1
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Zhang F, Woods TJ, Rauchfuss TB. Hybrids of [FeFe]- and [NiFe]-H 2ase Active Site Models. Organometallics 2023; 42:1607-1614. [PMID: 37928214 PMCID: PMC10624399 DOI: 10.1021/acs.organomet.3c00173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Complexes of the type (diphosphine)Ni(μ-SR)2Fe(CO)3 are investigated with azadithiolate (adt, HN(CH2S-)2) as the dithiolate. The resulting complexes are hybrid models for the active sites of the [NiFe]- and [FeFe]-hydrogenases. The key complex (dppv)Ni(μ-adt)Fe(CO)3 (3) was prepared from the complex Ni[(SCH2)2NCbz](dppv), which contains a Cbz-protected adt ligand (Cbz = C(O)OCH2Ph, dppv = cis-1,2-(Ph2P)2C2H2). This complex combines with Fe2(CO)9 to give (dppv)Ni[(μ-SCH2)2NCbz]Fe(CO)3, which is readily deprotected to give 3. Complex 3 undergoes protonation at both Fe and N to give successively [(dppv)Ni(μ-adt)FeH(CO)3]+ ([H3]+) and [(dppv)Ni(μ-adtH)FeH(CO)3]2+ ([H3H]2+). The redox properties and dynamics of these complexes resemble previously reported analogues with propanedithiolate. Solutions of [H3]+ readily degrade to [(dppv)Ni[(μ-SCH2)2NCH2]Fe(CO)3]+ ([4]+), which features a methylene group linking N and Fe. Complex [4]+ can be made in high yield by reaction of [H3]+ with CH2O, and this conversion was also demonstrated with 13CH2O. Complex [4]+ undergoes hydrogenolysis by photochemical reaction with H2 to give [(dppv)Ni[(μ-SCH2)2NMe]FeH(CO)3]+, the N-methylated analogue of [H3]+. Upon treatment ith Me3O+, [4]+ undergoes quaternization, giving [(dppv)Ni[(μ-SCH2)2N(Me)CH2]Fe(CO)3]2+. In contrast with the lability of [H3]+, the phosphine-substituted derivative [(dppv)Ni(μ-adt)FeH(CO)2(PPh3)]+ did not degrade. Most complexes were characterized by X-ray crystallography.
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Affiliation(s)
- Fanjun Zhang
- School of Chemical Sciences, University of Illinois, Urbana, Illinois 61801, United States; Present Address: School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, Shandong 273165, China (F.Z.)
| | - Toby J Woods
- School of Chemical Sciences, University of Illinois, Urbana, Illinois 61801, United States
| | - Thomas B Rauchfuss
- School of Chemical Sciences, University of Illinois, Urbana, Illinois 61801, United States
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2
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Gorantla KR, Mallik BS. Catalytic Mechanism of Competing Proton Transfer Events from Water and Acetic Acid by [Co II(bpbH 2)Cl 2] for Water Splitting Processes. J Phys Chem A 2022; 126:1321-1328. [PMID: 35172100 DOI: 10.1021/acs.jpca.1c07353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We performed first principles simulations to explore the water reduction process of the cobalt complex [CoII(bpbH2)Cl2], where bpbH2 = N,N'-bis(2'-pyridine carboxamide)-1,2-benzene. We considered the sequence steps of electron reduction followed by the proton addition process to observe the hydrogen evolution process. An experimental study of the catalyst showed that the increase in the acetic acid concentration triggers catalytic current and reduction of Co(II) to Co(I), and protonation occurred, yielding a Co(III)-H intermediate. Therefore, we used water and acetic acid as the proton sources. We compare the proton transfer kinetics from both the water and acetic acid. The reduction potentials and proton transfer kinetics from water or acetic acid to the reaction center were studied in a DMF solvent through the implicit solvent model. The first proton transfer from the acetic acid is more favorable, forming a CoIII-H complex and further reducing to CoII-H. The second proton transfer from water to the CoII-H moiety requires less free energy than acetic acid and is the rate-limiting step. The nature of the reduction process is also examined through the charge analysis, which reveals that the ligand becomes softer due to the C═O groups.
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Affiliation(s)
- Koteswara Rao Gorantla
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
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3
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Arrigoni F, Rovaletti A, Bertini L, Breglia R, De Gioia L, Greco C, Vertemara J, Zampella G, Fantucci P. Investigations of the electronic-molecular structure of bio-inorganic systems using modern methods of quantum chemistry. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2021.120728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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4
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Puthenkalathil R, Ensing B. Linear Scaling Relationships to Predict p Ka's and Reduction Potentials for Bioinspired Hydrogenase Catalysis. Inorg Chem 2022; 61:113-120. [PMID: 34955025 PMCID: PMC8753599 DOI: 10.1021/acs.inorgchem.1c02429] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Indexed: 11/29/2022]
Abstract
Biomimetic catalysts inspired by the active site of the [FeFe] hydrogenase enzyme can convert protons into molecular hydrogen. Minimizing the overpotential of the electrocatalytic process remains a major challenge for practical application of the catalyst. The catalytic cycle of the hydrogen production follows an ECEC mechanism (E represents an electron transfer step, and C refers to a chemical step), in which the electron and proton transfer steps can be either sequential or coupled (PCET). In this study, we have calculated the pKa's and the reduction potentials for a series of commonly used ligands (80 different complexes) using density functional theory. We establish that the required acid strength for protonation at the Fe-Fe site correlates with the standard reduction potential of the di-iron complexes with a linear energy relationship. These linear relationships allow for fast screening of ligands and tuning of the properties of the catalyst. Our study also suggests that bridgehead ligand properties, such as bulkiness and aromaticity, can be exploited to alter or even break the linear scaling relationships.
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Affiliation(s)
- Rakesh
C. Puthenkalathil
- Van ’t Hoff Institute for Molecular
Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Bernd Ensing
- Van ’t Hoff Institute for Molecular
Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
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5
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Torres A, Collado A, Gómez-Gallego M, Ramírez de Arellano C, Sierra MA. Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics. ACS ORGANIC & INORGANIC AU 2021; 2:23-33. [PMID: 36855407 PMCID: PMC9954209 DOI: 10.1021/acsorginorgau.1c00011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
TTF- and exTTF-containing [(μ-S2)Fe2(CO)6] complexes have been prepared by the photochemical reaction of TTF or exTTF and [(μ-S2)Fe2(CO)6]. These complexes are able to interact with PAHs. In the absence of air and in acid media an electrocatalytic dihydrogen evolution reaction (HER) occurs, similarly to analogous [(μ-S2)Fe2(CO)6] complexes. However, in the presence of air, the TTF and exTTF organic moieties strongly influence the electrochemistry of these systems. The reported data may be valuable in the design of [FeFe] hydrogenase mimics able to combine the HER properties of the [FeFe] cores with the unique TTF properties.
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Affiliation(s)
- Alejandro Torres
- Departamento
de Química Orgánica I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain,Center
for Innovation in Advanced Chemistry (ORFEO-CINQA), Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - Alba Collado
- Departamento
de Química Orgánica I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain,Center
for Innovation in Advanced Chemistry (ORFEO-CINQA), Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - Mar Gómez-Gallego
- Departamento
de Química Orgánica I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain,Center
for Innovation in Advanced Chemistry (ORFEO-CINQA), Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - Carmen Ramírez de Arellano
- Center
for Innovation in Advanced Chemistry (ORFEO-CINQA), Facultad de Química, Universidad Complutense, 28040 Madrid, Spain,Departamento
de Química Orgánica, Universidad
de Valencia, 46100 Valencia, Spain
| | - Miguel A. Sierra
- Departamento
de Química Orgánica I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain,Center
for Innovation in Advanced Chemistry (ORFEO-CINQA), Facultad de Química, Universidad Complutense, 28040 Madrid, Spain,Email for M.A.S.:
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6
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Orio M, Pantazis DA. Successes, challenges, and opportunities for quantum chemistry in understanding metalloenzymes for solar fuels research. Chem Commun (Camb) 2021; 57:3952-3974. [DOI: 10.1039/d1cc00705j] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Overview of the rich and diverse contributions of quantum chemistry to understanding the structure and function of the biological archetypes for solar fuel research, photosystem II and hydrogenases.
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Affiliation(s)
- Maylis Orio
- Aix-Marseille Université
- CNRS
- iSm2
- Marseille
- France
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für Kohlenforschung
- Kaiser-Wilhelm-Platz 1
- 45470 Mülheim an der Ruhr
- Germany
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7
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Barrozo A, Orio M. Molecular Electrocatalysts for the Hydrogen Evolution Reaction: Input from Quantum Chemistry. CHEMSUSCHEM 2019; 12:4905-4915. [PMID: 31557393 DOI: 10.1002/cssc.201901828] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 08/22/2019] [Indexed: 06/10/2023]
Abstract
In the pursuit of carbon-free fuels, hydrogen can be considered as an apt energy carrier. The design of molecular electrocatalysts for hydrogen production is important for the development of renewable energy sources that are abundant, inexpensive, and environmentally benign. Over the last 20 years, a large number of electrocatalysts have been developed, and considerable efforts have been directed toward the design of earth-abundant, first-row transition-metal complexes capable of promoting electrocatalytic hydrogen evolution reaction (HER). In this context, numerical approaches have emerged as powerful tools to study the catalytic performances of these complexes. This review covers some of the most significant theoretical mechanistic studies of biomimetic and bioinspired homogeneous HER catalysts. The approaches employed to study the free energy landscapes are discussed and methods used to obtain accurate estimates of relevant observables required to study the HER are presented. Furthermore, the structural and electronic parameters that govern the reactivity, and are necessary to achieve efficient hydrogen production, are discussed in view of future research directions.
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Affiliation(s)
- Alexandre Barrozo
- Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, 13397, Marseille, France
| | - Maylis Orio
- Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, 13397, Marseille, France
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8
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Borthakur B, Phukan AK. Can carbene decorated [FeFe]-hydrogenase model complexes catalytically produce dihydrogen? An insight from theory. Dalton Trans 2019; 48:11298-11307. [PMID: 31270518 DOI: 10.1039/c9dt01855g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclic alkyl amino carbene (CAAC) anchored [FeFe]-hydrogenase model complex featuring rotated conformation at one of the iron centers are found to be promising candidate for effective production of dihydrogen. A stepwise comparison of the complete mechanism using the CAAC stabilized model complex [1]0 has been performed with that of an experimentally isolated one ([2]0). Interestingly, the reduction events involved in the catalytic cycles are found to be more favorable than those previously reported for a similar experimentally known system. Furthermore, the computed ΔpKa values indicate that the distal iron center with a vacant coordination site is more basic compared to the amino nitrogen atom of the azadithiolate bridge. We also made an attempt to determine the oxidation states of the iron centers for the intermediates involved in the catalytic cycles on the basis of the computed Mössbauer isomer shift and Mulliken spin density values.
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Affiliation(s)
- Bitupon Borthakur
- Department of Chemical Sciences, Tezpur University, Napaam 784028, Assam, India.
| | - Ashwini K Phukan
- Department of Chemical Sciences, Tezpur University, Napaam 784028, Assam, India.
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9
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Viertl W, Pann J, Pehn R, Roithmeyer H, Bendig M, Rodríguez-Villalón A, Bereiter R, Heiderscheid M, Müller T, Zhao X, Hofer TS, Thompson ME, Shi S, Brueggeller P. Performance of enhanced DuBois type water reduction catalysts (WRC) in artificial photosynthesis - effects of various proton relays during catalysis. Faraday Discuss 2019; 215:141-161. [PMID: 30942209 DOI: 10.1039/c8fd00162f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Inspired by natural photosynthesis, features such as proton relays have been integrated into water reduction catalysts (WRC) for effective production of hydrogen. Research by DuBois et al. showed the crucial influence of these relays, largely in the form of pendant amine functions. In this work catalysts are presented containing innovative diphosphinoamine ligands: [M(ii)Cl2(PNP-C1)], [M(ii)(MeCN)2(PNP-C1)]2+, [M(ii)(PNP-C1)2]2+, and [M(ii)Cl(PNP-C2)]+ (M = Pt2+, Pd2+, Ni2+, Co2+; PNP-C1 = N,N-bis{(di(2-methoxyphenyl)phosphino)methyl}-N-alkylamine, PNP-C2 = N,N-bis{(di(2-methoxyphenyl)phosphino)ethyl}-N-alkylamine and alkyl = Me, Et, iso-Pr, Bz). Synthetic strategies and detailed characterisation are covered, including 1H-, 13C-, and 31P-NMR analysis, mass spectroscopy and single crystal X-ray diffractometry (XRD). The catalytic properties have been explored by changing the pendant amines and auxiliary methoxy coordination sites, as well as enlarging the ligand backbone. Moreover, confirmed by density functional theory (DFT) calculations based on XRD data in vacuo and solvent environment, two very different catalytic cycles are proposed. PNP-C1 shows a classical proton relay, whereas PNP-C2 allows an additional coordination of nitrogen, acting optionally like a pincer. Through new insights into efficiency and stability-increasing influences of proton relays in general, their number per metal centre, an enlarged ligand backbone and the use of solvato instead of halogenido complexes, substantial improvements have been made in catalytic performance over the DuBois et al. catalysts and recently self-made WRCs. The turnover number (TON) related to the single site of cost-efficient nickel WRCs is increased from 11.4 to 637, whereas a corresponding palladium catalyst gives TON as high as 2289.
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Affiliation(s)
- Wolfgang Viertl
- University of Innsbruck, Centrum for Chemistry and Biomedicine, Institute of General, Inorganic and Theoretical Chemistry, Innrain 82, 6020 Innsbruck, Austria
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10
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Koshiba K, Yamauchi K, Sakai K. Ligand‐Based PCET Reduction in a Heteroleptic Ni(bpy)(dithiolene) Electrocatalyst Giving Rise to Higher Metal Basicity Required for Hydrogen Evolution. ChemElectroChem 2019. [DOI: 10.1002/celc.201900400] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Keita Koshiba
- Department of Chemistry Faculty of ScienceKyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER)Kyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
| | - Kosei Yamauchi
- Department of Chemistry Faculty of ScienceKyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER)Kyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
| | - Ken Sakai
- Department of Chemistry Faculty of ScienceKyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER)Kyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
- Center for Molecular Systems (CMS)Kyushu University Motooka 744, Nishi-ku Fukuoka 819-0395 Japan
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11
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Borthakur B, Vargas A, Phukan AK. A Computational Study of Carbene Ligand Stabilization of Biomimetic Models of the Rotated H
red
State of [FeFe]‐Hydrogenase. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201900237] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Bitupon Borthakur
- Department of Chemical Sciences Tezpur University Napaam 784028 Assam India
| | - Alfredo Vargas
- Department of Chemistry, School of Life Sciences University of Sussex Brighton BN1 9QJ Sussex United Kingdom
| | - Ashwini K. Phukan
- Department of Chemical Sciences Tezpur University Napaam 784028 Assam India
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12
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Vogiatzis KD, Polynski MV, Kirkland JK, Townsend J, Hashemi A, Liu C, Pidko EA. Computational Approach to Molecular Catalysis by 3d Transition Metals: Challenges and Opportunities. Chem Rev 2019; 119:2453-2523. [PMID: 30376310 PMCID: PMC6396130 DOI: 10.1021/acs.chemrev.8b00361] [Citation(s) in RCA: 214] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Indexed: 12/28/2022]
Abstract
Computational chemistry provides a versatile toolbox for studying mechanistic details of catalytic reactions and holds promise to deliver practical strategies to enable the rational in silico catalyst design. The versatile reactivity and nontrivial electronic structure effects, common for systems based on 3d transition metals, introduce additional complexity that may represent a particular challenge to the standard computational strategies. In this review, we discuss the challenges and capabilities of modern electronic structure methods for studying the reaction mechanisms promoted by 3d transition metal molecular catalysts. Particular focus will be placed on the ways of addressing the multiconfigurational problem in electronic structure calculations and the role of expert bias in the practical utilization of the available methods. The development of density functionals designed to address transition metals is also discussed. Special emphasis is placed on the methods that account for solvation effects and the multicomponent nature of practical catalytic systems. This is followed by an overview of recent computational studies addressing the mechanistic complexity of catalytic processes by molecular catalysts based on 3d metals. Cases that involve noninnocent ligands, multicomponent reaction systems, metal-ligand and metal-metal cooperativity, as well as modeling complex catalytic systems such as metal-organic frameworks are presented. Conventionally, computational studies on catalytic mechanisms are heavily dependent on the chemical intuition and expert input of the researcher. Recent developments in advanced automated methods for reaction path analysis hold promise for eliminating such human-bias from computational catalysis studies. A brief overview of these approaches is presented in the final section of the review. The paper is closed with general concluding remarks.
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Affiliation(s)
| | | | - Justin K. Kirkland
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jacob Townsend
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Ali Hashemi
- Inorganic
Systems Engineering group, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Chong Liu
- Inorganic
Systems Engineering group, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Evgeny A. Pidko
- TheoMAT
group, ITMO University, Lomonosova 9, St. Petersburg 191002, Russia
- Inorganic
Systems Engineering group, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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13
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Unwin DG, Ghosh S, Ridley F, Richmond MG, Holt KB, Hogarth G. Models of the iron-only hydrogenase enzyme: structure, electrochemistry and catalytic activity of Fe2(CO)3(μ-dithiolate)(μ,κ1,κ2-triphos). Dalton Trans 2019; 48:6174-6190. [DOI: 10.1039/c9dt00700h] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A series of Fe2(triphos)(CO)3(μ-dithiolate) complexes have been prepared and studied as models of the diiron centre in [FeFe]-hydrogenases.
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Affiliation(s)
- David G. Unwin
- Department of Chemistry
- University College London
- London
- UK
| | - Shishir Ghosh
- Department of Chemistry
- University College London
- London
- UK
- Department of Chemistry
| | - Faith Ridley
- Department of Chemistry
- University College London
- London
- UK
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14
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Duan J, Senger M, Esselborn J, Engelbrecht V, Wittkamp F, Apfel UP, Hofmann E, Stripp ST, Happe T, Winkler M. Crystallographic and spectroscopic assignment of the proton transfer pathway in [FeFe]-hydrogenases. Nat Commun 2018; 9:4726. [PMID: 30413719 PMCID: PMC6226526 DOI: 10.1038/s41467-018-07140-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 10/18/2018] [Indexed: 11/29/2022] Open
Abstract
The unmatched catalytic turnover rates of [FeFe]-hydrogenases require an exceptionally efficient proton-transfer (PT) pathway to shuttle protons as substrates or products between bulk water and catalytic center. For clostridial [FeFe]-hydrogenase CpI such a pathway has been proposed and analyzed, but mainly on a theoretical basis. Here, eleven enzyme variants of two different [FeFe]-hydrogenases (CpI and HydA1) with substitutions in the presumptive PT-pathway are examined kinetically, spectroscopically, and crystallographically to provide solid experimental proof for its role in hydrogen-turnover. Targeting key residues of the PT-pathway by site directed mutagenesis significantly alters the pH-activity profile of these variants and in presence of H2 their cofactor is trapped in an intermediate state indicative of precluded proton-transfer. Furthermore, crystal structures coherently explain the individual levels of residual activity, demonstrating e.g. how trapped H2O molecules rescue the interrupted PT-pathway. These features provide conclusive evidence that the targeted positions are indeed vital for catalytic proton-transfer. [FeFe]-hydrogenases catalyze H2-evolution and -oxidation at very high turnover-rates. Here the authors provide experimental evidence for the proposed proton-transfer (PT) pathway by kinetically, spectroscopically, and crystallographically characterizing eleven mutants from the two [FeFe]-hydrogenases CpI and HydA1.
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Affiliation(s)
- Jifu Duan
- Department of Plant Biochemistry, Photobiotechnology, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Moritz Senger
- Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Julian Esselborn
- Department of Plant Biochemistry, Photobiotechnology, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Vera Engelbrecht
- Department of Plant Biochemistry, Photobiotechnology, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Florian Wittkamp
- Department of Chemistry and Biochemistry, Inorganic Chemistry Ι, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Ulf-Peter Apfel
- Department of Chemistry and Biochemistry, Inorganic Chemistry Ι, Ruhr-Universität Bochum, 44801, Bochum, Germany.,Fraunhofer UMSICHT, Osterfelder Straße, 346047, Oberhausen, Germany
| | - Eckhard Hofmann
- Department of Biophysics, Protein Crystallography, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Sven T Stripp
- Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Thomas Happe
- Department of Plant Biochemistry, Photobiotechnology, Ruhr-Universität Bochum, 44801, Bochum, Germany.
| | - Martin Winkler
- Department of Plant Biochemistry, Photobiotechnology, Ruhr-Universität Bochum, 44801, Bochum, Germany.
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15
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Yu X, Pang M, Zhang S, Hu X, Tung CH, Wang W. Terminal Thiolate-Dominated H/D Exchanges and H2 Release: Diiron Thiol–Hydride. J Am Chem Soc 2018; 140:11454-11463. [DOI: 10.1021/jacs.8b06996] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Xin Yu
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan, 250100, P. R. China
| | - Maofu Pang
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan, 250100, P. R. China
| | - Shengnan Zhang
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan, 250100, P. R. China
| | - Xinlong Hu
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan, 250100, P. R. China
| | - Chen-Ho Tung
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan, 250100, P. R. China
| | - Wenguang Wang
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, No. 27 South Shanda Road, Jinan, 250100, P. R. China
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16
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[FeFe]-Hydrogenase and its organic molecule mimics—Artificial and bioengineering application for hydrogenproduction. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2017. [DOI: 10.1016/j.jphotochemrev.2017.09.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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17
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Pelmenschikov V, Birrell JA, Pham CC, Mishra N, Wang H, Sommer C, Reijerse E, Richers CP, Tamasaku K, Yoda Y, Rauchfuss TB, Lubitz W, Cramer SP. Reaction Coordinate Leading to H 2 Production in [FeFe]-Hydrogenase Identified by Nuclear Resonance Vibrational Spectroscopy and Density Functional Theory. J Am Chem Soc 2017; 139:16894-16902. [PMID: 29054130 PMCID: PMC5699932 DOI: 10.1021/jacs.7b09751] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
[FeFe]-hydrogenases are metalloenzymes that reversibly reduce protons to molecular hydrogen at exceptionally high rates. We have characterized the catalytically competent hydride state (Hhyd) in the [FeFe]-hydrogenases from both Chlamydomonas reinhardtii and Desulfovibrio desulfuricans using 57Fe nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT). H/D exchange identified two Fe-H bending modes originating from the binuclear iron cofactor. DFT calculations show that these spectral features result from an iron-bound terminal hydride, and the Fe-H vibrational frequencies being highly dependent on interactions between the amine base of the catalytic cofactor with both hydride and the conserved cysteine terminating the proton transfer chain to the active site. The results indicate that Hhyd is the catalytic state one step prior to H2 formation. The observed vibrational spectrum, therefore, provides mechanistic insight into the reaction coordinate for H2 bond formation by [FeFe]-hydrogenases.
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Affiliation(s)
- Vladimir Pelmenschikov
- Institut für Chemie, Technische Universität Berlin , Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - James A Birrell
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Cindy C Pham
- Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States
| | - Nakul Mishra
- Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States
| | - Hongxin Wang
- Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States
| | - Constanze Sommer
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Edward Reijerse
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Casseday P Richers
- School of Chemical Sciences, University of Illinois , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States
| | - Kenji Tamasaku
- JASRI , Spring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Yoshitaka Yoda
- JASRI , Spring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Thomas B Rauchfuss
- School of Chemical Sciences, University of Illinois , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Stephen P Cramer
- Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States
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18
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Yu X, Tung CH, Wang W, Huynh MT, Gray DL, Hammes-Schiffer S, Rauchfuss TB. Interplay between Terminal and Bridging Diiron Hydrides in Neutral and Oxidized States. Organometallics 2017; 36:2245-2253. [PMID: 28781408 DOI: 10.1021/acs.organomet.7b00297] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This study describes the structural, spectroscopic, and electrochemical properties of electronically unsymmetrical diiron hydrides. The terminal hydride Cp*Fe(pdt)Fe(dppe)(CO)H ([1(t-H)]0, Cp*- = Me5C5-, pdt2- = CH2(CH2S-)2, dppe = Ph2PC2H4PPh2) was prepared by hydride reduction of [Cp*Fe(pdt)Fe(dppe)(CO)(NCMe)]+. As established by X-ray crystallography, [1(t-H)]0 features a terminal hydride ligand. Unlike previous examples of terminal diiron hydrides, [1(t-H)]0 does not isomerize to the bridging hydride [1(μ-H)]0. Oxidation of [1(t-H)]0 gives [1(t-H)]+, which was also characterized crystallographically as its BF4- salt. Density functional theory (DFT) calculations indicate that [1(t-H)]+ is best described as containing an Cp*FeIII center. In solution, [1(t-H)]+ isomerizes to [1(μ-H)]+, as anticipated by DFT. Reduction of [1(μ-H)]+ by Cp2Co afforded the diferrous bridging hydride [1(μ-H)]0. Electrochemical measurements and DFT calculations indicate that the couples [1(t-H)]+/0 and [1(μ-H)]+/0 differ by 210 mV. Qualitative measurements indicate that [1(t-H)]0 and [1(μ-H)]0 are close in free energy. Protonation of [1(t-H)]0 in MeCN solution affords H2 even with weak acids via hydride transfer. In contrast, protonation of [1(μ-H)]0 yields 0.5 equiv of H2 by a proposed protonation-induced electron transfer process. Isotopic labeling indicates that μ-H/D ligands are inert.
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Affiliation(s)
- Xin Yu
- School of Chemistry and Chemical Engineering, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100, People's Republic of China
| | - Chen-Ho Tung
- School of Chemistry and Chemical Engineering, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100, People's Republic of China
| | - Wenguang Wang
- School of Chemistry and Chemical Engineering, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100, People's Republic of China
| | - Mioy T Huynh
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Goodwin Avenue, Urbana, Illinois 61801, United States
| | - Danielle L Gray
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Goodwin Avenue, Urbana, Illinois 61801, United States
| | - Sharon Hammes-Schiffer
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Goodwin Avenue, Urbana, Illinois 61801, United States
| | - Thomas B Rauchfuss
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Goodwin Avenue, Urbana, Illinois 61801, United States
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19
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Reijerse EJ, Pham CC, Pelmenschikov V, Gilbert-Wilson R, Adamska-Venkatesh A, Siebel JF, Gee LB, Yoda Y, Tamasaku K, Lubitz W, Rauchfuss TB, Cramer SP. Direct Observation of an Iron-Bound Terminal Hydride in [FeFe]-Hydrogenase by Nuclear Resonance Vibrational Spectroscopy. J Am Chem Soc 2017; 139:4306-4309. [PMID: 28291336 PMCID: PMC5545132 DOI: 10.1021/jacs.7b00686] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
[FeFe]-hydrogenases catalyze the reversible reduction of protons to molecular hydrogen with extremely high efficiency. The active site ("H-cluster") consists of a [4Fe-4S]H cluster linked through a bridging cysteine to a [2Fe]H subsite coordinated by CN- and CO ligands featuring a dithiol-amine moiety that serves as proton shuttle between the protein proton channel and the catalytic distal iron site (Fed). Although there is broad consensus that an iron-bound terminal hydride species must occur in the catalytic mechanism, such a species has never been directly observed experimentally. Here, we present FTIR and nuclear resonance vibrational spectroscopy (NRVS) experiments in conjunction with density functional theory (DFT) calculations on an [FeFe]-hydrogenase variant lacking the amine proton shuttle which is stabilizing a putative hydride state. The NRVS spectra unequivocally show the bending modes of the terminal Fe-H species fully consistent with widely accepted models of the catalytic cycle.
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Affiliation(s)
- Edward J. Reijerse
- Max-Planck-Institut für Chemische Energiekonversion, Stitstrasse 34-36, 45470 Mülheim, Germany
| | - Cindy C. Pham
- Department of Chemistry, University of California, Davis, California 95616, United States
| | | | - Ryan Gilbert-Wilson
- School of Chemical Sciences, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | | | - Judith F. Siebel
- Max-Planck-Institut für Chemische Energiekonversion, Stitstrasse 34-36, 45470 Mülheim, Germany
| | - Leland B. Gee
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Yoshitaka Yoda
- Materials Dynamics Laboratory, RIKEN SPring-8, Hyogo 679-5148, Japan
| | - Kenji Tamasaku
- Materials Dynamics Laboratory, RIKEN SPring-8, Hyogo 679-5148, Japan
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Stitstrasse 34-36, 45470 Mülheim, Germany
| | - Thomas B. Rauchfuss
- School of Chemical Sciences, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Stephen P. Cramer
- Department of Chemistry, University of California, Davis, California 95616, United States
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20
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Sommer C, Adamska-Venkatesh A, Pawlak K, Birrell JA, Rüdiger O, Reijerse EJ, Lubitz W. Proton Coupled Electronic Rearrangement within the H-Cluster as an Essential Step in the Catalytic Cycle of [FeFe] Hydrogenases. J Am Chem Soc 2017; 139:1440-1443. [PMID: 28075576 DOI: 10.1021/jacs.6b12636] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The active site of [FeFe] hydrogenases, the H-cluster, consists of a [4Fe-4S] cluster connected via a bridging cysteine to a [2Fe] complex carrying CO and CN- ligands as well as a bridging aza-dithiolate ligand (ADT) of which the amine moiety serves as a proton shuttle between the protein and the H-cluster. During the catalytic cycle, the two subclusters change oxidation states: [4Fe-4S]H2+ ⇔ [4Fe-4S]H+ and [Fe(I)Fe(II)]H ⇔ [Fe(I)Fe(I)]H thereby enabling the storage of the two electrons needed for the catalyzed reaction 2H+ + 2e- ⇄ H2. Using FTIR spectro-electrochemistry on the [FeFe] hydrogenase from Chlamydomonas reinhardtii (CrHydA1) at different pH values, we resolve the redox and protonation events in the catalytic cycle and determine their intrinsic thermodynamic parameters. We show that the singly reduced state Hred of the H-cluster actually consists of two species: Hred = [4Fe-4S]H+ - [Fe(I)Fe(II)]H and HredH+ = [4Fe-4S]H2+ - [Fe(I)Fe(I)]H (H+) related by proton coupled electronic rearrangement. The two redox events in the catalytic cycle occur on the [4Fe-4S]H subcluster at similar midpoint-potentials (-375 vs -418 mV); the protonation event (Hred/HredH+) has a pKa ≈ 7.2.
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Affiliation(s)
- Constanze Sommer
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany
| | | | - Krzysztof Pawlak
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany
| | - James A Birrell
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany
| | - Olaf Rüdiger
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany
| | - Edward J Reijerse
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany
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21
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Sung MMH, Morris RH. Density Functional Theory Calculations Support the Additive Nature of Ligand Contributions to the pKa of Iron Hydride Phosphine Carbonyl Complexes. Inorg Chem 2016; 55:9596-9601. [DOI: 10.1021/acs.inorgchem.6b01274] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Molly M. H. Sung
- Davenport Laboratory, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Robert H. Morris
- Davenport Laboratory, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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22
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Schilter D, Camara JM, Huynh MT, Hammes-Schiffer S, Rauchfuss TB. Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides. Chem Rev 2016; 116:8693-749. [PMID: 27353631 PMCID: PMC5026416 DOI: 10.1021/acs.chemrev.6b00180] [Citation(s) in RCA: 397] [Impact Index Per Article: 49.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrogenase enzymes efficiently process H2 and protons at organometallic FeFe, NiFe, or Fe active sites. Synthetic modeling of the many H2ase states has provided insight into H2ase structure and mechanism, as well as afforded catalysts for the H2 energy vector. Particularly important are hydride-bearing states, with synthetic hydride analogues now known for each hydrogenase class. These hydrides are typically prepared by protonation of low-valent cores. Examples of FeFe and NiFe hydrides derived from H2 have also been prepared. Such chemistry is more developed than mimicry of the redox-inactive monoFe enzyme, although functional models of the latter are now emerging. Advances in physical and theoretical characterization of H2ase enzymes and synthetic models have proven key to the study of hydrides in particular, and will guide modeling efforts toward more robust and active species optimized for practical applications.
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Affiliation(s)
- David Schilter
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - James M. Camara
- Department of Chemistry, Yeshiva University, 500 West 185th Street, New York, New York 10033, United States
| | - Mioy T. Huynh
- Department of Chemistry, University of Illinois at Urbana–Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, University of Illinois at Urbana–Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Thomas B. Rauchfuss
- Department of Chemistry, University of Illinois at Urbana–Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
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23
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Abstract
Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.
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Affiliation(s)
- Robert H Morris
- Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
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24
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Ye K, Li YY, Liao RZ. DFT study of the mechanism of hydrogen evolution catalysed by molecular Ni, Co and Fe catalysts containing a diamine–tripyridine ligand. RSC Adv 2016. [DOI: 10.1039/c6ra20721a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Electrolysis of water to obtain hydrogen is a practical way to transform surplus electrical power into clean and sustainable hydrogen fuels.
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Affiliation(s)
- Ke Ye
- Key Laboratory of Material Chemistry for Energy Conversion and Storage
- Ministry of Education
- Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica
- Hubei Key Laboratory of Materials Chemistry and Service Failure
- School of Chemistry and Chemical Engineering
| | - Ying-Ying Li
- Key Laboratory of Material Chemistry for Energy Conversion and Storage
- Ministry of Education
- Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica
- Hubei Key Laboratory of Materials Chemistry and Service Failure
- School of Chemistry and Chemical Engineering
| | - Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage
- Ministry of Education
- Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica
- Hubei Key Laboratory of Materials Chemistry and Service Failure
- School of Chemistry and Chemical Engineering
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25
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Geri JB, Szymczak NK. A Proton-Switchable Bifunctional Ruthenium Complex That Catalyzes Nitrile Hydroboration. J Am Chem Soc 2015; 137:12808-14. [DOI: 10.1021/jacs.5b08406] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Jacob B. Geri
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, Michigan 48109-1055, United States
| | - Nathaniel K. Szymczak
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, Michigan 48109-1055, United States
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26
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Rauchfuss TB. Diiron azadithiolates as models for the [FeFe]-hydrogenase active site and paradigm for the role of the second coordination sphere. Acc Chem Res 2015; 48:2107-16. [PMID: 26079848 DOI: 10.1021/acs.accounts.5b00177] [Citation(s) in RCA: 212] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The [FeFe] hydrogenases (H2ases) catalyze the redox reaction that interconverts protons and H2. This area of biocatalysis has attracted attention because the metal-based chemistry is unusual, and the reactions have practical implications. The active site consists of a [4Fe-4S] cluster bridged to a [Fe2(μ-dithiolate)(CN)2(CO)3](z) center (z = 1- and 2-). The dithiolate cofactor is [HN(CH2S)2](2-), called the azadithiolate ([adt(H)](2-)). Although many derivatives of Fe2(SR)2(CO)6-xLx are electrocatalysts for the hydrogen evolution reaction (HER), most operate by slow nonbiomimetic pathways. Biomimetic hydrogenogenesis is thought to involve intermediates, wherein the hydride substrate is adjacent to the amine of the adt(H), being bonded to only one Fe center. Formation of terminal hydride complexes is favored when the diiron carbonyl models contain azadithiolate. Although unstable in the free state, the adt cofactor is stable once it is affixed to the Fe2 center. It can be prepared by alkylation of Fe2(SH)2(CO)6 with formaldehyde in the presence of ammonia (to give adt(H) derivatives) or amines (to give adt(R) derivatives). Weak acids protonate Fe2(adt(R))(CO)2(PR3)4 to give terminal hydrido (term-H) complexes. In contrast, protonation of the related 1,3-propanedithiolate (pdt(2-)) complexes Fe2(pdt)(CO)2(PR3)4 requires strong acids. The amine in the azadithiolate is a kinetically fast base, relaying protons to and from the iron, which is a kinetically slow base. The crystal structure of the doubly protonated model [(term-H)Fe2(Hadt(H))(CO)2(dppv)2](2+) confirms the presence of both ammonium and terminal hydrido centers, which interact through a dihydrogen bond (dppv = cis-C2H2(PPh2)2). DFT calculations indicate that this H---H interaction is sensitive to the counterions and is strengthened upon reduction of the diiron center. For the monoprotonated models, the hydride [(term-H)Fe2(adt(H))(CO)2(dppv)2](+) exists in equilibrium with the ammonium tautomer [Fe2(Hadt(H))(CO)2(dppv)2](+). Both [(term-H)Fe2(Hadt(H))(CO)2(dppv)2](2+) and [(term-H)Fe2(adt(H))(CO)2(dppv)2](+) are highly active electrocatalysts for HER. Catalysis is initiated by reduction of the diferrous center, which induces coupling of the protic ammonium center and the hydride ligand. In contrast, the propanedithiolate [(term-H)Fe2(pdt)(CO)2(dppv)2](+) is a poor electrocatalyst for HER. Oxidation of H2 has been demonstrated, starting with models for the oxidized state ("Hox"), for example, [Fe2(adt(H))(CO)3(dppv)(PMe3)](+). Featuring a distorted Fe(II)Fe(I) center, this Hox model reacts slowly with high pressures of H2 to give [(μ-H)Fe2(adt(H))(CO)3(dppv)(PMe3)](+). Highlighting the role of the proton relay, the propanedithiolate [Fe2(pdt)(CO)3(dppv)(PMe3)](+) is unreactive toward H2. The Hox-model + H2 reaction is accelerated in the presence of ferrocenium salts, which simulate the role of the attached [4Fe-4S] cluster. The redox-complemented complex [Fe2(adt(Bn))(CO)3(dppv)(FcP*)](n+) catalyzes both proton reduction and hydrogen oxidation (FcP* = (C5Me5)Fe(C5Me4CH2PEt2)).
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Affiliation(s)
- Thomas B. Rauchfuss
- School of Chemical Sciences, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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27
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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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