51
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Lennox JC, Dempsey JL. Influence of Proton Acceptors on the Proton-Coupled Electron Transfer Reaction Kinetics of a Ruthenium-Tyrosine Complex. J Phys Chem B 2017; 121:10530-10542. [PMID: 29130684 DOI: 10.1021/acs.jpcb.7b06443] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A polypyridyl ruthenium complex with fluorinated bipyridine ligands and a covalently bound tyrosine moiety was synthesized, and its photo-induced proton-coupled electron transfer (PCET) reactivity in acetonitrile was investigated with transient absorption spectroscopy. Using flash-quench methodology with methyl viologen as an oxidative quencher, a Ru3+ species is generated that is capable of initiating the intramolecular PCET oxidation of the tyrosine moiety. Using a series of substituted pyridine bases, the reaction kinetics were found to vary as a function of proton acceptor concentration and identity, with no significant H/D kinetic isotope effect. Through analysis of the kinetics traces and comparison to a control complex without the tyrosine moiety, PCET reactivity was found to proceed through an equilibrium electron transfer followed by proton transfer (ET-PT) pathway in which irreversible deprotonation of the tyrosine radical cation shifts the ET equilibrium, conferring a base dependence on the reaction. Comprehensive kinetics modeling allowed for deconvolution of complex kinetics and determination of rate constants for each elementary step. Across the five pyridine bases explored, spanning a range of 4.2 pKa units, a linear free-energy relationship was found for the proton transfer rate constant with a slope of 0.32. These findings highlight the influence that proton transfer driving force exerts on PCET reaction kinetics.
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Affiliation(s)
- J Christian Lennox
- Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States
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52
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Zhang H, Wu W, Mo Y. Study of proton-coupled electron transfer (PCET) with four explicit diabatic states at the ab initio level. COMPUT THEOR CHEM 2017. [DOI: 10.1016/j.comptc.2017.02.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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53
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Ponseca CS, Chábera P, Uhlig J, Persson P, Sundström V. Ultrafast Electron Dynamics in Solar Energy Conversion. Chem Rev 2017; 117:10940-11024. [DOI: 10.1021/acs.chemrev.6b00807] [Citation(s) in RCA: 211] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Carlito S. Ponseca
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Pavel Chábera
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Jens Uhlig
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Petter Persson
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Villy Sundström
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
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54
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Morris WD, Mayer JM. Separating Proton and Electron Transfer Effects in Three-Component Concerted Proton-Coupled Electron Transfer Reactions. J Am Chem Soc 2017; 139:10312-10319. [PMID: 28671470 DOI: 10.1021/jacs.7b03562] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Multiple-site concerted proton-electron transfer (MS-CPET) reactions were studied in a three-component system. 1-Hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOH) was oxidized to the stable radical TEMPO by electron transfer to ferrocenium oxidants coupled to proton transfer to various pyridine bases. These MS-CPET reactions contrast with the usual reactivity of TEMPOH by hydrogen atom transfer (HAT) to a single e-/H+ acceptor. The three-component reactions proceed by pre-equilibrium formation of a hydrogen-bonded adduct between TEMPOH and the pyridine base, and the adduct is then oxidized by the ferrocenium in a bimolecular MS-CPET step. The second-order rate constants, measured using stopped-flow kinetic techniques, spanned 4 orders of magnitude. An advantage of this system is that the MS-CPET driving force could be independently varied by changing either the pKa of the base or the reduction potential (E°) of the oxidant. Changes in ΔG°MS-CPET from either source had the same effect on the MS-CPET rate constants, and a combined Brønsted plot of ln(kMS-CPET) vs ln(Keq) was linear with a slope of 0.46. These results imply a synchronous concerted mechanism, in which the proton and electron transfer components of the CPET process make equal contributions to the rate constants. The only outliers to the Brønsted correlation are the reactions with sterically hindered pyridines, which apparently hinder the close approach of proton donor and acceptor that facilitates MS-CPET. These three-component reactions are compared with a related HAT reaction of TEMPOH, with the 2,4,6-tri-tert-butylphenoxyl radical. The MS-CPET and HAT oxidations of TEMPOH at the same driving force occurred with similar rate constants. While this is an imperfect comparison, the data suggest that the separation of the proton and electron to different reagents does not significantly inhibit the proton-coupled electron transfer process.
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Affiliation(s)
- Wesley D Morris
- Department of Chemistry, Yale University , New Haven, Connecticut 06511, United States
| | - James M Mayer
- Department of Chemistry, Yale University , New Haven, Connecticut 06511, United States
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55
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Lee KJ, Elgrishi N, Kandemir B, Dempsey JL. Electrochemical and spectroscopic methods for evaluating molecular electrocatalysts. Nat Rev Chem 2017. [DOI: 10.1038/s41570-017-0039] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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56
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Uraguchi D, Torii M, Ooi T. Acridinium Betaine as a Single-Electron-Transfer Catalyst: Design and Application to Dimerization of Oxindoles. ACS Catal 2017. [DOI: 10.1021/acscatal.7b00265] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daisuke Uraguchi
- Institute
of Transformative Bio-Molecules (WPI-ITbM) and Department of Applied
Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8601, Japan
| | - Masahiro Torii
- Institute
of Transformative Bio-Molecules (WPI-ITbM) and Department of Applied
Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8601, Japan
| | - Takashi Ooi
- Institute
of Transformative Bio-Molecules (WPI-ITbM) and Department of Applied
Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8601, Japan
- CREST,
Japan Science and Technology Agency (JST), Nagoya University, Nagoya 464-8601, Japan
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57
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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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58
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Pannwitz A, Prescimone A, Wenger OS. Ruthenium(II)-Pyridylimidazole Complexes as Photoreductants and PCET Reagents. Eur J Inorg Chem 2017. [DOI: 10.1002/ejic.201601403] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Andrea Pannwitz
- Department of Chemistry; University of Basel; St. Johanns-Ring 19 and Spitalstrasse 51 4056 Basel Switzerland
| | - Alessandro Prescimone
- Department of Chemistry; University of Basel; St. Johanns-Ring 19 and Spitalstrasse 51 4056 Basel Switzerland
| | - Oliver S. Wenger
- Department of Chemistry; University of Basel; St. Johanns-Ring 19 and Spitalstrasse 51 4056 Basel Switzerland
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59
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Waldie KM, Flajslik KR, McLoughlin E, Chidsey CED, Waymouth RM. Electrocatalytic Alcohol Oxidation with Ruthenium Transfer Hydrogenation Catalysts. J Am Chem Soc 2017; 139:738-748. [DOI: 10.1021/jacs.6b09705] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Kate M. Waldie
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Kristen R. Flajslik
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Elizabeth McLoughlin
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | | | - Robert M. Waymouth
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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60
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Elgrishi N, Kurtz DA, Dempsey JL. Reaction Parameters Influencing Cobalt Hydride Formation Kinetics: Implications for Benchmarking H(2)-Evolution Catalysts. J Am Chem Soc 2016; 139:239-244. [PMID: 27997157 DOI: 10.1021/jacs.6b10148] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The need for benchmarking hydrogen evolution catalysts has increasingly been recognized. The influence of acid choice on activity is often reduced to the overpotential for catalysis. Through the study of a stable cobalt hydride complex, we demonstrate the influence of acid choice, beyond pKa, on the kinetics of hydride formation. A linear free energy relationship between acid pKa and second-order rate constants is observed for weaker acids. For stronger acids, however, further increases in pKa do not correlate to increases in rate constants. Further, steric bulk around the acidic proton is shown to influence rate constants dramatically. Together, these observations reveal the complex factors dictating catalyst performance.
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Affiliation(s)
- Noémie Elgrishi
- Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States
| | - Daniel A Kurtz
- Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States
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61
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62
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Eisenhart TT, Howland WC, Dempsey JL. Proton-Coupled Electron Transfer Reactions with Photometric Bases Reveal Free Energy Relationships for Proton Transfer. J Phys Chem B 2016; 120:7896-905. [DOI: 10.1021/acs.jpcb.6b04011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Thomas T. Eisenhart
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - William C. Howland
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L. Dempsey
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
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63
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Walden AG, Kumar A, Lease N, Goldman AS, Miller AJM. Electrochemical and chemical routes to hydride loss from an iridium dihydride. Dalton Trans 2016; 45:9766-9. [PMID: 26979786 DOI: 10.1039/c6dt00522e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
With a view towards replacing sacrificial hydrogen acceptors in alkane dehydrogenation catalysis, electrochemical methods for oxidative activation of a pincer-ligated iridium hydride intermediate were explored. A 1H(+)/2e(-) oxidation process was observed in THF solvent, with net hydride loss leading to a reactive cationic intermediate that can be trapped by chloride. Analogous reactivity was observed with the concerted hydride transfer reagent Ph3C(+), connecting chemical and electrochemical hydride loss pathways.
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Affiliation(s)
- A G Walden
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA.
| | - A Kumar
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA and Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati - 781039, Assam, India
| | - N Lease
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA
| | - A S Goldman
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA
| | - A J M Miller
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA.
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64
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Elgrishi N, McCarthy BD, Rountree ES, Dempsey JL. Reaction Pathways of Hydrogen-Evolving Electrocatalysts: Electrochemical and Spectroscopic Studies of Proton-Coupled Electron Transfer Processes. ACS Catal 2016. [DOI: 10.1021/acscatal.6b00778] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Noémie Elgrishi
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Brian D. McCarthy
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Eric S. Rountree
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L. Dempsey
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
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65
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Zhang F, Jia J, Dong S, Wang W, Tung CH. Hydride Transfer from Iron(II) Hydride Compounds to NAD(P)+ Analogues. Organometallics 2016. [DOI: 10.1021/acs.organomet.6b00179] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Fanjun Zhang
- Key Laboratory of Colloid and
Interface Chemistry, Ministry of Education, School of Chemistry and
Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan 250100, People’s Republic of China
| | - Jiong Jia
- Key Laboratory of Colloid and
Interface Chemistry, Ministry of Education, School of Chemistry and
Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan 250100, People’s Republic of China
| | - Shuli Dong
- Key Laboratory of Colloid and
Interface Chemistry, Ministry of Education, School of Chemistry and
Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan 250100, People’s Republic of China
| | - Wenguang Wang
- Key Laboratory of Colloid and
Interface Chemistry, Ministry of Education, School of Chemistry and
Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan 250100, People’s Republic of China
| | - Chen-Ho Tung
- Key Laboratory of Colloid and
Interface Chemistry, Ministry of Education, School of Chemistry and
Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan 250100, People’s Republic of China
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66
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Soetbeer J, Dongare P, Hammarström L. Marcus-type driving force correlations reveal the mechanism of proton-coupled electron transfer for phenols and [Ru(bpy) 3] 3+ in water at low pH. Chem Sci 2016; 7:4607-4612. [PMID: 30155108 PMCID: PMC6013771 DOI: 10.1039/c6sc00597g] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Accepted: 04/01/2016] [Indexed: 11/21/2022] Open
Abstract
We examined PCET between a series of phenol derivatives and photogenerated [Ru(bpy)3]3+ in low pH (≤4) water using the laser flash-quench technique.
Proton-coupled electron transfer (PCET) from tyrosine and other phenol derivatives in water is an important elementary reaction in chemistry and biology. We examined PCET between a series of phenol derivatives and photogenerated [Ru(bpy)3]3+ in low pH (≤4) water using the laser flash-quench technique. From an analysis of the kinetic data using a Marcus-type free energy relationship, we propose that our model system follows a stepwise electron transfer-proton transfer (ETPT) pathway with a pH independent rate constant at low pH in water. This is in contrast to the concerted or proton-first (PTET) mechanisms that often dominate at higher pH and/or with buffers as primary proton acceptors. The stepwise mechanism remains competitive despite a significant change in the pKa and redox potential of the phenols which leads to a span of rate constants from 1 × 105 to 2 × 109 M–1 s–1. These results support our previous studies which revealed separate mechanistic regions for PCET reactions and also assigned phenol oxidation by [Ru(bpy)3]3+ at low pH to a stepwise PCET mechanism.
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Affiliation(s)
- Janne Soetbeer
- Department of Chemistry - Ångström Laboratory , Uppsala University , Box 523, SE-751 20 , Uppsala , Sweden . ;
| | - Prateek Dongare
- Department of Chemistry - Ångström Laboratory , Uppsala University , Box 523, SE-751 20 , Uppsala , Sweden . ;
| | - Leif Hammarström
- Department of Chemistry - Ångström Laboratory , Uppsala University , Box 523, SE-751 20 , Uppsala , Sweden . ;
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67
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Pitman C, Brereton KR, Miller AJM. Aqueous Hydricity of Late Metal Catalysts as a Continuum Tuned by Ligands and the Medium. J Am Chem Soc 2016; 138:2252-60. [PMID: 26777267 PMCID: PMC4768292 DOI: 10.1021/jacs.5b12363] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Indexed: 12/21/2022]
Abstract
Aqueous hydride transfer is a fundamental step in emerging alternative energy transformations such as H2 evolution and CO2 reduction. "Hydricity," the hydride donor ability of a species, is a key metric for understanding transition metal hydride reactivity, but comprehensive studies of aqueous hydricity are scarce. An extensive and self-consistent aqueous hydricity scale is constructed for a family of Ru and Ir hydrides that are key intermediates in aqueous catalysis. A reference hydricity is determined using redox potentiometry and spectrophotometric titration for a particularly water-soluble species. Then, relative hydricity values for a range of species are measured using hydride transfer equilibria, taking advantage of expedient new synthetic procedures for Ru and Ir hydrides. This large collection of hydricity values provides the most comprehensive picture so far of how ligands impact hydricity in water. Strikingly, we also find that hydricity can be viewed as a continuum in water: the free energy of hydride transfer changes with pH, buffer composition, and salts present in solution.
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Affiliation(s)
- Catherine
L. Pitman
- Department of Chemistry, University of
North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Kelsey R. Brereton
- Department of Chemistry, University of
North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Alexander J. M. Miller
- Department of Chemistry, University of
North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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68
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Dongare P, Maji S, Hammarström L. Direct Evidence of a Tryptophan Analogue Radical Formed in a Concerted Electron−Proton Transfer Reaction in Water. J Am Chem Soc 2016; 138:2194-9. [DOI: 10.1021/jacs.5b08294] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Prateek Dongare
- Department of Chemistry,
Ångström Laboratory, Uppsala University, Box 523, Uppsala SE-751 20, Sweden
| | - Somnath Maji
- Department of Chemistry,
Ångström Laboratory, Uppsala University, Box 523, Uppsala SE-751 20, Sweden
| | - Leif Hammarström
- Department of Chemistry,
Ångström Laboratory, Uppsala University, Box 523, Uppsala SE-751 20, Sweden
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69
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Pannwitz A, Wenger OS. Proton coupled electron transfer from the excited state of a ruthenium(ii) pyridylimidazole complex. Phys Chem Chem Phys 2016; 18:11374-82. [DOI: 10.1039/c6cp00437g] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Transfer of one electron and one proton from [Ru(bpy)2pyimH]2+ to monoquat (MQ+) upon photoexcitation, corresponding to net transfer of a hydrogen atom.
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Affiliation(s)
- Andrea Pannwitz
- Department of Chemistry
- University of Basel
- 4056 Basel
- Switzerland
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70
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Gloaguen F. Electrochemistry of Simple Organometallic Models of Iron-Iron Hydrogenases in Organic Solvent and Water. Inorg Chem 2015; 55:390-8. [PMID: 26641526 DOI: 10.1021/acs.inorgchem.5b02245] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synthetic models of the active site of iron-iron hydrogenases are currently the subjects of numerous studies aimed at developing H2-production catalysts based on cheap and abundant materials. In this context, the present report offers an electrochemist's view of the catalysis of proton reduction by simple binuclear iron(I) thiolate complexes. Although these complexes probably do not follow a biocatalytic pathway, we analyze and discuss the interplay between the reduction potential and basicity and how these antagonist properties impact the mechanisms of proton-coupled electron transfer to the metal centers. This question is central to any consideration of the activity at the molecular level of hydrogenases and related enzymes. In a second part, special attention is paid to iron thiolate complexes holding rigid and unsaturated bridging ligands. The complexes that enjoy mild reduction potentials and stabilized reduced forms are promising iron-based catalysts for the photodriven evolution of H2 in organic solvents and, more importantly, in water.
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Affiliation(s)
- Frederic Gloaguen
- UMR 6521, CNRS, Université de Bretagne Occidentale, CS 93837 , 29238 Brest, France
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71
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Kretchmer JS, Miller TF. Tipping the Balance between Concerted versus Sequential Proton-Coupled Electron Transfer. Inorg Chem 2015; 55:1022-31. [PMID: 26440812 DOI: 10.1021/acs.inorgchem.5b01821] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Joshua S. Kretchmer
- Department of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Thomas F. Miller
- Department of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
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72
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McCarthy BD, Donley CL, Dempsey JL. Electrode initiated proton-coupled electron transfer to promote degradation of a nickel(ii) coordination complex. Chem Sci 2015; 6:2827-2834. [PMID: 29403633 PMCID: PMC5761499 DOI: 10.1039/c5sc00476d] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Accepted: 02/25/2015] [Indexed: 11/21/2022] Open
Abstract
A Ni(ii) bisphosphine dithiolate compound degrades into an electrode-adsorbed film that can evolve hydrogen under reducing and protic conditions. An electrochemical study suggests that the degradation mechanism involves an initial concerted proton-electron transfer. The potential susceptibility of Ni-S bonds in molecular hydrogen evolution catalysts to degradation via C-S bond cleavage is discussed.
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Affiliation(s)
- Brian D McCarthy
- Department of Chemistry , University of North Carolina , Chapel Hill , North Carolina 27599-3290 , USA .
| | - Carrie L Donley
- Chapel Hill Analytical and Nanofabrication Laboratory , Department of Applied Physical Sciences , University of North Carolina , Chapel Hill , North Carolina 27599-3216 , USA
| | - Jillian L Dempsey
- Department of Chemistry , University of North Carolina , Chapel Hill , North Carolina 27599-3290 , USA .
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73
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74
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Bourrez M, Gloaguen F. Application of the energetic span model to the electrochemical catalysis of proton reduction by a diiron azadithiolate complex. NEW J CHEM 2015. [DOI: 10.1039/c5nj00770d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A method for the computation of TOF of catalysis of electrochemical reaction as a function of the potential was developed.
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Affiliation(s)
- Marc Bourrez
- UMR 6521
- CNRS
- Université de Bretagne Occidentale
- Brest
- France
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75
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Rioual S, Lescop B, Quentel F, Gloaguen F. A molecular material based on electropolymerized cobalt macrocycles for electrocatalytic hydrogen evolution. Phys Chem Chem Phys 2015; 17:13374-9. [DOI: 10.1039/c5cp01210d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electropolymerization of CoTAA gives an electrocatalytic material for the H2 evolution reaction in acidic aqueous solution.
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Affiliation(s)
| | - Benoit Lescop
- LMB EA 4522
- Université de Bretagne Occidentale
- Brest
- France
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