1
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Reid AG, Zelenke EA, Moberg ME, Dickie DA, Machan CW. Improving co-electrocatalytic carbon dioxide reduction by optimizing the relative potentials of the redox mediator and catalyst. Chem Commun (Camb) 2024; 60:8208-8211. [PMID: 39015067 DOI: 10.1039/d4cc01988a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
The effects of fixing the redox mediator (RM) reduction potential relative to a series of Cr-centered complexes capable of the reduction of CO2 to CO are disclosed. The greatest co-electrocatalytic activity enhancement is observed when the reduction potentials of the catalyst and RM are identical, implying that controlling the speciation of the Cr complex relative to RM activation is essential for improving catalytic performance. In all cases, the potential where co-catalytic activity is observed matches the reduction potential of the RM, regardless of the relative reduction potential of the Cr complex.
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Affiliation(s)
- Amelia G Reid
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
| | - Ethan A Zelenke
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
| | - Megan E Moberg
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
| | - Diane A Dickie
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
| | - Charles W Machan
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
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2
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Obisesan SV, Parvin M, Tao M, Ramos E, Saunders AC, Farnum BH, Goldsmith CR. Installing Quinol Proton/Electron Mediators onto Non-Heme Iron Complexes Enables Them to Electrocatalytically Reduce O 2 to H 2O at High Rates and Low Overpotentials. Inorg Chem 2024; 63:14126-14141. [PMID: 39008564 DOI: 10.1021/acs.inorgchem.4c01977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/17/2024]
Abstract
We prepare iron(II) and iron(III) complexes with polydentate ligands that contain quinols, which can act as electron proton transfer mediators. Although the iron(II) complex with N-(2,5-dihydroxybenzyl)-N,N',N'-tris(2-pyridinylmethyl)-1,2-ethanediamine (H2qp1) is inactive as an electrocatalyst, iron complexes with N,N'-bis(2,5-dihydroxybenzyl)-N,N'-bis(2-pyridinylmethyl)-1,2-ethanediamine (H4qp2) and N-(2,5-dihydroxybenzyl)-N,N'-bis(2-pyridinylmethyl)-1,2-ethanediamine (H2qp3) were found to be much more active and more selective for water production than a previously reported cobalt-H2qp1 electrocatalyst while operating at low overpotentials. The catalysts with H2qp3 can enter the catalytic cycle as either Fe(II) or Fe(III) species; entering the cycle through Fe(III) lowers the effective overpotential. On the basis of their TOF0 values, the successful iron-quinol complexes are better electrocatalysts for oxygen reduction than previously reported iron-porphyrin compounds, with the Fe(III)-H2qp3 arguably being the best homogeneous electrocatalyst for this reaction. With iron, the quinol-for-phenol substitution shifts the product selectivity from H2O2 to water with little impact on the overpotential, but unlike cobalt, this substitution also greatly improves the activity, as assessed by TOFmax, by hastening the protonation and oxygen binding steps. The addition of a second quinol further enhances the activity and selectivity for water but modestly increases the effective overpotential.
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Affiliation(s)
- Segun V Obisesan
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Maksuda Parvin
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Matthew Tao
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Eric Ramos
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Alexander C Saunders
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Byron H Farnum
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Christian R Goldsmith
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
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3
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Cook EN, Courter IM, Dickie DA, Machan CW. Controlling product selectivity during dioxygen reduction with Mn complexes using pendent proton donor relays and added base. Chem Sci 2024; 15:4478-4488. [PMID: 38516070 PMCID: PMC10952101 DOI: 10.1039/d3sc02611f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 02/12/2024] [Indexed: 03/23/2024] Open
Abstract
The catalytic reduction of dioxygen (O2) is important in biological energy conversion and alternative energy applications. In comparison to Fe- and Co-based systems, examples of catalytic O2 reduction by homogeneous Mn-based systems is relatively sparse. Motivated by this lack of knowledge, two Mn-based catalysts for the oxygen reduction reaction (ORR) containing a bipyridine-based non-porphyrinic ligand framework have been developed to evaluate how pendent proton donor relays alter activity and selectivity for the ORR, where Mn(p-tbudhbpy)Cl (1) was used as a control complex and Mn(nPrdhbpy)Cl (2) contains a pendent -OMe group in the secondary coordination sphere. Using an ammonium-based proton source, N,N'-diisopropylethylammonium hexafluorophosphate, we analyzed catalytic activity for the ORR: 1 was found to be 64% selective for H2O2 and 2 is quantitative for H2O2, with O2 binding to the reduced Mn(ii) center being the rate-determining step. Upon addition of the conjugate base, N,N'-diisopropylethylamine, the observed catalytic selectivity of both 1 and 2 shifted to H2O as the primary product. Interestingly, while the shift in selectivity suggests a change in mechanism for both 1 and 2, the catalytic activity of 2 is substantially enhanced in the presence of base and the rate-determining step becomes the bimetallic cleavage of the O-O bond in a Mn-hydroperoxo species. These data suggest that the introduction of pendent relay moieties can improve selectivity for H2O2 at the expense of diminished reaction rates from strong hydrogen bonding interactions. Further, although catalytic rate enhancements are observed with a change in product selectivity when base is added to buffer proton activity, the pendent relays stabilize dimer intermediates, limiting the maximum rate.
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Affiliation(s)
- Emma N Cook
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| | - Ian M Courter
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| | - Diane A Dickie
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| | - Charles W Machan
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
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4
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Bates JS, Johnson MR, Khamespanah F, Root TW, Stahl SS. Heterogeneous M-N-C Catalysts for Aerobic Oxidation Reactions: Lessons from Oxygen Reduction Electrocatalysts. Chem Rev 2023; 123:6233-6256. [PMID: 36198176 PMCID: PMC10073352 DOI: 10.1021/acs.chemrev.2c00424] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Nonprecious metal heterogeneous catalysts composed of first-row transition metals incorporated into nitrogen-doped carbon matrices (M-N-Cs) have been studied for decades as leading alternatives to Pt for the electrocatalytic O2 reduction reaction (ORR). More recently, similar M-N-C catalysts have been shown to catalyze the aerobic oxidation of organic molecules. This Focus Review highlights mechanistic similarities and distinctions between these two reaction classes and then surveys the aerobic oxidation reactions catalyzed by M-N-Cs. As the active-site structures and kinetic properties of M-N-C aerobic oxidation catalysts have not been extensively studied, the array of tools and methods used to characterize ORR catalysts are presented with the goal of supporting further advances in the field of aerobic oxidation.
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Affiliation(s)
- Jason S. Bates
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Mathew R. Johnson
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Fatemeh Khamespanah
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Thatcher W. Root
- Department of Chemical and Biological Engineering, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Shannon S. Stahl
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
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5
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Koellner CA, Reid AG, Machan CW. Co-electrocatalytic CO 2 reduction mediated by a dibenzophosphole oxide and a chromium complex. Chem Commun (Camb) 2023; 59:6359-6362. [PMID: 37139853 DOI: 10.1039/d3cc00166k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We report a co-electrocatalytic system for the selective reduction of CO2 to CO, comprised of a previously reported molecular Cr complex and 5-phenylbenzo[b]phosphindole-5-oxide (PhBPO) as a redox mediator. Under protic conditions, the co-electrocatalytic system attains a turnover frequency (TOF) of 15 s-1 and quantitative selectivity for CO. It is proposed that PhBPO interacts with the Cr-based catalyst, coordinating in an axial position trans to an intermediate hydroxycarbonyl species, M-CO2H, mediating electron transfer to the catalyst and lowering the barrier for C-OH bond cleavage.
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Affiliation(s)
- Connor A Koellner
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
| | - Amelia G Reid
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
| | - Charles W Machan
- Department of Chemistry, University of Virginia, McCormick Rd, PO Box 400319, Charlottesville, Virginia 22904-4319, USA.
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6
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Reid AG, Moberg ME, Koellner CA, Moreno JJ, Hooe SL, Baugh KR, Dickie DA, Machan CW. Comparisons of bpy and phen Ligand Backbones in Cr-Mediated (Co-)Electrocatalytic CO 2 Reduction. Organometallics 2023. [DOI: 10.1021/acs.organomet.2c00600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2023]
Affiliation(s)
- Amelia G. Reid
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Megan E. Moberg
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Connor A. Koellner
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Juan J. Moreno
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Shelby L. Hooe
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Kira R. Baugh
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Diane A. Dickie
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Charles W. Machan
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
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7
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Bhunia S, Ghatak A, Rana A, Dey A. Amine Groups in the Second Sphere of Iron Porphyrins Allow for Higher and Selective 4e -/4H + Oxygen Reduction Rates at Lower Overpotentials. J Am Chem Soc 2023; 145:3812-3825. [PMID: 36744304 DOI: 10.1021/jacs.2c13552] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Iron porphyrins with one or four tertiary amine groups in their second sphere are used to investigate the electrochemical O2 reduction reaction (ORR) in organic (homogeneous) and aqueous (heterogeneous) conditions. Both of these complexes show selective 4e-/4H+ reduction of oxygen to water at rates that are 2-3 orders of magnitude higher than those of iron tetraphenylporphyrin lacking these amines in the second sphere. In organic solvents, these amines get protonated, which leads to the lowering of overpotentials, and the rate of the ORR is enhanced almost 75,000 times relative to rates expected from the established scaling relationship for the ORR by iron porphyrins. In the aqueous medium, the same trend of higher ORR rates at a lower overpotential is observed. In situ resonance Raman data under heterogeneous aqueous conditions show that the presence of one amine group in the second sphere leads to a cleavage of the O-O bond in a FeIII-OOH intermediate as the rate-determining step (rds). The presence of four such amine groups enhances the rate of O-O bond cleavage such that this intermediate is no longer observed during the ORR; rather, the proton-coupled reduction of the FeIII-O2- intermediate with a H/D isotope effect of 10.6 is the rds. These data clearly demonstrate changes in the rds of the electrochemical ORR depending on the nature of second-sphere residues and explain their deviation from linear scaling relationships.
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Affiliation(s)
- Sarmistha Bhunia
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
| | - Arnab Ghatak
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
| | - Atanu Rana
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
| | - Abhishek Dey
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
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8
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Abstract
Homogeneous electrocatalysis has been well studied over the past several decades for the conversion of small molecules to useful products for green energy applications or as chemical feedstocks. However, in order for these catalyst systems to be used in industrial applications, their activity and stability must be improved. In naturally occurring enzymes, redox equivalents (electrons, often in a concerted manner with protons) are delivered to enzyme active sites by small molecules known as redox mediators (RMs). Inspired by this, co-electrocatalytic systems with homogeneous catalysts and RMs have been developed for the conversion of alcohols, nitrogen, unsaturated organic substrates, oxygen, and carbon dioxide. In these systems, the RMs have been shown to both increase the activity of the catalyst and shift selectivity to more desired products by altering catalytic cycles and/or avoiding high-energy intermediates. However, the area is currently underdeveloped and requires additional fundamental advancements in order to become a more general strategy. Here, we summarize the recent examples of homogeneous co-electrocatalysis and discuss possible future directions for the field.
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Affiliation(s)
- Amelia G Reid
- 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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9
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Sonet D, Cayla M, Méreau R, Morvan E, Lacoudre A, Vanthuyne N, Albalat M, Bassani DM, Scalabre A, Pouget E, Bibal B. Chiral Anthranyl Trifluoromethyl Alcohols: Structures, Oxidative Dearomatization and Chiroptical Properties. Chemistry 2022; 28:e202202695. [PMID: 36316221 DOI: 10.1002/chem.202202695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Indexed: 11/05/2022]
Abstract
Chiral trifluoromethyl alcohol groups were introduced at the hindered ortho positions of 9,10-diphenylanthracenes to investigate their effects on the physical properties and reactivity towards oxidative dearomatization. In such compact structures, the position in different quadrants and the preferred orientation of the -CH(OH)CF3 groups were determined by the relative and absolute configurations of each stereoisomer, respectively. As a consequence, the stereochemistry governs the organization of the H-bonded molecules in single crystals (homochiral dimers vs ribbon), whereas in chlorinated solvents, they all behave as discrete compounds. Concerning their reactivity, the stereospecific dearomative oxidation of these molecules leads to 9,10-bis-spiro-isobenzofuran-anthracenes, when using organic single-electron transfer oxidants. The chiroptical properties of the alcohols and the corresponding dearomatized products were compared and showed an important modulation of the intensity.
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Affiliation(s)
- Dorian Sonet
- Institut des Sciences Moléculaires UMR CNRS 5255, Univ. Bordeaux, CNRS, Bordeaux INP, 351 cours de la Libération, 33400, Talence, France
| | - Mattéo Cayla
- Institut des Sciences Moléculaires UMR CNRS 5255, Univ. Bordeaux, CNRS, Bordeaux INP, 351 cours de la Libération, 33400, Talence, France
| | - Raphaël Méreau
- Institut des Sciences Moléculaires UMR CNRS 5255, Univ. Bordeaux, CNRS, Bordeaux INP, 351 cours de la Libération, 33400, Talence, France
| | - Estelle Morvan
- Institut Européen de Chimie et Biologie UAR3033 CNRS, University of Bordeaux, INSERM US001, 2 rue Roger Escarpit, 33607, Pessac, France
| | - Aline Lacoudre
- Institut des Sciences Moléculaires UMR CNRS 5255, Univ. Bordeaux, CNRS, Bordeaux INP, 351 cours de la Libération, 33400, Talence, France
| | - Nicolas Vanthuyne
- Centrale Marseille, iSm2, Aix-Marseille Université, CNRS, 52 avenue Escadrille Normandie Niemen, 13013, Marseille, France
| | - Muriel Albalat
- Centrale Marseille, iSm2, Aix-Marseille Université, CNRS, 52 avenue Escadrille Normandie Niemen, 13013, Marseille, France
| | - Dario M Bassani
- Institut des Sciences Moléculaires UMR CNRS 5255, Univ. Bordeaux, CNRS, Bordeaux INP, 351 cours de la Libération, 33400, Talence, France
| | - Antoine Scalabre
- Chimie et Biologie des Membranes et des Nanoobjets, UMR CNRS 5248, Université de Bordeaux, 2 rue Roger Escarpit, 33607, Pessac, France
| | - Emilie Pouget
- Chimie et Biologie des Membranes et des Nanoobjets, UMR CNRS 5248, Université de Bordeaux, 2 rue Roger Escarpit, 33607, Pessac, France
| | - Brigitte Bibal
- Institut des Sciences Moléculaires UMR CNRS 5255, Univ. Bordeaux, CNRS, Bordeaux INP, 351 cours de la Libération, 33400, Talence, France
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10
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Obisesan SV, Rose C, Farnum BH, Goldsmith CR. Co(II) Complex with a Covalently Attached Pendent Quinol Selectively Reduces O 2 to H 2O. J Am Chem Soc 2022; 144:22826-22830. [DOI: 10.1021/jacs.2c08315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | | | | | - Christian R. Goldsmith
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama36849, United States
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11
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Cook EN, Hooe SL, Dickie DA, Machan CW. Homogeneous Catalytic Reduction of O 2 to H 2O by a Terpyridine-Based FeN 3O Complex. Inorg Chem 2022; 61:8387-8392. [PMID: 35594192 DOI: 10.1021/acs.inorgchem.2c00524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report a new terpyridine-based FeN3O catalyst, Fe(tpytbupho)Cl2, which reduces O2 to H2O. Variable concentration and variable temperature spectrochemical studies with decamethylferrocene as a chemical reductant in acetonitrile solution enabled the elucidation of key reaction parameters for the catalytic reduction of O2 to H2O by Fe(tpytbupho)Cl2. These mechanistic studies suggest that a 2 + 2 mechanism is operative, where hydrogen peroxide is produced as a discrete intermediate, prior to further reduction to H2O. Consistent with this proposal, the spectrochemically measured first-order rate constant k (s-1) value for H2O2 reduction is larger than that for O2 reduction. Further, significant H2O2 production is observed under hydrodynamic conditions in rotating ring-disk electrode measurements, where the product can be swept away from the cathode surface before further reduction occurs.
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Affiliation(s)
- Emma N Cook
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Shelby L Hooe
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Diane A Dickie
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Charles W Machan
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
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12
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Bates JS, Biswas S, Suh SE, Johnson MR, Mondal B, Root TW, Stahl SS. Chemical and Electrochemical O 2 Reduction on Earth-Abundant M-N-C Catalysts and Implications for Mediated Electrolysis. J Am Chem Soc 2022; 144:922-927. [PMID: 34985869 PMCID: PMC8833842 DOI: 10.1021/jacs.1c11126] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
M-N-C catalysts, incorporating non-precious-metal ions (e.g. M = Fe, Co) within a nitrogen-doped carbon support, have been the focus of broad interest for electrochemical O2 reduction and aerobic oxidation reactions. The present study explores the mechanistic relationship between the O2 reduction mechanism under electrochemical and chemical conditions. Chemical O2 reduction is investigated via the aerobic oxidation of a hydroquinone, in which the O-H bonds supply the protons and electrons needed for O2 reduction to water. Mechanistic studies have been conducted to elucidate whether the M-N-C catalyst couples two independent half-reactions (IHR), similar to electrode-mediated processes, or mediates a direct inner-sphere reaction (ISR) between O2 and the organic molecule. Kinetic data support the latter ISR pathway. This conclusion is reinforced by rate/potential correlations that reveal significantly different Tafel slopes, implicating different mechanisms for chemical and electrochemical O2 reduction.
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Affiliation(s)
- Jason S. Bates
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Sourav Biswas
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Sung-Eun Suh
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Mathew R. Johnson
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Biswajit Mondal
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Thatcher W. Root
- Department of Chemical and Biological Engineering, University of Wisconsin–Madison, 1415 Engineering Drive, Madison, WI 53706, USA,Corresponding Authors: ;
| | - Shannon S. Stahl
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, WI 53706, USA,Corresponding Authors: ;
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13
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Hooe SL, Moreno JJ, Reid AG, Cook EN, Machan CW. Mediated Inner-Sphere Electron Transfer Induces Homogeneous Reduction of CO 2 via Through-Space Electronic Conjugation. Angew Chem Int Ed Engl 2022; 61:e202109645. [PMID: 34695281 DOI: 10.1002/anie.202109645] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/24/2021] [Indexed: 11/11/2022]
Abstract
The electrocatalytic reduction of CO2 is an appealing method for converting renewable energy sources into value-added chemical feedstocks. We report a co-electrocatalytic system for the reduction of CO2 to CO comprised of a molecular Cr complex and dibenzothiophene-5,5-dioxide (DBTD) as a redox mediator, which achieves high activity (TOF=1.51-2.84×105 s-1 ) and quantitative selectivity. Under aprotic or protic conditions, DBTD produces a co-electrocatalytic response with 1 by coordinating trans to the site of CO2 binding and mediating electron transfer from the electrode with quantitative efficiency for CO. This assembly is reliant on through-space electronic conjugation between the π frameworks of DBTD and the bpy fragment of the catalyst ligand, with contributions from dispersive interactions and weak sulfone coordination.
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Affiliation(s)
- Shelby L Hooe
- Department of Chemistry, University of Virginia, McCormick Road, PO Box 400319, Charlottesville, VA, 22904-4319, USA
| | - Juan J Moreno
- Department of Chemistry, University of Virginia, McCormick Road, PO Box 400319, Charlottesville, VA, 22904-4319, USA
| | - Amelia G Reid
- Department of Chemistry, University of Virginia, McCormick Road, PO Box 400319, Charlottesville, VA, 22904-4319, USA
| | - Emma N Cook
- Department of Chemistry, University of Virginia, McCormick Road, PO Box 400319, Charlottesville, VA, 22904-4319, USA
| | - Charles W Machan
- Department of Chemistry, University of Virginia, McCormick Road, PO Box 400319, Charlottesville, VA, 22904-4319, USA
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14
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Hooe SL, Moreno JJ, Reid AG, Cook EN, Machan CW. Mediated Inner‐Sphere Electron Transfer Induces Homogeneous Reduction of CO
2
via Through‐Space Electronic Conjugation**. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202109645] [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]
Affiliation(s)
- Shelby L. Hooe
- Department of Chemistry University of Virginia McCormick Road, PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Juan J. Moreno
- Department of Chemistry University of Virginia McCormick Road, PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Amelia G. Reid
- Department of Chemistry University of Virginia McCormick Road, PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Emma N. Cook
- Department of Chemistry University of Virginia McCormick Road, PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Charles W. Machan
- Department of Chemistry University of Virginia McCormick Road, PO Box 400319 Charlottesville VA 22904-4319 USA
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15
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Reid AG, Moreno JJ, Hooe SL, Baugh KR, Thomas IH, Dickie DA, Machan CW. Inverse Potential Scaling in Co-Electrocatalytic Activity for CO 2 Reduction Through Redox Mediator Tuning and Catalyst Design. Chem Sci 2022; 13:9595-9606. [PMID: 36091894 PMCID: PMC9400620 DOI: 10.1039/d2sc03258a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 07/21/2022] [Indexed: 11/21/2022] Open
Abstract
Electrocatalytic CO2 reduction is an attractive strategy to mitigate the continuous rise in atmospheric CO2 concentrations and generate value-added chemical products. A possible strategy to increase the activity of molecular...
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Affiliation(s)
- Amelia G Reid
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Juan J Moreno
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Shelby L Hooe
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Kira R Baugh
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Isobel H Thomas
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Diane A Dickie
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Charles W Machan
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
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Cook EN, Machan CW. Bioinspired mononuclear Mn complexes for O 2 activation and biologically relevant reactions. Dalton Trans 2021; 50:16871-16886. [PMID: 34730590 DOI: 10.1039/d1dt03178c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A general interest in harnessing the oxidizing power of dioxygen (O2) continues to motivate research efforts on bioinspired and biomimetic complexes to better understand how metalloenzymes mediate these reactions. The ubiquity of Fe- and Cu-based enzymes attracts significant attention and has resulted in many noteworthy developments for abiotic systems interested in direct O2 reduction and small molecule activation. However, despite the existence of Mn-based metalloenzymes with important O2-dependent activity, there has been comparatively less focus on the development of these analogues relative to Fe- and Cu-systems. In this Perspective, we summarize important contributions to the development of bioinspired mononuclear Mn complexes for O2 activation and studies on their reactivity, emphasizing important design parameters in the primary and secondary coordination spheres and outlining mechanistic trends.
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Affiliation(s)
- Emma N Cook
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, VA 22904-4319, USA.
| | - Charles W Machan
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, VA 22904-4319, USA.
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Cook EN, Dickie DA, Machan CW. Catalytic Reduction of Dioxygen to Water by a Bioinspired Non-Heme Iron Complex via a 2+2 Mechanism. J Am Chem Soc 2021; 143:16411-16418. [PMID: 34606274 DOI: 10.1021/jacs.1c04572] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a bioinspired non-heme Fe complex with a tripodal [N3O]- ligand framework (Fe(PMG)(Cl)2) that is electrocatalytically active toward dioxygen reduction with acetic acid as a proton source in acetonitrile solution. Under electrochemical and chemical conditions, Fe(PMG)(Cl)2 selectively produces water via a 2+2 mechanism, where H2O2 is generated as a discrete intermediate species before further reduction to two equivalents of H2O. Mechanistic studies support a catalytic cycle for dioxygen reduction where an off-cycle peroxo dimer species is the resting state of the catalyst. Spectroscopic analysis of the reduced complex FeII(PMG)Cl shows the stoichiometric formation of an Fe(III)-hydroxide species following exposure to H2O2; no catalytic activity for H2O2 disproportionation is observed, although the complex is electrochemically active for H2O2 reduction to H2O. Electrochemical studies, spectrochemical experiments, and DFT calculations suggest that the carboxylate moiety of the ligand is sensitive to hydrogen-bonding interactions with the acetic acid proton donor upon reduction from Fe(III)/(II), favoring chloride loss trans to the tris-alkyl amine moiety of the ligand framework. These results offer insight into how mononuclear non-heme Fe active sites in metalloproteins distribute added charge and poise proton donors during reactions with dioxygen.
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Affiliation(s)
- Emma N Cook
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Diane A Dickie
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Charles W Machan
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
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