideal for obtaining vibrational, and thus structural, information on Fe sites, as it gives complete information on all vibrational normal modes containing Fe displacement. In this study, we present NRVS data on BZDOp and assign its structure using these data coupled to experimentally calibrated density functional theory calculations. From this NRVS structure, we define the mechanism for the peroxide shunt reaction. The relevance of the peroxide shunt to the native FeII/O2 reaction is evaluated. For the native FeII/O2 reaction, an FeIII-superoxo intermediate is found to react directly with substrate. This process, while uphill thermodynamically, is found to be driven by the highly favorable thermodynamics of proton-coupled electron transfer with an electron provided by the Rieske [2Fe-2S] center at a later step in the reaction. These results offer important insight into the relative reactivities of FeIII-superoxo and FeIII-hydroperoxo species in nonheme Fe biochemistry.
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Affiliation(s)
- Kyle D. Sutherlin
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Brent S. Rivard
- Department of Biochemistry, Molecular Biology, & Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lars H. Böttger
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Lei V. Liu
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Melanie S. Rogers
- Department of Biochemistry, Molecular Biology, & Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Martin Srnec
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- J. HeyrovskýInstitute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague 8, Czech Republic
| | - Kiyoung Park
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Yoshitaka Yoda
- Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan
| | - Shinji Kitao
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
| | | | - Makina Saito
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
| | - Makoto Seto
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
| | - Michael Hu
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - John D. Lipscomb
- Department of Biochemistry, Molecular Biology, & Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
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22
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Huynh MT, Mora SJ, Villalba M, Tejeda-Ferrari ME, Liddell PA, Cherry BR, Teillout AL, Machan CW, Kubiak CP, Gust D, Moore TA, Hammes-Schiffer S, Moore AL. Concerted One-Electron Two-Proton Transfer Processes in Models Inspired by the Tyr-His Couple of Photosystem II. ACS CENTRAL SCIENCE 2017; 3:372-380. [PMID: 28573198 PMCID: PMC5445534 DOI: 10.1021/acscentsci.7b00125] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Indexed: 05/28/2023]
Abstract
Nature employs a TyrZ-His pair as a redox relay that couples proton transfer to the redox process between P680 and the water oxidizing catalyst in photosystem II. Artificial redox relays composed of different benzimidazole-phenol dyads (benzimidazole models His and phenol models Tyr) with substituents designed to simulate the hydrogen bond network surrounding the TyrZ-His pair have been prepared. When the benzimidazole substituents are strong proton acceptors such as primary or tertiary amines, theory predicts that a concerted two proton transfer process associated with the electrochemical oxidation of the phenol will take place. Also, theory predicts a decrease in the redox potential of the phenol by ∼300 mV and a small kinetic isotope effect (KIE). Indeed, electrochemical, spectroelectrochemical, and KIE experimental data are consistent with these predictions. Notably, these results were obtained by using theory to guide the rational design of artificial systems and have implications for managing proton activity to optimize efficiency at energy conversion sites involving water oxidation and reduction.
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Affiliation(s)
- Mioy T. Huynh
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - S. Jimena Mora
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Matias Villalba
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | | | - Paul A. Liddell
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Brian R. Cherry
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Anne-Lucie Teillout
- Laboratoire
de Chimie Physique, Groupe d’Electrochimie et de Photoélectrochimie,
UMR 8000 CNRS, Université Paris-Sud, Batiment 350, 91405 Orsay Cedex, France
| | - Charles W. Machan
- Department
of Chemistry, University of Virginia, McCormick Road,
PO 400319, Charlottesville, Virginia 22904, United States
| | - Clifford P. Kubiak
- Department
of Chemistry and Biochemistry, University
of California, San Diego, 9500 Gilman Drive, MC 0358, La Jolla, California 92093, United States
| | - Devens Gust
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Thomas A. Moore
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Sharon Hammes-Schiffer
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - Ana L. Moore
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
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23
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Pinto da Silva L, Simkovitch R, Huppert D, Esteves da Silva JC. Combined experimental and theoretical study of the photochemistry of 4- and 3-hydroxycoumarin. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2017.01.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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24
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Glover SD, Parada GA, Markle TF, Ott S, Hammarström L. Isolating the Effects of the Proton Tunneling Distance on Proton-Coupled Electron Transfer in a Series of Homologous Tyrosine-Base Model Compounds. J Am Chem Soc 2017; 139:2090-2101. [DOI: 10.1021/jacs.6b12531] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Starla D. Glover
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Giovanny A. Parada
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Todd F. Markle
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Sascha Ott
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Leif Hammarström
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
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25
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Li H, Zhang MT. Tuning Excited-State Reactivity by Proton-Coupled Electron Transfer. Angew Chem Int Ed Engl 2016; 55:13132-13136. [DOI: 10.1002/anie.201607176] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Indexed: 11/05/2022]
Affiliation(s)
- Han Li
- Center of Basic Molecular Science (CBMS); Department of Chemistry; Tsinghua University; Beijing 100084 China
| | - Ming-Tian Zhang
- Center of Basic Molecular Science (CBMS); Department of Chemistry; Tsinghua University; Beijing 100084 China
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26
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Li H, Zhang MT. Tuning Excited-State Reactivity by Proton-Coupled Electron Transfer. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201607176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Han Li
- Center of Basic Molecular Science (CBMS); Department of Chemistry; Tsinghua University; Beijing 100084 China
| | - Ming-Tian Zhang
- Center of Basic Molecular Science (CBMS); Department of Chemistry; Tsinghua University; Beijing 100084 China
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27
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Simkovitch R, Pinto da Silva L, Esteves da Silva JCG, Huppert D. Comparison of the Photoprotolytic Processes of Three 7-Hydroxycoumarins. J Phys Chem B 2016; 120:10297-10310. [DOI: 10.1021/acs.jpcb.6b01383] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Ron Simkovitch
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | | | - Dan Huppert
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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28
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Markle TF, Zhang MT, Santoni MP, Johannissen LO, Hammarström L. Proton-Coupled Electron Transfer in a Series of Ruthenium-Linked Tyrosines with Internal Bases: Evaluation of a Tunneling Model for Experimental Temperature-Dependent Kinetics. J Phys Chem B 2016; 120:9308-21. [DOI: 10.1021/acs.jpcb.6b05885] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Todd F. Markle
- Department of Chemistry − Ångström
Laboratory, Uppsala University, P.O. Box 523, S-75120 Uppsala, Sweden
| | - Ming-Tian Zhang
- Department of Chemistry − Ångström
Laboratory, Uppsala University, P.O. Box 523, S-75120 Uppsala, Sweden
| | - Marie-Pierre Santoni
- Department of Chemistry − Ångström
Laboratory, Uppsala University, P.O. Box 523, S-75120 Uppsala, Sweden
| | - Linus O. Johannissen
- Department of Chemistry − Ångström
Laboratory, Uppsala University, P.O. Box 523, S-75120 Uppsala, Sweden
| | - Leif Hammarström
- Department of Chemistry − Ångström
Laboratory, Uppsala University, P.O. Box 523, S-75120 Uppsala, Sweden
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29
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Green O, Simkovitch R, Pinto da Silva L, Esteves da Silva JCG, Shabat D, Huppert D. Excited-State Proton Transfer and Formation of the Excited Tautomer of 3-Hydroxypyridine-Dipicolinium Cyanine Dye. J Phys Chem A 2016; 120:6184-99. [DOI: 10.1021/acs.jpca.6b04666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ori Green
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ron Simkovitch
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | | | - Doron Shabat
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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30
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Soudackov AV, Hammes-Schiffer S. Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion. J Chem Phys 2016; 143:194101. [PMID: 26590521 DOI: 10.1063/1.4935045] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton transfer and proton-coupled electron transfer in chemical and biological processes.
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Affiliation(s)
- Alexander V Soudackov
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Ave., Urbana, Illinois 61801, USA
| | - Sharon Hammes-Schiffer
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Ave., Urbana, Illinois 61801, USA
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31
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Jackson MN, Surendranath Y. Donor-Dependent Kinetics of Interfacial Proton-Coupled Electron Transfer. J Am Chem Soc 2016; 138:3228-34. [PMID: 26862666 DOI: 10.1021/jacs.6b00167] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The effect of the proton donor on the kinetics of interfacial concerted proton-electron transfer (CPET) to polycrystalline Au was probed indirectly by studying the rate of hydrogen evolution from trialkylammonium donors with different steric profiles, but the same pKa. Detailed kinetic studies point to a mechanism for HER catalysis that involves rate-limiting CPET from the proton donor to the electrode surface, allowing this catalytic reaction to serve as a proxy for the rate of interfacial CPET. In acetonitrile electrolyte, triethylammonium (TEAH(+)) displays up to 20-fold faster CPET kinetics than diisopropylethylammonium (DIPEAH(+)) at all measured potentials. In aqueous electrolyte, this steric constraint is largely lifted, suggesting a key role for water in mediating interfacial CPET. In acetonitrile, TEAH(+) also displays a much larger transfer coefficient (β = 0.7) than DIPEAH(+) (β = 0.4), and TEAH(+) displays a potential-dependent H/D kinetic isotope effect that is not observed for DIPEAH(+). These results demonstrate that proton donor structure strongly impacts the free energy landscape for CPET to extended solid surfaces and highlight the crucial role of the proton donor in the kinetics of electrocatalytic energy conversion reactions.
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Affiliation(s)
- Megan N Jackson
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Yogesh Surendranath
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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32
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Liu Y, Liu H, Song K, Xu Y, Shi Q. Theoretical Study of Proton Coupled Electron Transfer Reactions: The Effect of Hydrogen Bond Bending Motion. J Phys Chem B 2015; 119:8104-14. [DOI: 10.1021/acs.jpcb.5b02927] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yang Liu
- Beijing
National Laboratory
for Molecular Sciences, State Key Laboratory for Structural Chemistry
of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Hao Liu
- Beijing
National Laboratory
for Molecular Sciences, State Key Laboratory for Structural Chemistry
of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Kai Song
- Beijing
National Laboratory
for Molecular Sciences, State Key Laboratory for Structural Chemistry
of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Yang Xu
- Beijing
National Laboratory
for Molecular Sciences, State Key Laboratory for Structural Chemistry
of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Qiang Shi
- Beijing
National Laboratory
for Molecular Sciences, State Key Laboratory for Structural Chemistry
of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
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33
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Heppner D, Kjaergaard CH, Solomon EI. Mechanism of the reduction of the native intermediate in the multicopper oxidases: insights into rapid intramolecular electron transfer in turnover. J Am Chem Soc 2014; 136:17788-801. [PMID: 25490729 PMCID: PMC4291763 DOI: 10.1021/ja509150j] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Indexed: 12/20/2022]
Abstract
The multicopper oxidases (MCOs) are the family of enzymes that catalyze the 4-electron reduction of O2 to H2O coupled to the four 1-electron oxidations of substrate. In the catalytic cycle electrons are transferred intramolecularly over ∼13 Å from a Type 1 (T1) Cu site that accepts electrons from substrate to a trinuclear Cu cluster (TNC) where O2 is reduced to H2O at rapid rates consistent with turnover (560 s(-1)). The oxygen reduction mechanism for the MCOs is well-characterized, whereas the rereduction is less understood. Our initial study of Rhus vernicifera Laccase (Heppner et al. J. Am. Chem. Soc. 2013, 135, 12212) experimentally established that the native intermediate (NI), the species formed upon O-O bond cleavage, is reduced with an IET rate >700 s(-1) and is the catalytically relevant fully oxidized form of the enzyme, rather than the resting state. In this report, we present kinetic and spectroscopic results coupled to DFT calculations that evaluate the mechanism of the 3 e(-)/3 H(+) reduction of NI, where all three catalytically relevant intramolecular electron transfer (IET) steps are rapid and involve three different structural changes. These three rapid IET processes reflect the sophisticated mechanistic control of the TNC to enable rapid turnover. All three IET processes are fast due to the associated protonation of the bridging oxo and hydroxo ligands, generated by O-O cleavage, to form water products that are extruded from the TNC upon full reduction, thereby defining a unifying mechanism for oxygen reduction and rapid IET by the TNC in the catalytic cycle of the MCOs.
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Affiliation(s)
- David
E. Heppner
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Christian H. Kjaergaard
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
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34
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Theoretical Study of the Nontraditional Enol-Based Photoacidity of Firefly Oxyluciferin. Chemphyschem 2014; 16:455-64. [DOI: 10.1002/cphc.201402533] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/16/2014] [Indexed: 11/07/2022]
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Pinto da Silva L, Esteves da Silva JCG. Chemiexcitation Induced Proton Transfer: Enolate Oxyluciferin as the Firefly Bioluminophore. J Phys Chem B 2014; 119:2140-8. [DOI: 10.1021/jp5036458] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Luís Pinto da Silva
- Centro de Investigação
em Química, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal
| | - Joaquim C. G. Esteves da Silva
- Centro de Investigação
em Química, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal
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36
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Solis BH, Hammes-Schiffer S. Proton-coupled electron transfer in molecular electrocatalysis: theoretical methods and design principles. Inorg Chem 2014; 53:6427-43. [PMID: 24731018 DOI: 10.1021/ic5002896] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Molecular electrocatalysts play an essential role in a wide range of energy conversion processes. The objective of electrocatalyst design is to maximize the turnover frequency and minimize the overpotential for the overall catalytic cycle. Typically, the catalytic cycle is dominated by key proton-coupled electron transfer (PCET) processes comprised of sequential or concerted electron and proton transfer steps. Theoretical methods have been developed to investigate the mechanisms, thermodynamics, and kinetics of PCET processes in electrocatalytic cycles. Electronic structure methods can be used to calculate the reduction potentials and pKa's and to generate thermodynamic schemes, free energy reaction pathways, and Pourbaix diagrams, which indicate the most stable species under certain conditions. These types of calculations have assisted in identifying the thermodynamically favorable mechanisms under specified experimental conditions, such as acid strength and overpotential. Such calculations have also revealed linear correlations among the thermodynamic properties, which can be used to predict the impact of modifying the ligands, substituents, or metal centers. The thermodynamic properties can be tuned with electron-withdrawing or electron-donating substituents. Ligand modification can exploit the role of noninnocent ligands. For example, ligand protonation typically decreases the overpotential. Calculations of rate constants for electron and proton transfer, as well as concerted PCET, have assisted in identifying the kinetically favorable mechanisms under specified conditions. The concerted PCET mechanism is thought to lower the overpotential required for catalysis by avoiding high-energy intermediates. Rate constant calculations have revealed that the concerted mechanism involving intramolecular proton transfer will be favored by designing more flexible ligands that facilitate the proton donor-acceptor motion while also maintaining a sufficiently short equilibrium proton donor-acceptor distance. Overall, theoretical methods have assisted in the interpretation of experimental data and the design of more effective molecular electrocatalysts.
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Affiliation(s)
- Brian H Solis
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States
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37
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Reaction mechanisms of CO2 electrochemical reduction on Cu(111) determined with density functional theory. J Catal 2014. [DOI: 10.1016/j.jcat.2014.01.013] [Citation(s) in RCA: 295] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Savarese M, Netti PA, Rega N, Adamo C, Ciofini I. Intermolecular proton shuttling in excited state proton transfer reactions: insights from theory. Phys Chem Chem Phys 2014; 16:8661-6. [DOI: 10.1039/c4cp00068d] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The mechanism of intermolecular proton shuttling involved in a prototypical excited state proton transfer reaction is disclosed using DFT and TD-DFT.
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Affiliation(s)
- Marika Savarese
- Dipartimento di Chimica ‘Paolo Corradini’
- Università di Napoli Federico II
- Complesso Universitario di M.S.Angelo
- 80126 Napoli, Italy
- Center for Advanced Biomaterials for Health Care@CRIB
| | - Paolo A. Netti
- Dipartimento di Chimica ‘Paolo Corradini’
- Università di Napoli Federico II
- Complesso Universitario di M.S.Angelo
- 80126 Napoli, Italy
- Center for Advanced Biomaterials for Health Care@CRIB
| | - Nadia Rega
- Dipartimento di Chimica ‘Paolo Corradini’
- Università di Napoli Federico II
- Complesso Universitario di M.S.Angelo
- 80126 Napoli, Italy
- Center for Advanced Biomaterials for Health Care@CRIB
| | - Carlo Adamo
- LECIME
- Laboratoire d'Electrochimie
- Chimie des Interfaces et Modélisation pour l'Energie
- UMR
- France
| | - Ilaria Ciofini
- LECIME
- Laboratoire d'Electrochimie
- Chimie des Interfaces et Modélisation pour l'Energie
- UMR
- France
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Savarese M, Netti PA, Adamo C, Rega N, Ciofini I. Exploring the Metric of Excited State Proton Transfer Reactions. J Phys Chem B 2013; 117:16165-73. [DOI: 10.1021/jp406301p] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Marika Savarese
- Dipartimento
di Chimica ‘Paolo Corradini’, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, 80126 Napoli, Italy
- Center
for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di Tecnologia, Largo Barsanti e Matteucci n, 53 80125 Napoli, Italy
| | - Paolo A. Netti
- Center
for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di Tecnologia, Largo Barsanti e Matteucci n, 53 80125 Napoli, Italy
| | - Carlo Adamo
- Laboratoire
d’Electrochimie, Chimie des Interfaces et Modelisation pour
l’Energie, CNRS UMR-7575, Ecole Nationale Supérieure de Chimie de Paris, Chimie ParisTech, 11 rue P. et M. Curie, F-75231 Paris Cedex 05, France
- Institut Universitaire de France, 103 Bd Saint-Michel, F-75005 Paris, France
| | - Nadia Rega
- Dipartimento
di Chimica ‘Paolo Corradini’, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, 80126 Napoli, Italy
- Center
for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di Tecnologia, Largo Barsanti e Matteucci n, 53 80125 Napoli, Italy
| | - Ilaria Ciofini
- Laboratoire
d’Electrochimie, Chimie des Interfaces et Modelisation pour
l’Energie, CNRS UMR-7575, Ecole Nationale Supérieure de Chimie de Paris, Chimie ParisTech, 11 rue P. et M. Curie, F-75231 Paris Cedex 05, France
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Mineo H, Chao SD, Kato T, Yamanouchi K. Breakdown of Born-Oppenheimer Approximation as a Physical Mechanism for Ultrafast Hydrogen Migrations in Strong Laser Driven Molecules. J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.201300077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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41
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Luber S, Adamczyk K, Nibbering ETJ, Batista VS. Photoinduced Proton Coupled Electron Transfer in 2-(2′-Hydroxyphenyl)-Benzothiazole. J Phys Chem A 2013; 117:5269-79. [DOI: 10.1021/jp403342w] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Sandra Luber
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut,
United States
| | - Katrin Adamczyk
- Max-Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, 12489 Berlin-Adlershof, Germany
| | - Erik T. J. Nibbering
- Max-Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, 12489 Berlin-Adlershof, Germany
| | - Victor S. Batista
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut,
United States
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42
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Amin M, Vogt L, Vassiliev S, Rivalta I, Sultan MM, Bruce D, Brudvig GW, Batista VS, Gunner MR. Electrostatic effects on proton coupled electron transfer in oxomanganese complexes inspired by the oxygen-evolving complex of photosystem II. J Phys Chem B 2013; 117:6217-26. [PMID: 23570540 DOI: 10.1021/jp403321b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The influence of electrostatic interactions on the free energy of proton coupled electron transfer in biomimetic oxomanganese complexes inspired by the oxygen-evolving complex (OEC) of photosystem II (PSII) are investigated. The reported study introduces an enhanced multiconformer continuum electrostatics (MCCE) model, parametrized at the density functional theory (DFT) level with a classical valence model for the oxomanganese core. The calculated pKa's and oxidation midpoint potentials (E(m)'s) match experimental values for eight complexes, indicating that purely electrostatic contributions account for most of the observed couplings between deprotonation and oxidation state transitions. We focus on pKa's of terminal water ligands in [Mn(II/III)(H2O)6](2+/3+) (1), [Mn(III)(P)(H2O)2](3-) (2, P = 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinato), [Mn2(IV,IV)(μ-O)2(terpy)2(H2O)2](4+) (3, terpy = 2,2':6',2″-terpyridine), and [Mn3(IV,IV,IV)(μ-O)4(phen)4(H2O)2](4+) (4, phen = 1,10-phenanthroline) and the pKa's of μ-oxo bridges and Mn E(m)'s in [Mn2(μ-O)2(bpy)4] (5, bpy = 2,2'-bipyridyl), [Mn2(μ-O)2(salpn)2] (6, salpn = N,N'-bis(salicylidene)-1,3-propanediamine), [Mn2(μ-O)2(3,5-di(Cl)-salpn)2] (7), and [Mn2(μ-O)2(3,5-di(NO2)-salpn)2] (8). The analysis of complexes 6-8 highlights the strong coupling between electron and proton transfers, with any Mn oxidation lowering the pKa of an oxo bridge by 10.5 ± 0.9 pH units. The model also accounts for changes in the E(m)'s by ligand substituents, such as found in complexes 6-8, due to the electron withdrawing Cl (7) and NO2 (8). The reported study provides the foundation for analysis of electrostatic effects in other oxomanganese complexes and metalloenzymes, where proton coupled electron transfer plays a fundamental role in redox-leveling mechanisms.
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Affiliation(s)
- Muhamed Amin
- Department of Physics, City College of New York, New York, New York 10031, United States
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43
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Horvath S, Fernandez LE, Appel AM, Hammes-Schiffer S. pH-dependent reduction potentials and proton-coupled electron transfer mechanisms in hydrogen-producing nickel molecular electrocatalysts. Inorg Chem 2013; 52:3643-52. [PMID: 23477912 DOI: 10.1021/ic302056j] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The nickel-based P2(Ph)N2(Bn) electrocatalysts comprised of a nickel atom and two 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane ligands catalyze H2 production in acetonitrile. Recent electrochemical experiments revealed a linear dependence of the Ni(II/I) reduction potential on pH with a slope of 57 mV/pH unit, implicating a proton-coupled electron transfer (PCET) process with the same number of electrons and protons transferred. The combined theoretical and experimental studies herein provide an explanation for this pH dependence in the context of the overall proposed catalytic mechanism. In the proposed mechanisms, the catalytic cycle begins with a series of intermolecular proton transfers from an acid to the pendant amine ligand and electrochemical electron transfers to the nickel center to produce the doubly protonated Ni(0) species, a precursor to H2 evolution. The calculated Ni(II/I) reduction potentials of the doubly protonated species are in excellent agreement with the experimentally observed reduction potential in the presence of strong acid, suggesting that the catalytically active species leading to the peak observed in these cyclic voltammetry (CV) experiments is doubly protonated. The Ni(I/0) reduction potential was found to be slightly more positive than the Ni(II/I) reduction potential, indicating that the Ni(I/0) reduction occurs spontaneously after the Ni(II/I) reduction, as implied by the experimental observation of a single CV peak. These results suggest that the PCET process observed in the CV experiments is a two-electron/two-proton process corresponding to an initial double protonation followed by two reductions. On the basis of the experimental and theoretical data, the complete thermodynamic scheme and the Pourbaix diagram were generated for this catalyst. The Pourbaix diagram, which identifies the most thermodynamically stable species at each reduction potential and pH value, illustrates that this catalyst undergoes different types of PCET processes for various pH ranges. These thermodynamic insights will aid in the design of more effective molecular catalysts for H2 production.
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Affiliation(s)
- Samantha Horvath
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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44
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Fernandez LE, Horvath S, Hammes-Schiffer S. Theoretical Design of Molecular Electrocatalysts with Flexible Pendant Amines for Hydrogen Production and Oxidation. J Phys Chem Lett 2013; 4:542-546. [PMID: 26281752 DOI: 10.1021/jz3020277] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The design of hydrogen oxidation and production electrocatalysts is important for the development of alternative renewable energy sources. The overall objective is to maximize the turnover frequency and minimize the overpotential. We use computational methods to examine a variety of nickel-based molecular electrocatalysts with pendant amines. Our studies focus on the proton-coupled electron transfer (PCET) process involving electron transfer between the complex and the electrode and intramolecular proton transfer between the nickel center and the nitrogen of the pendant amine. The concerted PCET mechanism, which tends to require a lower overpotential, is favored by a smaller equilibrium Ni-N distance and a more flexible pendant amine ligand, thereby decreasing the energetic penalty for the nitrogen to approach the nickel center for proton transfer. Our calculations provide predictions about designing catalysts that incorporate these properties. These design principles will be useful for developing the next generation of hydrogen catalysts.
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Affiliation(s)
- Laura E Fernandez
- †Department of Chemistry, 104 Chemistry Building, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Samantha Horvath
- ‡Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Sharon Hammes-Schiffer
- ‡Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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45
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Huo P, Wang JP, Shao MY, Sun YG, Ji SF, Zhu QY, Dai J. A redox active proton transfer and hydrogen-bonding system of tetrathiafulvalene-dicarboxylic acid and pyridine bases. Phys Chem Chem Phys 2012; 14:16229-35. [PMID: 23138356 DOI: 10.1039/c2cp42836a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen bonds are important in supramolecular chemistry and responsible for proton transfer processes. This manuscript reports new hydrogen-bonding systems of redox-active acid-base assemblies consisting of dimethylthio-tetrathiafulvalene dicarboxylic acid (H(2)L) coupled with pyridine (py), 2,2'-bipyridine (2,2'-bpy), and 4,4'-bipyridine (4,4'-bpy). The (1)H NMR chemical shifts of the pyridines and the redox potential shifts of the tetrathiafulvalene moiety indicate that proton-transfer and strong hydrogen-bonding interactions exist between the acid and the bases in aprotic solvents. The results of cyclic voltammetry show a two-step square reaction with a redox and proton transfer coupled mechanism. The nature of the hydrogen bonds was characterized by X-ray single crystal analysis. In contrast to the mono-carboxyl-py system, in this ortho-substituted dicarboxyl-py system one proton of the H(2)L transfers completely from the carboxyl to the py group. The conjugated intramolecular and intermolecular hydrogen bonds are responsible for the proton transfer.
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Affiliation(s)
- Peng Huo
- Department of Chemistry & Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, Suzhou 215123, P. R. China
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46
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Mališ M, Loquais Y, Gloaguen E, Biswal HS, Piuzzi F, Tardivel B, Brenner V, Broquier M, Jouvet C, Mons M, Došlić N, Ljubić I. Unraveling the Mechanisms of Nonradiative Deactivation in Model Peptides Following Photoexcitation of a Phenylalanine Residue. J Am Chem Soc 2012; 134:20340-51. [DOI: 10.1021/ja3054942] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Momir Mališ
- Division
of Physical Chemistry, Ruđer Bošković Institute, Bijenička
cesta 54, HR-10002 Zagreb, Croatia
| | - Yohan Loquais
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - Eric Gloaguen
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - Himansu S. Biswal
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - François Piuzzi
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - Benjamin Tardivel
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - Valérie Brenner
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - Michel Broquier
- Université Paris-Sud 11, CLUPS / CNRS, LUMAT FR 2764, Bât
106, Orsay, F-91405, France
- CNRS, Université Paris-Sud 11, ISMO, UMR 8624, Bât 210, Orsay,
F-91405, France
| | - Christophe Jouvet
- Université Paris-Sud 11, CLUPS / CNRS, LUMAT FR 2764, Bât
106, Orsay, F-91405, France
- CNRS, Université Paris-Sud 11, ISMO, UMR 8624, Bât 210, Orsay,
F-91405, France
| | - Michel Mons
- CEA, IRAMIS, SPAM, Lab. Francis
Perrin, URA 2453, CEA-Saclay, Bât
522, Gif-sur-Yvette, F-91191, France
- CNRS, INC & INP, Lab. Francis Perrin, URA 2453, CEA-Saclay, Bât 522, Gif-sur-Yvette, F-91191, France
| | - Nađa Došlić
- Division
of Physical Chemistry, Ruđer Bošković Institute, Bijenička
cesta 54, HR-10002 Zagreb, Croatia
| | - Ivan Ljubić
- Division
of Physical Chemistry, Ruđer Bošković Institute, Bijenička
cesta 54, HR-10002 Zagreb, Croatia
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Basarić N, Došlić N, Ivković J, Wang YH, Mališ M, Wan P. Very Efficient Generation of Quinone Methides through Excited State Intramolecular Proton Transfer to a Carbon Atom. Chemistry 2012; 18:10617-23. [DOI: 10.1002/chem.201201144] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Indexed: 11/09/2022]
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48
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Insights into proton-coupled electron transfer mechanisms of electrocatalytic H2 oxidation and production. Proc Natl Acad Sci U S A 2012; 109:15663-8. [PMID: 22529352 DOI: 10.1073/pnas.1118333109] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The design of molecular electrocatalysts for H(2) oxidation and production is important for the development of alternative renewable energy sources that are abundant, inexpensive, and environmentally benign. Recently, nickel-based molecular electrocatalysts with pendant amines that act as proton relays for the nickel center were shown to effectively catalyze H(2) oxidation and production. We developed a quantum mechanical approach for studying proton-coupled electron transfer processes in these types of molecular electrocatalysts. This theoretical approach is applied to a nickel-based catalyst in which phosphorous atoms are directly bonded to the nickel center, and nitrogen atoms of the ligand rings act as proton relays. The catalytic step of interest involves electron transfer between the nickel complex and the electrode as well as intramolecular proton transfer between the nickel and nitrogen atoms. This process can occur sequentially, with either the electron or proton transferring first, or concertedly, with the electron and proton transferring simultaneously without a stable intermediate. The electrochemical rate constants are calculated as functions of overpotential for the concerted electron-proton transfer reaction and the two electron transfer reactions in the sequential mechanisms. Our calculations illustrate that the concerted electron-proton transfer standard rate constant will increase as the equilibrium distance between the nickel and nitrogen atoms decreases and as the pendant amines become more flexible to facilitate the contraction of this distance with a lower energy penalty. This approach identifies the favored mechanisms under various experimental conditions and provides insight into the impact of substituents on the nitrogen and phosphorous atoms.
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49
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Bonin J, Costentin C, Robert M, Savéant JM, Tard C. Hydrogen-bond relays in concerted proton-electron transfers. Acc Chem Res 2012; 45:372-81. [PMID: 22029773 DOI: 10.1021/ar200132f] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Reaction mechanisms in which electron and proton transfers are coupled are central to a huge number of processes, both natural and synthetic. Moreover, most of the new approaches to address modern energy challenges involve proton-coupled electron transfer (PCET). Recent research has focused on the possibility that the two steps are concerted, that is, concerted proton-electron transfer (CPET) reactions, rather than stepwise pathways in which proton transfer precedes (PET) or follows (EPT) electron transfer. CPET pathways have the advantage of bypassing the high-energy intermediates of stepwise pathways, although this thermodynamic benefit may have a kinetic cost. Concerted processes require short distances between the group being oxidized and the proton acceptor (and vice versa for a reduction process), which usually involves the formation of a hydrogen bond. Unlike the electron in outer-sphere electron-transfer reactions, the distance a proton may travel in a CPET is therefore rather limited. The idea has recently emerged, however, that this distance may be substantially increased via a H-bond relay located between the electron-transfer-triggered proton source and the proton acceptor. Generally speaking, the relay is a group bearing a H atom able to accept a H-bond from the moiety being oxidized and, at the same time, to form a H-bond with the proton-accepting group without going through a protonated intermediate. Although these molecules do not retain all the properties of chains of water molecules engaged in Grotthuss-type transport of a proton, the OH group in these molecules does possess a fundamental property of water molecules: namely, it is both a hydrogen-bond acceptor and a hydrogen-bond donor. Despite centuries of study, the mechanisms of proton movement in water remain active experimental and theoretical research areas, but so far with no connection to CPET reactions. In this Account, we bring together recent results concerning (i) the oxidative response of molecules containing a H-bond relay and (ii) the oxidation of phenol with water (in water) as the proton acceptor. In the first case, a nondestructive electrochemical method (cyclic voltammetry) was used to investigate the oxidation of phenol molecules containing one H-bond relay and an amine proton acceptor compared with a similar amino phenol deprived of relay. In the second, the kinetics of phenol oxidation with water (in water) as proton acceptor is contrasted with that of conventional proton acceptors (such as hydrogen phosphate and pyridine) to afford evidence of the concerted nature of Grotthuss-type proton displacement with electron transfer. First indications were provided by the same electrochemical method, whereas a more complete kinetic characterization was obtained from laser flash photolysis. Older electrochemical results concerning the reduction of superoxide ion in the presence of water are also examined. The result is a timely picture of current insight into concerted mechanisms involving electron transfer coupled with proton transport over simple H-bond relays and over H-bond networks.
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Affiliation(s)
- Julien Bonin
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Univ - CNRS No 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
| | - Cyrille Costentin
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Univ - CNRS No 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
| | - Marc Robert
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Univ - CNRS No 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
| | - Jean-Michel Savéant
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Univ - CNRS No 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
| | - Cédric Tard
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Univ - CNRS No 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
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Markle TF, Tenderholt AL, Mayer JM. Probing quantum and dynamic effects in concerted proton-electron transfer reactions of phenol-base compounds. J Phys Chem B 2012; 116:571-84. [PMID: 22148459 PMCID: PMC3974916 DOI: 10.1021/jp2091736] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The oxidation of three phenols, which contain an intramolecular hydrogen bond to a pendent pyridine or amine group, has been shown, in a previous experimental study, to undergo concerted proton-electron transfer (CPET). In this reaction, the electron is transferred to an outer-sphere oxidant, and the proton is transferred from the oxygen to nitrogen atom. In the present study, this reaction is studied computationally using a version of Hammes-Schiffer's multistate continuum theory where CPET is formulated as a transmission frequency between neutral and cation vibrational-electronic states. The neutral and cation proton vibrational wave functions are computed from one-dimensional potential energy surfaces (PESs) for the transferring proton in a fixed heavy atom framework. The overlap integrals for these neutral/cation wave functions, considering several initial (i.e., neutral) and final (i.e., cation) vibrational states, are used to evaluate the relative rates of oxidation. The analysis is extended to heavy atom configurations with various proton donor-acceptor (i.e., O-N) distances to assess the importance of heavy atom "gating". Such changes in d(ON) dramatically affect the nature of the proton PESs and wave functions. Surprisingly, the most reactive configurations have similar donor-acceptor distances despite the large (~0.2 Å) differences in the optimized structures. These theoretical results qualitatively reproduce the experimental faster reactivity of the reaction of the pyridyl derivative 1 versus the CH(2)-pyridyl 2, but the computed factor of 5 is smaller than the experimental 10(2). The amine derivative is calculated to react similarly to 1, which does not agree with the experiments, likely due to some of the simplifying assumptions made in applying the theory. The computed kinetic isotope effects (KIEs) and their temperature dependence are in agreement with experimental results.
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Affiliation(s)
| | - Adam L. Tenderholt
- Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700
| | - James M. Mayer
- Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700
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