1
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Mangue J, Wehrung I, Pécaut J, Ménage S, Orio M, Torelli S. Bio-inspired copper complexes with Cu 2S cores: (solvent) effects on oxygen reduction reactions. Dalton Trans 2024; 53:15576-15582. [PMID: 39229908 DOI: 10.1039/d4dt01629g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
The need for effective alternative energy sources and "green" industrial processes is a more crucial societal topic than ever. In this context, mastering oxygen reduction reactions (ORRs) is a key step to develop fuel cells or to propose alternatives to energy-intensive setups such as the anthraquinone process for hydrogen peroxide production. Achieving this goal using bio-inspired metal complexes based on abundant and non-toxic elements could provide an environmentally friendly option. Given the prevalence of Cu-containing active sites capable of reductive activation of dioxygen in nature, the development of Cu-based catalysts for the ORR thus appears to be a relevant approach. We herein report the preparation, full characterization and (TD)DFT investigation of a new dinuclear mixed-valent copper complex 6 exhibiting a Cu2S core and a bridging triflate anion. Its ORR activity was compared with that of its parent catalyst 1. Two types of solvents were used, acetonitrile and acetone, and various catalyst/Me8Fc (electron source) ratios were tested. Our results highlight a counterintuitive solvent effect for 1 and a drastic drop in the activity for 6 in coordinating acetonitrile together with the modification of its chemical structure.
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Affiliation(s)
- Jordan Mangue
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
| | - Iris Wehrung
- Aix Marseille Univ. Centrale Med., ISM2, Marseille, France.
| | - Jacques Pécaut
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, SYMMES, UMR 5819, F-38000 Grenoble, France
| | - Stéphane Ménage
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
| | - Maylis Orio
- Aix Marseille Univ. Centrale Med., ISM2, Marseille, France.
| | - Stéphane Torelli
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
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2
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Cook EN, Flaxman LA, Reid AG, Dickie DA, Machan CW. Acid Strength Effects on Dimerization during Metal-Free Catalytic Dioxygen Reduction. J Am Chem Soc 2024; 146:24892-24900. [PMID: 39205655 PMCID: PMC11403605 DOI: 10.1021/jacs.4c05708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
Development of earth-abundant catalysts for the reduction of dioxygen (ORR) is essential for the development of alternative industrial processes and energy sources. Here, we report a transition metal-free dicationic organocatalyst (Ph2Phen2+) for the ORR. The ORR performance of this compound was studied in acetonitrile solution under both electrochemical conditions and spectrochemical conditions, using halogenated acetic acid derivatives spanning a pKa range of 12.65 to 20.3. Interestingly, it was found that under electrochemical conditions, a kinetically relevant peroxo dimer species forms with all acids. However, under spectrochemical conditions, strong acids diminish the kinetic contribution of this dimer to the observed rate due to lower catalyst concentrations, whereas weaker acids were still rate-limited by the dimer equilibrium. Together, these results provide insight into the mechanisms of ORR by organic-based, metal-free catalysts, suggesting that balancing redox activity and unsaturated character of these molecules with respect to the pKa of intermediates can enable reaction tuning analogous to transition metal-based systems.
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Affiliation(s)
- Emma N Cook
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Luke A Flaxman
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Amelia G Reid
- 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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3
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Maguire S, Strachan G, Norvaiša K, Donohoe C, Gomes-da-Silva LC, Senge MO. Porphyrin Atropisomerism as a Molecular Engineering Tool in Medicinal Chemistry, Molecular Recognition, Supramolecular Assembly, and Catalysis. Chemistry 2024; 30:e202401559. [PMID: 38787350 DOI: 10.1002/chem.202401559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 05/18/2024] [Accepted: 05/24/2024] [Indexed: 05/25/2024]
Abstract
Porphyrin atropisomerism, which arises from restricted σ-bond rotation between the macrocycle and a sufficiently bulky substituent, was identified in 1969 by Gottwald and Ullman in 5,10,15,20-tetrakis(o-hydroxyphenyl)porphyrins. Henceforth, an entirely new field has emerged utilizing this transformative tool. This review strives to explain the consequences of atropisomerism in porphyrins, the methods which have been developed for their separation and analysis and present the diverse array of applications. Porphyrins alone possess intriguing properties and a structure which can be easily decorated and molded for a specific function. Therefore, atropisomerism serves as a transformative tool, making it possible to obtain even a specific molecular shape. Atropisomerism has been thoroughly exploited in catalysis and molecular recognition yet presents both challenges and opportunities in medicinal chemistry.
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Affiliation(s)
- Sophie Maguire
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, D02R590, Ireland
| | - Grant Strachan
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, D02R590, Ireland
| | - Karolis Norvaiša
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, D02R590, Ireland
| | - Claire Donohoe
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, D02R590, Ireland
- CQC, Coimbra Chemistry Centre, University of Coimbra, Coimbra, 3004-535, Portugal
| | | | - Mathias O Senge
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin, D02R590, Ireland
- Institute for Advanced Study (TUM-IAS), Focus Group-Molecular and Interfacial Engineering of Organic Nanosystems, Technical University of Munich, Lichtenberg Str. 2a, 85748, Garching, Germany
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4
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Qi Z, Lu Z, Guo X, Jiang J, Liu S, Sun J, Wang X, Zhu J, Fu Y. Constructing Directional Electrostatic Potential Difference via Gradient Nitrogen Doping for Efficient Oxygen Reduction Reaction. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2401221. [PMID: 38593294 DOI: 10.1002/smll.202401221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 03/14/2024] [Indexed: 04/11/2024]
Abstract
Nitrogen doping has been recognized as an important strategy to enhance the oxygen reduction reaction (ORR) activity of carbon-encapsulated transition metal catalysts (TM@C). However, previous reports on nitrogen doping have tended to result in a random distribution of nitrogen atoms, which leads to disordered electrostatic potential differences on the surface of carbon layers, limiting further control over the materials' electronic structure. Herein, a gradient nitrogen doping strategy to prepare nitrogen-deficient graphene and nitrogen-rich carbon nanotubes encapsulated cobalt nanoparticles catalysts (Co@CNTs@NG) is proposed. The unique gradient nitrogen doping leads to a gradual increase in the electrostatic potential of the carbon layer from the nitrogen-rich region to the nitrogen-deficient region, facilitating the directed electron transfer within these layers and ultimately optimizing the charge distribution of the material. Therefore, this strategy effectively regulates the density of state and work function of the material, further optimizing the adsorption of oxygen-containing intermediates and enhancing ORR activity. Theoretical and experimental results show that under controlled gradient nitrogen doping, Co@CNTs@NG exhibits significantly ORR performance (Eonset = 0.96 V, E1/2 = 0.86 V). At the same time, Co@CNTs@NG also displays excellent performance as a cathode material for Zn-air batteries, with peak power density of 132.65 mA cm-2 and open-circuit voltage (OCV) of 1.51 V. This work provides an effective gradient nitrogen doping strategy to optimize the ORR performance.
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Affiliation(s)
- Zhijie Qi
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Zhenjie Lu
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Xiangjie Guo
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Jun Jiang
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Shujun Liu
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Jingwen Sun
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Xin Wang
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Junwu Zhu
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Yongsheng Fu
- Key Laboratory for Soft Chemistry and Functional Materials, School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
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5
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Liu S, Kumar K, Bell T, Ramamoorthy A, Van Winkle D, Lenhert S. Lipid-Based Catalysis Demonstrated by Bilayer-Enabled Ester Hydrolysis. MEMBRANES 2024; 14:168. [PMID: 39195420 DOI: 10.3390/membranes14080168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 07/22/2024] [Accepted: 07/22/2024] [Indexed: 08/29/2024]
Abstract
Lipids have not traditionally been considered likely candidates for catalyzing reactions in biological systems. However, there is significant evidence that aggregates of amphiphilic compounds are capable of catalyzing reactions in synthetic organic chemistry. Here, we demonstrate the potential for the hydrophobic region of a lipid bilayer to provide an environment suitable for catalysis by means of a lipid aggregate capable of speeding up a chemical reaction. By bringing organic molecules into the nonpolar or hydrophobic region of a lipid bilayer, reactions can be catalyzed by individual or collections of small, nonpolar, or amphiphilic molecules. We demonstrate this concept by the ester hydrolysis of calcein-AM to produce a fluorescent product, which is a widely used assay for esterase activity in cells. The reaction was first carried out in a two-phase octanol-water system, with the organic phase containing the cationic amphiphiles cetyltrimethylammonium bromide (CTAB) or octadecylamine. The octanol phase was then replaced with phospholipid vesicles in water, where the reaction was also found to be carried out. The reaction was monitored using quantitative fluorescence, which revealed catalytic turnover numbers on a scale of 10-7 to 10-8 s-1 for each system, which is much slower than enzymatic catalysis. The reaction product was characterized by 1H-NMR measurements, which were consistent with ester hydrolysis. The implications of thinking about lipids and lipid aggregates as catalytic entities are discussed in the context of biochemistry, pharmacology, and synthetic biology.
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Affiliation(s)
- Shu Liu
- Department of Biological Science and Integrative Nanoscience Institute, Florida State University, Tallahassee, FL 32306, USA
- Department of Physics, Florida State University, Tallahassee, FL 32306, USA
| | - Kiran Kumar
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
- Department of Chemical and Biomedical Engineering, FAMU-FSU, Tallahassee, FL 32310, USA
| | - Tracey Bell
- Department of Biological Science and Integrative Nanoscience Institute, Florida State University, Tallahassee, FL 32306, USA
| | - Ayyalusamy Ramamoorthy
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
- Department of Chemical and Biomedical Engineering, FAMU-FSU, Tallahassee, FL 32310, USA
| | - David Van Winkle
- Department of Physics, Florida State University, Tallahassee, FL 32306, USA
| | - Steven Lenhert
- Department of Biological Science and Integrative Nanoscience Institute, Florida State University, Tallahassee, FL 32306, USA
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6
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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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7
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Bhunia P, Gomila RM, Frontera A, Ghosh A. Shift of the reduction potential of nickel(II) Schiff base complexes in the presence of redox innocent metal ions. Dalton Trans 2024; 53:12316-12330. [PMID: 38984589 DOI: 10.1039/d4dt00953c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024]
Abstract
With the objective of gaining insight into the modulation of the reduction potential of the Ni(II/I) couple, we have synthesized two mononuclear nickel(II) complexes, NiLen (H2Len = N,N'-bis(3-methoxysalicylidene)-1,2-diamino-2-methylpropane) and NiLpn (H2Lpn = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane) of two N2O4 donor ligands and recorded their cyclic voltammograms. Both the nickel complexes show reversible reduction processes for the Ni(II/I) couple in acetonitrile solution but the reduction potential of NiLpn (E1/2 = -1.883 V) is 188 mV more positive than that of NiLen (E1/2 = -2.071 V). In the presence of redox inactive metal ions (Li+, Na+, K+, Mg2+, Ca2+ and Ba2+), the reduction potentials are shifted by 49-331 mV and 99-435 mV towards positive values compared to NiLen and NiLpn, respectively. The shift increases with the decrease of the pKa of the respective aqua-complexes of the metal ion but is poorly co-linear; however, better linearity is found when the shift of the mono- and bi-positive metal ion aqua complexes is plotted separately. Spectrophotometric titrations of these two nickel complexes with the guest metal ions in acetonitrile showed a well-anchored isosbestic point in all cases, confirming the adduct formation of NiLen and NiLpn with the metal ions. Structural analysis of single crystals, [(NiLen)Li(H2O)2]·ClO4 (1), [(NiLpn)Li(H2O)]·ClO4 (2), [(NiLpn)2Na]·BF4 (3) and [(NiLpn)2Ba(H2O)(ClO4)]·ClO4 (4), also corroborates the heterometallic adduct formation. The orbital energies of the optimised heterometallic adducts from which electron transfers originated were calculated in order to explain the observed reduction process. A strong linear connection between the calculated orbital energies and the experimental E1/2 values was observed. According to MEP and 2D vector field plots, the largest shift for divalent metal ions is most likely caused by the local electric field that they impose in addition to Lewis acidity.
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Affiliation(s)
- Pradip Bhunia
- Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata-700 009, India.
| | - Rosa M Gomila
- Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain.
| | - Antonio Frontera
- Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain.
| | - Ashutosh Ghosh
- Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata-700 009, India.
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8
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Branch K, Johnson ER, Nichols EM. Porphyrin Aggregation under Homogeneous Conditions Inhibits Electrocatalysis: A Case Study on CO 2 Reduction. ACS CENTRAL SCIENCE 2024; 10:1251-1261. [PMID: 38947202 PMCID: PMC11212130 DOI: 10.1021/acscentsci.4c00121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 05/08/2024] [Accepted: 05/20/2024] [Indexed: 07/02/2024]
Abstract
Metalloporphyrins are widely used as homogeneous electrocatalysts for transformations relevant to clean energy and sustainable organic synthesis. Metalloporphyrins are well-known to aggregate due to π-π stacking, but surprisingly, the influence of aggregation on homogeneous electrocatalytic performance has not been investigated previously. Herein, we present three structurally related iron meso-phenylporphyrins whose aggregation properties are different in commonly used N,N-dimethylformamide (DMF) electrolyte. Both spectroscopy and light scattering provide evidence of extensive porphyrin aggregation under conventional electrocatalytic conditions. Using the electrocatalytic reduction of CO2 to CO as a test reaction, cyclic voltammetry reveals an inverse dependence of the kinetics on the catalyst concentration. The inhibition extends to bulk performance, where up to 75% of the catalyst at 1 mM is inactive compared to at 0.25 mM. We additionally report how aggregation is perturbed by organic additives, axial ligands, and redox state. Periodic boundary calculations provide additional insights into aggregate stability as a function of metalloporphyrin structure. Finally, we generalize the aggregation phenomenon by surveying metalloporphyrins with different metals and substituents. This study demonstrates that homogeneous metalloporphyrins can aggregate severely in well-solubilizing organic electrolytes, that aggregation can be easily modulated through experimental conditions, and that the extent of aggregation must be considered for accurate catalytic benchmarking.
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Affiliation(s)
- Kaitlin
L. Branch
- Department
of Chemistry, The University of British
Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Erin R. Johnson
- Department
of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
| | - Eva M. Nichols
- Department
of Chemistry, The University of British
Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
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9
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Cheng R, He X, Li K, Ran B, Zhang X, Qin Y, He G, Li H, Fu C. Rational Design of Organic Electrocatalysts for Hydrogen and Oxygen Electrocatalytic Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2402184. [PMID: 38458150 DOI: 10.1002/adma.202402184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Indexed: 03/10/2024]
Abstract
Efficient electrocatalysts are pivotal for advancing green energy conversion technologies. Organic electrocatalysts, as cost-effective alternatives to noble-metal benchmarks, have garnered attention. However, the understanding of the relationships between their properties and electrocatalytic activities remains ambiguous. Plenty of research articles regarding low-cost organic electrocatalysts started to gain momentum in 2010 and have been flourishing recently though, a review article for both entry-level and experienced researchers in this field is still lacking. This review underscores the urgent need to elucidate the structure-activity relationship and design suitable electrode structures, leveraging the unique features of organic electrocatalysts like controllability and compatibility for real-world applications. Organic electrocatalysts are classified into four groups: small molecules, oligomers, polymers, and frameworks, with specific structural and physicochemical properties serving as activity indicators. To unlock the full potential of organic electrocatalysts, five strategies are discussed: integrated structures, surface property modulation, membrane technologies, electrolyte affinity regulation, and addition of anticorrosion species, all aimed at enhancing charge efficiency, mass transfer, and long-term stability during electrocatalytic reactions. The review offers a comprehensive overview of the current state of organic electrocatalysts and their practical applications, bridging the understanding gap and paving the way for future developments of more efficient green energy conversion technologies.
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Affiliation(s)
- Ruiqi Cheng
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China
| | - Xiaoqian He
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China
| | - Kaiqi Li
- Christopher Ingold Laboratory, Department of Chemistry, University College London, London, WC1H 0AJ, UK
| | - Biao Ran
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China
| | - Xinlong Zhang
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China
| | - Yonghong Qin
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China
| | - Guanjie He
- Christopher Ingold Laboratory, Department of Chemistry, University College London, London, WC1H 0AJ, UK
| | - Huanxin Li
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London, WC1E 7JE, UK
| | - Chaopeng Fu
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China
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10
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Nishiori D, Menzel JP, Armada N, Reyes Cruz EA, Nannenga BL, Batista VS, Moore GF. Breaking a Molecular Scaling Relationship Using an Iron-Iron Fused Porphyrin Electrocatalyst for Oxygen Reduction. J Am Chem Soc 2024; 146:11622-11633. [PMID: 38639470 DOI: 10.1021/jacs.3c08586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
The design of efficient electrocatalysts is limited by scaling relationships governing trade-offs between thermodynamic and kinetic performance metrics. This ″iron law″ of electrocatalysis arises from synthetic design strategies, where structural alterations to a catalyst must balance nucleophilic versus electrophilic character. Efforts to circumvent this fundamental impasse have focused on bioinspired applications of extended coordination spheres and charged sites proximal to a catalytic center. Herein, we report evidence for breaking a molecular scaling relationship involving electrocatalysis of the oxygen reduction reaction (ORR) by leveraging ligand design. We achieve this using a binuclear catalyst (a diiron porphyrin), featuring a macrocyclic ligand with extended electronic conjugation. This ligand motif delocalizes electrons across the molecular scaffold, improving the catalyst's nucleophilic and electrophilic character. As a result, our binuclear catalyst exhibits low overpotential and high catalytic turnover frequency, breaking the traditional trade-off between these two metrics.
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Affiliation(s)
- Daiki Nishiori
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
- Center for Applied Structural Discovery (CASD), The Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
| | - Jan Paul Menzel
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Nicholas Armada
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
- Center for Applied Structural Discovery (CASD), The Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
| | - Edgar A Reyes Cruz
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
- Center for Applied Structural Discovery (CASD), The Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
| | - Brent L Nannenga
- Center for Applied Structural Discovery (CASD), The Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
- Chemical Engineering, School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
- Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Gary F Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
- Center for Applied Structural Discovery (CASD), The Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
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11
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Santra A, Das A, Kaur S, Jain P, Ingole PP, Paria S. Catalytic reduction of oxygen to water by non-heme iron complexes: exploring the effect of the secondary coordination sphere proton exchanging site. Chem Sci 2024; 15:4095-4105. [PMID: 38487234 PMCID: PMC10935699 DOI: 10.1039/d3sc06753j] [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: 12/15/2023] [Accepted: 02/01/2024] [Indexed: 03/17/2024] Open
Abstract
In this study, we prepared non-heme FeIII complexes (1, 2, and 3) of an N4 donor set of ligands (H2L, Me2L, and BPh2L). 1 is supported by a monoanionic bispyridine-dioxime ligand (HL). In 2 and 3, the primary coordination sphere of Fe remained similar to that in 1, except that the oxime protons of the ligand were replaced with two methyl groups and a bridging -BPh2 moiety, respectively. X-ray structures of the FeII complexes (1a and 3a) revealed similar Fe-N distances; however, they were slightly elongated in 2a. The FeIII/FeII potential of 1, 2, and 3 appeared at -0.31 V, -0.25 V, and 0.07 V vs. Fc+/Fc, respectively, implying that HL and Me2L have comparable donor properties. However, BPh2L is more electron deficient than HL or Me2L. 1 showed electrocatalytic oxygen reduction reaction (ORR) activity in acetonitrile in the presence of trifluoroacetic acid (TFAH) as the proton source at Ecat/2 = -0.45 V and revealed selective 4e-/4H+ reduction of O2 to H2O. 1 showed an effective overpotential (ηeff) of 0.98 V and turnover frequency (TOFmax) of 1.02 × 103 s-1. Kinetic studies revealed a kcat of 2.7 × 107 M-2 s-1. Strikingly, 2 and 3 remained inactive for electrocatalytic ORR, which established the essential role of the oxime scaffolds in the electrocatalytic ORR of 1. Furthermore, a chemical ORR of 1 has been investigated using decamethylferrocene as the electron source. For 1, a similar rate equation was noted to that of the electrocatalytic pathway. A kcat of 6.07 × 104 M-2 s-1 was found chemically. Complex 2, however, underwent a very slow chemical ORR. Complex 3 chemically enhances the 4e-/4H+ reduction of O2 and exhibits a TOF of 0.24 s-1 and a kcat value of 2.47 × 102 M-1 s-1. Based on the experimental observations, we demonstrate that the oxime backbone of the ligand in 1 works as a proton exchanging site in the 4e-/4H+ reduction of O2. The study describes how the ORR is affected by the tuning of the ligand scaffold in a family of non-heme Fe complexes.
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Affiliation(s)
- Aakash Santra
- Department of Chemistry, Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India
| | - Avijit Das
- Department of Chemistry, Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India
| | - Simarjeet Kaur
- Department of Chemistry, Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India
| | - Priya Jain
- Department of Chemistry, Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India
| | - Pravin P Ingole
- Department of Chemistry, Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India
| | - Sayantan Paria
- Department of Chemistry, Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India
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12
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Chirila A, Hu Y, Linehan JC, Dixon DA, Wiedner ES. Thermodynamic and Kinetic Activity Descriptors for the Catalytic Hydrogenation of Ketones. J Am Chem Soc 2024; 146:6866-6879. [PMID: 38437011 DOI: 10.1021/jacs.3c13876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
Activity descriptors are a powerful tool for the design of catalysts that can efficiently utilize H2 with minimal energy losses. In this study, we develop the use of hydricity and H- self-exchange rates as thermodynamic and kinetic descriptors for the hydrogenation of ketones by molecular catalysts. Two complexes with known hydricity, HRh(dmpe)2 and HCo(dmpe)2, were investigated for the catalytic hydrogenation of ketones under mild conditions (1.5 atm and 25 °C). The rhodium catalyst proved to be an efficient catalyst for a wide range of ketones, whereas the cobalt catalyst could only hydrogenate electron-deficient ketones. Using a combination of experiment and electronic structure theory, thermodynamic hydricity values were established for 46 alkoxide/ketone pairs in both acetonitrile and tetrahydrofuran solvents. Through comparison of the hydricities of the catalysts and substrates, it was determined that catalysis was observed only for catalyst/ketone pairs with an exergonic H- transfer step. Mechanistic studies revealed that H- transfer was the rate-limiting step for catalysis, allowing for the experimental and computation construction of linear free-energy relationships (LFERs) for H- transfer. Further analysis revealed that the LFERs could be reproduced using Marcus theory, in which the H- self-exchange rates for the HRh/Rh+ and ketone/alkoxide pairs were used to predict the experimentally measured catalytic barriers within 2 kcal mol-1. These studies significantly expand the scope of catalytic reactions that can be analyzed with a thermodynamic hydricity descriptor and firmly establish Marcus theory as a valid approach to develop kinetic descriptors for designing catalysts for H- transfer reactions.
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Affiliation(s)
- Andrei Chirila
- Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Yiqin Hu
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - John C Linehan
- Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - David A Dixon
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Eric S Wiedner
- Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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13
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Tanjedrew N, Thammanatpong K, Surawatanawong P, Chakthranont P, Chantarojsiri T, Unjarern T, Kiatisevi S. Tunable Metal-Free Imidazole-Benzimidazole Electrocatalysts for Oxygen Reduction in Aqueous Solutions. Chemistry 2024; 30:e202302854. [PMID: 37924228 DOI: 10.1002/chem.202302854] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/03/2023] [Accepted: 11/03/2023] [Indexed: 11/06/2023]
Abstract
A series of metal-free imidazole-benzimidazole catalysts (ImBenz-H, ImBenz-NO2 , ImBenz-OCH3 ) for oxygen reduction reaction (ORR) were prepared. We demonstrate that the electrocatalytic O2 reduction by ImBenz-NO2 with the electron-withdrawing group showed high selectivity toward H2 O with the number of electrons transferred (n=3.7) in a neutral aqueous solution. The highest ORR selectivity toward H2 O2 was achieved using ImBenz-H (n=2.4) in an alkaline solution. Electrochemical studies of reaction kinetics disclosed that the highest turnover frequencies were obtained from ImBenz-H in both neutral and alkaline aqueous solutions. The results prove that the ORR selectivity is tunable by modulating the substituent of the ImBenz catalysts. Furthermore, DFT calculations suggested that the ORR mechanism of ImBenz-H involves the electron transfer from imidazole-benzimidazole to O2 resulting in the formation of H2 O2 which supports the redox active properties of the catalysts ImBenz.
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Affiliation(s)
- Narisara Tanjedrew
- Department of Chemistry and, Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Kittimeth Thammanatpong
- Department of Chemistry and, Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Panida Surawatanawong
- Department of Chemistry and, Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Pongkarn Chakthranont
- National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Pathum Thani, 12120, Thailand
| | - Teera Chantarojsiri
- Department of Chemistry and, Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Takdanai Unjarern
- Department of Chemistry and, Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Supavadee Kiatisevi
- Department of Chemistry and, Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
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14
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Langerman M, van Langevelde PH, van de Vijver JJ, Siegler MA, Hetterscheid DGH. Scaling Relation between the Reduction Potential of Copper Catalysts and the Turnover Frequency for the Oxygen and Hydrogen Peroxide Reduction Reactions. Inorg Chem 2023; 62:19593-19602. [PMID: 37976110 DOI: 10.1021/acs.inorgchem.3c02939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Changes in the electronic structure of copper complexes can have a remarkable impact on the catalytic rates, selectivity, and overpotential of electrocatalytic reactions. We have investigated the effect of the half-wave potential (E1/2) of the CuII/CuI redox couples of four copper complexes with different pyridylalkylamine ligands. A linear relationship was found between E1/2 of the catalysts and the logarithm of the maximum rate constant of the reduction of O2 and H2O2. Computed binding constants of the binding of O2 to CuI, which is the rate-determining step of the oxygen reduction reaction, also correlate with E1/2. Higher catalytic rates were found for catalysts with more negative E1/2 values, while catalytic reactions with lower overpotentials were found for complexes with more positive E1/2 values. The reduction of O2 is more strongly affected by the E1/2 than the H2O2 rates, resulting in that the faster catalysts are prone to accumulate peroxide, while the catalysts operating with a low overpotential are set up to accommodate the 4-electron reduction to water. This work shows that the E1/2 is an important descriptor in copper-mediated O2 reduction and that producing hydrogen peroxide selectively close to its equilibrium potential at 0.68 V vs reversible hydrogen electrode (RHE) may not be easy.
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Affiliation(s)
- Michiel Langerman
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Phebe H van Langevelde
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Johannes J van de Vijver
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, 3400 North Charles St., Baltimore, Maryland 21218, United States
| | - Dennis G H Hetterscheid
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
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15
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Saini A, Das C, Rai S, Guha A, Dolui D, Majumder P, Dutta A. A homogeneous cobalt complex mediated electro and photocatalytic O 2/H 2O interconversion in neutral water. iScience 2023; 26:108189. [PMID: 37920669 PMCID: PMC10618691 DOI: 10.1016/j.isci.2023.108189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/25/2023] [Accepted: 10/10/2023] [Indexed: 11/04/2023] Open
Abstract
The O2/H2O redox couple is vital in various renewable energy conversion strategies. This work delves into the Co(L-histidine)2 complex, a functional mimic of oxygen-carrying metalloproteins, and its electrochemical behavior driving the bidirectional oxygen reduction (ORR) and oxygen evolution (OER) activity in neutral water. This complex electrocatalyzes O2 via two distinct pathways: a two-electron O2/H2O2 reduction (catalytic rate = 250 s-1) and a four-electron O2 to H2O production (catalytic rate = 66 s-1). The formation of the key trans-μ-1,2-Co(III)-peroxo intermediate expedites this process. Additionally, this complex effectively oxidizes water to O2 (catalytic rate = 15606 s-1) at anodic potentials via a Co(IV)-oxo species. Additionally, this complex executes the ORR and OER under photocatalytic conditions in neutral water in the presence of appropriate photosensitizer (Eosin-Y) and redox mediators (triethanolamine/ORR and Na2S2O8/OER) at an appreciable rate. These results highlight one of the early examples of both electro- and photoactive bidirectional ORR/OER catalysts operational in neutral water.
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Affiliation(s)
- Abhishek Saini
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Chandan Das
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Surabhi Rai
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
- National Center of Excellence in CCU, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Aritra Guha
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Dependu Dolui
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Piyali Majumder
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Arnab Dutta
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
- Interdisciplinary Program in Climate Studies, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
- National Center of Excellence in CCU, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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16
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Skavenborg ML, Møller MS, Miller CJ, Hjelm J, Waite TD, McKenzie CJ. Electrocatalysis of the Oxygen Reduction Reaction by Copper Complexes with Tetradentate Tripodal Ligands. Inorg Chem 2023; 62:18219-18227. [PMID: 37877669 DOI: 10.1021/acs.inorgchem.3c02738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
The tetradentate tripodal ligand scaffold is capable of supporting the expected geometries of the copper ion during the oxygen reduction reaction (ORR) catalysis. As such, we probed the reactivity of copper complexes with these types of ligands by electronically and structurally tweaking the tris(pyridin 2-ylmethyl)amine (tmpa) scaffold by progressively replacing the terminal pyridines with carboxylate donors. This work shows that systems with one carboxylato donor (bpg = bis(pyridin-2-ylmethyl)glycine), (bpp = (3-(bis(pyridin-2-ylmethyl)amino)propanoic acid)) are active in electrocatalyzing the homogeneous ORR under circumneutral aqueous conditions. Turnover frequencies in the range from 105 to 106 s-1, on par with that for Cu-tmpa under identical conditions, were obtained. It is noteworthy that the CuII/CuI redox potentials for the Cu-bpg, Cu-bpp, and Cu-tmpa systems in phosphate-buffered water (pH 7, under Ar) are similar at -0.409, -0.375, and -0.401 V vs Ag/AgCl, respectively. This is rationalized by the influence of the Lewis acidity of the copper ions on the water coligand. Corroborating this are pKa values for [Cu(tmpa)(H2O)]2+, Cu(bpg)(H2O)]+, and [Cu(bpp)(H2O)]+ of 6.6, 8.8, and 10.2, respectively. Thus, the overall charge of the solution species for all three complexes will be +1 at pH 7 and this will be an important determinant for the redox potentials and, in turn, the catalytic overpotentials, which are also similar. A cis carboxylato donor offers H-bonding possibilities for exogenous resting state water and intermediate hydroperoxo coligands. This is reflected by the higher pKa values for Cu-bpp and Cu-bpg compared with that for Cu-tmpa, with the Cu-bpp system furnishing the least strained H-bonding.
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Affiliation(s)
- Mathias L Skavenborg
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M 5230, Denmark
- Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Mads Sondrup Møller
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M 5230, Denmark
| | - Christopher J Miller
- Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Johan Hjelm
- Technical University of Denmark, Department of Energy Conversion and Storage, Fysikvej, Building 310, 2800 Kgs Lyngby, Denmark
| | - T David Waite
- Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Christine J McKenzie
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M 5230, Denmark
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17
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Teindl K, Patrick BO, Nichols EM. Linear Free Energy Relationships and Transition State Analysis of CO 2 Reduction Catalysts Bearing Second Coordination Spheres with Tunable Acidity. J Am Chem Soc 2023; 145:17176-17186. [PMID: 37499125 DOI: 10.1021/jacs.3c03919] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
In molecular catalysts, protic functional groups in the secondary coordination sphere (SCS) work in conjunction with an exogenous acid to relay protons to the active site of electrochemical CO2 reduction; however, it is not well understood how the acidity of the SCS and exogenous acid together determine the kinetics of catalytic turnover. To evaluate the relative contributions of proton transfer driving forces, we synthesized a series of modular iron tetraphenylporphyrin electrocatalysts bearing SCS amides of tunable pKa (17.6 to 20.0 in dimethyl sulfoxide (DMSO)) and employed phenols of variable acidity (15.3 to 19.1) as exogenous acids. This system allowed us to (1) evaluate contributions from proton transfer driving forces associated with either the SCS or exogenous acid and (2) obtain mechanistic insights into CO2 reduction as a function of pKa. A series of linear free-energy relationships show that kinetics become increasingly sensitive to variations in SCS pKa when more acidic exogenous acids are used (0.82 ≥ Brønsted α ≥ 0.13), as well as to variations in exogenous acid pKa when SCS acidity is increased (0.62 ≥ Brønsted α ≥ 0.32). An Eyring analysis suggests that the rate-determining transition state becomes more ordered with decreasing SCS acidity, which is consistent with the proposal that SCS acidity modulates charge accumulation and solvation at the rate-limiting transition state. Together, these insights enable the optimization of activation barriers as a function of both SCS and exogenous acid pKa and can further guide the rational design of electrocatalytic systems wherein contributions from all participants in a proton relay are considered.
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Affiliation(s)
- Kaeden Teindl
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Brian O Patrick
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Eva M Nichols
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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18
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Mondal B, Dinda S, Karjule N, Mondal S, Raja Kottaichamy A, Volokh M, Shalom M. The Implications of Coupling an Electron Transfer Mediated Oxidation with a Proton Coupled Electron Transfer Reduction in Hybrid Water Electrolysis. CHEMSUSCHEM 2023; 16:e202202271. [PMID: 36576299 DOI: 10.1002/cssc.202202271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 12/27/2022] [Accepted: 12/28/2022] [Indexed: 05/20/2023]
Abstract
Electrolysis of water is a sustainable route to produce clean hydrogen. Full water-splitting requires a high applied potential, in part because of the pH-dependency of the H2 and O2 evolution reactions (HER and OER), which are proton-coupled electron transfer (PCET) reactions. Therefore, the minimum required potential will not change at different pHs. TEMPO [(2,2,6,6-tetramethyl-1-piperidin-1-yl)oxyl], a stable free-radical that undergoes fast electro-oxidation by a single-electron transfer (ET) process, is pH-independent. Here, we show that the combination of PCET and ET processes enables hydrogen production from water at low cell potentials below the theoretical value for full water-splitting by simple pH adjustment. As a case study, we combined the HER with the oxidation of benzylamine by anodically oxidized TEMPO. The pH-independent electrocatalytic oxidation of TEMPO permits the operation of a hybrid water-splitting cell that shows promise to perform at a low cell potential (≈1 V) and neutral pH conditions.
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Affiliation(s)
- Biswajit Mondal
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
- Discipline of Chemistry, IIT Gandhinagar Palaj, Gandhinagr, 382355, Gujarat, India
| | - Soumitra Dinda
- Discipline of Chemistry, IIT Gandhinagar Palaj, Gandhinagr, 382355, Gujarat, India
| | - Neeta Karjule
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
| | - Sanjit Mondal
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
| | - Alagar Raja Kottaichamy
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
| | - Michael Volokh
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
| | - Menny Shalom
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
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19
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Zhao Y, Adiyeri Saseendran DP, Huang C, Triana CA, Marks WR, Chen H, Zhao H, Patzke GR. Oxygen Evolution/Reduction Reaction Catalysts: From In Situ Monitoring and Reaction Mechanisms to Rational Design. Chem Rev 2023; 123:6257-6358. [PMID: 36944098 DOI: 10.1021/acs.chemrev.2c00515] [Citation(s) in RCA: 69] [Impact Index Per Article: 69.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are core steps of various energy conversion and storage systems. However, their sluggish reaction kinetics, i.e., the demanding multielectron transfer processes, still render OER/ORR catalysts less efficient for practical applications. Moreover, the complexity of the catalyst-electrolyte interface makes a comprehensive understanding of the intrinsic OER/ORR mechanisms challenging. Fortunately, recent advances of in situ/operando characterization techniques have facilitated the kinetic monitoring of catalysts under reaction conditions. Here we provide selected highlights of recent in situ/operando mechanistic studies of OER/ORR catalysts with the main emphasis placed on heterogeneous systems (primarily discussing first-row transition metals which operate under basic conditions), followed by a brief outlook on molecular catalysts. Key sections in this review are focused on determination of the true active species, identification of the active sites, and monitoring of the reactive intermediates. For in-depth insights into the above factors, a short overview of the metrics for accurate characterizations of OER/ORR catalysts is provided. A combination of the obtained time-resolved reaction information and reliable activity data will then guide the rational design of new catalysts. Strategies such as optimizing the restructuring process as well as overcoming the adsorption-energy scaling relations will be discussed. Finally, pending current challenges and prospects toward the understanding and development of efficient heterogeneous catalysts and selected homogeneous catalysts are presented.
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Affiliation(s)
- Yonggui Zhao
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | | | - Chong Huang
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Carlos A Triana
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Walker R Marks
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Hang Chen
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Han Zhao
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Greta R Patzke
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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20
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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: 16] [Impact Index Per Article: 16.0] [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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21
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Harraz DM, Weng S, Surendranath Y. Electrochemically Quantifying Oxygen Reduction Selectivity in Nonaqueous Electrolytes. ACS Catal 2023. [DOI: 10.1021/acscatal.2c04564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Deiaa M. Harraz
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sophia Weng
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yogesh Surendranath
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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22
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Mazzucato M, Gavioli L, Balzano V, Berretti E, Rizzi GA, Badocco D, Pastore P, Zitolo A, Durante C. Synergistic Effect of Sn and Fe in Fe-N x Site Formation and Activity in Fe-N-C Catalyst for ORR. ACS APPLIED MATERIALS & INTERFACES 2022; 14:54635-54648. [PMID: 36468946 PMCID: PMC9756292 DOI: 10.1021/acsami.2c13837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
Iron-nitrogen-carbon (Fe-N-C) materials emerged as one of the best non-platinum group material (non-PGM) alternatives to Pt/C catalysts for the electrochemical reduction of O2 in fuel cells. Co-doping with a secondary metal center is a possible choice to further enhance the activity toward oxygen reduction reaction (ORR). Here, classical Fe-N-C materials were co-doped with Sn as a secondary metal center. Sn-N-C according to the literature shows excellent activity, in particular in the fuel cell setup; here, the same catalyst shows a non-negligible activity in 0.5 M H2SO4 electrolyte but not as high as expected, meaning the different and uncertain nature of active sites. On the other hand, in mixed Fe, Sn-N-C catalysts, the presence of Sn improves the catalytic activity that is linked to a higher Fe-N4 site density, whereas the possible synergistic interaction of Fe-N4 and Sn-Nx found no confirmation. The presence of Fe-N4 and Sn-Nx was thoroughly determined by extended X-ray absorption fine structure and NO stripping technique; furthermore, besides the typical voltammetric technique, the catalytic activity of Fe-N-C catalyst was determined and also compared with that of the gas diffusion electrode (GDE), which allows a fast and reliable screening for possible implementation in a full cell. This paper therefore explores the effect of Sn on the formation, activity, and selectivity of Fe-N-C catalysts in both acid and alkaline media by tuning the Sn/Fe ratio in the synthetic procedure, with the ratio 1/2 showing the best activity, even higher than that of the iron-only containing sample (jk = 2.11 vs 1.83 A g-1). Pt-free materials are also tested for ORR in GDE setup in both performance and durability tests.
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Affiliation(s)
- Marco Mazzucato
- Department
of Chemical Sciences, University of Padova, Via Marzolo 1, 35131Padova, Italy
| | - Luca Gavioli
- i-LAMP
& Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Via della Garzetta 46, 25133Brescia, Italy
| | - Vincenzo Balzano
- i-LAMP
& Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Via della Garzetta 46, 25133Brescia, Italy
| | - Enrico Berretti
- Institute
of Chemistry of Organometallic Compounds (ICCOM)—National Research
Council (CNR), Via Madonna
del Piano 10, 50019Sesto Fiorentino, Italy
| | - Gian Andrea Rizzi
- Department
of Chemical Sciences, University of Padova, Via Marzolo 1, 35131Padova, Italy
| | - Denis Badocco
- Department
of Chemical Sciences, University of Padova, Via Marzolo 1, 35131Padova, Italy
| | - Paolo Pastore
- Department
of Chemical Sciences, University of Padova, Via Marzolo 1, 35131Padova, Italy
| | - Andrea Zitolo
- Synchrotron
SOLEIL, L’Orme des Merisiers, BP 48 Saint Aubin, 91192Gif-sur-Yvette, France
| | - Christian Durante
- Department
of Chemical Sciences, University of Padova, Via Marzolo 1, 35131Padova, Italy
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23
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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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24
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Cordeiro Junior PJM, Martins AS, Pereira GBS, Rocha FV, Rodrigo MAR, Lanza MRDV. High-performance gas-diffusion electrodes for H2O2 electrosynthesis. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.141067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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25
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Groff BD, Mayer JM. Optimizing Catalysis by Combining Molecular Scaling Relationships: Iron Porphyrin-Catalyzed Electrochemical Oxygen Reduction as a Case Study. ACS Catal 2022. [DOI: 10.1021/acscatal.2c04190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Benjamin D. Groff
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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26
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Arima H, Nakazono T, Wada T. Proton Relay Effects on Oxygen Reduction Reaction Catalyzed by Dinuclear Cobalt Polypyridyl Complexes with OH Groups on Bipyridine Ligands. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2022. [DOI: 10.1246/bcsj.20220104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Hiroaki Arima
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan
| | - Takashi Nakazono
- Research Center for Artificial Photosynthesis (ReCAP), Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Tohru Wada
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan
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27
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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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28
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Wiedner ES, Appel AM, Raugei S, Shaw WJ, Bullock RM. Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines. Chem Rev 2022; 122:12427-12474. [PMID: 35640056 DOI: 10.1021/acs.chemrev.1c01001] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Pendant amines play an invaluable role in chemical reactivity, especially for molecular catalysts based on earth-abundant metals. As inspired by [FeFe]-hydrogenases, which contain a pendant amine positioned for cooperative bifunctionality, synthetic catalysts have been developed to emulate this multifunctionality through incorporation of a pendant amine in the second coordination sphere. Cyclic diphosphine ligands containing two amines serve as the basis for a class of catalysts that have been extensively studied and used to demonstrate the impact of a pendant base. These 1,5-diaza-3,7-diphosphacyclooctanes, now often referred to as "P2N2" ligands, have profound effects on the reactivity of many catalysts. The resulting [Ni(PR2NR'2)2]2+ complexes are electrocatalysts for both the oxidation and production of H2. Achieving the optimal benefit of the pendant amine requires that it has suitable basicity and is properly positioned relative to the metal center. In addition to the catalytic efficacy demonstrated with [Ni(PR2NR'2)2]2+ complexes for the oxidation and production of H2, catalysts with diphosphine ligands containing pendant amines have also been demonstrated for several metals for many different reactions, both in solution and immobilized on surfaces. The impact of pendant amines in catalyst design continues to expand.
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29
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30
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Amanullah S, Saha P, Dey A. Recent developments in the synthesis of bio-inspired iron porphyrins for small molecule activation. Chem Commun (Camb) 2022; 58:5808-5828. [PMID: 35474535 DOI: 10.1039/d2cc00430e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nature utilizes a diverse set of tetrapyrrole-based macrocycles (referred to as porphyrinoids) for catalyzing various biological processes. Investigation of the differences in electronic structure and reactivity in these reactions have revealed striking differences that lead to diverse reactivity from, apparently, similar looking active sites. Therefore, the role of the different heme cofactors as well as the distal superstructure in the proteins is important to understand. This article summarizes the role of a few synthetic metallo-porphyrinoids towards catalyzing several small molecule activation reactions, such as the ORR, NiRR, CO2RR, etc. The major focus of the article is to enlighten the synthetic routes to the well-decorated active-site mimic in a tailor-made fashion pursuing a retrosynthetic approach, learning from the biosynthesis of the cofactors. Techniques and the role of the second-sphere residues on the reaction rate, selectivity, etc. are incorporated emulating the basic amino acid residues fencing the active sites. These bioinspired mimics play an important role towards understanding the role of the prosthetic groups as well as the basic residues towards any reaction occurring in Nature.
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Affiliation(s)
- Sk Amanullah
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata, WB 700032, India.
| | - Paramita Saha
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata, WB 700032, India.
| | - Abhishek Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata, WB 700032, India.
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31
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Bhunia S, Ghatak A, Dey A. Second Sphere Effects on Oxygen Reduction and Peroxide Activation by Mononuclear Iron Porphyrins and Related Systems. Chem Rev 2022; 122:12370-12426. [PMID: 35404575 DOI: 10.1021/acs.chemrev.1c01021] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation and reduction of O2 and H2O2 by synthetic and biosynthetic iron porphyrin models have proved to be a versatile platform for evaluating second-sphere effects deemed important in naturally occurring heme active sites. Advances in synthetic techniques have made it possible to install different functional groups around the porphyrin ligand, recreating artificial analogues of the proximal and distal sites encountered in the heme proteins. Using judicious choices of these substituents, several of the elegant second-sphere effects that are proposed to be important in the reactivity of key heme proteins have been evaluated under controlled environments, adding fundamental insight into the roles played by these weak interactions in nature. This review presents a detailed description of these efforts and how these have not only demystified these second-sphere effects but also how the knowledge obtained resulted in functional mimics of these heme enzymes.
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Affiliation(s)
- Sarmistha Bhunia
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
| | - Arnab Ghatak
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
| | - Abhishek Dey
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
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32
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Cai Q, Tran LK, Qiu T, Eddy JW, Pham TN, Yap GPA, Rosenthal J. An Easily Prepared Monomeric Cobalt(II) Tetrapyrrole Complex That Efficiently Promotes the 4e -/4H + Peractivation of O 2 to Water. Inorg Chem 2022; 61:5442-5451. [PMID: 35358381 DOI: 10.1021/acs.inorgchem.1c03766] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The selective 4e-/4H+ reduction of dioxygen to water is an important reaction that takes place at the cathode of fuel cells. Monomeric aromatic tetrapyrroles (such as porphyrins, phthalocyanines, and corroles) coordinated to Co(II) or Co(III) have been considered as oxygen reduction catalysts due to their low cost and relative ease of synthesis. However, these systems have been repeatedly shown to be selective for O2 reduction by the less desired 2e-/2H+ pathway to yield hydrogen peroxide. Herein, we report the initial synthesis and study of a Co(II) tetrapyrrole complex based on a nonaromatic isocorrole scaffold that is competent for 4e-/4H+ oxygen reduction reaction (ORR). This Co(II) 10,10-dimethyl isocorrole (Co[10-DMIC]) is obtained in just four simple steps and has excellent yield from a known dipyrromethane synthon. Evaluation of the steady state spectroscopic and redox properties of Co[10-DMIC] against those of Co porphyrin (cobalt 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin, [Co(TPFPP)]) and corrole (cobalt 5,10,15-tris(pentafluorophenyl)corrole triphenylphosphine, Co[TPFPC](PPh3)) homologues demonstrated that the spectroscopic and electrochemical properties of the isocorrole are distinct from those displayed by more traditional aromatic tetrapyrroles. Further, the investigation of the ORR activity of Co[10-DMIC] using a combination of electrochemical and chemical reduction studies revealed that this simple, unadorned monomeric Co(II) tetrapyrrole is ∼85% selective for the 4e-/4H+ reduction of O2 to H2O over the more kinetically facile 2e-/2H+ process that delivers H2O2. In contrast, the same ORR evaluations conducted for the Co porphyrin and corrole homologues demonstrated that these traditional aromatic systems catalyze the 2e-/2H+ conversion of O2 to H2O2 with near complete selectivity. Despite being a simple, easily prepared, monomeric tetrapyrrole platform, Co[10-DMIC] supports an ORR catalysis that has historically only been achieved using elaborate porphyrinoid-based architectures that incorporate pendant proton-transfer groups or ditopic molecular clefts or that impose cofacially oriented O2 binding sites. Accordingly, Co[10-DMIC] represents the first simple, unadorned, monomeric metalloisocorrole complex that can be easily prepared and shows a privileged performance for the 4e-/4H+ peractivation of O2 to water as compared to other simple cobalt containing tetrapyrroles.
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Affiliation(s)
- Qiuqi Cai
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Linh K Tran
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Tian Qiu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Jennifer W Eddy
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Trong-Nhan Pham
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Glenn P A Yap
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Joel Rosenthal
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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33
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Hsu WC, Wang YH. Homogeneous Water Oxidation Catalyzed by First-Row Transition Metal Complexes: Unveiling the Relationship between Turnover Frequency and Reaction Overpotential. CHEMSUSCHEM 2022; 15:e202102378. [PMID: 34881515 DOI: 10.1002/cssc.202102378] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/07/2021] [Indexed: 06/13/2023]
Abstract
The utilization of earth-abundant low-toxicity metal ions in the construction of highly active and efficient molecular catalysts promoting the water oxidation reaction is important for developing a sustainable artificial energy cycle. However, the kinetic and thermodynamic properties of the currently available molecular water oxidation catalysts (MWOCs) have not been comprehensively investigated. This Review summarizes the current status of MWOCs based on first-row transition metals in terms of their turnover frequency (TOF, a kinetic property) and overpotential (η, a thermodynamic property) and uses the relationship between log(TOF) and η to assess catalytic performance. Furthermore, the effects of the same ligand classes on these MWOCs are discussed in terms of TOF and η, and vice versa. The collective analysis of these relationships provides a metric for the direct comparison of catalyst systems and identifying factors crucial for catalyst design.
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Affiliation(s)
- Wan-Chi Hsu
- Department of Chemistry, National Tsing Hua University, 101, Sec 2, Kuang-Fu Rd., Hsinchu, 30013, Taiwan
| | - Yu-Heng Wang
- Department of Chemistry, National Tsing Hua University, 101, Sec 2, Kuang-Fu Rd., Hsinchu, 30013, Taiwan
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34
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Treviño RE, Shafaat HS. Protein-based models offer mechanistic insight into complex nickel metalloenzymes. Curr Opin Chem Biol 2022; 67:102110. [PMID: 35101820 DOI: 10.1016/j.cbpa.2021.102110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/22/2021] [Accepted: 12/06/2021] [Indexed: 11/03/2022]
Abstract
There are ten nickel enzymes found across biological systems, each with a distinct active site and reactivity that spans reductive, oxidative, and redox-neutral processes. We focus on the reductive enzymes, which catalyze reactions that are highly germane to the modern-day climate crisis: [NiFe] hydrogenase, carbon monoxide dehydrogenase, acetyl coenzyme A synthase, and methyl coenzyme M reductase. The current mechanistic understanding of each enzyme system is reviewed along with existing knowledge gaps, which are addressed through the development of protein-derived models, as described here. This opinion is intended to highlight the advantages of using robust protein scaffolds for modeling multiscale contributions to reactivity and inspire the development of novel artificial metalloenzymes for other small molecule transformations.
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Affiliation(s)
- Regina E Treviño
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
| | - Hannah S Shafaat
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.
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35
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Singha A, Mittra K, Dey A. Synthetic heme dioxygen adducts: electronic structure and reactivity. TRENDS IN CHEMISTRY 2022. [DOI: 10.1016/j.trechm.2021.10.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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36
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Nie W, McCrory C. Strategies for Breaking Molecular Scaling Relationships for the Electrochemical CO 2 Reduction Reaction. Dalton Trans 2022; 51:6993-7010. [DOI: 10.1039/d2dt00333c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electrocatalytic CO2 reduction reaction (CO2RR) is a promising strategy for converting CO2 to fuels and value-added chemicals using renewable energy sources. Molecular electrocatalysts show promise for the selective conversion...
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37
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Posada-Pérez S, Escayola S, Poater J, Solà M, Poater A. Ni(I)-TPA Stabilization by Hydrogen Bond formation on the Second Coordination Sphere: a DFT Characterization. Dalton Trans 2022; 51:12585-12595. [DOI: 10.1039/d2dt01355j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ni(I) compounds are less common than those of either Ni(0) or Ni(II). Recently, a series of Ni(I) tris(2 pyridylmethyl)amine (TPA) complexes were synthetized through the reduction of Ni(II)-TPA complexes and...
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38
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Song P, Li Y, Yin S. Mechanistic insights into homogeneous electrocatalytic reaction for energy storage using finite element simulation. Chin J Chem Eng 2021. [DOI: 10.1016/j.cjche.2021.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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39
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Synthesis and redox properties of heterobimetallic Re(bpyCrown-M)(CO)3Cl complexes, where M = Na+, K+, Ca2+, and Ba2+. Polyhedron 2021. [DOI: 10.1016/j.poly.2021.115385] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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40
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Matute RA, Toro-Labbé A, Oyarzún MP, Ramirez S, Ortega DE, Oyarce K, Silva N, Zagal JH. Mapping experimental and theoretical reactivity descriptors of fe macrocyclic complexes deposited on graphite or on multi walled carbon nanotubes for the oxidation of thiols: Thioglycolic acid oxidation. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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41
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Li Y, Wang N, Lei H, Li X, Zheng H, Wang H, Zhang W, Cao R. Bioinspired N4-metallomacrocycles for electrocatalytic oxygen reduction reaction. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.213996] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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42
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Nichols AW, Cook EN, Gan YJ, Miedaner PR, Dressel JM, Dickie DA, Shafaat HS, Machan CW. Pendent Relay Enhances H 2O 2 Selectivity during Dioxygen Reduction Mediated by Bipyridine-Based Co-N 2O 2 Complexes. J Am Chem Soc 2021; 143:13065-13073. [PMID: 34380313 DOI: 10.1021/jacs.1c03381] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Generally, cobalt-N2O2 complexes show selectivity for hydrogen peroxide during electrochemical dioxygen (O2) reduction. We recently reported a Co(III)-N2O2 complex with a 2,2'-bipyridine-based ligand backbone which showed alternative selectivity: H2O was observed as the primary reduction product from O2 (71 ± 5%) with decamethylferrocene as a chemical reductant and acetic acid as a proton donor in methanol solution. We hypothesized that the key selectivity difference in this case arises in part from increased favorability of protonation at the distal O position of the key intermediate Co(III)-hydroperoxide species. To interrogate this hypothesis, we have prepared a new Co(III) compound that contains pendent -OMe groups poised to direct protonation toward the proximal O atom of this hydroperoxo intermediate. Mechanistic studies in acetonitrile (MeCN) solution reveal two regimes are possible in the catalytic response, dependent on added acid strength and the presence of the pendent proton donor relay. In the presence of stronger acids, the activity of the complex containing pendent relays becomes O2 dependent, implying a shift to Co(III)-superoxide protonation as the rate-determining step. Interestingly, the inclusion of the relay results in primarily H2O2 production in MeCN, despite minimal difference between the standard reduction potentials of the three complexes tested. EPR spectroscopic studies indicate the formation of Co(III)-superoxide species in the presence of exogenous base, with greater O2 reactivity observed in the presence of the pendent -OMe groups.
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Affiliation(s)
- Asa W Nichols
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Emma N Cook
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Yunqiao J Gan
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Ave., Columbus, Ohio 43210, United States
| | - Peter R Miedaner
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Julia M Dressel
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Diane A Dickie
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, Virginia 22904-4319, United States
| | - Hannah S Shafaat
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Ave., Columbus, Ohio 43210, United States
| | - Charles W Machan
- Department of Chemistry, University of Virginia, McCormick Rd., PO Box 400319, Charlottesville, Virginia 22904-4319, United States
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43
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Determining the Overpotential of Electrochemical Fuel Synthesis Mediated by Molecular Catalysts: Recommended Practices, Standard Reduction Potentials, and Challenges. ChemElectroChem 2021. [DOI: 10.1002/celc.202100576] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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44
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Martin DJ, Mayer JM. Oriented Electrostatic Effects on O 2 and CO 2 Reduction by a Polycationic Iron Porphyrin. J Am Chem Soc 2021; 143:11423-11434. [PMID: 34292718 DOI: 10.1021/jacs.1c03132] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Next-generation energy technologies require improved methods for rapid and efficient chemical-to-electrical energy transformations. One new approach has been to include atomically positioned, electrostatic motifs in molecular catalysts to stabilize high-energy, charged intermediates. For example, an iron porphyrin bearing four cationic, o-N,N,N-trimethylanilinium groups (o-[N(CH3)3]+) has recently been used to catalyze the complex, multistep O2 and CO2 reduction reactions (ORR and CO2RR) with fast rates and at low overpotentials. The success of this catalyst is attributed, at least in part, to specific charge-charge interactions between the atomically positioned o-[N(CH3)3]+ groups and the bound substrate. However, by nature of the mono-ortho substitution pattern, there are four possible atropisomers of this metalloporphyrin and thus four unique electrostatic environments. This work reports that each of the four individual atropisomers catalyzes both the ORR and CO2RR with fast rates and low overpotentials. The maximum turnover frequencies vary among the atropisomers, by a factor of 60 for the ORR and a factor of 5 for CO2RR. For the ORR, the αβαβ isomer is the fastest and has the highest overpotential, while for the CO2RR the αααα isomer is the fastest and has the highest overpotential. The role of charge positioning is complex and can affect more than a single step such as CO2 binding. These data offer a first-of-a-kind perspective on atomically positioned charge and highlight the significance of high charge density, rather than orientation, on the thermodynamics and kinetics of multistep molecular electrochemical transformations.
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Affiliation(s)
- Daniel J Martin
- 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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Ramuglia AR, Budhija V, Ly KH, Marquardt M, Schwalbe M, Weidinger IM. An Iron Porphyrin Complex with Pendant Pyridine Substituents Facilitates Electrocatalytic CO
2
Reduction via Second Coordination Sphere Effects. ChemCatChem 2021. [DOI: 10.1002/cctc.202100625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Anthony R. Ramuglia
- Fakultät Chemie und Lebensmittelchemie Technische Universität Dresden Zellescher Weg 19 01069 Dresden Germany
| | - Vishal Budhija
- Institute of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Khoa H. Ly
- Fakultät Chemie und Lebensmittelchemie Technische Universität Dresden Zellescher Weg 19 01069 Dresden Germany
| | - Michael Marquardt
- Institute of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Matthias Schwalbe
- Institute of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Inez M. Weidinger
- Fakultät Chemie und Lebensmittelchemie Technische Universität Dresden Zellescher Weg 19 01069 Dresden Germany
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46
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Arima H, Wada M, Nakazono T, Wada T. Tuning Oxygen Reduction Catalysis of Dinuclear Cobalt Polypyridyl Complexes by the Bridging Structure. Inorg Chem 2021; 60:9402-9415. [PMID: 33988979 DOI: 10.1021/acs.inorgchem.1c00293] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The four-electron oxygen reduction reaction (4e--ORR) is the mainstay in chemical energy conversion. Elucidation of factors influencing the catalyst's reaction rate and selectivity is important in the development of more active catalysts of 4e--ORR. In this study, we investigated chemical and electrochemical 4e--ORR catalyzed by Co2(μ-O2) complexes bridged by xanthene (1) and anthracene (3) and by a Co2(OH)2 complex bridged by anthraquinone (2). In the chemical ORR using Fe(CpMe)2 as a reductant in acidic PhCN, we found that 1 showed the highest initial turnover frequency (TOFinit = 6.8 × 102 s-1) and selectivity for 4e--ORR (96%) in three complexes. The detailed kinetic analyses have revealed that the rate-determining steps (RDSs) in the catalytic cycles of 1-3 have the O2 addition to [CoII2(OH2)2]4+ as an intermediate in common. In the only case that complex 1 was used as a catalyst, kcat depended on proton concentration because the reaction rate of the O2 addition to [CoII2(OH2)2]4+ was so fast as compared to that of the concerted PCET process of 1. Through X-ray, Raman, and electrochemical analyses and stoichiometric reactions, we found the face-to-face structure of 1 characterized by a slightly flexible xanthene was advantageous in capturing O2 and stabilizing the Co2(μ-O2) structure, thus increasing both the reaction rate and selectivity for 4e--ORR.
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Affiliation(s)
- Hiroaki Arima
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
| | - Misato Wada
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
| | - Takashi Nakazono
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
| | - Tohru Wada
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
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47
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Mondal P, Ishigami I, Gérard EF, Lim C, Yeh SR, de Visser SP, Wijeratne GB. Proton-coupled electron transfer reactivities of electronically divergent heme superoxide intermediates: a kinetic, thermodynamic, and theoretical study. Chem Sci 2021; 12:8872-8883. [PMID: 34257888 PMCID: PMC8246096 DOI: 10.1039/d1sc01952j] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 05/26/2021] [Indexed: 01/11/2023] Open
Abstract
Heme superoxides are one of the most versatile metallo-intermediates in biology, and they mediate a vast variety of oxidation and oxygenation reactions involving O2(g). Overall proton-coupled electron transfer (PCET) processes they facilitate may proceed via several different mechanistic pathways, attributes of which are not yet fully understood. Herein we present a detailed investigation into concerted PCET events of a series of geometrically similar, but electronically disparate synthetic heme superoxide mimics, where unprecedented, PCET feasibility-determining electronic effects of the heme center have been identified. These electronic factors firmly modulate both thermodynamic and kinetic parameters that are central to PCET, as supported by our experimental and theoretical observations. Consistently, the most electron-deficient superoxide adduct shows the strongest driving force for PCET, whereas the most electron-rich system remains unreactive. The pivotal role of these findings in understanding significant heme systems in biology, as well as in alternative energy applications is also discussed.
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Affiliation(s)
- Pritam Mondal
- Department of Chemistry, University of Alabama at Birmingham Birmingham AL 35205 USA
| | - Izumi Ishigami
- Department of Physiology and Biophysics, Albert Einstein College of Medicine The Bronx New York 10461 USA
| | - Emilie F Gérard
- Manchester Institute of Biotechnology, Department of Chemical Engineering and Analytical Science, The University of Manchester 131 Princess Street Manchester M1 7DN UK
| | - Chaeeun Lim
- Department of Chemistry, University of Alabama at Birmingham Birmingham AL 35205 USA
| | - Syun-Ru Yeh
- Department of Physiology and Biophysics, Albert Einstein College of Medicine The Bronx New York 10461 USA
| | - Sam P de Visser
- Manchester Institute of Biotechnology, Department of Chemical Engineering and Analytical Science, The University of Manchester 131 Princess Street Manchester M1 7DN UK
| | - Gayan B Wijeratne
- Department of Chemistry, University of Alabama at Birmingham Birmingham AL 35205 USA
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48
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Wang VCC. Beyond the Active Site: Mechanistic Investigations of the Role of the Secondary Coordination Sphere and Beyond in Multi-electron Electrocatalytic Reactions. ACS Catal 2021. [DOI: 10.1021/acscatal.0c04770] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vincent C.-C. Wang
- Department of Chemistry, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan, Republic of China
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49
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Hooe SL, Cook EN, Reid AG, Machan CW. Non-covalent assembly of proton donors and p-benzoquinone anions for co-electrocatalytic reduction of dioxygen. Chem Sci 2021; 12:9733-9741. [PMID: 34349945 PMCID: PMC8293985 DOI: 10.1039/d1sc01271a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 06/16/2021] [Indexed: 01/01/2023] Open
Abstract
The two-electron and two-proton p-hydroquinone/p-benzoquinone (H2Q/BQ) redox couple has mechanistic parallels to the function of ubiquinone in the electron transport chain. This proton-dependent redox behavior has shown applicability in catalytic aerobic oxidation reactions, redox flow batteries, and co-electrocatalytic oxygen reduction. Under nominally aprotic conditions in non-aqueous solvents, BQ can be reduced by up to two electrons in separate electrochemically reversible reactions. With weak acids (AH) at high concentrations, potential inversion can occur due to favorable hydrogen-bonding interactions with the intermediate monoanion [BQ(AH)m]˙−. The solvation shell created by these interactions can mediate a second one-electron reduction coupled to proton transfer at more positive potentials ([BQ(AH)m]˙− + nAH + e− ⇌ [HQ(AH)(m+n)−1(A)]2−), resulting in an overall two electron reduction at a single potential at intermediate acid concentrations. Here we show that hydrogen-bonded adducts of reduced quinones and the proton donor 2,2,2-trifluoroethanol (TFEOH) can mediate the transfer of electrons to a Mn-based complex during the electrocatalytic reduction of dioxygen (O2). The Mn electrocatalyst is selective for H2O2 with only TFEOH and O2 present, however, with BQ present under sufficient concentrations of TFEOH, an electrogenerated [H2Q(AH)3(A)2]2− adduct (where AH = TFEOH) alters product selectivity to 96(±0.5)% H2O in a co-electrocatalytic fashion. These results suggest that hydrogen-bonded quinone anions can function in an analogous co-electrocatalytic manner to H2Q. Non-covalent interactions between reduced p-benzoquinone species and weak acids stabilize intermediates which can switch dioxygen reduction selectivity from H2O2 to H2O for a molecular Mn catalyst.![]()
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Affiliation(s)
- Shelby L Hooe
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Emma N Cook
- Department of Chemistry, University of Virginia PO Box 400319 Charlottesville VA 22904-4319 USA
| | - Amelia G Reid
- 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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50
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Ali A, Prakash D, Majumder P, Ghosh S, Dutta A. Flexible Ligand in a Molecular Cu Electrocatalyst Unfurls Bidirectional O 2/H 2O Conversion in Water. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01542] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Afsar Ali
- Chemistry Discipline, Indian Institute of Technology Gandhinagar, Palaj 382355, India
| | - Divyansh Prakash
- Chemistry Discipline, Indian Institute of Technology Gandhinagar, Palaj 382355, India
| | - Piyali Majumder
- Biological Engineering Discipline, Indian Institute of Technology Gandhinagar, Palaj 382355, India
| | - Soumya Ghosh
- Tata Institute of Fundamental Research (TIFR), Hyderabad, Telengana 500046, India
| | - Arnab Dutta
- Chemistry Discipline, Indian Institute of Technology Gandhinagar, Palaj 382355, India
- Chemistry Department, Indian Institute of Technology Bombay, Powai 400076, India
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