1
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Zhao X, Yang JD, Cheng JP. Revisiting the Electrochemistry of TEMPOH Analogues in Acetonitrile. J Org Chem 2023; 88:540-547. [PMID: 36573883 DOI: 10.1021/acs.joc.2c02537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hydroxylamines, represented by 1-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOH), are widely involved as active species in various chemical and electrochemical oxidations. The electrochemical behavior of TEMPOH is crucial to understanding the mechanisms of TEMPO-mediated redox sequences. However, compared to abundant studies on TEMPOH electrochemistry in aqueous solutions, the sole value of its oxidation potential Eox(TEMPOH) in organic solutions was reported to be 0.7 V (vs Fc in acetonitrile), seemingly conflicting with experimentally observed facile oxidation of TEMPOH. Herein, the electrochemistry of TEMPOH derivatives in acetonitrile was revisited, featuring much smaller oxidation potentials (about 0 V) than literature ones. Acid/base effects and kinetic studies lent credibility to these new values. Such a 0.7 V energy discrepancy impelled us to review the thermodynamic properties and oxidation mechanisms of TEMPOH deduced from the old value.
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Affiliation(s)
- Xiao Zhao
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Jin-Dong Yang
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Jin-Pei Cheng
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China.,State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
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2
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Agarwal RG, Coste SC, Groff BD, Heuer AM, Noh H, Parada GA, Wise CF, Nichols EM, Warren JJ, Mayer JM. Free Energies of Proton-Coupled Electron Transfer Reagents and Their Applications. Chem Rev 2021; 122:1-49. [PMID: 34928136 DOI: 10.1021/acs.chemrev.1c00521] [Citation(s) in RCA: 134] [Impact Index Per Article: 44.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We present an update and revision to our 2010 review on the topic of proton-coupled electron transfer (PCET) reagent thermochemistry. Over the past decade, the data and thermochemical formalisms presented in that review have been of value to multiple fields. Concurrently, there have been advances in the thermochemical cycles and experimental methods used to measure these values. This Review (i) summarizes those advancements, (ii) corrects systematic errors in our prior review that shifted many of the absolute values in the tabulated data, (iii) provides updated tables of thermochemical values, and (iv) discusses new conclusions and opportunities from the assembled data and associated techniques. We advocate for updated thermochemical cycles that provide greater clarity and reduce experimental barriers to the calculation and measurement of Gibbs free energies for the conversion of X to XHn in PCET reactions. In particular, we demonstrate the utility and generality of reporting potentials of hydrogenation, E°(V vs H2), in almost any solvent and how these values are connected to more widely reported bond dissociation free energies (BDFEs). The tabulated data demonstrate that E°(V vs H2) and BDFEs are generally insensitive to the nature of the solvent and, in some cases, even to the phase (gas versus solution). This Review also presents introductions to several emerging fields in PCET thermochemistry to give readers windows into the diversity of research being performed. Some of the next frontiers in this rapidly growing field are coordination-induced bond weakening, PCET in novel solvent environments, and reactions at material interfaces.
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Affiliation(s)
- Rishi G Agarwal
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Scott C Coste
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Benjamin D Groff
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Abigail M Heuer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Hyunho Noh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Giovanny A Parada
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry, The College of New Jersey, Ewing, New Jersey 08628, United States
| | - Catherine F Wise
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Eva M Nichols
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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3
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Spedalotto G, Lovisari M, McDonald AR. Reactivity Properties of Mixed- and High-Valent Bis(μ-Hydroxide)-Dinickel Complexes. ACS OMEGA 2021; 6:28162-28170. [PMID: 34723014 PMCID: PMC8554787 DOI: 10.1021/acsomega.1c04225] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 09/22/2021] [Indexed: 06/13/2023]
Abstract
Despite their potential role in enzymatic systems, there is a dearth of hydroxide-bridged high-valent oxidants. We recently reported the synthesis and characterization of NiIINiIII(μ-OH)2 (2) and Ni2 III(μ-OH)2 (3) species supported by a dicarboxamidate ligand (N,N'-bis(2,6-dimethyl-phenyl)-2,2-dimethylmalonamide). Herein, we explore the oxidative reactivity of these species using a series of para-substituted 2,6-di-tert-butyl-phenols (4-X-2,6-DTBP, X = -OCH3, -CH2CH3, -CH3, -C(CH3)3, -H, -Br, -CN, and -NO2) as a mechanistic probe. Interestingly, upon reaction of 3 with the substrates, the formation of a new transient species, 2', was observed. 2' is postulated to be a protic congener of 2. All three species were demonstrated to react with the substituted phenols through a hydrogen atom transfer reaction mechanism, which was elucidated further by analysis of the postreaction mixtures. Critically, 3 was demonstrated to react at far superior rates to 2 and 2', and oxidized substrates more efficiently than any bis-μ-oxo-Ni2 III reported to date. The kinetic superiority of 3 with respect to 2 and 2' was attributed to a stronger bond in the product of oxidation by 3 when compared to those calculated for 2 and 2'.
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4
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Thuéry P, Harrowfield J. Uranyl ion complexes with 2,2′:6′,2′′-terpyridine-4′-carboxylate. Interpenetration of networks involving “expanded ligands”. CrystEngComm 2021. [DOI: 10.1039/d1ce01215k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
2,2′:6′,2′′-Terpyridine-4′-carboxylate (tpyc−) forms both homo- and heterometallic uranyl ion complexes including a chiral, twofold interpenetrated polymer involving the “expanded ligand” Ni(tpyc)2.
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Affiliation(s)
- Pierre Thuéry
- Université Paris-Saclay, CEA, CNRS, NIMBE, 91191 Gif-sur-Yvette, France
| | - Jack Harrowfield
- Université de Strasbourg, ISIS, 8 allée Gaspard Monge, 67083 Strasbourg, France
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5
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Kojima T. Study on Proton-Coupled Electron Transfer in Transition Metal Complexes. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20200213] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Takahiko Kojima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
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6
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Nichols AW, Hooe SL, Kuehner JS, Dickie DA, Machan CW. Electrocatalytic CO2 Reduction to Formate with Molecular Fe(III) Complexes Containing Pendent Proton Relays. Inorg Chem 2020; 59:5854-5864. [DOI: 10.1021/acs.inorgchem.9b03341] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Asa W. Nichols
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Shelby L. Hooe
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Joseph S. Kuehner
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Diane A. Dickie
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Charles W. Machan
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904-4319, United States
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7
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Swords WB, Meyer GJ, Hammarström L. Excited-state proton-coupled electron transfer within ion pairs. Chem Sci 2020; 11:3460-3473. [PMID: 34109019 PMCID: PMC8152629 DOI: 10.1039/c9sc04941j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The use of light to drive proton-coupled electron transfer (PCET) reactions has received growing interest, with recent focus on the direct use of excited states in PCET reactions (ES-PCET). Electrostatic ion pairs provide a scaffold to reduce reaction orders and have facilitated many discoveries in electron-transfer chemistry. Their use, however, has not translated to PCET. Herein, we show that ion pairs, formed solely through electrostatic interactions, provide a general, facile means to study an ES-PCET mechanism. These ion pairs formed readily between salicylate anions and tetracationic ruthenium complexes in acetonitrile solution. Upon light excitation, quenching of the ruthenium excited state occurred through ES-PCET oxidation of salicylate within the ion pair. Transient absorption spectroscopy identified the reduced ruthenium complex and oxidized salicylate radical as the primary photoproducts of this reaction. The reduced reaction order due to ion pairing allowed the first-order PCET rate constants to be directly measured through nanosecond photoluminescence spectroscopy. These PCET rate constants saturated at larger driving forces consistent with approaching the Marcus barrierless region. Surprisingly, a proton-transfer tautomer of salicylate, with the proton localized on the carboxylate functional group, was present in acetonitrile. A pre-equilibrium model based on this tautomerization provided non-adiabatic electron-transfer rate constants that were well described by Marcus theory. Electrostatic ion pairs were critical to our ability to investigate this PCET mechanism without the need to covalently link the donor and acceptor or introduce specific hydrogen bonding sites that could compete in alternate PCET pathways.
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Affiliation(s)
- Wesley B Swords
- Department of Chemistry, Ångström Laboratories, Uppsala University Box 523 SE75120 Uppsala Sweden .,Department of Chemistry, University of North Carolina at Chapel Hill Chapel Hill 27599 USA
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill Chapel Hill 27599 USA
| | - Leif Hammarström
- Department of Chemistry, Ångström Laboratories, Uppsala University Box 523 SE75120 Uppsala Sweden
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8
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Chu J, Carroll TG, Wu G, Telser J, Dobrovetsky R, Ménard G. Probing Hydrogen Atom Transfer at a Phosphorus(V) Oxide Bond Using a "Bulky Hydrogen Atom" Surrogate: Analogies to PCET. J Am Chem Soc 2018; 140:15375-15383. [PMID: 30382703 DOI: 10.1021/jacs.8b09063] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Recent computational studies suggest that the phosphate support in the commercial vanadium phosphate oxide (VPO) catalyst may play a critical role in initiating butane C-H bond activation through a mechanism termed reduction-coupled oxo activation (ROA) similar to proton-coupled electron transfer (PCET); however, no experimental evidence exists to support this mechanism. Herein, we present molecular model compounds, (Ph2N)3V═N-P(O)Ar2 (Ar = C6F5 (2a), Ph (2b)), which are reactive to both weak H atom donors and a Me3Si• (a "bulky hydrogen atom" surrogate) donor, 1,4-bis(trimethylsilyl)pyrazine. While the former reaction led to product decomposition, the latter resulted in the isolation of the reduced, silylated complexes (Ph2N)3V-N═P(OSiMe3)Ar2 (3a/b). Detailed analyses of possible reaction pathways, involving the isolation and full characterization of potential stepwise square-scheme intermediates, as well as the determination of minimum experimentally and computationally derived thermochemical values, are described. We find that stepwise electron transfer (ET) + silylium transfer (ST) or concerted EST mechanisms are most likely. This study provides the first experimental evidence supporting a ROA mechanism and may inform future studies in homogeneous or heterogeneous C-H activation chemistry, as well as open up a possible new avenue for main group/transition metal cooperative redox reactivity.
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Affiliation(s)
- Jiaxiang Chu
- Department of Chemistry and Biochemistry , University of California , Santa Barbara , California 93106 , United States
| | - Timothy G Carroll
- Department of Chemistry and Biochemistry , University of California , Santa Barbara , California 93106 , United States
| | - Guang Wu
- Department of Chemistry and Biochemistry , University of California , Santa Barbara , California 93106 , United States
| | - Joshua Telser
- Department of Biological, Chemical, and Physical Sciences , Roosevelt University , Chicago , Illinois 60605 , United States
| | - Roman Dobrovetsky
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences , Tel Aviv University , Tel Aviv 69978 , Israel
| | - Gabriel Ménard
- Department of Chemistry and Biochemistry , University of California , Santa Barbara , California 93106 , United States
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9
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Darcy JW, Koronkiewicz B, Parada GA, Mayer JM. A Continuum of Proton-Coupled Electron Transfer Reactivity. Acc Chem Res 2018; 51:2391-2399. [PMID: 30234963 DOI: 10.1021/acs.accounts.8b00319] [Citation(s) in RCA: 168] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Proton-coupled electron transfer (PCET) covers a wide range of reactions involving the transfer(s) of electrons and protons. The best-known PCET reaction, hydrogen atom transfer (HAT), has been studied in detail for more than a century. HAT is generally described as the concerted transfer of a hydrogen atom (H• ≡ H+ + e-) from one group to another, Y + H-X → Y-H + X, but a strict definition of HAT has been difficult to establish. Distinctions are more challenging when the transfer of "H•" involves e- and H+ that transfer to/from spatially distinct sites or even completely separate reagents (multiple-site concerted proton-electron transfer, MS-CPET). MS-CPET reactivity is increasingly proposed in biological and synthetic contexts, and some reactions typically described as HAT more resemble MS-CPET. Despite that HAT and MS-CPET reactions "look different," we argue here that these reactions lie on a reactivity continuum, and that they are governed by many of the same key parameters. This Account walks the reader across this PCET reactivity continuum, using a series of studies to show the strong similarities of reactions that move protons and electrons in seemingly different ways. To prepare for our stroll, we describe the thermochemical and kinetic frameworks for HAT and MS-CPET. The driving force for a solution HAT reaction is most easily discussed as the difference in the bond dissociation free energies (BDFEs) of the reactants and products. BDFEs can be analyzed as sums of electron and proton transfer steps and can therefore be obtained from p Ka and E° values. Even though MS-CPET reactions do not make and break H-X bonds in the same way as HAT, the same thermochemical description can be used with the introduction of an effective BDFE (BDFEeff). The BDFEeff of a reductant/acid pair is the free energy of that pair to form H•, which can be obtained from p Ka and E° values in an analogous fashion to a standard BDFE. When the PCET thermochemistry is known, HAT and PCET rate constants can be understood and often predicted using linear free energy relationships (the Brønsted catalysis law) and Marcus theory type approaches. After this background, we walk the reader through a continuum of PCET reactivity. Our journey begins with a study of metal-mediated HAT from hydrocarbon substrates to a metal-oxo complex and travels to the MS-CPET end of the reactivity spectrum, involving the transfer of H+ and e- from the hydroxylamine TEMPOH to two completely separate molecules. These examples, and those in between, are all analyzed within the same thermodynamic and kinetic framework. A description of the first examples of MS-CPET with C-H bonds uses the same framework and highlights the importance of hydrogen bonding and preorganization. The examples and analyses show that the reactions along the PCET continuum are more similar than they are different, and that attempts to divide these reactions into subcategories can obscure much of the essential chemistry. We hope that developing the many common features of these reactions will help experts and newcomers alike to explore exciting new territories in PCET reactivity.
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Affiliation(s)
- Julia W. Darcy
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Brian Koronkiewicz
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Giovanny A. Parada
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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10
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Pirovano P, Farquhar ER, Swart M, McDonald AR. Tuning the Reactivity of Terminal Nickel(III)-Oxygen Adducts for C-H Bond Activation. J Am Chem Soc 2016; 138:14362-14370. [PMID: 27739688 DOI: 10.1021/jacs.6b08406] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two metastable NiIII complexes, [NiIII(OAc)(L)] and [NiIII(ONO2)(L)] (L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate, OAc = acetate), were prepared, adding to the previously prepared [NiIII(OCO2H)(L)], with the purpose of probing the properties of terminal late-transition metal oxidants. These high-valent oxidants were prepared by the one-electron oxidation of their NiII precursors ([NiII(OAc)(L)]- and [NiII(ONO2)(L)]-) with tris(4-bromophenyl)ammoniumyl hexachloroantimonate. Fascinatingly, the reaction between any [NiII(X)(L)]- and NaOCl/acetic acid (AcOH) or cerium ammonium nitrate ((NH4)2[CeIV(NO3)6], CAN), yielded [NiIII(OAc)(L)] and [NiIII(ONO2)(L)], respectively. An array of spectroscopic characterizations (electronic absorption, electron paramagnetic resonance, X-ray absorption spectroscopies), electrochemical methods, and computational predictions (density functional theory) have been used to determine the structural, electronic, and magnetic properties of these highly reactive metastable oxidants. The NiIII-oxidants proved competent in the oxidation of phenols (weak O-H bonds) and a series of hydrocarbon substrates (some with strong C-H bonds). Kinetic investigation of the reactions with di-tert-butylphenols showed a 15-fold enhanced reaction rate for [NiIII(ONO2)(L)] compared to [NiIII(OCO2H)(L)] and [NiIII(OAc)(L)], demonstrating the effect of electron-deficiency of the O-ligand on oxidizing power. The oxidation of a series of hydrocarbons by [NiIII(OAc)(L)] was further examined. A linear correlation between the rate constant and the bond dissociation energy of the C-H bonds in the substrates was indicative of a hydrogen atom transfer mechanism. The reaction rate with dihydroanthracene (k2 = 8.1 M-1 s-1) compared favorably with the most reactive high-valent metal-oxidants, and showcases the exceptional reactivity of late transition metal-oxygen adducts.
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Affiliation(s)
- Paolo Pirovano
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin , College Green, Dublin 2, Ireland
| | - Erik R Farquhar
- Case Western Reserve University Center for Synchrotron Biosciences, National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Marcel Swart
- ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain.,Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona , Campus Montilivi, 17003 Girona, Spain
| | - Aidan R McDonald
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin , College Green, Dublin 2, Ireland
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11
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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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12
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Mitome H, Ishizuka T, Kotani H, Shiota Y, Yoshizawa K, Kojima T. Mechanistic Insights into C–H Oxidations by Ruthenium(III)-Pterin Complexes: Impact of Basicity of the Pterin Ligand and Electron Acceptability of the Metal Center on the Transition States. J Am Chem Soc 2016; 138:9508-20. [DOI: 10.1021/jacs.6b03785] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hiroumi Mitome
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Tomoya Ishizuka
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Hiroaki Kotani
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Yoshihito Shiota
- Institute
for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute
for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Takahiko Kojima
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
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13
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Shen GB, Xia K, Li XT, Li JL, Fu YH, Yuan L, Zhu XQ. Prediction of Kinetic Isotope Effects for Various Hydride Transfer Reactions Using a New Kinetic Model. J Phys Chem A 2016; 120:1779-99. [DOI: 10.1021/acs.jpca.5b10135] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Guang-Bin Shen
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Ke Xia
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Xiu-Tao Li
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Jun-Ling Li
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Yan-Hua Fu
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Lin Yuan
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Xiao-Qing Zhu
- Department of Chemistry, The State Key Laboratory
of Elemento-Organic Chemistry and the ‡Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
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14
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Xie YF, Jia AQ, Zhu H, Shi HT, Zhang QF. A tetranuclear ruthenium complex with bridging pyridine-2,4-dicarboxylato ligands forming a square metallamacrocycle. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2016. [DOI: 10.1515/znb-2015-0158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Treatment of [RuCl2(PPh3)3] with equimolar amounts of 2,4-pyridinedicarboxylic acid (2,4-dipicH2) in the presence of Et3N afforded a tetranuclear complex [Ru(μ-2,4-dipic)(PPh3)2]4 (1) as red crystals. The crystal and molecular structure of [Ru(μ-2,4-dipic)(PPh3)2]4·CHCl3·8H2O (1·CHCl3·8H2O) was determined by single-crystal X-ray diffraction. Each ruthenium center in 1 is six-coordinated with two phosphorus atoms from triphenylphosphine ligands, one nitrogen atom from a pyridyl moiety and three oxygen atoms from two 2,4-dipic2– ligands. 2,4-Pyridinedicarboxylate dianions (2,4-dipic2–) act as bridging ligands to form the stable tetranuclear metallamacrocyclic compound. The electrochemical properties of 1 were also investigated.
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Affiliation(s)
- Yu-Feng Xie
- Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Ma’anshan, Anhui 243002, P.R. China
| | - Ai-Quan Jia
- Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Ma’anshan, Anhui 243002, P.R. China
| | - Hang Zhu
- Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Ma’anshan, Anhui 243002, P.R. China
| | - Hua-Tian Shi
- Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Ma’anshan, Anhui 243002, P.R. China
| | - Qian-Feng Zhang
- Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Ma’anshan, Anhui 243002, P.R. China
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15
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Walpita J, Yang X, Khatmullin R, Luk HL, Hadad CM, Glusac KD. Pourbaix diagrams in weakly coupled systems: a case study involving acridinol and phenanthridinol pseudobases. J PHYS ORG CHEM 2015. [DOI: 10.1002/poc.3516] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Janitha Walpita
- Department of Chemistry; Bowling Green State University; Bowling Green OH 43403 USA
| | - Xin Yang
- Department of Chemistry; Bowling Green State University; Bowling Green OH 43403 USA
| | - Renat Khatmullin
- Department of Chemistry; Bowling Green State University; Bowling Green OH 43403 USA
| | - Hoi Ling Luk
- Department of Chemistry; Bowling Green State University; Bowling Green OH 43403 USA
| | - Christopher M. Hadad
- Department of Chemistry and Biochemistry; The Ohio State University; Columbus OH 43210 USA
| | - Ksenija D. Glusac
- Department of Chemistry; Bowling Green State University; Bowling Green OH 43403 USA
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16
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Xie YF, Jia AQ, Zhu H, Shi HT, Zhang QF. Synthesis and reactivity of ruthenium(II) complexes with 1,5-cyclooctadiene and pyridine-2,6-dicarboxylato ligands. Inorganica Chim Acta 2015. [DOI: 10.1016/j.ica.2015.08.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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17
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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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18
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Tarantino KT, Miller DC, Callon TA, Knowles RR. Bond-weakening catalysis: conjugate aminations enabled by the soft homolysis of strong N-H bonds. J Am Chem Soc 2015; 137:6440-3. [PMID: 25945955 PMCID: PMC4657442 DOI: 10.1021/jacs.5b03428] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability of redox-active metal centers to weaken the bonds in associated ligands is well precedented, but has rarely been utilized as a mechanism of substrate activation in catalysis. Here we describe a catalytic bond-weakening protocol for conjugate amination wherein the strong N-H bonds in N-aryl amides (N-H bond dissociation free energies ∼100 kcal/mol) are destabilized by ∼33 kcal/mol upon by coordination to a reducing titanocene complex, enabling their abstraction by the weak H-atom acceptor TEMPO through a proton-coupled electron transfer process. Significantly, this soft homolysis mechanism provides a method to generate closed-shell, metalated nucleophiles under neutral conditions in the absence of a Brønsted base.
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Affiliation(s)
- Kyle T. Tarantino
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - David C. Miller
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Ted A. Callon
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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19
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Abstract
An enormous variety of biological redox reactions are accompanied by changes in proton content at enzyme active sites, in their associated cofactors, in substrates and/or products, and between protein interfaces. Understanding this breadth of reactivity is an ongoing chemical challenge. A great many workers have developed and investigated biomimetic model complexes to build new ways of thinking about the mechanistic underpinnings of such complex biological proton-coupled electron transfer (PCET) reactions. Of particular importance are those model reactions that involve transfer of one proton (H(+)) and one electron (e(-)), which is equivalent to transfer of a hydrogen atom (H(•)). In this Current Topic, we review key concepts in PCET reactivity and describe important advances in biomimetic PCET chemistry, with a special emphasis on research that has enhanced efforts to understand biological PCET reactions.
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Affiliation(s)
- Jeffrey J. Warren
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC, Canada V5A 1S6
| | - James M. Mayer
- Yale University, Department of Chemistry, P.O. Box 208107, 225 Prospect Street, New Haven, CT 06520-8107
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20
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Xie YF, Zhu H, Shi HT, Jia AQ, Zhang QF. Ruthenium complexes containing pyridine-2,6-dicarboxylato ligands. Inorganica Chim Acta 2015. [DOI: 10.1016/j.ica.2014.12.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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21
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Mardanya S, Karmakar S, Maity D, Baitalik S. Ruthenium(II) and Osmium(II) Mixed Chelates Based on Pyrenyl–Pyridylimidazole and 2,2′-Bipyridine Ligands as Efficient DNA Intercalators and Anion Sensors. Inorg Chem 2014; 54:513-26. [DOI: 10.1021/ic502271k] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Sourav Mardanya
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
| | - Srikanta Karmakar
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
| | - Dinesh Maity
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
| | - Sujoy Baitalik
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
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22
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Karmakar S, Maity D, Mardanya S, Baitalik S. Multichromophoric Bimetallic Ru(II) Terpyridine Complexes Based on Pyrenyl-bis-phenylimidazole Spacer: Synthesis, Photophysics, Spectroelectrochemistry, and TD-DFT Calculations. Inorg Chem 2014; 53:12036-49. [DOI: 10.1021/ic501741r] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Srikanta Karmakar
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
| | - Dinesh Maity
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
| | - Sourav Mardanya
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
| | - Sujoy Baitalik
- Department of Chemistry,
Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
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23
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Sánchez-Márquez J, Zorrilla D, Sánchez-Coronilla A, de los Santos DM, Navas J, Fernández-Lorenzo C, Alcántara R, Martín-Calleja J. Introducing “UCA-FUKUI” software: reactivity-index calculations. J Mol Model 2014; 20:2492. [DOI: 10.1007/s00894-014-2492-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 10/06/2014] [Indexed: 10/24/2022]
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24
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Affiliation(s)
- Joshua P. Layfield
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Sharon Hammes-Schiffer
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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25
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Chen J, Kuss-Petermann M, Wenger OS. Distance Dependence of Bidirectional Concerted Proton-Electron Transfer in Phenol-Ru(2,2′-bipyridine)32+Dyads. Chemistry 2014; 20:4098-104. [DOI: 10.1002/chem.201304256] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Indexed: 11/08/2022]
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26
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Sánchez-Coronilla A, Sánchez-Márquez J, Zorrilla D, Martín EI, de los Santos DM, Navas J, Fernández-Lorenzo C, Alcántara R, Martín-Calleja J. Convergent study of Ru–ligand interactions through QTAIM, ELF, NBO molecular descriptors and TDDFT analysis of organometallic dyes. Mol Phys 2014. [DOI: 10.1080/00268976.2014.884729] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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27
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Bronner C, Wenger OS. Long-range proton-coupled electron transfer in phenol–Ru(2,2′-bipyrazine)32+ dyads. Phys Chem Chem Phys 2014; 16:3617-22. [DOI: 10.1039/c3cp55071k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Abstract
Proton-coupled electron transfer (PCET) plays a crucial role in many enzymatic reactions and is relevant for a variety of processes including water oxidation, nitrogen fixation, and carbon dioxide reduction. Much of the research on PCET has focused on transfers between molecules in their electronic ground states, but increasingly researchers are investigating PCET between photoexcited reactants. This Account describes recent studies of excited-state PCET with d(6) metal complexes emphasizing work performed in my laboratory. Upon photoexcitation, some complexes release an electron and a proton to benzoquinone reaction partners. Others act as combined electron-proton acceptors in the presence of phenols. As a result, we can investigate photoinduced PCET involving electron and proton transfer in a given direction, a process that resembles hydrogen-atom transfer (HAT). In other studies, the photoexcited metal complexes merely serve as electron donors or electron acceptors because the proton donating and accepting sites are located on other parts of the molecular PCET ensemble. We and others have used this multisite design to explore so-called bidirectional PCET which occurs in many enzymes. A central question in all of these studies is whether concerted proton-electron transfer (CPET) can compete kinetically with sequential electron and proton transfer steps. Short laser pulses can trigger excited-state PCET, making it possible to investigate rapid reactions. Luminescence spectroscopy is a convenient tool for monitoring PCET, but unambiguous identification of reaction products can require a combination of luminescence spectroscopy and transient absorption spectroscopy. Nevertheless, in some cases, distinguishing between PCET photoproducts and reaction products formed by simple photoinduced electron transfer (ET) (reactions that don't include proton transfer) is tricky. Some of the studies presented here deal directly with this important problem. In one case study we employed a cyclometalated iridium(III) complex. Our other studies with ruthenium(II) complexes and phenols focused on systematic variations of the reaction free energies for the CPET, ET, and proton transfer (PT) steps to explore their influence on the overall PCET reaction. Still other work with rhenium(I) complexes concentrated on the question of how the electronic structure of the metal-to-ligand charge transfer (MLCT) excited states affects PCET. We used covalent rhenium(I)-phenol dyads to explore the influence of the electron donor-electron acceptor distance on bidirectional PCET. In covalent triarylamine-Ru(bpy)₃²⁺/Os(bpy)₃²⁺-anthraquinone triads (bpy = 2,2'-bipyridine), hydrogen-bond donating solvents significantly lengthened the lifetimes of photogenerated electron/hole pairs because of hydrogen-bonding to the quinone radical anion. Until now, comparatively few researchers have investigated this variation of PCET: the strengthening of H-bonds upon photoreduction.
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Affiliation(s)
- Oliver S. Wenger
- Departement Chemie, Universität Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
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29
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Kuss-Petermann M, Wenger OS. Photoacid Behavior versus Proton-Coupled Electron Transfer in Phenol–Ru(bpy)32+ Dyads. J Phys Chem A 2013; 117:5726-33. [DOI: 10.1021/jp402567m] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Martin Kuss-Petermann
- Institut für Anorganische
Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, D-37077 Göttingen, Germany
| | - Oliver S. Wenger
- Departement für
Chemie, Universität Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
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30
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Warren JJ, Menzeleev AR, Kretchmer JS, Miller TF, Gray HB, Mayer JM. Long Range Proton-Coupled Electron Transfer Reactions of Bis(imidazole) Iron Tetraphenylporphyrins Linked to Benzoates. J Phys Chem Lett 2013; 4:519-523. [PMID: 23493584 PMCID: PMC3593309 DOI: 10.1021/jz400029w] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Concerted proton-electron transfer (CPET) reactions in iron carboxy-tetraphenylporphyrin complexes have been investigated using both experimental and theoretical methods. Synthetic heme models abstract H+ and e- from the hydroxylamine TEMPOH or an ascorbate derivative, and the kinetics of the TEMPOH reaction indicate concerted transfer of H+ and e-. Phenylene linker domains vary the electron donor/acceptor separation by approximately 4 Å. The rate data and extensive molecular simulations show that the electronic coupling decay constant (β) depends on conformational flexibility and solvation associated with the linker domain. Our best estimate of β is 0.23 ± 0.07 Å-1, a value that is near the low end of the range (0.2-0.5 Å-1) established for electron transfer reactions involving related linkers. This is the first analysis of β for a CPET reaction.
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Affiliation(s)
- Jeffrey J. Warren
- University of Washington, Department of Chemistry, Box 351700 Seattle, WA 91195-1700
- California Institute of Technology, Department of Chemistry, 1200 E. California Blvd. Pasadena, CA 91125
| | - Artur R. Menzeleev
- California Institute of Technology, Department of Chemistry, 1200 E. California Blvd. Pasadena, CA 91125
| | - Joshua S. Kretchmer
- California Institute of Technology, Department of Chemistry, 1200 E. California Blvd. Pasadena, CA 91125
| | - Thomas F. Miller
- California Institute of Technology, Department of Chemistry, 1200 E. California Blvd. Pasadena, CA 91125
| | - Harry B. Gray
- California Institute of Technology, Department of Chemistry, 1200 E. California Blvd. Pasadena, CA 91125
| | - James M. Mayer
- University of Washington, Department of Chemistry, Box 351700 Seattle, WA 91195-1700
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31
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Yang J, Hu RX, Zhang MB. Construction of monomers and chains assembled by 3d/4f metals and 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine. J SOLID STATE CHEM 2012. [DOI: 10.1016/j.jssc.2012.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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32
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Zhang N, Yang J, Hu RX, Zhang MB. Syntheses and Structures of Terpyridine-Metal Complexes. Z Anorg Allg Chem 2012. [DOI: 10.1002/zaac.201200339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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33
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Kuss-Petermann M, Wolf H, Stalke D, Wenger OS. Influence of Donor–Acceptor Distance Variation on Photoinduced Electron and Proton Transfer in Rhenium(I)–Phenol Dyads. J Am Chem Soc 2012; 134:12844-54. [DOI: 10.1021/ja3053046] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Martin Kuss-Petermann
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Hilke Wolf
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Dietmar Stalke
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Oliver S. Wenger
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
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34
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Manner VW, Lindsay AD, Mader EA, Harvey JN, Mayer JM. Spin-forbidden hydrogen atom transfer reactions in a cobalt biimidazoline system. Chem Sci 2012. [DOI: 10.1039/c1sc00387a] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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35
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Warren JJ, Mayer JM. Proton-coupled electron transfer reactions at a heme-propionate in an iron-protoporphyrin-IX model compound. J Am Chem Soc 2011; 133:8544-51. [PMID: 21524059 DOI: 10.1021/ja201663p] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A heme model system has been developed in which the heme-propionate is the only proton donating/accepting site, using protoporphyrin IX-monomethyl esters (PPIX(MME)) and N-methylimidazole (MeIm). Proton-coupled electron transfer (PCET) reactions of these model compounds have been examined in acetonitrile solvent. (PPIX(MME))Fe(III)(MeIm)(2)-propionate (Fe(III)~CO(2)) is readily reduced by the ascorbate derivative 5,6-isopropylidine ascorbate to give (PPIX(MME))Fe(II)(MeIm)(2)-propionic acid (Fe(II)~CO(2)H). An excess of the hydroxylamine TEMPOH or of hydroquinone similarly reduces Fe(III)~CO(2), and TEMPO and benzoquinone oxidize Fe(II)~CO(2)H to return to Fe(III)~CO(2). The measured equilibrium constants, and the determined pK(a) and E(1/2) values, indicate that Fe(II)~CO(2)H has an effective bond dissociation free energy (BDFE) of 67.8 ± 0.6 kcal mol(-1). In these PPIX models, electron transfer occurs at the iron center and proton transfer occurs at the remote heme propionate. According to thermochemical and other arguments, the TEMPOH reaction occurs by concerted proton-electron transfer (CPET), and a similar pathway is indicated for the ascorbate derivative. Based on these results, heme propionates should be considered as potential key components of PCET/CPET active sites in heme proteins.
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Affiliation(s)
- Jeffrey J Warren
- Beckman Institute, California Institute of Technology, MC 139-74, Pasadena, California 91125-0001, USA.
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36
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Warren JJ, Tronic TA, Mayer JM. Thermochemistry of proton-coupled electron transfer reagents and its implications. Chem Rev 2010; 110:6961-7001. [PMID: 20925411 PMCID: PMC3006073 DOI: 10.1021/cr100085k] [Citation(s) in RCA: 1193] [Impact Index Per Article: 85.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Jeffrey J. Warren
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
| | - Tristan A. Tronic
- 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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37
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Terpyridine- and 2,6-dipyrazinylpyridine-coordinated ruthenium(II) complexes: Synthesis, characterization and application in TiO2-based dye-sensitized solar cells. J Photochem Photobiol A Chem 2010. [DOI: 10.1016/j.jphotochem.2010.06.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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38
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Synthesis, structures and photocatalytic properties of a mononuclear copper complex with pyridine-carboxylato ligands. INORG CHEM COMMUN 2010. [DOI: 10.1016/j.inoche.2010.01.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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39
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Rajeev R, Sunoj R. On the Origin of Reversible Hydrogen Activation by PhosphineâBoranes. Chemistry 2009; 15:12846-55. [DOI: 10.1002/chem.200900663] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Manner VW, Mayer JM. Concerted proton-electron transfer in a ruthenium terpyridyl-benzoate system with a large separation between the redox and basic sites. J Am Chem Soc 2009; 131:9874-5. [PMID: 19569636 DOI: 10.1021/ja902942g] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To understand how the separation between the electron and proton-accepting sites affects proton-coupled electron transfer (PCET) reactivity, we have prepared ruthenium complexes with 4'-(4-carboxyphenyl)terpyridine ligands, and studied reactivity with hydrogen atom donors (H-X). Ru(II)(pydic)(tpy-PhCOOH) (Ru(II)PhCOOH), was synthesized in one pot from [(p-cymene)RuCl(2)](2), sodium 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine ([Na(+)]tpy-PhCOO(-)), and disodium pyridine-2,6-dicarboxylate (Na(2)pydic). Ru(II)PhCOOH plus (n)Bu(4)NOH in DMF yields the deprotonated Ru(II) complex, (n)Bu(4)N[Ru(II)(pydic)(tpy-PhCOO)] (Ru(II)PhCOO(-)). The Ru(III) complex (Ru(III)PhCOO) has been isolated by one-electron oxidation of Ru(II)PhCOO(-) with triarylaminium radical cations (NAr(3)(*+)). The bond dissociation free energy (BDFE) of the O-H bond in Ru(II)PhCOOH is calculated from pK(a) and E(1/2) measurements as 87 kcal mol(-1), making Ru(III)PhCOO a strong hydrogen atom acceptor. There are 10 bonds and ca. 11.2 A separating the metal from the carboxylate basic site in Ru(III)PhCOO. Even with this separation, Ru(III)PhCOO oxidizes the hydrogen atom donor TEMPOH (BDFE = 66.5 kcal mol(-1), DeltaG(o)(rxn) = -21 kcal mol(-1)) by removal of an electron and a proton to form Ru(II)PhCOOH and TEMPO radical in a concerted proton-electron transfer (CPET) process. The second order rate constant for this reaction is (1.1 +/- 0.1) x 10(5) M(-1) s(-1) with k(H)/k(D) = 2.1 +/- 0.2, similar to the observed kinetics in an analogous system without the phenyl spacer, Ru(III)(pydic)(tpy-COO(-)) (Ru(III)COO). In contrast, hydrogen transfer from 2,6-di-tert-butyl-p-methoxyphenol [(t)Bu(2)(OMe)ArOH] to Ru(III)PhCOO is several orders of magnitude slower than the analogous reaction with Ru(III)COO.
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Affiliation(s)
- Virginia W Manner
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
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41
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Matsumoto T, Ohkubo K, Honda K, Yazawa A, Furutachi H, Fujinami S, Fukuzumi S, Suzuki M. Aliphatic C−H Bond Activation Initiated by a (μ-η2:η2-Peroxo)dicopper(II) Complex in Comparison with Cumylperoxyl Radical. J Am Chem Soc 2009; 131:9258-67. [DOI: 10.1021/ja809822c] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Takahiro Matsumoto
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Kei Ohkubo
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Kaoru Honda
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Akiko Yazawa
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Hideki Furutachi
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Shuhei Fujinami
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Shunichi Fukuzumi
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Masatatsu Suzuki
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan, and Department of Material and Life Science, Graduate School of Engineering, Osaka University, and SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
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42
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Waidmann CR, Zhou X, Tsai EA, Kaminsky W, Hrovat DA, Borden WT, Mayer JM. Slow hydrogen atom transfer reactions of oxo- and hydroxo-vanadium compounds: the importance of intrinsic barriers. J Am Chem Soc 2009; 131:4729-43. [PMID: 19292442 PMCID: PMC2735118 DOI: 10.1021/ja808698x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reactions are described that interconvert vanadium(IV) oxo-hydroxo complexes [V(IV)O(OH)(R(2)bpy)(2)]BF(4) (1a-c) and vanadium(V) dioxo complexes [V(V)O(2)(R(2)bpy)(2)]BF(4) (2a-c) [R(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridine ((t)Bu(2)bpy), a; 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy), b; 2,2'-bipyridine (bpy), c]. These are rare examples of pairs of isolated, sterically unencumbered, first-row metal-oxo/hydroxo complexes that differ by a hydrogen atom (H(+) + e(-)). The V(IV)-(t)Bu(2)bpy derivative 1a has a useful (1)H NMR spectrum, despite being paramagnetic. Complex 2a abstracts H(*) from organic substrates with weak O-H and C-H bonds, converting 2,6-(t)Bu(2)-4-MeO-C(6)H(2)OH (ArOH) and 2,2,6,6-tetramethyl-N-hydroxypiperidine (TEMPOH) to their corresponding radicals ArO(*) and TEMPO, hydroquinone to benzoquinone, and dihydroanthracene to anthracene. The equilibrium constant for 2a + ArOH <==> 1a + ArO(*) is (4 +/- 2) x 10(-3), implying that the VO-H bond dissociation free energy (BDFE) is 70.6 +/- 1.2 kcal mol(-1). Consistent with this value, 1a is oxidized by 2,4,6-(t)Bu(3)C(6)H(2)O(*). All of these reactions are surprisingly slow, typically occurring over hours at ambient temperatures. The net hydrogen-atom pseudo-self-exchange 1a + 2b <==> 2a + 1b, using the (t)Bu- and Me-bpy substituents as labels, also occurs slowly, with k(se) = 1.3 x 10(-2) M(-1) s(-1) at 298 K, DeltaH(double dagger) = 15 +/- 2 kcal mol(-1), and DeltaS(double dagger) = 16 +/- 5 cal mol(-1) K. Using this k(se) and the BDFE, the vanadium reactions are shown to follow the Marcus cross relation moderately well, with calculated rate constants within 10(2) of the observed values. The vanadium self-exchange reaction is ca. 10(6) slower than that for the related Ru(IV)O(py)(bpy)(2)(2+)/Ru(III)OH(py)(bpy)(2)(2+) self-exchange. The origin of this dramatic difference has been probed with DFT calculations on the self-exchange reactions of 1c + 2c and on monocationic ruthenium complexes with pyrrolate or fluoride in place of the py ligands. The calculations reproduce the difference in barrier heights and show that transfer of a hydrogen atom involves more structural reorganization for vanadium than the Ru analogues. The vanadium complexes have larger changes in the metal-oxo and metal-hydroxo bond lengths, which is traced to the difference in d-orbital occupancy in the two systems. This study thus highlights the importance of intrinsic barriers in the transfer of a hydrogen atom, in addition to the thermochemical (bond strength) factors that have been previously emphasized.
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Affiliation(s)
- Christopher R. Waidmann
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
| | - Xin Zhou
- Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070
| | - Erin A. Tsai
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
| | - Werner Kaminsky
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
- UW crystallographic facility
| | - David A. Hrovat
- Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070
| | - Weston Thatcher Borden
- Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070
| | - James M. Mayer
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
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Mader EA, Manner VW, Markle TF, Wu A, Franz JA, Mayer JM. Trends in ground-state entropies for transition metal based hydrogen atom transfer reactions. J Am Chem Soc 2009; 131:4335-45. [PMID: 19275235 PMCID: PMC2723939 DOI: 10.1021/ja8081846] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors M(II)LH and oxyl radicals. [Fe(II)(H(2)bip)(3)](2+), [Fe(II)(H(2)bim)(3)](2+), [Co(II)(H(2)bim)(3)](2+), and Ru(II)(acac)(2)(py-imH) [H(2)bip = 2,2'-bi-1,4,5,6-tetrahydropyrimidine, H(2)bim = 2,2'-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2'-pyridyl)imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or (t)Bu(3)PhO(*) (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex M(III)L and TEMPOH or (t)Bu(3)PhOH. Solution equilibrium measurements for the reaction of [Co(II)(H(2)bim)(3)](2+) with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer, -41 +/- 2 cal mol(-1) K(-1). This is even more negative than the DeltaS(o)(HAT) = -30 +/- 2 cal mol(-1) K(-1) for the two iron complexes and the DeltaS(o)(HAT) for Ru(II)(acac)(2)(py-imH) + TEMPO, 4.9 +/- 1.1 cal mol(-1) K(-1), as reported earlier. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [Fe(II)(H(2)bip)(3)](2+) + TEMPO, thus also confirming DeltaS(o)(HAT). Calorimetry on TEMPOH + (t)Bu(3)PhO(*) gives DeltaH(o)(HAT) = -11.2 +/- 0.5 kcal mol(-1) which matches the enthalpy predicted from the difference in literature solution BDEs. A brief evaluation of the literature thermochemistry of TEMPOH and (t)Bu(3)PhOH supports the common assumption that DeltaS(o)(HAT) approximately 0 for HAT reactions of organic and small gas-phase molecules. However, this assumption does not hold for transition metal based HAT reactions. The trend in magnitude of |DeltaS(o)(HAT)| for reactions with TEMPO, Ru(II)(acac)(2)(py-imH) << [Fe(II)(H(2)bip)(3)](2+) = [Fe(II)(H(2)bim)(3)](2+) < [Co(II)(H(2)bim)(3)](2+), is surprisingly well predicted by the trends for electron transfer half-reaction entropies, DeltaS(o)(ET), in aprotic solvents. This is because both DeltaS(o)(ET) and DeltaS(o)(HAT) have substantial contributions from vibrational entropy, which varies significantly with the metal center involved. The close connection between DeltaS(o)(HAT) and DeltaS(o)(ET) provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects.
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Affiliation(s)
- Elizabeth A Mader
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA
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Wu A, Mayer JM. Hydrogen atom transfer reactions of a ruthenium imidazole complex: hydrogen tunneling and the applicability of the Marcus cross relation. J Am Chem Soc 2008; 130:14745-54. [PMID: 18841973 PMCID: PMC2633126 DOI: 10.1021/ja805067h] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction of Ru(II)(acac)2(py-imH) (Ru(II)imH) with TEMPO(*) (2,2,6,6-tetramethylpiperidine-1-oxyl radical) in MeCN quantitatively gives Ru(III)(acac)2(py-im) (Ru(III)im) and the hydroxylamine TEMPO-H by transfer of H(*) (H(+) + e(-)) (acac = 2,4-pentanedionato, py-imH = 2-(2'-pyridyl)imidazole). Kinetic measurements of this reaction by UV-vis stopped-flow techniques indicate a bimolecular rate constant k(3H) = 1400 +/- 100 M(-1) s(-1) at 298 K. The reaction proceeds via a concerted hydrogen atom transfer (HAT) mechanism, as shown by ruling out the stepwise pathways of initial proton or electron transfer due to their very unfavorable thermochemistry (Delta G(o)). Deuterium transfer from Ru(II)(acac)2(py-imD) (Ru(II)imD) to TEMPO(*) is surprisingly much slower at k(3D) = 60 +/- 7 M(-1) s(-1), with k(3H)/k(3D) = 23 +/- 3 at 298 K. Temperature-dependent measurements of this deuterium kinetic isotope effect (KIE) show a large difference between the apparent activation energies, E(a3D) - E(a3H) = 1.9 +/- 0.8 kcal mol(-1). The large k(3H)/k(3D) and DeltaE(a) values appear to be greater than the semiclassical limits and thus suggest a tunneling mechanism. The self-exchange HAT reaction between Ru(II)imH and Ru(III)im, measured by (1)H NMR line broadening, occurs with k(4H) = (3.2 +/- 0.3) x 10(5) M(-1) s(-1) at 298 K and k(4H)/k(4D) = 1.5 +/- 0.2. Despite the small KIE, tunneling is suggested by the ratio of Arrhenius pre-exponential factors, log(A(4H)/A(4D)) = -0.5 +/- 0.3. These data provide a test of the applicability of the Marcus cross relation for H and D transfers, over a range of temperatures, for a reaction that involves substantial tunneling. The cross relation calculates rate constants for Ru(II)imH(D) + TEMPO(*) that are greater than those observed: k(3H,calc)/k(3H) = 31 +/- 4 and k(3D,calc)/k(3D) = 140 +/- 20 at 298 K. In these rate constants and in the activation parameters, there is a better agreement with the Marcus cross relation for H than for D transfer, despite the greater prevalence of tunneling for H. The cross relation does not explicitly include tunneling, so close agreement should not be expected. In light of these results, the strengths and weaknesses of applying the cross relation to HAT reactions are discussed.
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Affiliation(s)
- Adam Wu
- Department of Chemistry, University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA
| | - James M. Mayer
- Department of Chemistry, University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA
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