1
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Li M, Maisuradze M, Mullaliu A, Carlomagno I, Aquilanti G, Plaisier JR, Giorgetti M. Structural Evolution of Manganese Prussian Blue Analogue in Aqueous ZnSO 4 Electrolyte. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2404584. [PMID: 39105446 DOI: 10.1002/smll.202404584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Revised: 07/22/2024] [Indexed: 08/07/2024]
Abstract
Among different Prussian Blue Analogues (PBAs), manganese hexacyanoferrate (MnHCF), with open framework and two abundant electroactive metal sites, exhibits high potential for the grid-scale aqueous rechargeable zinc-ion batteries (ARZIBs) application. Until now, the intercalation mechanism of Zn2+ into MnHCF has not been clearly illustrated. In this work, combining different synchrotron X-ray techniques, the structural and microscopic evolution of MnHCF in 3 m ZnSO4 electrolyte is comprehensively studied, and a thorough understanding of the intercalation/release dynamic, in terms of local and long-range domain, is provided. The elemental distribution and structural information of Fe, Mn, Zn inside MnHCF electrodes is obtained from the X-ray fluorescence (XRF) elemental maps and X-ray absorption spectroscopy (XAS). The in-depth analysis of extended X-ray absorption fine structure (EXAFS) signals confirm that the rearrangement of Mn site, evidencing the cleavage of the Mn─N bond with the formation of a Mn─O bond, in an octahedral environment. The phase transformation of MnHCF takes place exclusively during the 1st cycle, and a mixture of rhombohedral and cubic zinc hexacynoferrate (ZnHCF) phases are formed during the first charge process. Thereafter, the newly formed cubic ZnHCF phase becomes the only stable one, existing in the subsequent cycles and exhibiting excellent electrochemical stability.
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Affiliation(s)
- Min Li
- Department of Industrial Chemistry, University of Bologna, Campus Navile, Via Piero Gobetti 85, Bologna, 40139, Italy
| | - Mariam Maisuradze
- Department of Industrial Chemistry, University of Bologna, Campus Navile, Via Piero Gobetti 85, Bologna, 40139, Italy
| | | | - Ilaria Carlomagno
- Elettra - Sincrotrone Trieste, s.s. 14, km 163.5, Trieste, 34149, Italy
| | | | | | - Marco Giorgetti
- Department of Industrial Chemistry, University of Bologna, Campus Navile, Via Piero Gobetti 85, Bologna, 40139, Italy
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2
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Azadmanesh J, Slobodnik K, Struble LR, Lutz WE, Coates L, Weiss KL, Myles DAA, Kroll T, Borgstahl GEO. Revealing the atomic and electronic mechanism of human manganese superoxide dismutase product inhibition. Nat Commun 2024; 15:5973. [PMID: 39013847 PMCID: PMC11252399 DOI: 10.1038/s41467-024-50260-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 07/05/2024] [Indexed: 07/18/2024] Open
Abstract
Human manganese superoxide dismutase (MnSOD) is a crucial oxidoreductase that maintains the vitality of mitochondria by converting superoxide (O2●-) to molecular oxygen (O2) and hydrogen peroxide (H2O2) with proton-coupled electron transfers (PCETs). Human MnSOD has evolved to be highly product inhibited to limit the formation of H2O2, a freely diffusible oxidant and signaling molecule. The product-inhibited complex is thought to be composed of a peroxide (O22-) or hydroperoxide (HO2-) species bound to Mn ion and formed from an unknown PCET mechanism. PCET mechanisms of proteins are typically not known due to difficulties in detecting the protonation states of specific residues that coincide with the electronic state of the redox center. To shed light on the mechanism, we combine neutron diffraction and X-ray absorption spectroscopy of the product-bound, trivalent, and divalent states of the enzyme to reveal the positions of all the atoms, including hydrogen, and the electronic configuration of the metal ion. The data identifies the product-inhibited complex, and a PCET mechanism of inhibition is constructed.
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Affiliation(s)
- Jahaun Azadmanesh
- Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE, 68198-6805, USA
| | - Katelyn Slobodnik
- Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE, 68198-6805, USA
| | - Lucas R Struble
- Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE, 68198-6805, USA
| | - William E Lutz
- Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE, 68198-6805, USA
| | - Leighton Coates
- Second Target Station, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN, 37831, USA
| | - Kevin L Weiss
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN, 37831, USA
| | - Dean A A Myles
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN, 37831, USA
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Gloria E O Borgstahl
- Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE, 68198-6805, USA.
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3
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Lee Y, Moon D, Cho J. Controlling Redox Potential of a Manganese(III)-Bis(hydroxo) Complex through Protonation and the Hydrogen-Atom Transfer Reactivity. J Am Chem Soc 2024; 146:15796-15805. [PMID: 38829358 DOI: 10.1021/jacs.4c01927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
A series of mononuclear manganese(III)-hydroxo and -aqua complexes, [MnIII(TBDAP)(OH)2]+ (1), [MnIII(TBDAP)(OH)(OH2)]2+ (2) and [MnIII(TBDAP)(OH2)2]3+ (3), were prepared from a manganese(II) precursor and confirmed using various methods including X-ray crystallography. Thermodynamic analysis showed that protonation from hydroxo to aqua species resulted in increased redox potentials (E1/2) in the order of 1 (-0.15 V) < 2 (0.56 V) < 3 (1.11 V), while pKa values exhibited a reverse trend in the order of 3 (3.87) < 2 (11.84). Employing the Bordwell Equation, the O-H bond dissociation free energies (BDFE) of [MnII(TBDAP)(OH)(OH2)]+ and [MnII(TBDAP)(OH2)2]2+, related to the driving force of 1 and 2 in hydrogen atom transfer (HAT), were determined as 75.3 and 77.3 kcal mol-1, respectively. It was found that the thermodynamic driving force of 2 in HAT becomes greater than that of 1 as the redox potential of 2 increases through protonation from 1 to 2. Kinetic studies on electrophilic reactions using a variety of substrates revealed that 1 is only weakly reactive with O-H bonds, whereas 2 can activate aliphatic C-H bonds in addition to O-H bonds. The reaction rates increased by 1.4 × 104-fold for the O-H bonds by 2 over 1, which was explained by the difference in BDFE and the tunneling effect. Furthermore, 3, possessing the highest redox potential value, was found to undergo an aromatic C-H bond activation reaction under mild conditions. These results provide valuable insights into enhancing electrophilic reactivity by modulating the redox potential of manganese(III)-hydroxo and -aqua complexes through protonation.
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Affiliation(s)
- Yuri Lee
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Dohyun Moon
- Beamline Department, Pohang Accelerator Laboratory, Pohang 37673, Republic of Korea
| | - Jaeheung Cho
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
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4
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Borgstahl G, Azadmanesh J, Slobodnik K, Struble L, Cone E, Dasgupta M, Lutz W, Kumar S, Natarajan A, Coates L, Weiss K, Myles D, Kroll T. The role of Tyr34 in proton-coupled electron transfer of human manganese superoxide dismutase. RESEARCH SQUARE 2024:rs.3.rs-4494128. [PMID: 38946943 PMCID: PMC11213228 DOI: 10.21203/rs.3.rs-4494128/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) plays a crucial role in controlling levels of reactive oxygen species (ROS) by converting superoxide (O2 ●-) to molecular oxygen (O2) and hydrogen peroxide (H2O2) with proton-coupled electron transfers (PCETs). The reactivity of human MnSOD is determined by the state of a key catalytic residue, Tyr34, that becomes post-translationally inactivated by nitration in various diseases associated with mitochondrial dysfunction. We previously reported that Tyr34 has an unusual pKa due to its proximity to the Mn metal and undergoes cyclic deprotonation and protonation events to promote the electron transfers of MnSOD. To shed light on the role of Tyr34 MnSOD catalysis, we performed neutron diffraction, X-ray spectroscopy, and quantum chemistry calculations of Tyr34Phe MnSOD in various enzymatic states. The data identifies the contributions of Tyr34 in MnSOD activity that support mitochondrial function and presents a thorough characterization of how a single tyrosine modulates PCET catalysis.
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5
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Yang S, Liu X, Li S, Yuan W, Yang L, Wang T, Zheng H, Cao R, Zhang W. The mechanism of water oxidation using transition metal-based heterogeneous electrocatalysts. Chem Soc Rev 2024; 53:5593-5625. [PMID: 38646825 DOI: 10.1039/d3cs01031g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The water oxidation reaction, a crucial process for solar energy conversion, has garnered significant research attention. Achieving efficient energy conversion requires the development of cost-effective and durable water oxidation catalysts. To design effective catalysts, it is essential to have a fundamental understanding of the reaction mechanisms. This review presents a comprehensive overview of recent advancements in the understanding of the mechanisms of water oxidation using transition metal-based heterogeneous electrocatalysts, including Mn, Fe, Co, Ni, and Cu-based catalysts. It highlights the catalytic mechanisms of different transition metals and emphasizes the importance of monitoring of key intermediates to explore the reaction pathway. In addition, advanced techniques for physical characterization of water oxidation intermediates are also introduced, for the purpose of providing information for establishing reliable methodologies in water oxidation research. The study of transition metal-based water oxidation electrocatalysts is instrumental in providing novel insights into understanding both natural and artificial energy conversion processes.
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Affiliation(s)
- Shujiao Yang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Xiaohan Liu
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Sisi Li
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Wenjie Yuan
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Luna Yang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Ting Wang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Haoquan Zheng
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Rui Cao
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
| | - Wei Zhang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
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6
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Azadmanesh J, Slobodnik K, Struble LR, Cone EA, Dasgupta M, Lutz WE, Kumar S, Natarajan A, Coates L, Weiss KL, Myles DAA, Kroll T, Borgstahl GEO. The role of Tyr34 in proton-coupled electron transfer of human manganese superoxide dismutase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596464. [PMID: 38853997 PMCID: PMC11160768 DOI: 10.1101/2024.05.29.596464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) plays a crucial role in controlling levels of reactive oxygen species (ROS) by converting superoxide (O 2 •- ) to molecular oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ) with proton-coupled electron transfers (PCETs). The reactivity of human MnSOD is determined by the state of a key catalytic residue, Tyr34, that becomes post-translationally inactivated by nitration in various diseases associated with mitochondrial dysfunction. We previously reported that Tyr34 has an unusual pK a due to its proximity to the Mn metal and undergoes cyclic deprotonation and protonation events to promote the electron transfers of MnSOD. To shed light on the role of Tyr34 MnSOD catalysis, we performed neutron diffraction, X-ray spectroscopy, and quantum chemistry calculations of Tyr34Phe MnSOD in various enzymatic states. The data identifies the contributions of Tyr34 in MnSOD activity that support mitochondrial function and presents a thorough characterization of how a single tyrosine modulates PCET catalysis.
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7
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Guo M, Braun A, Sokaras D, Kroll T. Iron Kβ X-ray Emission Spectroscopy: The Origin of Spectral Features from Atomic to Molecular Systems Using Multi-configurational Calculations. J Phys Chem A 2024; 128:1260-1273. [PMID: 38329897 DOI: 10.1021/acs.jpca.3c07949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Kβ X-ray emission spectroscopy (XES) is widely used to fingerprint the local spin of transition-metal ions, including in pump-probe experiments, to identify excited states or in chemical and biological reactions to characterize short-lived intermediates. In this study, the spectra of ferrous and ferric complexes for various spin states were measured experimentally and described theoretically through restricted active space (RAS) calculations including dynamic correlations. Through the RAS calculations from simple atomic models to complex molecular systems, spectral effects such as the exchange interactions, crystal-field strength, and covalent orbital mixing were evaluated and discussed. The calculations find that only the spectral features of low-spin cases show a dependence on the crystal-field strength, particularly for ferrous low spin. The effect of the covalent orbital mixing strength on the first moment of the Kβ1,3 main line and the Kβ1,3-Kβ' energy splitting is quantitatively described. Clear relationships are found within a given nominal spin but less between different spin states, which calls for careful selection of reference spectra in future experiments. This study further advances our understanding of the correlation between changes in experimental spectral features and their corresponding electronic structure information.
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Affiliation(s)
- Meiyuan Guo
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
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8
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Borgstahl G, Azadmanesh J, Slobodnik K, Struble L, Lutz W, Coates L, Weiss K, Myles D, Kroll T. Revealing the atomic and electronic mechanism of human manganese superoxide dismutase product inhibition. RESEARCH SQUARE 2024:rs.3.rs-3880128. [PMID: 38405788 PMCID: PMC10889052 DOI: 10.21203/rs.3.rs-3880128/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) is a crucial oxidoreductase that maintains the vitality of mitochondria by converting O 2 ∙ - to O 2 and H 2 O 2 with proton-coupled electron transfers (PCETs). Since changes in mitochondrial H 2 O 2 concentrations are capable of stimulating apoptotic signaling pathways, human MnSOD has evolutionarily gained the ability to be highly inhibited by its own product, H 2 O 2 . A separate set of PCETs is thought to regulate product inhibition, though mechanisms of PCETs are typically unknown due to difficulties in detecting the protonation states of specific residues that coincide with the electronic state of the redox center. To shed light on the underlying mechanism, we combined neutron diffraction and X-ray absorption spectroscopy of the product-bound, trivalent, and divalent states to reveal the all-atom structures and electronic configuration of the metal. The data identifies the product-inhibited complex for the first time and a PCET mechanism of inhibition is constructed.
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9
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Azadmanesh J, Slobodnik K, Struble LR, Lutz WE, Coates L, Weiss KL, Myles DAA, Kroll T, Borgstahl GEO. Revealing the atomic and electronic mechanism of human manganese superoxide dismutase product inhibition. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.26.577433. [PMID: 38328249 PMCID: PMC10849630 DOI: 10.1101/2024.01.26.577433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) is a crucial oxidoreductase that maintains the vitality of mitochondria by converting O 2 ●- to O 2 and H 2 O 2 with proton-coupled electron transfers (PCETs). Since changes in mitochondrial H 2 O 2 concentrations are capable of stimulating apoptotic signaling pathways, human MnSOD has evolutionarily gained the ability to be highly inhibited by its own product, H 2 O 2 . A separate set of PCETs is thought to regulate product inhibition, though mechanisms of PCETs are typically unknown due to difficulties in detecting the protonation states of specific residues that coincide with the electronic state of the redox center. To shed light on the underlying mechanism, we combined neutron diffraction and X-ray absorption spectroscopy of the product-bound, trivalent, and divalent states to reveal the all-atom structures and electronic configuration of the metal. The data identifies the product-inhibited complex for the first time and a PCET mechanism of inhibition is constructed.
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10
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Chrysina M, Drosou M, Castillo RG, Reus M, Neese F, Krewald V, Pantazis DA, DeBeer S. Nature of S-States in the Oxygen-Evolving Complex Resolved by High-Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy. J Am Chem Soc 2023; 145:25579-25594. [PMID: 37970825 PMCID: PMC10690802 DOI: 10.1021/jacs.3c06046] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 10/13/2023] [Accepted: 10/13/2023] [Indexed: 11/19/2023]
Abstract
Photosystem II, the water splitting enzyme of photosynthesis, utilizes the energy of sunlight to drive the four-electron oxidation of water to dioxygen at the oxygen-evolving complex (OEC). The OEC harbors a Mn4CaO5 cluster that cycles through five oxidation states Si (i = 0-4). The S3 state is the last metastable state before the O2 evolution. Its electronic structure and nature of the S2 → S3 transition are key topics of persisting controversy. Most spectroscopic studies suggest that the S3 state consists of four Mn(IV) ions, compared to the Mn(III)Mn(IV)3 of the S2 state. However, recent crystallographic data have received conflicting interpretations, suggesting either metal- or ligand-based oxidation, the latter leading to an oxyl radical or a peroxo moiety in the S3 state. Herein, we utilize high-energy resolution fluorescence detected (HERFD) X-ray absorption spectroscopy to obtain a highly resolved description of the Mn K pre-edge region for all S-states, paying special attention to use chemically unperturbed S3 state samples. In combination with quantum chemical calculations, we achieve assignment of specific spectroscopic features to geometric and electronic structures for all S-states. These data are used to confidently discriminate between the various suggestions concerning the electronic structure and the nature of oxidation events in all observable catalytic intermediates of the OEC. Our results do not support the presence of either peroxo or oxyl in the active configuration of the S3 state. This establishes Mn-centered storage of oxidative equivalents in all observable catalytic transitions and constrains the onset of the O-O bond formation until after the final light-driven oxidation event.
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Affiliation(s)
- Maria Chrysina
- Max-Planck-Institut
für Chemische Energiekonversion, Stiftstr. 34-36, Mülheim
an der Ruhr 45470, Germany
- Institute
of Nanoscience & Nanotechnology, NCSR “Demokritos”, Athens 15310, Greece
| | - Maria Drosou
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an der Ruhr 45470, Germany
| | - Rebeca G. Castillo
- Max-Planck-Institut
für Chemische Energiekonversion, Stiftstr. 34-36, Mülheim
an der Ruhr 45470, Germany
- Laboratory
of Ultrafast Spectroscopy (LSU) and Lausanne Centre for Ultrafast
Science, École Polytechnique Fédérale
de Lausanne (EPFL), Lausanne CH-1015, Switzerland
| | - Michael Reus
- Max-Planck-Institut
für Chemische Energiekonversion, Stiftstr. 34-36, Mülheim
an der Ruhr 45470, Germany
| | - Frank Neese
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an der Ruhr 45470, Germany
| | - Vera Krewald
- Department
of Chemistry, Technical University of Darmstadt, Peter-Grünberg-Str. 4, Darmstadt 64287, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an der Ruhr 45470, Germany
| | - Serena DeBeer
- Max-Planck-Institut
für Chemische Energiekonversion, Stiftstr. 34-36, Mülheim
an der Ruhr 45470, Germany
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11
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Singh P, Lee Y, Mayfield JR, Singh R, Denler MC, Jones SD, Day VW, Nordlander E, Jackson TA. Enhanced Understanding of Structure-Function Relationships for Oxomanganese(IV) Complexes. Inorg Chem 2023; 62:18357-18374. [PMID: 37314463 DOI: 10.1021/acs.inorgchem.3c00600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A series of manganese(II) and oxomanganese(IV) complexes supported by neutral, pentadentate ligands with varied equatorial ligand-field strength (N3pyQ, N2py2I, and N4pyMe2) were synthesized and then characterized using structural and spectroscopic methods. On the basis of electronic absorption spectroscopy, the [MnIV(O)(N4pyMe2)]2+ complex has the weakest equatorial ligand field among a set of similar MnIV-oxo species. In contrast, [MnIV(O)(N2py2I)]2+ shows the strongest equatorial ligand-field strength for this same series. We examined the influence of these changes in electronic structure on the reactivity of the oxomanganese(IV) complexes using hydrocarbons and thioanisole as substrates. The [MnIV(O)(N3pyQ)]2+ complex, which contains one quinoline and three pyridine donors in the equatorial plane, ranks among the fastest MnIV-oxo complexes in C-H bond and thioanisole oxidation. While a weak equatorial ligand field has been associated with high reactivity, the [MnIV(O)(N4pyMe2)]2+ complex is only a modest oxidant. Buried volume plots suggest that steric factors dampen the reactivity of this complex. Trends in reactivity were examined using density functional theory (DFT)-computed bond dissociation free energies (BDFEs) of the MnIIIO-H and MnIV ═ O bonds. We observe an excellent correlation between MnIV═O BDFEs and rates of thioanisole oxidation, but more scatter is observed between hydrocarbon oxidation rates and the MnIIIO-H BDFEs.
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Affiliation(s)
- Priya Singh
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Yuri Lee
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Jaycee R Mayfield
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Reena Singh
- Lund University, Chemical Physics, Department of Chemistry, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Melissa C Denler
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Shannon D Jones
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Victor W Day
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Ebbe Nordlander
- Lund University, Chemical Physics, Department of Chemistry, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Timothy A Jackson
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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12
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Brunclik SA, Opalade AA, Jackson TA. Electronic structure contributions to O-O bond cleavage reactions for Mn III-alkylperoxo complexes. Dalton Trans 2023; 52:13878-13894. [PMID: 37526920 DOI: 10.1039/d3dt01672b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Synthetic manganese catalysts that activate hydrogen peroxide perform a variety of hydrocarbon oxidation reactions. The most commonly proposed mechanism for these catalysts involves the generation of a manganese(III)-hydroperoxo intermediate that decays via heterolytic O-O bond cleavage to generate a Mn(V)-oxo species that initiates substrate oxidation. Due to the paucity of well-defined MnIII-hydroperoxo complexes, MnIII-alkylperoxo complexes are often employed to understand the factors that affect the O-O cleavage reaction. Herein, we examine the decay pathways of the MnIII-alkylperoxo complexes [MnIII(OOtBu)(6Medpaq)]+ and [MnIII(OOtBu)(N4S)]+, which have distinct coordination environments (N5- and N4S-, respectively). Through the use of density functional theory (DFT) calculations and comparisons with published experimental data, we are able to rationalize the differences in the decay pathways of these complexes. For the [MnIII(OOtBu)(N4S)]+ system, O-O homolysis proceeds via a two-state mechanism that involves a crossing from the quintet reactant to a triplet state. A high energy singlet state discourages O-O heterolysis for this complex. In contrast, while quintet-triplet crossing is unfavorable for [MnIII(OOtBu)(6Medpaq)]+, a relatively low-energy single state accounts for the observation of both O-O homolysis and heterolysis products for this complex. The origins of these differences in decay pathways are linked to variations in the electronic structures of the MnIII-alkylperoxo complexes.
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Affiliation(s)
- Samuel A Brunclik
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, KS 66045, USA.
| | - Adedamola A Opalade
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, KS 66045, USA.
| | - Timothy A Jackson
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, KS 66045, USA.
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Fehse M, Etxebarria N, Otaegui L, Cabello M, Martín-Fuentes S, Cabañero MA, Monterrubio I, Elkjær CF, Fabelo O, Enkubari NA, López del Amo JM, Casas-Cabanas M, Reynaud M. Influence of Transition-Metal Order on the Reaction Mechanism of LNMO Cathode Spinel: An Operando X-ray Absorption Spectroscopy Study. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2022; 34:6529-6540. [PMID: 35910538 PMCID: PMC9332344 DOI: 10.1021/acs.chemmater.2c01360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
An operando dual-edge X-ray absorption spectroscopy on both transition-metal ordered and disordered LiNi0.5Mn1.5O4 during electrochemical delithiation and lithiation was carried out. The large data set was analyzed via a chemometric approach to gain reliable insights into the redox activity and the local structural changes of Ni and Mn throughout the electrochemical charge and discharge reaction. Our findings confirm that redox activity relies predominantly on the Ni2+/4+ redox couple involving a transient Ni3+ phase. Interestingly, a reversible minority contribution of Mn3+/4+ is also evinced in both LNMO materials. While the reaction steps and involved reactants of both ordered and disordered LNMO materials generally coincide, we highlight differences in terms of reaction dynamics as well as in local structural evolution induced by the TM ordering.
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Affiliation(s)
- Marcus Fehse
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Naiara Etxebarria
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Laida Otaegui
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Marta Cabello
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Silvia Martín-Fuentes
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Maria Angeles Cabañero
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Iciar Monterrubio
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
- Inorganic
Chemistry Department, Science and Technology Faculty, Basque Country University (UPV/EHU), 48940 Leioa, Bilbao, Spain
| | | | - Oscar Fabelo
- Institut
Laue Langevin, 38042 Cedex Grenoble, France
| | - Nahom Asres Enkubari
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Juan Miguel López del Amo
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
| | - Montse Casas-Cabanas
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
- Ikerbasque
- Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Marine Reynaud
- Center
for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein
48, 01510 Vitoria-Gasteiz, Spain
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14
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Yang J, Dong HT, Seo MS, Larson VA, Lee YM, Shearer J, Lehnert N, Nam W. The Oxo-Wall Remains Intact: A Tetrahedrally Distorted Co(IV)-Oxo Complex. J Am Chem Soc 2021; 143:16943-16959. [PMID: 34609879 DOI: 10.1021/jacs.1c04919] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this paper, we report the preparation, spectroscopic and theoretical characterization, and reactivity studies of a Co(IV)-oxo complex bearing an N4-macrocyclic coligand, 12-TBC (12-TBC = 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane). On the basis of the ligand and the structure of the Co(II) precursor, [CoII(12-TBC)(CF3SO3)2], one would assume that this species corresponds to a tetragonal Co(IV)-oxo complex, but the spectroscopic data do not support this notion. Co K-edge XAS data show that the treatment of the Co(II) precursor with iodosylbenzene (PhIO) as an oxidant at -40 °C in the presence of a proton source leads to a distinct shift in the Co K-edge, in agreement with the formation of a Co(IV) intermediate. The presence of the oxo group is further demonstrated by resonance Raman (rRaman) spectroscopy. Interestingly, the EPR data of this complex show a high degree of rhombicity, indicating structural distortion. This is further supported by the EXAFS data. Using DFT calculations, a structural model is developed for this complex with a ligand-protonated structure that features a Co═O···HN hydrogen bond and a four-coordinate Co center in a seesaw-shaped coordination geometry. Magnetic circular dichroism (MCD) spectroscopy further supports this finding. The hydrogen bond leads to an interesting polarization of the Co-oxo π-bonds, where one O(p) lone-pair is stabilized and leads to a regular Co(d) interaction, whereas the other π-bond shows an inverted ligand field. The reactivity of this complex in hydrogen atom and oxygen atom transfer reactions is discussed as well.
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Affiliation(s)
- Jindou Yang
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Mi Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Virginia A Larson
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Jason Shearer
- Department of Chemistry, Trinity University, San Antonio, Texas 78212-7200, United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, China
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15
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Shi W, Quan Y, Lan G, Ni K, Song Y, Jiang X, Wang C, Lin W. Bifunctional Metal-Organic Layers for Tandem Catalytic Transformations Using Molecular Oxygen and Carbon Dioxide. J Am Chem Soc 2021; 143:16718-16724. [PMID: 34592814 DOI: 10.1021/jacs.1c07963] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Tandem catalytic reactions improve atom- and step-economy over traditional synthesis but are limited by the incompatibility of the required catalysts. Herein, we report the design of bifunctional metal-organic layers (MOLs), HfOTf-Fe and HfOTf-Mn, consisting of triflate (OTf)-capped Hf6 secondary building units (SBUs) as strong Lewis acidic centers and metalated TPY ligands as metal active sites for tandem catalytic transformations using O2 and CO2 as coreactants. HfOTf-Fe effectively transforms hydrocarbons into cyanohydrins via tandem oxidation with O2 and silylcyanation whereas HfOTf-Mn converts styrenes into styrene carbonates via tandem epoxidation and CO2 insertion. Density functional theory calculations revealed the involvement of a high-spin FeIV (S = 2) center in the challenging oxidation of the sp3 C-H bond. This work highlights the potential of MOLs as a tunable platform to incorporate multiple catalysts for tandem transformations.
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Affiliation(s)
- Wenjie Shi
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,College of Chemistry and Chemical Engineering, iCHEM, State Key Laboratory of Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005, People's Republic of China
| | - Yangjian Quan
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Guangxu Lan
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Kaiyuan Ni
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Yang Song
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Xiaomin Jiang
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Cheng Wang
- College of Chemistry and Chemical Engineering, iCHEM, State Key Laboratory of Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005, People's Republic of China
| | - Wenbin Lin
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
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16
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Sagar S, Parween A, Mandal TK, Lewis W, Naskar S. Mn(IV), Co(II) and Ni(II) complexes of the Schiff bases of 2-hydroxy-naphthaldehyde with amino alcohols: synthesis, characterization and electrochemical study; DFT study and Catecholase activity of Mn(IV) complex. J COORD CHEM 2020. [DOI: 10.1080/00958972.2020.1832657] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Shipra Sagar
- Department of Chemistry, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, India
| | - Arfa Parween
- Department of Chemistry, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, India
| | - Tarun K. Mandal
- Faculty Councils for PG studies, Vidyasagar University, Medinipur, West Bengal, India
| | - William Lewis
- School of Chemistry, University of Nottingham, Nottingham, UK
| | - Subhendu Naskar
- Department of Chemistry, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, India
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17
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Mayfield JR, Grotemeyer EN, Jackson TA. Concerted proton-electron transfer reactions of manganese-hydroxo and manganese-oxo complexes. Chem Commun (Camb) 2020; 56:9238-9255. [PMID: 32578605 PMCID: PMC7429365 DOI: 10.1039/d0cc01201g] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The enzymes manganese superoxide dismutase and manganese lipoxygenase use MnIII-hydroxo centres to mediate proton-coupled electron transfer (PCET) reactions with substrate. As manganese is earth-abundant and inexpensive, manganese catalysts are of interest for synthetic applications. Recent years have seen exciting reports of enantioselective C-H bond oxidation by Mn catalysts supported by aminopyridyl ligands. Such catalysts offer economic and environmentally-friendly alternatives to conventional reagents and catalysts. Mechanistic studies of synthetic catalysts highlight the role of Mn-oxo motifs in attacking substrate C-H bonds, presumably by a concerted proton-electron transfer (CPET) step. (CPET is a sub-class of PCET, where the proton and electron are transferred in the same step.) Knowledge of geometric and electronic influences for CPET reactions of Mn-hydroxo and Mn-oxo adducts enhances our understanding of biological and synthetic manganese centers and informs the design of new catalysts. In this Feature article, we describe kinetic, spectroscopic, and computational studies of MnIII-hydroxo and MnIV-oxo complexes that provide insight into the basis for the CPET reactivity of these species. Systematic perturbations of the ligand environment around MnIII-hydroxo and MnIV-oxo motifs permit elucidation of structure-activity relationships. For MnIII-hydroxo centers, electron-deficient ligands enhance oxidative reactivity. However, ligand perturbations have competing consequences, as changes in the MnIII/II potential, which represents the electron-transfer component for CPET, is offset by compensating changes in the pKa of the MnII-aqua product, which represents the proton-transfer component for CPET. For MnIV-oxo systems, a multi-state reactivity model inspired the development of significantly more reactive complexes. Weakened equatorial donation to the MnIV-oxo unit results in large rate enhancements for C-H bond oxidation and oxygen-atom transfer reactions. These results demonstrate that the local coordination environment can be rationally changed to enhance reactivity of MnIII-hydroxo and MnIV-oxo adducts.
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Affiliation(s)
- Jaycee R Mayfield
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, KS 66045, USA.
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18
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Larson VA, Battistella B, Ray K, Lehnert N, Nam W. Iron and manganese oxo complexes, oxo wall and beyond. Nat Rev Chem 2020; 4:404-419. [PMID: 37127969 DOI: 10.1038/s41570-020-0197-9] [Citation(s) in RCA: 139] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2020] [Indexed: 11/09/2022]
Abstract
High-valent metal-oxo species with multiply-bonded M-O groups have been proposed as key intermediates in many biological and abiological catalytic oxidation reactions. These intermediates are implicated as active oxidants in alkane hydroxylation, olefin epoxidation and other oxidation reactions. For example, [FeivO(porphyrinato•-)]+ cofactors bearing π-radical porphyrinato•- ligands oxidize organic substrates in cytochrome P450 enzymes, which are common to many life forms. Likewise, high-valent Mn-oxo species are active for H2O oxidation in photosystem II. The chemistry of these native reactive species has inspired chemists to prepare highly oxidized transition-metal complexes as functional mimics. Although many synthetic Fe-O and Mn-O complexes now exist, the analogous oxo complexes of the late transition metals (groups 9-11) are rare. Indeed, late-transition-metal-oxo complexes of tetragonal (fourfold) symmetry should be electronically unstable, a rule commonly referred to as the 'oxo wall'. A few late metal-oxos have been prepared by targeting other symmetries or unusual spin states. These complexes have been studied using spectroscopic and theoretical methods. This Review describes mononuclear non-haem Fe-O and Mn-O species, the nature of the oxo wall and recent advances in the preparation of oxo complexes of Co, Ni and Cu beyond the oxo wall.
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19
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Vibbert HB, Filatov AS, Hopkins MD. Synthesis, Structure, and Bonding of d
3
Molybdenum–Oxo Complexes. Angew Chem Int Ed Engl 2020; 59:10581-10586. [DOI: 10.1002/anie.202001379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/09/2020] [Indexed: 11/05/2022]
Affiliation(s)
- Hunter B. Vibbert
- Department of Chemistry The University of Chicago Chicago IL 60637 USA
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20
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Vibbert HB, Filatov AS, Hopkins MD. Synthesis, Structure, and Bonding of d
3
Molybdenum–Oxo Complexes. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202001379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Hunter B. Vibbert
- Department of Chemistry The University of Chicago Chicago IL 60637 USA
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21
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Mondal S, Sahu K, Patra B, Jena S, Biswal HS, Kar S. A new synthesis of porphyrins via a putative trans-manganese(iv)-dihydroxide intermediate. Dalton Trans 2020; 49:1424-1432. [PMID: 31915769 DOI: 10.1039/c9dt03573g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new method for the synthesis of meso-substituted porphyrins was developed. In this two-step methodology, the first step involves the condensation of pyrroles/dipyrromethanes with aldehydes in a water-methanol mixture under acidic conditions. The second step involves manganese induced cyclization followed by oxidation via PhIO/O2. This methodology has been useful for the synthesis of a wide range of trans-A2B2 porphyrins and also symmetric porphyrins in moderate to good yields. A detailed investigation of the manganese induced cyclization reaction has allowed us to characterize a Mn-porphyrinogen complex. A series of analytical and spectroscopic techniques and DFT calculations have led us to the conclusion that the putative intermediate species are trans-manganese(iv)-dihydroxide complexes. EPR and magnetic susceptibility measurements helped us to assign the oxidation state of the manganese complexes in their native state. The assumption of trans-manganese(iv)-dihydroxide as the true intermediate for this porphyrin synthesis has been authenticated via in situ UV-Vis experiments. This new methodology is certainly different from other previously reported methodologies in many aspects and most importantly these reactions can be easily performed on a gram scale for the synthesis of porphyrins.
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Affiliation(s)
- Sruti Mondal
- School of Chemical Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, 752050, India.
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22
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Massie AA, Denler MC, Singh R, Sinha A, Nordlander E, Jackson TA. Structural Characterization of a Series of N5-Ligated Mn IV -Oxo Species. Chemistry 2020; 26:900-912. [PMID: 31693757 PMCID: PMC7388070 DOI: 10.1002/chem.201904434] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 10/23/2019] [Indexed: 11/05/2022]
Abstract
Analysis of extended X-ray absorption fine structure (EXAFS) data for the MnIV -oxo complexes [MnIV (O)(DMM N4py)]2+ , [MnIV (O)(2pyN2B)]2+ , and [MnIV (O)(2pyN2Q)]2+ (DMM N4py=N,N-bis(4-methoxy-3,5-dimethyl-2-pyridylmethyl)-N-bis(2-pyridyl)methylamine; 2pyN2B=(N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine, and 2pyN2Q=N,N-bis(2-pyridyl)-N,N-bis(2-quinolylmethyl)methanamine) afforded Mn=O and Mn-N bond lengths. The Mn=O distances for [MnIV (O)(DMM N4py)]2+ and [MnIV (O)(2pyN2B)]2+ are 1.72 and 1.70 Å, respectively. In contrast, the Mn=O distance for [MnIV (O)(2pyN2Q)]2+ was significantly longer (1.76 Å). We attribute this long distance to sample heterogeneity, which is reasonable given the reduced stability of [MnIV (O)(2pyN2Q)]2+ . The Mn=O distances for [MnIV (O)(DMM N4py)]2+ and [MnIV (O)(2pyN2B)]2+ could only be well-reproduced using DFT-derived models that included strong hydrogen-bonds between second-sphere solvent 2,2,2-trifluoroethanol molecules and the oxo ligand. These results suggest an important role for the 2,2,2-trifluoroethanol solvent in stabilizing MnIV -oxo adducts. The DFT methods were extended to investigate the structure of the putative [MnIV (O)(N4py)]2+ ⋅(HOTf)2 adduct. These computations suggest that a MnIV -hydroxo species is most consistent with the available experimental data.
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Affiliation(s)
- Allyssa A. Massie
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, KS 66045, USA
| | - Melissa C. Denler
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, KS 66045, USA
| | - Reena Singh
- Lund University, Chemical Physics, Department of Chemistry, Box 124, SE-221 00 Lund, Sweden
| | - Arup Sinha
- Lund University, Chemical Physics, Department of Chemistry, Box 124, SE-221 00 Lund, Sweden
- Department of Chemistry, School of Advanced Science, Vellore Institute of Technology, Vellore - 632014 Tamil Nadu, India
| | - Ebbe Nordlander
- Lund University, Chemical Physics, Department of Chemistry, Box 124, SE-221 00 Lund, Sweden
| | - Timothy A. Jackson
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, KS 66045, USA
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Cao R, Thomas KE, Ghosh A, Sarangi R. X-ray absorption spectroscopy of archetypal chromium porphyrin and corrole derivatives. RSC Adv 2020; 10:20572-20578. [PMID: 35517776 PMCID: PMC9054285 DOI: 10.1039/d0ra02335c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 05/13/2020] [Indexed: 01/16/2023] Open
Abstract
A Cr K-edge XAS study of paradigmatic chromium porphyrin and corrole derivatives has been carried out, providing key data for the Cr(iv) and Cr(v) oxidation states.
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Affiliation(s)
- Rui Cao
- Stanford Synchrotron Radiation Lightsource
- SLAC National Accelerator Laboratory
- Stanford University
- Menlo Park
- USA
| | - Kolle E. Thomas
- Department of Chemistry
- UiT – the Arctic University of Norway
- N-9037 Tromsø
- Norway
| | - Abhik Ghosh
- Department of Chemistry
- UiT – the Arctic University of Norway
- N-9037 Tromsø
- Norway
| | - Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource
- SLAC National Accelerator Laboratory
- Stanford University
- Menlo Park
- USA
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24
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Grass A, Wannipurage D, Lord RL, Groysman S. Group-transfer chemistry at transition metal centers in bulky alkoxide ligand environments. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.213044] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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25
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Sun W, Tang X, Yang Q, Xu Y, Wu F, Guo S, Zhang Y, Wu M, Wang Y. Coordination-Induced Interlinked Covalent- and Metal-Organic-Framework Hybrids for Enhanced Lithium Storage. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1903176. [PMID: 31379103 DOI: 10.1002/adma.201903176] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 07/06/2019] [Indexed: 06/10/2023]
Abstract
Covalent organic frameworks (COF) or metal-organic frameworks have attracted significant attention for various applications due to their intriguing tunable micro/mesopores and composition/functionality control. Herein, a coordination-induced interlinked hybrid of imine-based covalent organic frameworks and Mn-based metal-organic frameworks (COF/Mn-MOF) based on the MnN bond is reported. The effective molecular-level coordination-induced compositing of COF and MOF endows the hybrid with unique flower-like microsphere morphology and superior lithium-storage performances that originate from activated Mn centers and the aromatic benzene ring. In addition, hollow or core-shell MnS trapped in N and S codoped carbon (MnS@NS-C-g and MnS@NS-C-l) are also derived from the COF/Mn-MOF hybrid and they exhibit good lithium-storage properties. The design strategy of COF-MOF hybrid can shed light on the promising hybridization on porous organic framework composites with molecular-level structural adjustment, nano/microsized morphology design, and property optimization.
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Affiliation(s)
- Weiwei Sun
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Xuxu Tang
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Qinsi Yang
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Yi Xu
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Fan Wu
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Siyu Guo
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Yanfeng Zhang
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Minghong Wu
- Shanghai Applied Radiation Institute, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
| | - Yong Wang
- School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai, 200444, P. R. China
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26
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Krewald V, Neese F, Pantazis DA. Implications of structural heterogeneity for the electronic structure of the final oxygen-evolving intermediate in photosystem II. J Inorg Biochem 2019; 199:110797. [PMID: 31404888 DOI: 10.1016/j.jinorgbio.2019.110797] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 07/18/2019] [Accepted: 08/01/2019] [Indexed: 10/26/2022]
Abstract
Heterogeneity in intermediate catalytic states of the oxygen-evolving complex (OEC) of Photosystem II is known from a wide range of experimental and theoretical data, but its potential implications for the mechanism of water oxidation remain unexplored. We delineate the consequences of structural heterogeneity for the final step of the catalytic cycle by tracing the evolution of three spectroscopically relevant and structurally distinct components of the last metastable S3 state to the transient O2-evolving S4 state of the OEC. Using quantum chemical calculations, we show that each S3 isomer leads to a different electronic structure formulation for the active S4 state. Crucially, in addition to previously hypothesized Mn(IV)-oxyl species, we establish for the first time, how a genuine Mn(V)-oxo can be obtained in the catalytically active S4 state: this takes the form of a five-coordinate and locally high-spin (SMn = 1) Mn(V) site. This formulation for the S4 state evolves naturally from a preceding S3-state structural intermediate that contains a quasi-trigonal-bipyramidal Mn(IV) ion. The results strongly suggest that water binding in the S3 state is not prerequisite for reaching the oxygen-evolving S4 state of the complex, supporting the notion that both substrates are preloaded at the beginning of the catalytic cycle. This scenario allows true four-electron metal-centered hole accumulation to precede OO bond formation and hence the latter can proceed via a genuine even-electron mechanism. This can occur as intramolecular nucleophilic coupling of two oxo units synchronously with the binding of a water substrate for the next catalytic cycle.
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Affiliation(s)
- Vera Krewald
- Theoretische Chemie, Fachbereich Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 4, 64287 Darmstadt, Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
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Zhang B, Zhang J, Shi J, Tan D, Liu L, Zhang F, Lu C, Su Z, Tan X, Cheng X, Han B, Zheng L, Zhang J. Manganese acting as a high-performance heterogeneous electrocatalyst in carbon dioxide reduction. Nat Commun 2019; 10:2980. [PMID: 31278257 PMCID: PMC6611886 DOI: 10.1038/s41467-019-10854-1] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 05/17/2019] [Indexed: 12/24/2022] Open
Abstract
Developing highly efficient electrocatalysts based on cheap and earth-abundant metals for CO2 reduction is of great importance. Here we demonstrate that the electrocatalytic activity of manganese-based heterogeneous catalyst can be significantly improved through halogen and nitrogen dual-coordination to modulate the electronic structure of manganese atom. Such an electrocatalyst for CO2 reduction exhibits a maximum CO faradaic efficiency of 97% and high current density of ~10 mA cm−2 at a low overpotential of 0.49 V. Moreover, the turnover frequency can reach 38347 h−1 at overpotential of 0.49 V, which is the highest among the reported heterogeneous electrocatalysts for CO2 reduction. In situ X-ray absorption experiment and density-functional theory calculation reveal the modified electronic structure of the active manganese site, on which the free energy barrier for intermediate formation is greatly reduced, thus resulting in a great improvement of CO2 reduction performance. While renewable CO2 conversion provides a means to remove and recycle waste emissions, there are few earth-abundant materials that are both efficient and active. Here, authors prepare N-doped carbon with atomic manganese as high-performance CO2 reduction electrocatalyst.
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Affiliation(s)
- Bingxing Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Jianling Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. .,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
| | - Jinbiao Shi
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Dongxing Tan
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Lifei Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Fanyu Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Cheng Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Zhuizhui Su
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Xiuniang Tan
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Xiuyan Cheng
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Buxing Han
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Lirong Zheng
- Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Jing Zhang
- Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, P. R. China
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Oswald VF, Weitz AC, Biswas S, Ziller JW, Hendrich MP, Borovik AS. Manganese-Hydroxido Complexes Supported by a Urea/Phosphinic Amide Tripodal Ligand. Inorg Chem 2018; 57:13341-13350. [PMID: 30299920 DOI: 10.1021/acs.inorgchem.8b01886] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrogen bonds (H-bonds) within the secondary coordination sphere are often invoked as essential noncovalent interactions that lead to productive chemistry in metalloproteins. Incorporating these types of effects within synthetic systems has proven a challenge in molecular design that often requires the use of rigid organic scaffolds to support H-bond donors or acceptors. We describe the preparation and characterization of a new hybrid tripodal ligand ([H2pout]3-) that contains two monodeprotonated urea groups and one phosphinic amide. The urea groups serve as H-bond donors, while the phosphinic amide group serves as a single H-bond acceptor. The [H2pout]3- ligand was utilized to stabilize a series of Mn-hydroxido complexes in which the oxidation state of the metal center ranges from 2+ to 4+. The molecular structure of the MnIII-OH complex demonstrates that three intramolecular H-bonds involving the hydroxido ligand are formed. Additional evidence for the formation of intramolecular H-bonds was provided by vibrational spectroscopy in which the energy of the O-H vibration supports its assignment as an H-bond donor. The stepwise oxidation of [MnIIH2pout(OH)]2- to its higher oxidized analogs was further substantiated by electrochemical measurements and results from electronic absorbance and electron paramagnetic resonance spectroscopies. Our findings illustrate the utility of controlling both the primary and secondary coordination spheres to achieve structurally similar Mn-OH complexes with varying oxidation states.
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Affiliation(s)
- Victoria F Oswald
- Department of Chemistry , University of California-Irvine , 1102 Natural Sciences II , Irvine , California 92697 , United States
| | - Andrew C Weitz
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Saborni Biswas
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Joseph W Ziller
- Department of Chemistry , University of California-Irvine , 1102 Natural Sciences II , Irvine , California 92697 , United States
| | - Michael P Hendrich
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - A S Borovik
- Department of Chemistry , University of California-Irvine , 1102 Natural Sciences II , Irvine , California 92697 , United States
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29
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Denler MC, Wijeratne GB, Rice DB, Colmer HE, Day VW, Jackson TA. Mn III-Peroxo adduct supported by a new tetradentate ligand shows acid-sensitive aldehyde deformylation reactivity. Dalton Trans 2018; 47:13442-13458. [PMID: 30183042 PMCID: PMC6176719 DOI: 10.1039/c8dt02300j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The new tetradentate L7BQ ligand (L7BQ = 1,4-di(quinoline-8-yl)-1,4-diazepane) has been synthesized and shown to support MnII and MnIII-peroxo complexes. X-ray crystallography of the [MnII(L7BQ)(OTf)2] complex shows a monomeric MnII center with the L7BQ ligand providing four donor nitrogen atoms in the equatorial field, with two triflate ions bound in the axial positions. When this species is treated with H2O2 and Et3N at -40 °C, a MnIII-peroxo adduct, [MnIII(O2)(L7BQ)]+ is formed. The formation of this new intermediate is supported by a variety of spectroscopic techniques, including electronic absorption, Mn K-edge X-ray absorption and electron paramagnetic resonance methods. Evaluation of extended X-ray absorption fine structure data for [MnIII(O2)(L7BQ)]+ resolved Mn-O bond distances of 1.85 Å, which are on the short end of those previously reported for crystallographically characterized MnIII-peroxo adducts. An analysis of the X-ray pre-edge region of [MnIII(O2)(L7BQ)]+ revealed a large pre-edge area of 20.8 units. Time-dependent density functional theory computations indicate that the pre-edge intensity is due to Mn 4p-3d mixing caused by geometric distortions from centrosymmetry induced by both the peroxo and L7BQ ligands. The reactivity of [MnIII(O2)(L7BQ)]+ towards aldehydes was assessed through reaction with cyclohexanecarboxaldehyde and 2-phenylpropionaldehyde. From these experiments, it was determined that [MnIII(O2)(L7BQ)]+ only reacts with aldehydes in the presence of acid. Specifically, the addition of cyclohexanecarboxylic acid to [MnIII(O2)(L7BQ)]+ converts the MnIII-peroxo adduct to a new intermediate that could be responsible for the observed aldehyde deformylation activity. These observations underscore the challenges in identifying the reactive metal species in aldehyde deformylation reactions.
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Affiliation(s)
- Melissa C Denler
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
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30
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Jeong D, Yan JJ, Noh H, Hedman B, Hodgson KO, Solomon EI, Cho J. Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201802641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Donghyun Jeong
- Department of Emerging Materials Science DGIST Daegu 42988 Korea
| | - James J. Yan
- Department of Chemistry Stanford University Stanford CA 94305 USA
| | - Hyeonju Noh
- Department of Emerging Materials Science DGIST Daegu 42988 Korea
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Menlo Park CA 94025 USA
| | - Keith O. Hodgson
- Department of Chemistry Stanford University Stanford CA 94305 USA
- Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Menlo Park CA 94025 USA
| | - Edward I. Solomon
- Department of Chemistry Stanford University Stanford CA 94305 USA
- Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Menlo Park CA 94025 USA
| | - Jaeheung Cho
- Department of Emerging Materials Science DGIST Daegu 42988 Korea
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31
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Jeong D, Yan JJ, Noh H, Hedman B, Hodgson KO, Solomon EI, Cho J. Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid. Angew Chem Int Ed Engl 2018; 57:7764-7768. [PMID: 29701293 PMCID: PMC6013404 DOI: 10.1002/anie.201802641] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/05/2018] [Indexed: 11/06/2022]
Abstract
Naphthalene oxidation with metal-oxygen intermediates is a difficult reaction in environmental and biological chemistry. Herein, we report that a MnIV bis(hydroxo) complex, which was fully characterized by various physicochemical methods, such as ESI-MS, UV/Vis, and EPR analysis, X-ray diffraction, and XAS, can be employed for the oxidation of naphthalene in the presence of acid to afford 1,4-naphthoquinone. Redox titration of the MnIV bis(hydroxo) complex gave a one-electron reduction potential of 1.09 V, which is the most positive potential for all reported nonheme MnIV bis(hydroxo) species as well as MnIV oxo analogues. Kinetic studies, including kinetic isotope effect analysis, suggest that the naphthalene oxidation occurs through a rate-determining electron transfer process.
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Affiliation(s)
- Donghyun Jeong
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
| | - James J Yan
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - Hyeonju Noh
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA, 94025, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA, 94025, USA
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA, 94025, USA
| | - Jaeheung Cho
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
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32
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Pushkar Y, Davis KM, Palenik MC. Model of the Oxygen Evolving Complex Which Is Highly Predisposed to O-O Bond Formation. J Phys Chem Lett 2018; 9:3525-3531. [PMID: 29863871 DOI: 10.1021/acs.jpclett.8b00800] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Light-driven water oxidation is a fundamental reaction in the biosphere. The Mn4Ca cluster of photosystem II cycles through five redox states termed S0-S4, after which oxygen is evolved. Critically, the timing of O-O bond formation within the Kok cycle remains unknown. By combining recent crystallographic, spectroscopic, and DFT results, we demonstrate an atomistic S3 state model with the possibility of a low barrier to O-O bond formation prior to the final oxidation step. Furthermore, the associated one electron oxidized S4 state does not provide more advantages in terms of spin alignment or the energy of O-O bond formation. We propose that a high energy peroxide isoform of the S3 state can preferentially be oxidized by Tyr zox in the course of final electron transfer leading to O2 evolution. Such a mechanism may explain the peculiar kinetic behavior of O2 evolution as well as serve as an evolutionary adaptation to avoid release of the harmful peroxides.
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Affiliation(s)
- Yulia Pushkar
- Department of Physics and Astronomy , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Katherine M Davis
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - Mark C Palenik
- Chemistry Division , Naval Research Laboratory , NRC Research Associate, Code 6189, 4555 Overlook Avenue SW , Washington, DC 20375 , United States
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33
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Rice DB, Jones SD, Douglas JT, Jackson TA. NMR Studies of a MnIII-hydroxo Adduct Reveal an Equilibrium between MnIII-hydroxo and μ-Oxodimanganese(III,III) Species. Inorg Chem 2018; 57:7825-7837. [DOI: 10.1021/acs.inorgchem.8b00917] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Derek B. Rice
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Shannon D. Jones
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Justin T. Douglas
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Timothy A. Jackson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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34
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Halbach RL, Gygi D, Bloch ED, Anderson BL, Nocera DG. Structurally characterized terminal manganese(iv) oxo tris(alkoxide) complex. Chem Sci 2018; 9:4524-4528. [PMID: 29896395 PMCID: PMC5958342 DOI: 10.1039/c8sc01164h] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 04/16/2018] [Indexed: 12/22/2022] Open
Abstract
First structurally characterized Mn(iv) oxo.
A Mn(iv) complex featuring a terminal oxo ligand, [MnIV(O)(ditox)3][K(15-C-5)2] (3; ditox = tBu2MeCO–, 15-C-5 = 15-crown-5-ether) has been isolated and structurally characterized. Treatment of the colorless precursor [MnII(ditox)3][K(15-C-5)2] (2) with iodosobenzene affords 3 as a green free-flowing powder in high yields. The X-ray crystal structure of 3 reveals a pseudotetrahedral geometry about the central Mn, which features a terminal oxo (d(Mn–Oterm = 1.628(2) Å)). EPR spectroscopy, SQUID magnetometry, and Evans method magnetic susceptibility indicate that 3 consists of a high-spin S = 3/2 Mn(iv) metal center. 3 promotes C–H bond activation by a hydrogen atom abstraction. The [MnIV(O)(ditox)3]– furnishes a model for the proposed terminal oxo of the unique manganese of the oxygen evolving complex of photosystem II.
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Affiliation(s)
- Robert L Halbach
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA .
| | - David Gygi
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA .
| | - Eric D Bloch
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA .
| | - Bryce L Anderson
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA .
| | - Daniel G Nocera
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA .
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35
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Moonshiram D, Garrido‐Barros P, Gimbert‐Suriñach C, Picón A, Liu C, Zhang X, Karnahl M, Llobet A. Elucidating the Nature of the Excited State of a Heteroleptic Copper Photosensitizer by using Time‐Resolved X‐ray Absorption Spectroscopy. Chemistry 2018; 24:6464-6472. [DOI: 10.1002/chem.201800330] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Dooshaye Moonshiram
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34–36 Mülheim an der Ruhr 45470 Germany
- Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16 43007 Tarragona Spain
| | - Pablo Garrido‐Barros
- Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16 43007 Tarragona Spain
- Departament de Química Física i Inorganica Universitat Rovira i Virgili Campus Sescelades, C/Marcellí Domingo, s/n 43007 Tarragona Spain
| | - Carolina Gimbert‐Suriñach
- Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16 43007 Tarragona Spain
| | - Antonio Picón
- Grupo de Investigacion en Aplicaciones del Laser y Fotonica Universidad de Salamanca 37008 Salamanca Spain
- Departamento de Química, Modulo 13 Universidad Autónoma de Madrid Cantoblanco 28049 Madrid Spain
| | - Cunming Liu
- X-ray Science Division Argonne National Laboratory 9700 S. Cass Avenue Lemont IL 60439 USA
| | - Xiaoyi Zhang
- X-ray Science Division Argonne National Laboratory 9700 S. Cass Avenue Lemont IL 60439 USA
| | - Michael Karnahl
- University of Stuttgart Institute of Organic Chemistry Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Antoni Llobet
- Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16 43007 Tarragona Spain
- Departament de Química Universitat Autonoma de Barcelona 08193 Cerdanyola del Valles Barcelona Spain
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36
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Rice DB, Massie AA, Jackson TA. Manganese-Oxygen Intermediates in O-O Bond Activation and Hydrogen-Atom Transfer Reactions. Acc Chem Res 2017; 50:2706-2717. [PMID: 29064667 DOI: 10.1021/acs.accounts.7b00343] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biological systems capitalize on the redox versatility of manganese to perform reactions involving dioxygen and its derivatives superoxide, hydrogen peroxide, and water. The reactions of manganese enzymes influence both human health and the global energy cycle. Important examples include the detoxification of reactive oxygen species by manganese superoxide dismutase, biosynthesis by manganese ribonucleotide reductase and manganese lipoxygenase, and water splitting by the oxygen-evolving complex of photosystem II. Although these enzymes perform very different reactions and employ structurally distinct active sites, manganese intermediates with peroxo, hydroxo, and oxo ligation are commonly proposed in catalytic mechanisms. These intermediates are also postulated in mechanisms of synthetic manganese oxidation catalysts, which are of interest due to the earth abundance of manganese. In this Account, we describe our recent efforts toward understanding O-O bond activation pathways of MnIII-peroxo adducts and hydrogen-atom transfer reactivity of MnIV-oxo and MnIII-hydroxo complexes. In biological and synthetic catalysts, peroxomanganese intermediates are commonly proposed to decay by either Mn-O or O-O cleavage pathways, although it is often unclear how the local coordination environment influences the decay mechanism. To address this matter, we generated a variety of MnIII-peroxo adducts with varied ligand environments. Using parallel-mode EPR and Mn K-edge X-ray absorption techniques, the decay pathway of one MnIII-peroxo complex bearing a bulky macrocylic ligand was investigated. Unlike many MnIII-peroxo model complexes that decay to oxo-bridged-MnIIIMnIV dimers, decay of this MnIII-peroxo adduct yielded mononuclear MnIII-hydroxo and MnIV-oxo products, potentially resulting from O-O bond activation of the MnIII-peroxo unit. These results highlight the role of ligand sterics in promoting the formation of mononuclear products and mark an important step in designing MnIII-peroxo complexes that convert cleanly to high-valent Mn-oxo species. Although some synthetic MnIV-oxo complexes show great potential for oxidizing substrates with strong C-H bonds, most MnIV-oxo species are sluggish oxidants. Both two-state reactivity and thermodynamic arguments have been put forth to explain these observations. To address these issues, we generated a series of MnIV-oxo complexes supported by neutral, pentadentate ligands with systematically perturbed equatorial donation. Kinetic investigations of these complexes revealed a correlation between equatorial ligand-field strength and hydrogen-atom and oxygen-atom transfer reactivity. While this trend can be understood on the basis of the two-state reactivity model, the reactivity trend also correlates with variations in MnIII/IV reduction potential caused by changes in the ligand field. This work demonstrates the dramatic influence simple ligand perturbations can have on reactivity but also illustrates the difficulties in understanding the precise basis for a change in reactivity. In the enzyme manganese lipoxygenase, an active-site MnIII-hydroxo adduct initiates substrate oxidation by abstracting a hydrogen atom from a C-H bond. Precedent for this chemistry from synthetic MnIII-hydroxo centers is rare. To better understand hydrogen-atom transfer by MnIII centers, we developed a pair of MnIII-hydroxo complexes, formed in high yield from dioxygen oxidation of MnII precursors, capable of attacking weak O-H and C-H bonds. Kinetic and computational studies show a delicate interplay between thermodynamic and steric influences in hydrogen-atom transfer reactivity, underscoring the potential of MnIII-hydroxo units as mild oxidants.
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Affiliation(s)
- Derek B. Rice
- Department of Chemistry and
Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Allyssa A. Massie
- Department of Chemistry and
Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Timothy A. Jackson
- Department of Chemistry and
Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
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Guo M, Lee YM, Gupta R, Seo MS, Ohta T, Wang HH, Liu HY, Dhuri SN, Sarangi R, Fukuzumi S, Nam W. Dioxygen Activation and O-O Bond Formation Reactions by Manganese Corroles. J Am Chem Soc 2017; 139:15858-15867. [PMID: 29056043 PMCID: PMC5711437 DOI: 10.1021/jacs.7b08678] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Activation of dioxygen (O2) in enzymatic and biomimetic reactions has been intensively investigated over the past several decades. More recently, O-O bond formation, which is the reverse of the O2-activation reaction, has been the focus of current research. Herein, we report the O2-activation and O-O bond formation reactions by manganese corrole complexes. In the O2-activation reaction, Mn(V)-oxo and Mn(IV)-peroxo intermediates were formed when Mn(III) corroles were exposed to O2 in the presence of base (e.g., OH-) and hydrogen atom (H atom) donor (e.g., THF or cyclic olefins); the O2-activation reaction did not occur in the absence of base and H atom donor. Moreover, formation of the Mn(V)-oxo and Mn(IV)-peroxo species was dependent on the amounts of base present in the reaction solution. The role of the base was proposed to lower the oxidation potential of the Mn(III) corroles, thereby facilitating the binding of O2 and forming a Mn(IV)-superoxo species. The putative Mn(IV)-superoxo species was then converted to the corresponding Mn(IV)-hydroperoxo species by abstracting a H atom from H atom donor, followed by the O-O bond cleavage of the putative Mn(IV)-hydroperoxo species to form a Mn(V)-oxo species. We have also shown that addition of hydroxide ion to the Mn(V)-oxo species afforded the Mn(IV)-peroxo species via O-O bond formation and the resulting Mn(IV)-peroxo species reverted to the Mn(V)-oxo species upon addition of proton, indicating that the O-O bond formation and cleavage reactions between the Mn(V)-oxo and Mn(IV)-peroxo complexes are reversible. The present study reports the first example of using the same manganese complex in both O2-activation and O-O bond formation reactions.
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Affiliation(s)
- Mian Guo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Ranjana Gupta
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Mi Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Takehiro Ohta
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, RSC-UH LP Center, Hyogo 679-5148, Japan
| | - Hua-Hua Wang
- Department of Chemistry, South China University of Technology, Guangzhou 510641, China
| | - Hai-Yang Liu
- Department of Chemistry, South China University of Technology, Guangzhou 510641, China
| | - Sunder N. Dhuri
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- Department of Chemistry, Goa University, Goa 403 206, India
| | - Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
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38
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Mn K-edge X-ray absorption studies of mononuclear Mn(III)–hydroxo complexes. J Biol Inorg Chem 2017; 22:1281-1293. [DOI: 10.1007/s00775-017-1501-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 10/13/2017] [Indexed: 11/25/2022]
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39
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Jensen SC, Davis KM, Sullivan B, Hartzler DA, Seidler GT, Casa DM, Kasman E, Colmer HE, Massie AA, Jackson TA, Pushkar Y. X-ray Emission Spectroscopy of Biomimetic Mn Coordination Complexes. J Phys Chem Lett 2017; 8:2584-2589. [PMID: 28524662 DOI: 10.1021/acs.jpclett.7b01209] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the function of Mn ions in biological and chemical redox catalysis requires precise knowledge of their electronic structure. X-ray emission spectroscopy (XES) is an emerging technique with a growing application to biological and biomimetic systems. Here, we report an improved, cost-effective spectrometer used to analyze two biomimetic coordination compounds, [MnIV(OH)2(Me2EBC)]2+ and [MnIV(O)(OH)(Me2EBC)]+, the second of which contains a key MnIV═O structural fragment. Despite having the same formal oxidation state (MnIV) and tetradentate ligands, XES spectra from these two compounds demonstrate different electronic structures. Experimental measurements and DFT calculations yield different localized spin densities for the two complexes resulting from MnIV-OH conversion to MnIV═O. The relevance of the observed spectroscopic changes is discussed for applications in analyzing complex biological systems such as photosystem II. A model of the S3 intermediate state of photosystem II containing a MnIV═O fragment is compared to recent time-resolved X-ray diffraction data of the same state.
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Affiliation(s)
- Scott C Jensen
- Department of Physics and Astronomy, Purdue University , West Lafayette, Indiana 47907, United States
| | - Katherine M Davis
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Brendan Sullivan
- Department of Physics and Astronomy, Purdue University , West Lafayette, Indiana 47907, United States
| | - Daniel A Hartzler
- Department of Physics and Astronomy, Purdue University , West Lafayette, Indiana 47907, United States
| | - Gerald T Seidler
- Department of Physics, University of Washington , Seattle, Washington 98195, United States
| | - Diego M Casa
- Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Elina Kasman
- Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Hannah E Colmer
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Allyssa A Massie
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Timothy A Jackson
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Yulia Pushkar
- Department of Physics and Astronomy, Purdue University , West Lafayette, Indiana 47907, United States
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40
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Massie AA, Denler MC, Cardoso LT, Walker AN, Hossain MK, Day VW, Nordlander E, Jackson TA. Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)‐Oxo Complexes. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201612309] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | | | | | | | - M. Kamal Hossain
- Chemical Physics Department of Chemistry Lund University Box 124 22100 Lund Sweden
| | - Victor W. Day
- Department of Chemistry University of Kansas Lawrence KS USA
| | - Ebbe Nordlander
- Chemical Physics Department of Chemistry Lund University Box 124 22100 Lund Sweden
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41
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Massie AA, Denler MC, Cardoso LT, Walker AN, Hossain MK, Day VW, Nordlander E, Jackson TA. Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)-Oxo Complexes. Angew Chem Int Ed Engl 2017; 56:4178-4182. [PMID: 28300349 DOI: 10.1002/anie.201612309] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 02/03/2017] [Indexed: 11/06/2022]
Abstract
Manganese(IV)-oxo complexes are often invoked as intermediates in Mn-catalyzed C-H bond activation reactions. While many synthetic MnIV -oxo species are mild oxidants, other members of this class can attack strong C-H bonds. The basis for these reactivity differences is not well understood. Here we describe a series of MnIV -oxo complexes with N5 pentadentate ligands that modulate the equatorial ligand field of the MnIV center, as assessed by electronic absorption, electron paramagnetic resonance, and Mn K-edge X-ray absorption methods. Kinetic experiments show dramatic rate variations in hydrogen-atom and oxygen-atom transfer reactions, with faster rates corresponding to weaker equatorial ligand fields. For these MnIV -oxo complexes, the rate enhancements are correlated with both 1) the energy of a low-lying 4 E excited state, which has been postulated to be involved in a two-state reactivity model, and 2) the MnIII/IV reduction potentials.
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Affiliation(s)
- Allyssa A Massie
- Department of Chemistry, University of Kansas, Lawrence, KS, USA
| | - Melissa C Denler
- Department of Chemistry, University of Kansas, Lawrence, KS, USA
| | | | - Ashlie N Walker
- Department of Chemistry, University of Kansas, Lawrence, KS, USA
| | - M Kamal Hossain
- Chemical Physics, Department of Chemistry, Lund University, Box 124, 22100, Lund, Sweden
| | - Victor W Day
- Department of Chemistry, University of Kansas, Lawrence, KS, USA
| | - Ebbe Nordlander
- Chemical Physics, Department of Chemistry, Lund University, Box 124, 22100, Lund, Sweden
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42
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Rees JA, Bjornsson R, Kowalska JK, Lima FA, Schlesier J, Sippel D, Weyhermüller T, Einsle O, Kovacs JA, DeBeer S. Comparative electronic structures of nitrogenase FeMoco and FeVco. Dalton Trans 2017; 46:2445-2455. [PMID: 28154874 PMCID: PMC5322470 DOI: 10.1039/c7dt00128b] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 01/25/2017] [Indexed: 12/17/2022]
Abstract
An investigation of the active site cofactors of the molybdenum and vanadium nitrogenases (FeMoco and FeVco) was performed using high-resolution X-ray spectroscopy. Synthetic heterometallic iron-sulfur cluster models and density functional theory calculations complement the study of the MoFe and VFe holoproteins using both non-resonant and resonant X-ray emission spectroscopy. Spectroscopic data show the presence of direct iron-heterometal bonds, which are found to be weaker in FeVco. Furthermore, the interstitial carbide is found to perturb the electronic structures of the cofactors through highly covalent Fe-C bonding. The implications of these conclusions are discussed in light of the differential reactivity of the molybdenum and vanadium nitrogenases towards various substrates. Possible functional roles for both the heterometal and the interstitial carbide are detailed.
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Affiliation(s)
- Julian A Rees
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany. and Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.
| | - Ragnar Bjornsson
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany. and Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland
| | - Joanna K Kowalska
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany.
| | - Frederico A Lima
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany. and Centro Nacional de Pesquisa em Energia e Materiais Brazilian Synchrotron Light Laboratory - LNLS Rua Giuseppe Máximo Scolfaro, 10.000 13083-970 Campinas SP, Brazil
| | - Julia Schlesier
- Institute for Biochemistry and BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University Freiburg, Germany.
| | - Daniel Sippel
- Institute for Biochemistry and BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University Freiburg, Germany.
| | - Thomas Weyhermüller
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany.
| | - Oliver Einsle
- Institute for Biochemistry and BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University Freiburg, Germany.
| | - Julie A Kovacs
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany. and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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43
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K- and L-edge X-ray Absorption Spectroscopy (XAS) and Resonant Inelastic X-ray Scattering (RIXS) Determination of Differential Orbital Covalency (DOC) of Transition Metal Sites. Coord Chem Rev 2017; 345:182-208. [PMID: 28970624 DOI: 10.1016/j.ccr.2017.02.004] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Continual advancements in the development of synchrotron radiation sources have resulted in X-ray based spectroscopic techniques capable of probing the electronic and structural properties of numerous systems. This review gives an overview of the application of metal K-edge and L-edge X-ray absorption spectroscopy (XAS), as well as K resonant inelastic X-ray scattering (RIXS), to the study of electronic structure in transition metal sites with emphasis on experimentally quantifying 3d orbital covalency. The specific sensitivities of K-edge XAS, L-edge XAS, and RIXS are discussed emphasizing the complementary nature of the methods. L-edge XAS and RIXS are sensitive to mixing between 3d orbitals and ligand valence orbitals, and to the differential orbital covalency (DOC), that is, the difference in the covalencies for different symmetry sets of the d orbitals. Both L-edge XAS and RIXS are highly sensitive to and enable separation of and donor bonding and back bonding contributions to bonding. Applying ligand field multiplet simulations, including charge transfer via valence bond configuration interactions, DOC can be obtained for direct comparison with density functional theory calculations and to understand chemical trends. The application of RIXS as a probe of frontier molecular orbitals in a heme enzyme demonstrates the potential of this method for the study of metal sites in highly covalent coordination sites in bioinorganic chemistry.
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44
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Jin K, Seo H, Hayashi T, Balamurugan M, Jeong D, Go YK, Hong JS, Cho KH, Kakizaki H, Bonnet-Mercier N, Kim MG, Kim SH, Nakamura R, Nam KT. Mechanistic Investigation of Water Oxidation Catalyzed by Uniform, Assembled MnO Nanoparticles. J Am Chem Soc 2017; 139:2277-2285. [PMID: 28029792 DOI: 10.1021/jacs.6b10657] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The development of active water oxidation catalysts is critical to achieve high efficiency in overall water splitting. Recently, sub-10 nm-sized monodispersed partially oxidized manganese oxide nanoparticles were shown to exhibit not only superior catalytic performance for oxygen evolution, but also unique electrokinetics, as compared to their bulk counterparts. In the present work, the water-oxidizing mechanism of partially oxidized MnO nanoparticles was investigated using integrated in situ spectroscopic and electrokinetic analyses. We successfully demonstrated that, in contrast to previously reported manganese (Mn)-based catalysts, Mn(III) species are stably generated on the surface of MnO nanoparticles via a proton-coupled electron transfer pathway. Furthermore, we confirmed as to MnO nanoparticles that the one-electron oxidation step from Mn(II) to Mn(III) is no longer the rate-determining step for water oxidation and that Mn(IV)═O species are generated as reaction intermediates during catalysis.
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Affiliation(s)
- Kyoungsuk Jin
- Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea
| | - Hongmin Seo
- Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea
| | - Toru Hayashi
- Department of Applied Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.,Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science (CSRS) , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Mani Balamurugan
- Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea
| | - Donghyuk Jeong
- Western Seoul Center, Korea Basic Science Institute (KBSI) , 150, Bukahyeon-ro, Seodaemun-gu, Seoul 120-140, Korea
| | - Yoo Kyung Go
- Western Seoul Center, Korea Basic Science Institute (KBSI) , 150, Bukahyeon-ro, Seodaemun-gu, Seoul 120-140, Korea
| | - Jung Sug Hong
- Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea
| | - Kang Hee Cho
- Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea
| | - Hirotaka Kakizaki
- Department of Applied Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.,Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science (CSRS) , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Nadège Bonnet-Mercier
- Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science (CSRS) , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Min Gyu Kim
- Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Korea
| | - Sun Hee Kim
- Western Seoul Center, Korea Basic Science Institute (KBSI) , 150, Bukahyeon-ro, Seodaemun-gu, Seoul 120-140, Korea
| | - Ryuhei Nakamura
- Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science (CSRS) , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Ki Tae Nam
- Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea
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45
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Leto DF, Massie AA, Rice DB, Jackson TA. Spectroscopic and Computational Investigations of a Mononuclear Manganese(IV)-Oxo Complex Reveal Electronic Structure Contributions to Reactivity. J Am Chem Soc 2016; 138:15413-15424. [PMID: 27802057 DOI: 10.1021/jacs.6b08661] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The mononuclear Mn(IV)-oxo complex [MnIV(O)(N4py)]2+, where N4py is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine, has been proposed to attack C-H bonds by an excited-state reactivity pattern [ Cho, K.-B.; Shaik, S.; Nam, W. J. Phys. Chem. Lett. 2012 , 3 , 2851 - 2856 (DOI: 10.1021/jz301241z )]. In this model, a 4E excited state is utilized to provide a lower-energy barrier for hydrogen-atom transfer. This proposal is intriguing, as it offers both a rationale for the relatively high hydrogen-atom-transfer reactivity of [MnIV(O)(N4py)]2+ and a guideline for creating more reactive complexes through ligand modification. Here we employ a combination of electronic absorption and variable-temperature magnetic circular dichroism (MCD) spectroscopy to experimentally evaluate this excited-state reactivity model. Using these spectroscopic methods, in conjunction with time-dependent density functional theory (TD-DFT) and complete-active space self-consistent-field calculations (CASSCF), we define the ligand-field and charge-transfer excited states of [MnIV(O)(N4py)]2+. Through a graphical analysis of the signs of the experimental C-term MCD signals, we unambiguously assign a low-energy MCD feature of [MnIV(O)(N4py)]2+ as the 4E excited state predicted to be involved in hydrogen-atom-transfer reactivity. The CASSCF calculations predict enhanced MnIII-oxyl character on the excited-state 4E surface, consistent with previous DFT calculations. Potential-energy surfaces, developed using the CASSCF methods, are used to determine how the energies and wave functions of the ground and excited states evolved as a function of Mn═O distance. The unique insights into ground- and excited-state electronic structure offered by these spectroscopic and computational studies are harmonized with a thermodynamic model of hydrogen-atom-transfer reactivity, which predicts a correlation between transition-state barriers and driving force.
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Affiliation(s)
- Domenick F Leto
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Allyssa A Massie
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Derek B Rice
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Timothy A Jackson
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
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46
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Manna S, Mistri S, Bhunia A, Paul A, Zangrando E, Manna SC. Manganese(IV) complex with a polydentate Schiff base ligand: synthesis, crystal structure, TDDFT calculation, electronic absorption and EPR spectral study. J COORD CHEM 2016. [DOI: 10.1080/00958972.2016.1248949] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Soumen Manna
- Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, India
| | - Soumen Mistri
- Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, India
| | - Apurba Bhunia
- Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, India
| | - Aparup Paul
- Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, India
| | - Ennio Zangrando
- Department of Pharmaceutical and Chemical Sciences, University of Trieste, Trieste, Italy
| | - Subal Chandra Manna
- Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, India
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47
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Chatterjee R, Han G, Kern J, Gul S, Fuller FD, Garachtchenko A, Young ID, Weng TC, Nordlund D, Alonso-Mori R, Bergmann U, Sokaras D, Hatakeyama M, Yachandra VK, Yano J. Structural Changes Correlated with Magnetic Spin State Isomorphism in the S 2 State of the Mn 4CaO 5 Cluster in the Oxygen-Evolving Complex of Photosystem II. Chem Sci 2016; 7:5236-5248. [PMID: 28044099 PMCID: PMC5201215 DOI: 10.1039/c6sc00512h] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/26/2016] [Indexed: 12/19/2022] Open
Abstract
The Mn4CaO5 cluster in Photosystem II catalyzes the four-electron redox reaction of water oxidation in natural photosynthesis. This catalytic reaction cycles through four intermediate states (Si, i = 0 to 4), involving changes in the redox state of the four Mn atoms in the cluster. Recent studies suggest the presence and importance of isomorphous structures within the same redox/intermediate S-state. It is highly likely that geometric and electronic structural flexibility play a role in the catalytic mechanism. Among the catalytic intermediates that have been identified experimentally thus far, there is clear evidence of such isomorphism in the S2 state, with a high-spin (5/2) (HS) and a low spin (1/2) (LS) form, identified and characterized by their distinct electron paramagnetic resonance (EPR spectroscopy) signals. We studied these two S2 isomers with Mn extended X-ray absorption fine structure (EXAFS) and absorption and emission spectroscopy (XANES/XES) to characterize the structural and electronic structural properties. The geometric and electronic structure of the HS and LS S2 states are different as determined using Mn EXAFS and XANES/XES, respectively. The Mn K-edge XANES and XES for the HS form are different from the LS and indicate a slightly lower positive charge on the Mn atoms compared to the LS form. Based on the EXAFS results which are clearly different, we propose possible structural differences between the two spin states. Such structural and magnetic redox-isomers if present at room temperature, will likely play a role in the mechanism for water-exchange/oxidation in photosynthesis.
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Affiliation(s)
- Ruchira Chatterjee
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Guangye Han
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Jan Kern
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
- LCLS
, SLAC National Accelerator Laboratory
,
Menlo Park
, CA
, USA
| | - Sheraz Gul
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Franklin D. Fuller
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Anna Garachtchenko
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Iris D. Young
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Tsu-Chien Weng
- Center for High Pressure Science &Technology Advanced Research
,
Shanghai
, China
| | - Dennis Nordlund
- SSRL
, SLAC National Accelerator Laboratory
,
Menlo Park
, CA
, USA
| | | | - Uwe Bergmann
- PULSE
, SLAC National Accelerator Laboratory
,
Menlo Park
, CA
, USA
| | | | | | - Vittal K. Yachandra
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division
, Lawrence Berkeley National Laboratory
,
MS 66-0200, 1 Cyclotron Rd.
, Berkeley
, CA 94720-8099
, USA
.
;
; Tel: +1 510 486 4366
; Tel: +1 510 486 4963
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48
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Gerey B, Gouré E, Fortage J, Pécaut J, Collomb MN. Manganese-calcium/strontium heterometallic compounds and their relevance for the oxygen-evolving center of photosystem II. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2016.04.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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49
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Leto DF, Massie AA, Colmer HE, Jackson TA. X-Band Electron Paramagnetic Resonance Comparison of Mononuclear Mn(IV)-oxo and Mn(IV)-hydroxo Complexes and Quantum Chemical Investigation of Mn(IV) Zero-Field Splitting. Inorg Chem 2016; 55:3272-82. [PMID: 27002928 DOI: 10.1021/acs.inorgchem.5b02309] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
X-band electron paramagnetic resonance (EPR) spectroscopy was used to probe the ground-state electronic structures of mononuclear Mn(IV) complexes [Mn(IV)(OH)2(Me2EBC)](2+) and [Mn(IV)(O)(OH)(Me2EBC)](+). These compounds are known to effect C-H bond oxidation reactions by a hydrogen-atom transfer mechanism. They provide an ideal system for comparing Mn(IV)-hydroxo versus Mn(IV)-oxo motifs, as they differ by only a proton. Simulations of 5 K EPR data, along with analysis of variable-temperature EPR signal intensities, allowed for the estimation of ground-state zero-field splitting (ZFS) and (55)Mn hyperfine parameters for both complexes. From this analysis, it was concluded that the Mn(IV)-oxo complex [Mn(IV)(O)(OH)(Me2EBC)](+) has an axial ZFS parameter D (D = +1.2(0.4) cm(-1)) and rhombicity (E/D = 0.22(1)) perturbed relative to the Mn(IV)-hydroxo analogue [Mn(IV)(OH)2(Me2EBC)](2+) (|D| = 0.75(0.25) cm(-1); E/D = 0.15(2)), although the complexes have similar (55)Mn values (a = 7.7 and 7.5 mT, respectively). The ZFS parameters for [Mn(IV)(OH)2(Me2EBC)](2+) were compared with values obtained previously through variable-temperature, variable-field magnetic circular dichroism (VTVH MCD) experiments. While the VTVH MCD analysis can provide a reasonable estimate of the magnitude of D, the E/D values were poorly defined. Using the ZFS parameters reported for these complexes and five other mononuclear Mn(IV) complexes, we employed coupled-perturbed density functional theory (CP-DFT) and complete active space self-consistent field (CASSCF) calculations with second-order n-electron valence-state perturbation theory (NEVPT2) correction, to compare the ability of these two quantum chemical methods for reproducing experimental ZFS parameters for Mn(IV) centers. The CP-DFT approach was found to provide reasonably acceptable values for D, whereas the CASSCF/NEVPT2 method fared worse, considerably overestimating the magnitude of D in several cases. Both methods were poor in reproducing experimental E/D values. Overall, this work adds to the limited investigations of Mn(IV) ground-state properties and provides an initial assessment for calculating Mn(IV) ZFS parameters with quantum chemical methods.
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Affiliation(s)
- Domenick F Leto
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, United States
| | - Allyssa A Massie
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, United States
| | - Hannah E Colmer
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, United States
| | - Timothy A Jackson
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, United States
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50
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Colmer HE, Howcroft AW, Jackson TA. Formation, Characterization, and O-O Bond Activation of a Peroxomanganese(III) Complex Supported by a Cross-Clamped Cyclam Ligand. Inorg Chem 2016; 55:2055-69. [PMID: 26908013 DOI: 10.1021/acs.inorgchem.5b02398] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Although there have been reports describing the nucleophilic reactivity of peroxomanganese(III) intermediates, as well as their conversion to high-valent oxo-bridged dimers, it remains a challenge to activate peroxomanganese(III) species for conversion to high-valent, mononuclear manganese complexes. Herein, we report the generation, characterization, and activation of a peroxomanganese(III) adduct supported by the cross-clamped, macrocyclic Me2EBC ligand (4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). This ligand is known to support high-valent, mononuclear Mn(IV) species with well-defined spectroscopic properties, which provides an opportunity to identify mononuclear Mn(IV) products from O-O bond activation of the corresponding Mn(III)-peroxo adduct. The peroxomanganese(III) intermediate, [Mn(III)(O2)(Me2EBC)](+), was prepared at low-temperature by the addition of KO2 to [Mn(II)(Cl)2(Me2EBC)] in CH2Cl2, and this complex was characterized by electronic absorption, electron paramagnetic resonance (EPR), and Mn K-edge X-ray absorption (XAS) spectroscopies. The electronic structure of the [Mn(III)(O2)(Me2EBC)](+) intermediate was examined by density functional theory (DFT) and time-dependent (TD) DFT calculations. Detailed spectroscopic investigations of the decay products of [Mn(III)(O2)(Me2EBC)](+) revealed the presence of mononuclear Mn(III)-hydroxo species or a mixture of mononuclear Mn(IV) and Mn(III)-hydroxo species. The nature of the observed decay products depended on the amount of KO2 used to generate [Mn(III)(O2)(Me2EBC)](+). The Mn(III)-hydroxo product was characterized by Mn K-edge XAS, and shifts in the pre-edge transition energies and intensities relative to [Mn(III)(O2)(Me2EBC)](+) provide a marker for differences in covalency between peroxo and nonperoxo ligands. To the best of our knowledge, this work represents the first observation of a mononuclear Mn(IV) center upon decay of a nonporphyrinoid Mn(III)-peroxo center.
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Affiliation(s)
- Hannah E Colmer
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Anthony W Howcroft
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
| | - Timothy A Jackson
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
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