1
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Kornowicz A, Pietrzak T, Korona K, Terlecki M, Justyniak I, Kubas A, Lewiński J. Fresh Impetus in the Chemistry of Calcium Peroxides. J Am Chem Soc 2024; 146:18938-18947. [PMID: 38847558 PMCID: PMC11258691 DOI: 10.1021/jacs.4c00906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Revised: 05/22/2024] [Accepted: 05/22/2024] [Indexed: 07/18/2024]
Abstract
Redox-inactive metal ions are essential in modulating the reactivity of various oxygen-containing metal complexes and metalloenzymes, including photosystem II (PSII). The heart of this unique membrane-protein complex comprises the Mn4CaO5 cluster, in which the Ca2+ ion acts as a critical cofactor in the splitting of water in PSII. However, there is still a lack of studies involving Ca-based reactive oxygen species (ROS) systems, and the exact nature of the interaction between the Ca2+ center and ROS in PSII still generates intense debate. Here, harnessing a novel Ca-TEMPO complex supported by the β-diketiminate ligand to control the activation of O2, we report the isolation and structural characterization of hitherto elusive Ca peroxides, a homometallic Ca hydroperoxide and a heterometallic Ca/K peroxide. Our studies indicate that the presence of K+ cations is a key factor controlling the outcome of the oxygenation reaction of the model Ca-TEMPO complex. Combining experimental observations with computational investigations, we also propose a mechanistic rationalization for the reaction outcomes. The designed approach demonstrates metal-TEMPO complexes as a versatile platform for O2 activation and advances the understanding of Ca/ROS systems.
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Affiliation(s)
- Arkadiusz Kornowicz
- Institute
of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Tomasz Pietrzak
- Faculty
of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
| | - Krzesimir Korona
- Faculty
of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
| | - Michał Terlecki
- Faculty
of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
| | - Iwona Justyniak
- Institute
of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Adam Kubas
- Institute
of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Janusz Lewiński
- Institute
of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
- Faculty
of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
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2
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De Tovar J, Leblay R, Wang Y, Wojcik L, Thibon-Pourret A, Réglier M, Simaan AJ, Le Poul N, Belle C. Copper-oxygen adducts: new trends in characterization and properties towards C-H activation. Chem Sci 2024; 15:10308-10349. [PMID: 38994420 PMCID: PMC11234856 DOI: 10.1039/d4sc01762e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 05/11/2024] [Indexed: 07/13/2024] Open
Abstract
This review summarizes the latest discoveries in the field of C-H activation by copper monoxygenases and more particularly by their bioinspired systems. This work first describes the recent background on copper-containing enzymes along with additional interpretations about the nature of the active copper-oxygen intermediates. It then focuses on relevant examples of bioinorganic synthetic copper-oxygen intermediates according to their nuclearity (mono to polynuclear). This includes a detailed description of the spectroscopic features of these adducts as well as their reactivity towards the oxidation of recalcitrant Csp3 -H bonds. The last part is devoted to the significant expansion of heterogeneous catalytic systems based on copper-oxygen cores (i.e. within zeolite frameworks).
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Affiliation(s)
- Jonathan De Tovar
- Université Grenoble-Alpes, CNRS, Département de Chimie Moléculaire Grenoble France
| | - Rébecca Leblay
- Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Institut des Sciences Moléculaires de Marseille Marseille France
| | - Yongxing Wang
- Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Institut des Sciences Moléculaires de Marseille Marseille France
| | - Laurianne Wojcik
- Université de Brest, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique Brest France
| | | | - Marius Réglier
- Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Institut des Sciences Moléculaires de Marseille Marseille France
| | - A Jalila Simaan
- Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Institut des Sciences Moléculaires de Marseille Marseille France
| | - Nicolas Le Poul
- Université de Brest, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique Brest France
| | - Catherine Belle
- Université Grenoble-Alpes, CNRS, Département de Chimie Moléculaire Grenoble France
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3
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Mondal S, Zhang W, Zhang S. Thermodynamics of Proton-Coupled Electron Transfer at Tricopper μ-Oxo/Hydroxo/Aqua Complexes. J Am Chem Soc 2024; 146:15036-15044. [PMID: 38770819 DOI: 10.1021/jacs.3c14420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Multicopper oxidases (MCOs) utilize a tricopper active site to reduce dioxygen to water through 4H+ 4e- proton-coupled electron transfer (PCET). Understanding the thermodynamics of PCET at a tricopper cluster is essential for elucidating how MCOs harness the oxidative power of O2 while mitigating oxidative damage. In this study, we determined the O-H bond dissociation free energies (BDFEs) and pKa values of a series of tricopper hydroxo and tricopper aqua complexes as synthetic models of the tricopper site in MCOs. Tricopper intermediates on the path of alternating electron and proton transfer (ET-PT-ET-PT-ET) have modest BDFE(O-H) values in the range of 53.0-57.1 kcal/mol. In contrast, those not on the path of ET-PT-ET-PT-ET display much higher (78.1 kcal/mol) or lower (44.7 kcal/mol) BDFE(O-H) values. Additionally, the pKa of bridging OH and OH2 motifs increase by 8-16 pKa units per oxidation state. The same oxidation state changes have a lesser impact on the pKa of N-H motif in the secondary coordination sphere, with an increase of ca. 5 pKa units per oxidation state. The steeper pKa increase of the tricopper center promotes proton transfer from the secondary coordination sphere. Overall, our study shed light on the PCET pathway least prone to decomposition, elucidating why tricopper centers are an optimal choice for promoting efficient oxygen reduction reaction.
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Affiliation(s)
- Saikat Mondal
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Weiyao Zhang
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Shiyu Zhang
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
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4
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Cosby TPL, Bhattacharjee A, Henneberry SK, LeBlanc J, Caputo CB. Unlocking Lewis acidity via the redox non-innocence of a phenothiazine-substituted borane. Chem Commun (Camb) 2024; 60:5391-5394. [PMID: 38586997 DOI: 10.1039/d4cc01059k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
We describe a new approach to enhancing Lewis acidity, through the single electron oxidation of a borane with a pendant phenothiazine. This results in the formation of a persistent radical cation with increased electrophilicity. Computational and experimental studies indicate this radical cation significantly enhances the Lewis acidity and catalytic activity compared to its neutral analog. These results illustrate the viability of this approach in turning on the Lewis acidity of relatively inert boranes.
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Affiliation(s)
- Taylor P L Cosby
- Department of Chemistry, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
| | - Avik Bhattacharjee
- Department of Chemistry, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
| | - Samantha K Henneberry
- Department of Chemistry, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
| | - Jesse LeBlanc
- Department of Chemistry, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
| | - Christopher B Caputo
- Department of Chemistry, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
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5
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Hess KM, Leach IF, Wijtenhorst L, Lee H, Klein JEMN. Valence Tautomerism Induced Proton Coupled Electron Transfer:X-H Bond Oxidation with a Dinuclear Au(II) Hydroxide Complex. Angew Chem Int Ed Engl 2024; 63:e202318916. [PMID: 38324462 DOI: 10.1002/anie.202318916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 01/25/2024] [Accepted: 02/05/2024] [Indexed: 02/09/2024]
Abstract
We report the preparation and characterization of the dinuclear AuII hydroxide complex AuII 2(L)2(OH)2 (L=N,N'-bis (2,6-dimethyl) phenylformamidinate) and study its reactivity towards weak X-H bonds. Through the interplay of kinetic analysis and computational studies, we demonstrate that the oxidation of cyclohexadiene follows a concerted proton-coupled electron transfer (cPCET) mechanism, a rare type of reactivity for Au complexes. We find that the Au-Au σ-bond undergoes polarization in the PCET event leading to an adjustment of oxidation levels for both Au centers prior to C(sp3)-H bond cleavage. We thus describe the oxidation event as a valence tautomerism-induced PCET where the basicity of one reduced Au-OH unit provides a proton acceptor and the second more oxidized Au center serves as an electron acceptor. The coordination of these events allows for unprecedented radical-type reactivity by a closed shell AuII complex.
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Affiliation(s)
- Kristopher M Hess
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747, AG Groningen, The Netherlands
| | - Isaac F Leach
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747, AG Groningen, The Netherlands
| | - Lisa Wijtenhorst
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747, AG Groningen, The Netherlands
| | - Hangyul Lee
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747, AG Groningen, The Netherlands
| | - Johannes E M N Klein
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747, AG Groningen, The Netherlands
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6
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Keshari K, Santra A, Velasco L, Sauvan M, Kaur S, Ugale AD, Munshi S, Marco JF, Moonshiram D, Paria S. Functional Model of Compound II of Cytochrome P450: Spectroscopic Characterization and Reactivity Studies of a Fe IV-OH Complex. JACS AU 2024; 4:1142-1154. [PMID: 38559734 PMCID: PMC10976569 DOI: 10.1021/jacsau.3c00844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 02/12/2024] [Accepted: 02/26/2024] [Indexed: 04/04/2024]
Abstract
Herein, we show that the reaction of a mononuclear FeIII(OH) complex (1) with N-tosyliminobenzyliodinane (PhINTs) resulted in the formation of a FeIV(OH) species (3). The obtained complex 3 was characterized by an array of spectroscopic techniques and represented a rare example of a synthetic FeIV(OH) complex. The reaction of 1 with the one-electron oxidizing agent was reported to form a ligand-oxidized FeIII(OH) complex (2). 3 revealed a one-electron reduction potential of -0.22 V vs Fc+/Fc at -15 °C, which was 150 mV anodically shifted than 2 (Ered = -0.37 V vs Fc+/Fc at -15 °C), inferring 3 to be more oxidizing than 2. 3 reacted spontaneously with (4-OMe-C6H4)3C• to form (4-OMe-C6H4)3C(OH) through rebound of the OH group and displayed significantly faster reactivity than 2. Further, activation of the hydrocarbon C-H and the phenolic O-H bond by 2 and 3 was compared and showed that 3 is a stronger oxidant than 2. A detailed kinetic study established the occurrence of a concerted proton-electron transfer/hydrogen atom transfer reaction of 3. Studying one-electron reduction of 2 and 3 using decamethylferrocene (Fc*) revealed a higher ket of 3 than 2. The study established that the primary coordination sphere around Fe and the redox state of the metal center is very crucial in controlling the reactivity of high-valent Fe-OH complexes. Further, a FeIII(OMe) complex (4) was synthesized and thoroughly characterized, including X-ray structure determination. The reaction of 4 with PhINTs resulted in the formation of a FeIV(OMe) species (5), revealing the presence of two FeIV species with isomer shifts of -0.11 mm/s and = 0.17 mm/s in the Mössbauer spectrum and showed FeIV/FeIII potential at -0.36 V vs Fc+/Fc couple in acetonitrile at -15 °C. The reactivity studies of 5 were investigated and compared with the FeIV(OH) complex (3).
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Affiliation(s)
- Kritika Keshari
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
| | - Aakash Santra
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
| | - Lucía Velasco
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Maxime Sauvan
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Simarjeet Kaur
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
| | - Ashok D. Ugale
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Sandip Munshi
- School
of Chemical Science, Indian Association
for the Cultivation of Science, Raja S C Mulliick Road, Kolkata 700032, India
| | - J. F. Marco
- Instituto
de Quimica Fisica Blas Cabrera, Consejo
Superior de Investigaciones Científicas, C. de Serrano, 119, Serrano, Madrid 28006, Spain
| | - Dooshaye Moonshiram
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Sayantan Paria
- Department
of Chemistry, Indian Institute of Technology
Delhi, Hauz Khas, New Delhi 110016, India
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7
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Pavun A, Niess R, Scheibel LA, Seidl M, Hohloch S. A mesoionic carbene stabilized nickel(II) hydroxide complex: a facile precursor for C-H activation chemistry. Dalton Trans 2024; 53:2749-2761. [PMID: 38226674 DOI: 10.1039/d3dt03746k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2024]
Abstract
We report the synthesis of a new nickel(II) hydroxide complex 2 supported by a rigid, tridentate triazolylidene-carbazolid ligand. The complex can be accessed in high yields following a simple and stepwise extraction protocol using dichloromethane and aqueous ammonium chloride followed by aqeous sodium hydroxide solution. We found that complex 2 is highly basic, undergoing various deprotonation/desilylation reactions with E-H and C-H acidic and silylated compounds. In this context we synthesized a variety of novel, functionalized nickel(II) complexes with trimethylsilylolate (3), trityl sulfide (4), tosyl amide (5), azido (6), pyridine (7), acetylide (8, 9), fluoroarene (10 & 11) and enolate (12) ligands. We furthermore found that 2 reacts with malonic acid dimethyl ester in a knoevennagel-type condensation reaction, giving access to a new enolate ligand in complex 13, consisting of two malonic acid units. Furthermore, complex 2 reacts with acetonitrile to form the cyanido complex 14. The formation of complexes 13 and 14 is particularly interesting, as they underline the potential of complex 2 in both C-C bond formation and cleavage reactions.
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Affiliation(s)
- Anna Pavun
- Universität Innsbruck, Department of General, Inorganic and Theoretical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Raffael Niess
- Universität Innsbruck, Department of General, Inorganic and Theoretical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Lucas A Scheibel
- Universität Innsbruck, Department of General, Inorganic and Theoretical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Michael Seidl
- Universität Innsbruck, Department of General, Inorganic and Theoretical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Stephan Hohloch
- Universität Innsbruck, Department of General, Inorganic and Theoretical Chemistry, Innrain 80-82, 6020 Innsbruck, Austria.
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8
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Liu Y, Harnden KA, Van Stappen C, Dikanov SA, Lu Y. A designed Copper Histidine-brace enzyme for oxidative depolymerization of polysaccharides as a model of lytic polysaccharide monooxygenase. Proc Natl Acad Sci U S A 2023; 120:e2308286120. [PMID: 37844252 PMCID: PMC10614608 DOI: 10.1073/pnas.2308286120] [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: 05/19/2023] [Accepted: 09/03/2023] [Indexed: 10/18/2023] Open
Abstract
The "Histidine-brace" (His-brace) copper-binding site, composed of Cu(His)2 with a backbone amine, is found in metalloproteins with diverse functions. A primary example is lytic polysaccharide monooxygenase (LPMO), a class of enzymes that catalyze the oxidative depolymerization of polysaccharides, providing not only an energy source for native microorganisms but also a route to more effective industrial biomass conversion. Despite its importance, how the Cu His-brace site performs this unique and challenging oxidative depolymerization reaction remains to be understood. To answer this question, we have designed a biosynthetic model of LPMO by incorporating the Cu His-brace motif into azurin, an electron transfer protein. Spectroscopic studies, including ultraviolet-visible (UV-Vis) absorption and electron paramagnetic resonance, confirm copper binding at the designed His-brace site. Moreover, the designed protein is catalytically active towards both cellulose and starch, the native substrates of LPMO, generating degraded oligosaccharides with multiturnovers by C1 oxidation. It also performs oxidative cleavage of the model substrate 4-nitrophenyl-D-glucopyranoside, achieving a turnover number ~9% of that of a native LPMO assayed under identical conditions. This work presents a rationally designed artificial metalloenzyme that acts as a structural and functional mimic of LPMO, which provides a promising system for understanding the role of the Cu His-brace site in LPMO activity and potential application in polysaccharide degradation.
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Affiliation(s)
- Yiwei Liu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL61801
- Department of Chemistry, University of Texas at Austin, Austin, TX78712
| | - Kevin A. Harnden
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL61801
| | - Casey Van Stappen
- Department of Chemistry, University of Texas at Austin, Austin, TX78712
| | - Sergei A. Dikanov
- Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, IL61801
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL61801
- Department of Chemistry, University of Texas at Austin, Austin, TX78712
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9
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Hall K, Joseph C, Ayuso-Fernández I, Tamhankar A, Rieder L, Skaali R, Golten O, Neese F, Røhr ÅK, Jannuzzi SAV, DeBeer S, Eijsink VGH, Sørlie M. A Conserved Second Sphere Residue Tunes Copper Site Reactivity in Lytic Polysaccharide Monooxygenases. J Am Chem Soc 2023; 145:18888-18903. [PMID: 37584157 PMCID: PMC10472438 DOI: 10.1021/jacs.3c05342] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Indexed: 08/17/2023]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are powerful monocopper enzymes that can activate strong C-H bonds through a mechanism that remains largely unknown. Herein, we investigated the role of a conserved glutamine/glutamate in the second coordination sphere. Mutation of the Gln in NcAA9C to Glu, Asp, or Asn showed that the nature and distance of the headgroup to the copper fine-tune LPMO functionality and copper reactivity. The presence of Glu or Asp close to the copper lowered the reduction potential and decreased the ratio between the reduction and reoxidation rates by up to 500-fold. All mutants showed increased enzyme inactivation, likely due to changes in the confinement of radical intermediates, and displayed changes in a protective hole-hopping pathway. Electron paramagnetic resonance (EPR) and X-ray absorption spectroscopic (XAS) studies gave virtually identical results for all NcAA9C variants, showing that the mutations do not directly perturb the Cu(II) ligand field. DFT calculations indicated that the higher experimental reoxidation rate observed for the Glu mutant could be reconciled if this residue is protonated. Further, for the glutamic acid form, we identified a Cu(III)-hydroxide species formed in a single step on the H2O2 splitting path. This is in contrast to the Cu(II)-hydroxide and hydroxyl intermediates, which are predicted for the WT and the unprotonated glutamate variant. These results show that this second sphere residue is a crucial determinant of the catalytic functioning of the copper-binding histidine brace and provide insights that may help in understanding LPMOs and LPMO-inspired synthetic catalysts.
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Affiliation(s)
- Kelsi
R. Hall
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Chris Joseph
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Iván Ayuso-Fernández
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Ashish Tamhankar
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Lukas Rieder
- Institute
for Molecular Biotechnology, Graz University
of Technology, 8010, Graz, Austria
| | - Rannei Skaali
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Ole Golten
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Frank Neese
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Åsmund K. Røhr
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Sergio A. V. Jannuzzi
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Serena DeBeer
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Vincent G. H. Eijsink
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Morten Sørlie
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
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10
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Bera M, Kaur S, Keshari K, Santra A, Moonshiram D, Paria S. Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies. Inorg Chem 2023; 62:5387-5399. [PMID: 36972560 DOI: 10.1021/acs.inorgchem.2c04168] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
The formation of Cu(III) species are often invoked as the key intermediate in Cu-catalyzed organic transformation reactions. In this study, we synthesized Cu(II) (1) and Cu(III) (3) complexes supported by a bisamidate-bisalkoxide ligand consisting of an ortho-phenylenediamine (o-PDA) scaffold and characterized them through an array of spectroscopic techniques, including UV-visible, electron paramagnetic resonance, X-ray crystallography, and 1H nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy. The Cu-N/O bond distances in 3 are ∼0.1 Å reduced compared to 1, implying a significant increase in 3's overall effective nuclear charge. Further, a Cu(III) complex (4) of a bisamidate-bisalkoxide ligand containing a trans-cyclohexane-1,2-diamine moiety exhibits nearly identical Cu-N/O bond distances to that of 3, inferring that the redox-active o-PDA backbone is not oxidized upon one-electron oxidation of the Cu(II) complex (1). In addition, a considerable difference in the 1s → 4p and 1s → 3d transition energy was observed in the X-ray absorption near-edge structure data of 3 vs 1, which is typical for the metal-centered oxidation process. Electrochemical measurements of the Cu(II) complex (1) in acetonitrile exhibited two consecutive redox couples at -0.9 and 0.4 V vs the Fc+/Fc reference electrode. One-electron oxidation reaction of 3 further resulted in the formation of a ligand-oxidized Cu complex (3a), which was characterized in depth. Reactivity studies of species 3 and 3a were explored toward the activation of the C-H/O-H bonds. A bond dissociation free energy (BDFE) value of ∼69 kcal/mol was estimated for the O-H bond of the Cu(II) complex formed upon transfer of hydrogen atom to 3. The study represents a thorough spectroscopic characterization of high-valent Cu complexes and sheds light on the PCET reactivity studies of Cu(III) complexes.
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Affiliation(s)
- Moumita Bera
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Simarjeet Kaur
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Kritika Keshari
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Aakash Santra
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Dooshaye Moonshiram
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Sayantan Paria
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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11
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Hagemann MM, Hedegård ED. Molecular Mechanism of Substrate Oxidation in Lytic Polysaccharide Monooxygenases: Insight from Theoretical Investigations. Chemistry 2023; 29:e202202379. [PMID: 36207279 PMCID: PMC10107554 DOI: 10.1002/chem.202202379] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Indexed: 12/12/2022]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper enzymes that today comprise a large enzyme superfamily, grouped into the distinct members AA9-AA17 (with AA12 exempted). The LPMOs have the potential to facilitate the upcycling of biomass waste products by boosting the breakdown of cellulose and other recalcitrant polysaccharides. The cellulose biopolymer is the main component of biomass waste and thus comprises a large, unexploited resource. The LPMOs work through a catalytic, oxidative reaction whose mechanism is still controversial. For instance, the nature of the intermediate performing the oxidative reaction is an open question, and the same holds for the employed co-substrate. Here we review theoretical investigations addressing these questions. The applied theoretical methods are usually based on quantum mechanics (QM), often combined with molecular mechanics (QM/MM). We discuss advantages and disadvantages of the employed theoretical methods and comment on the interplay between theoretical and experimental results.
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Affiliation(s)
- Marlisa M Hagemann
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
| | - Erik D Hedegård
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
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12
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Bower JK, Reese MS, Mazin IM, Zarnitsa LM, Cypcar AD, Moore CE, Sokolov AY, Zhang S. C(sp 3)-H cyanation by a formal copper(iii) cyanide complex. Chem Sci 2023; 14:1301-1307. [PMID: 36756315 PMCID: PMC9891353 DOI: 10.1039/d2sc06573h] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 01/05/2023] [Indexed: 01/18/2023] Open
Abstract
High-valent metal oxo complexes are prototypical intermediates for the activation and hydroxylation of alkyl C-H bonds. Substituting the oxo ligand with other functional groups offers the opportunity for additional C-H functionalization beyond C-O bond formation. However, few species aside from metal oxo complexes have been reported to both activate and functionalize alkyl C-H bonds. We herein report the first example of an isolated copper(iii) cyanide complex (LCuIIICN) and its C-H cyanation reactivity. We found that the redox potential (E ox) of substrates, instead of C-H bond dissociation energy, is a key determinant of the rate of PCET, suggesting an oxidative asynchronous CPET or ETPT mechanism. Among substrates with the same BDEs, those with low redox potentials transfer H atoms up to a million-fold faster. Capitalizing on this mechanistic insight, we found that LCuIIICN is highly selective for cyanation of amines, which is predisposed to oxidative asynchronous or stepwise transfer of H+/e-. Our study demonstrates that the asynchronous effect of PCET is an appealing tool for controlling the selectivity of C-H functionalization.
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Affiliation(s)
- Jamey K. Bower
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Maxwell S. Reese
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Ilia M. Mazin
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Lina M. Zarnitsa
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Andrew D. Cypcar
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Curtis E. Moore
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Alexander Yu. Sokolov
- Department of Chemistry and Biochemistry, The Ohio State University100 W. 18 AveColumbusOH43210USA
| | - Shiyu Zhang
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH 43210 USA
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13
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Maldonado-Domínguez M, Srnec M. Quantifiable polarity match effect on C-H bond cleavage reactivity and its limits in reaction design. Dalton Trans 2023; 52:1399-1412. [PMID: 36644790 DOI: 10.1039/d2dt04018b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
When oxidants favour cleaving a strong C-H bond at the expense of weaker ones, which are otherwise inherently preferred due to their favourable reaction energy, reactivity factors such as the polarity match effect are often invoked. Polarity match follows the intuition of electrophilic (nucleophilic) oxidants reacting faster with nucleophilic (electrophilic) C-H bonds. Nevertheless, this concept is purely qualitative and is best suited for a posteriori rationalization of experimental observations. Here, we propose and inspect two methods to quantify polar effects in C-H cleavage reactions, one by computation via the difference of atomic charges (Δq) of reacting atoms, and one amenable to experimental measurement through asynchronicity factors, η. By their application to three case studies, we observe that both Δq and η faithfully capture the notion of polarity match. The polarity match model, however, proves insufficient as a predictor of H-atom abstraction reactivity and we discourage its use as a standalone variable in reaction design. Besides this caveat, η and Δq (through its mapping on η) allow the implementation of polarity match into a Marcus-type model of reactivity, alleviating its shortcomings and making reaction planning feasible.
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Affiliation(s)
- Mauricio Maldonado-Domínguez
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic.
| | - Martin Srnec
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic.
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14
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Hintz H, Bower J, Tang J, LaLama M, Sevov C, Zhang S. Copper-Catalyzed Electrochemical C-H Fluorination. CHEM CATALYSIS 2023; 3:100491. [PMID: 36743279 PMCID: PMC9894310 DOI: 10.1016/j.checat.2022.100491] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We report the systematic development of an electrooxidative methodology that translates stoichiometric C-H fluorination reactivity of an isolable CuIII fluoride complex into a catalytic process. The critical challenges of electrocatalysis with a highly reactive CuIII species were addressed by the judicious selection of electrolyte, F- source, and sacrificial electron acceptor. Catalyst-controlled C-H fluorination occurs with a preference for hydridic C-H bonds with high bond dissociation energies over weaker but less hydridic C-H bonds. The selectivity is driven by an oxidative asynchronous proton-coupled elelctron transfer (PCET) at an electrophilic CuIII-F complex. We further demonstrate that the asynchronicity factor of hydrogen atom transfer η can be used as a guideline to rationalize the selectivity of C-H fluorination.
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Affiliation(s)
- Heather Hintz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
| | - Jamey Bower
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
| | - Jinghua Tang
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
| | - Matthew LaLama
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
| | - Christo Sevov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
| | - Shiyu Zhang
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
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15
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Jeong D, Kim H, Cho J. Oxidation of Aldehydes into Carboxylic Acids by a Mononuclear Manganese(III) Iodosylbenzene Complex through Electrophilic C-H Bond Activation. J Am Chem Soc 2023; 145:888-897. [PMID: 36598425 DOI: 10.1021/jacs.2c09274] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The oxidation of aldehyde is one of the fundamental reactions in the biological system. Various synthetic procedures and catalysts have been developed to convert aldehydes into corresponding carboxylic acids efficiently under ambient conditions. In this work, we report the oxidation of aldehydes by a mononuclear manganese(III) iodosylbenzene complex, [MnIII(TBDAP)(OIPh)(OH)]2+ (1), with kinetic and mechanistic studies in detail. The reaction of 1 with aldehydes resulted in the formation of corresponding carboxylic acids via a pre-equilibrium state. Hammett plot and reaction rates of 1 with 1°-, 2°-, and 3°-aldehydes revealed the electrophilicity of 1 in the aldehyde oxidation. A kinetic isotope effect experiment and reactivity of 1 toward cyclohexanecarboxaldehyde (CCA) analogues indicate that the reaction of 1 with aldehyde occurs through the rate-determining C-H bond activation at the formyl group. The reaction rate of 1 with CCA is correlated to the bond dissociation energy of the formyl group plotting a linear correlation with other aliphatic C-H bonds. Density functional theory calculations found that 1 electrostatically interacts with CCA at the pre-equilibrium state in which the C-H bond activation of the formyl group is performed as the most feasible pathway. Surprisingly, the rate-determining step is characterized as hydride transfer from CCA to 1, affording an (oxo)methylium intermediate. At the fundamental level, it is revealed that the hydride transfer is composed of H atom abstraction followed by a fast electron transfer. Catalytic reactions of aldehydes by 1 are also presented with a broad substrate scope. This novel mechanistic study gives better insights into the metal oxygen chemistry and would be prominently valuable for development of transition metal catalysts.
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Affiliation(s)
- Donghyun Jeong
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan44919, Republic of Korea
| | - Hyokyung Kim
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan44919, Republic of Korea
| | - Jaeheung Cho
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan44919, Republic of Korea.,Graduate School of Carbon Neutrality, Ulsan National Institute of Science and Technology (UNIST), Ulsan44919, Republic of Korea
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16
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Schröder GC, O'Dell WB, Webb SP, Agarwal PK, Meilleur F. Capture of activated dioxygen intermediates at the copper-active site of a lytic polysaccharide monooxygenase. Chem Sci 2022; 13:13303-13320. [PMID: 36507176 PMCID: PMC9683017 DOI: 10.1039/d2sc05031e] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 10/19/2022] [Indexed: 11/24/2022] Open
Abstract
Metalloproteins perform a diverse array of redox-related reactions facilitated by the increased chemical functionality afforded by their metallocofactors. Lytic polysaccharide monooxygenases (LPMOs) are a class of copper-dependent enzymes that are responsible for the breakdown of recalcitrant polysaccharides via oxidative cleavage at the glycosidic bond. The activated copper-oxygen intermediates and their mechanism of formation remains to be established. Neutron protein crystallography which permits direct visualization of protonation states was used to investigate the initial steps of oxygen activation directly following active site copper reduction in Neurospora crassa LPMO9D. Herein, we cryo-trap an activated dioxygen intermediate in a mixture of superoxo and hydroperoxo states, and we identify the conserved second coordination shell residue His157 as the proton donor. Density functional theory calculations indicate that both superoxo and hydroperoxo active site states are stable. The hydroperoxo formed is potentially an early LPMO catalytic reaction intermediate or the first step in the mechanism of hydrogen peroxide formation in the absence of substrate. We observe that the N-terminal amino group of the copper coordinating His1 remains doubly protonated directly following molecular oxygen reduction by copper. Aided by molecular dynamics and mining minima free energy calculations we establish that the conserved second-shell His161 in MtPMO3* displays conformational flexibility in solution and that this flexibility is also observed, though to a lesser extent, in His157 of NcLPMO9D. The imidazolate form of His157 observed in our structure following oxygen intermediate protonation can be attributed to abolished His157 flexibility due steric hindrance in the crystal as well as the solvent-occluded active site environment due to crystal packing. A neutron crystal structure of NcLPMO9D at low pH further supports occlusion of the active site since His157 remains singly protonated even at acidic conditions.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State UniversityRaleighNC 27695USA,Neutron Scattering Division, Oak Ridge National LaboratoryOak RidgeTN 37831USA
| | - William B. O'Dell
- Department of Molecular and Structural Biochemistry, North Carolina State UniversityRaleighNC 27695USA,Neutron Scattering Division, Oak Ridge National LaboratoryOak RidgeTN 37831USA
| | - Simon P. Webb
- VeraChem LLC12850 Middlebrook Rd. Ste 205GermantownMD 20874-5244USA
| | - Pratul K. Agarwal
- Department of Physiological Sciences and High-Performance Computing Center, Oklahoma State UniversityStillwaterOK 74078USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State UniversityRaleighNC 27695USA,Neutron Scattering Division, Oak Ridge National LaboratoryOak RidgeTN 37831USA
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17
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Maldonado-Domínguez M, Srnec M. H-Atom Abstraction Reactivity through the Lens of Asynchronicity and Frustration with Their Counteracting Effects on Barriers. Inorg Chem 2022; 61:18811-18822. [DOI: 10.1021/acs.inorgchem.2c03269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Mauricio Maldonado-Domínguez
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 18223, Czech Republic
| | - Martin Srnec
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 18223, Czech Republic
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18
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Cooney SE, Fertig AA, Buisch MR, Brennessel WW, Matson EM. Coordination-induced bond weakening of water at the surface of an oxygen-deficient polyoxovanadate cluster. Chem Sci 2022; 13:12726-12737. [PMID: 36519047 PMCID: PMC9645371 DOI: 10.1039/d2sc04843d] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/10/2022] [Indexed: 10/19/2023] Open
Abstract
Hydrogen-atom (H-atom) transfer at the surface of heterogeneous metal oxides has received significant attention owing to its relevance in energy conversion and storage processes. Here, we present the synthesis and characterization of an organofunctionalized polyoxovanadate cluster, (calix)V6O5(OH2)(OMe)8 (calix = 4-tert-butylcalix[4]arene). Through a series of equilibrium studies, we establish the BDFE(O-H)avg of the aquo ligand as 62.4 ± 0.2 kcal mol-1, indicating substantial bond weaking of water upon coordination to the cluster surface. Subsequent kinetic isotope effect studies and Eyring analysis indicate the mechanism by which the hydrogenation of organic substrates occurs proceeds through a concerted proton-electron transfer from the aquo ligand. Atomistic resolution of surface reactivity presents a novel route of hydrogenation reactivity from metal oxide surfaces through H-atom transfer from surface-bound water molecules.
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Affiliation(s)
- Shannon E Cooney
- Department of Chemistry, University of Rochester Rochester NY 14627 USA
| | - Alex A Fertig
- Department of Chemistry, University of Rochester Rochester NY 14627 USA
| | | | | | - Ellen M Matson
- Department of Chemistry, University of Rochester Rochester NY 14627 USA
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19
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Bouchey C, Shopov DY, Gruen AD, Tolman WB. Mimicking the Cu Active Site of Lytic Polysaccharide Monooxygenase Using Monoanionic Tridentate N-Donor Ligands. ACS OMEGA 2022; 7:35217-35232. [PMID: 36211076 PMCID: PMC9535706 DOI: 10.1021/acsomega.2c04432] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 09/02/2022] [Indexed: 06/16/2023]
Abstract
In an effort to prepare small molecule mimics of the active site of lytic polysaccharide monooxygenase (LPMO), three monoanionic tridentate N donor ligands comprising a central deprotonated amide group flanked by two neutral donors were prepared, and their coordination chemistry with Cu(I) and Cu(II) was evaluated. With Cu(I), a dimer formed, which was characterized by X-ray crystallography and NMR spectroscopy. A variety of mononuclear and dinuclear Cu(II) species with a range of auxiliary ligands (MeCN, Cl-, OH-, OAc-, OBz-, CO3 2-) were prepared and characterized by X-ray diffraction and various spectroscopies (UV-vis, EPR). The complexes exhibit structural similarities to the LPMO active site.
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Affiliation(s)
- Caitlin
J. Bouchey
- Department
of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - Dimitar Y. Shopov
- Department
of Chemistry, Washington University in St.
Louis, One Brookings Drive, Campus Box 1134, St.
Louis, Missouri 63130, United States
| | - Aaron D. Gruen
- Department
of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - William B. Tolman
- Department
of Chemistry, Washington University in St.
Louis, One Brookings Drive, Campus Box 1134, St.
Louis, Missouri 63130, United States
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20
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Cha J, Lee E, Yandulov DV. Mechanistic Studies for Pd(II)(O 2) Reduction Generating Pd(0) and H 2O: Formation of Pd(OH) 2 as a Key Intermediate. Inorg Chem 2022; 61:14544-14552. [PMID: 36050901 DOI: 10.1021/acs.inorgchem.2c01139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Molecular oxygen (O2) remains to be an ideal yet underutilized feedstock for the oxidative transformation of organic substrates and renewable energy systems such as fuel cells. Palladium (Pd) has shown particular promise in enabling these applications. The present study describes a Pd-mediated O2 reduction to water via C-H activation of 9,10-dihydroanthracene (DHA) by a Pd(II) η2-peroxo complex 1O2. The reaction yields stoichiometric anthracene and Pd(0) product 1 and is notable in two respects. First, plots of concentrations of the reaction participants over time have distinctly sigmoidal shapes, indicating that conversion accelerates over time and implying autocatalysis. Second, the reaction proceeds via a genuine monometallic Pd(II) dihydroxide 1(OH)2 directly observed to grow and decay as an intermediate. Confirming its role as an intermediate, the dihydroxide 1(OH)2 was found to mediate C-H oxidation of DHA on par in activity with the peroxo compound 1O2. Mechanistic studies with density functional theory (DFT) calculations suggested that both 1O2 and 1(OH)2 react with DHA by hydrogen atom transfer (HAT) and that autocatalysis in the 1O2 reaction results from oxidative addition of the initial Pd(II) complex 1O2 to the Pd(0) product 1. This reaction forms a transient bis(μ-oxo) Pd(II) dimer 1O21 that is more active in the HAT oxidation of DHA than the initial 1O2.
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Affiliation(s)
- Jeongmin Cha
- Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.,Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Dmitry V Yandulov
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States.,Department of Biology and Biotechnology, National Research University Higher School of Economics, Moscow 117418, Russia
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21
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McKee ML. Exploring the Reaction Mechanism of C-H Oxidation by Copper-Salen Complexes. J Phys Chem A 2022; 126:4969-4980. [PMID: 35861503 DOI: 10.1021/acs.jpca.2c03344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of C-H oxidation of propylene (C3H6) and 1-phenyl-1-pentyne (C3H7-C≡C-Ph) by HOOR (R═Me, tBu) and 3O2 by a copper-salen complex was explored by computations. The most noteworthy step is the complexation of two Cu salens to the peroxide to form either the LCuOH/LCuOR pair or an OH-bridged complex LCu(μ-OH)CuL plus OR. The latter pathway involves an avoided crossing of two triplet electronic states. The LCuOH complex can abstract a hydrogen atom from C3H6 and the C3H5 radical plus 3O2 forms the complex LCuOOC3H5. Migration of a hydrogen to the proximal oxygen atom reforms LCuOH and acrolein HC(O)CH═CH2.
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Affiliation(s)
- Michael L McKee
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama36849, United States
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22
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Engbers S, Leach IF, Havenith RWA, Klein JEMN. Homolytic X‐H Bond Cleavage at a Gold(III) Hydroxide: Insights into One‐Electron Events at Gold. Chemistry 2022; 28:e202200599. [PMID: 35506505 PMCID: PMC9401072 DOI: 10.1002/chem.202200599] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Indexed: 11/17/2022]
Abstract
C(sp3)‐H and O−H bond breaking steps in the oxidation of 1,4‐cyclohexadiene and phenol by a Au(III)‐OH complex were studied computationally. The analysis reveals that for both types of bonds the initial X−H cleavage step proceeds via concerted proton coupled electron transfer (cPCET), reflecting electron transfer from the substrate directly to the Au(III) centre and proton transfer to the Au‐bound oxygen. This mechanistic picture is distinct from the analogous formal Cu(III)‐OH complexes studied by the Tolman group (J. Am. Chem. Soc. 2019, 141, 17236–17244), which proceed via hydrogen atom transfer (HAT) for C−H bonds and cPCET for O−H bonds. Hence, care should be taken when transferring concepts between Cu−OH and Au−OH species. Furthermore, the ability of Au−OH complexes to perform cPCET suggests further possibilities for one‐electron chemistry at the Au centre, for which only limited examples exist.
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Affiliation(s)
- Silène Engbers
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen (The Netherlands
| | - Isaac F. Leach
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen (The Netherlands
- Zernike Institute for Advanced Materials Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen (The Netherlands
| | - Remco W. A. Havenith
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen (The Netherlands
- Zernike Institute for Advanced Materials Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen (The Netherlands
- Ghent Quantum Chemistry Group Department of Chemistry Ghent University Ghent 9000 Gent Belgium
| | - Johannes E. M. N. Klein
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen (The Netherlands
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23
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Kwon YM, Lee Y, Schmautz AK, Jackson TA, Wang D. C-H Bond Activation by a Mononuclear Nickel(IV)-Nitrate Complex. J Am Chem Soc 2022; 144:12072-12080. [PMID: 35767834 DOI: 10.1021/jacs.2c02454] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The recent focus on developing high-valent non-oxo-metal complexes for late transition metals has proven to be an effective strategy to study the rich chemistry of these high-valent species while bypassing the synthetic challenges of obtaining the oxo-metal counterparts. In our continuing work of exploring late transition metal complexes of unusually high oxidation states, we have obtained in the present study a formal mononuclear Ni(IV)-nitrate complex (2) upon 1-e- oxidation of its Ni(III) derivatives (1-OH and 1-NO3). Characterization of these Ni complexes by combined spectroscopic and computational approaches enables deep understanding of their geometric and electronic structures, bonding interactions, and spectroscopic properties, showing that all of them are square planar complexes and exhibit strong π-covalency with the amido N-donors of the N3 ligand. Furthermore, results obtained from X-ray absorption spectroscopy and density functional theory calculations provide strong support for the assignment of the Ni(IV) oxidation state of complex 2, albeit with strong ligand-to-metal charge donation. Notably, 2 is able to oxidize hydrocarbons with C-H bond strength in the range of 76-92 kcal/mol, representing a rare example of high-valent late transition metal complexes capable of activating strong sp3 C-H bonds.
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Affiliation(s)
- Yubin M Kwon
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Yuri Lee
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Anna K Schmautz
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Timothy A Jackson
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Dong Wang
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana 59812, United States
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24
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Theoretical perspective on mononuclear copper-oxygen mediated C–H and O–H activations: A comparison between biological and synthetic systems. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(21)63974-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Park Y, Kim S, Kim K, Shin B, Jang Y, Cho KB, Cho J. Structure and Reactivity of Nonporphyrinic Terminal Manganese(IV)-Hydroxide Complexes in the Oxidative Electrophilic Reaction. Inorg Chem 2022; 61:4292-4301. [PMID: 35226491 DOI: 10.1021/acs.inorgchem.1c03104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
High-valent transition metal-hydroxide complexes have been proposed as essential intermediates in biological and synthetic catalytic reactions. In this work, we report the single-crystal X-ray structure and spectroscopic characteristics of a mononuclear nonporphyrinic MnIV-(OH) complex, [MnIV(Me3-TPADP)(OH)(OCH2CH3)]2+ (2), using various physicochemical methods. Likewise, [MnIV(Me3-TPADP)(OH)(OCH2CF3)]2+ (3), which is thermally stable at room temperature, was also synthesized and characterized spectroscopically. The MnIV-(OH) adducts are capable of performing oxidation reactions with external organic substrates such as C-H bond activation, sulfoxidation, and epoxidation. Kinetic studies, involving the Hammett correlation and kinetic isotope effect, and product analyses indicate that 2 and 3 exhibit electrophilic oxidative reactivity toward hydrocarbons. Density functional theory calculations support the assigned electronic structure and show that direct C-H bond activation of the MnIV-(OH) species is indeed possible.
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Affiliation(s)
- Younwoo Park
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.,Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Seonghan Kim
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.,Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Kyungmin Kim
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.,Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Bongki Shin
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Youngchae Jang
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Kyung-Bin Cho
- Department of Chemistry, Jeonbuk National University, Jeonju 54896, Korea
| | - Jaeheung Cho
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea
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Wu S, Kaur J, Karl TA, Tian X, Barham JP. Synthetische molekulare Photoelektrochemie: neue synthetische Anwendungen, mechanistische Einblicke und Möglichkeiten zur Skalierung. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202107811] [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)
- Shangze Wu
- Universität Regensburg Fakultät für Chemie und Pharmazie 93040 Regensburg Deutschland
| | - Jaspreet Kaur
- Universität Regensburg Fakultät für Chemie und Pharmazie 93040 Regensburg Deutschland
| | - Tobias A. Karl
- Universität Regensburg Fakultät für Chemie und Pharmazie 93040 Regensburg Deutschland
| | - Xianhai Tian
- Universität Regensburg Fakultät für Chemie und Pharmazie 93040 Regensburg Deutschland
| | - Joshua P. Barham
- Universität Regensburg Fakultät für Chemie und Pharmazie 93040 Regensburg Deutschland
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Bouchey CJ, Tolman WB. Involvement of a Formally Copper(III) Nitrite Complex in Proton-Coupled Electron Transfer and Nitration of Phenols. Inorg Chem 2022; 61:2662-2668. [PMID: 35078314 PMCID: PMC9835712 DOI: 10.1021/acs.inorgchem.1c03790] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A unique high-valent copper nitrite species, LCuNO2, was accessed via the reversible one-electron oxidation of [M][LCuNO2] (M = NBu4+ or PPN+). The complex LCuNO2 reacts with 2,4,6-tri-tert-butylphenol via a typical proton-coupled electron transfer (PCET) to yield LCuTHF and the 2,4,6-tri-tert-butylphenoxyl radical. The reaction between LCuNO2 and 2,4-di-tert-butylphenol was more complicated. It yielded two products: the coupled bisphenol product expected from a H-atom abstraction and 2,4-di-tert-butyl-6-nitrophenol, the product of an unusual anaerobic nitration. Various mechanisms for the latter transformation were considered.
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Affiliation(s)
- Caitlin J Bouchey
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, Campus Box 1134, St. Louis, Missouri 63130, United States
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - William B Tolman
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, Campus Box 1134, St. Louis, Missouri 63130, United States
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28
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Copper monooxygenase reactivity: Do consensus mechanisms accurately reflect experimental observations? J Inorg Biochem 2022; 231:111780. [DOI: 10.1016/j.jinorgbio.2022.111780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/21/2022]
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29
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Goetz MK, Schneider JE, Filatov AS, Jesse KA, Anderson JS. Enzyme-Like Hydroxylation of Aliphatic C-H Bonds From an Isolable Co-Oxo Complex. J Am Chem Soc 2021; 143:20849-20862. [PMID: 34856101 DOI: 10.1021/jacs.1c09280] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The selective hydroxylation of aliphatic C-H bonds remains a challenging but broadly useful transformation. Nature has evolved systems that excel at this reaction, exemplified by cytochrome P450 enzymes, which use an iron-oxo intermediate to activate aliphatic C-H bonds with k1 > 1400 s-1 at 4 °C. Many synthetic catalysts have been inspired by these enzymes and are similarly proposed to use transition metal-oxo intermediates. However, most examples of well-characterized transition metal-oxo species are not capable of reacting with strong, aliphatic C-H bonds, resulting in a lack of understanding of what factors facilitate this reactivity. Here, we report the isolation and characterization of a new terminal CoIII-oxo complex, PhB(AdIm)3CoIIIO. Upon oxidation, a transient CoIV-oxo intermediate is generated that is capable of hydroxylating aliphatic C-H bonds with an extrapolated k1 for C-H activation >130 s-1 at 4 °C, comparable to values observed in cytochrome P450 enzymes. Experimental thermodynamic values and DFT analysis demonstrate that, although the initial C-H activation step in this reaction is endergonic, the overall reaction is driven by an extremely exergonic radical rebound step, similar to what has been proposed in cytochrome P450 enzymes. The rapid C-H hydroxylation reactivity displayed in this well-defined system provides insight into how hydroxylation is accomplished by biological systems and similarly potent synthetic oxidants.
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Affiliation(s)
- McKenna K Goetz
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Joseph E Schneider
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Alexander S Filatov
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Kate A Jesse
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - John S Anderson
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
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30
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Panda C, Doyle LM, Gericke R, McDonald AR. Rapid Iron(III)−Fluoride‐Mediated Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202112683] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Chakadola Panda
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
| | - Lorna M. Doyle
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
| | - Robert Gericke
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
- Current address: Helmholtz-Zentrum Dresden-Rossendorf e. V. Institute of Resource Ecology Bautzner Landstrasse 400 01328 Dresden Germany
| | - Aidan R. McDonald
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
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31
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Schröder GC, Meilleur F. Metalloprotein catalysis: structural and mechanistic insights into oxidoreductases from neutron protein crystallography. Acta Crystallogr D Struct Biol 2021; 77:1251-1269. [PMID: 34605429 PMCID: PMC8489226 DOI: 10.1107/s2059798321009025] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
Metalloproteins catalyze a range of reactions, with enhanced chemical functionality due to their metal cofactor. The reaction mechanisms of metalloproteins have been experimentally characterized by spectroscopy, macromolecular crystallography and cryo-electron microscopy. An important caveat in structural studies of metalloproteins remains the artefacts that can be introduced by radiation damage. Photoreduction, radiolysis and ionization deriving from the electromagnetic beam used to probe the structure complicate structural and mechanistic interpretation. Neutron protein diffraction remains the only structural probe that leaves protein samples devoid of radiation damage, even when data are collected at room temperature. Additionally, neutron protein crystallography provides information on the positions of light atoms such as hydrogen and deuterium, allowing the characterization of protonation states and hydrogen-bonding networks. Neutron protein crystallography has further been used in conjunction with experimental and computational techniques to gain insight into the structures and reaction mechanisms of several transition-state metal oxidoreductases with iron, copper and manganese cofactors. Here, the contribution of neutron protein crystallography towards elucidating the reaction mechanism of metalloproteins is reviewed.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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32
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Abstract
The fields of C-H functionalization and photoredox catalysis have garnered enormous interest and utility in the past several decades. Many different scientific disciplines have relied on C-H functionalization and photoredox strategies including natural product synthesis, drug discovery, radiolabeling, bioconjugation, materials, and fine chemical synthesis. In this Review, we highlight the use of photoredox catalysis in C-H functionalization reactions. We separate the review into inorganic/organometallic photoredox catalysts and organic-based photoredox catalytic systems. Further subdivision by reaction class-either sp2 or sp3 C-H functionalization-lends perspective and tactical strategies for use of these methods in synthetic applications.
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Affiliation(s)
- Natalie Holmberg-Douglas
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - David A Nicewicz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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33
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Panda C, Doyle LM, Gericke R, McDonald AR. Rapid Iron(III)-Fluoride-Mediated Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2021; 60:26281-26286. [PMID: 34582619 PMCID: PMC9298026 DOI: 10.1002/anie.202112683] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Indexed: 01/08/2023]
Abstract
We anticipate high-valent metal-fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H-F bond (in the product) that drives HAT oxidation. We prepared a dimeric FeIII (F)-F-FeIII (F) complex (1) by reacting [FeII (NCCH3 )2 (TPA)](ClO4 )2 (TPA=tris(2-pyridylmethyl)amine) with difluoro(phenyl)-λ3 -iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Brønsted acids to yield a monomeric [FeIII (TPA)(F)(X)]+ complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive FeIII reagent for oxidative C-H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive FeIII and FeIV oxidants.
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Affiliation(s)
- Chakadola Panda
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Lorna M Doyle
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Robert Gericke
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland.,Current address: Helmholtz-Zentrum Dresden-Rossendorf e. V., Institute of Resource Ecology, Bautzner Landstrasse 400, 01328, Dresden, Germany
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
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34
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Barman SK, Yang MY, Parsell TH, Green MT, Borovik AS. Semiempirical method for examining asynchronicity in metal-oxido-mediated C-H bond activation. Proc Natl Acad Sci U S A 2021; 118:e2108648118. [PMID: 34465626 PMCID: PMC8433561 DOI: 10.1073/pnas.2108648118] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The oxidation of substrates via the cleavage of thermodynamically strong C-H bonds is an essential part of mammalian metabolism. These reactions are predominantly carried out by enzymes that produce high-valent metal-oxido species, which are directly responsible for cleaving the C-H bonds. While much is known about the identity of these transient intermediates, the mechanistic factors that enable metal-oxido species to accomplish such difficult reactions are still incomplete. For synthetic metal-oxido species, C-H bond cleavage is often mechanistically described as synchronous, proton-coupled electron transfer (PCET). However, data have emerged that suggest that the basicity of the M-oxido unit is the key determinant in achieving enzymatic function, thus requiring alternative mechanisms whereby proton transfer (PT) has a more dominant role than electron transfer (ET). To bridge this knowledge gap, the reactivity of a monomeric MnIV-oxido complex with a series of external substrates was studied, resulting in a spread of over 104 in their second-order rate constants that tracked with the acidity of the C-H bonds. Mechanisms that included either synchronous PCET or rate-limiting PT, followed by ET, did not explain our results, which led to a proposed PCET mechanism with asynchronous transition states that are dominated by PT. To support this premise, we report a semiempirical free energy analysis that can predict the relative contributions of PT and ET for a given set of substrates. These findings underscore why the basicity of M-oxido units needs to be considered in C-H functionalization.
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Affiliation(s)
- Suman K Barman
- Department of Chemistry, University of California Irvine, CA 92697;
| | - Meng-Yin Yang
- Department of Chemistry, University of California Irvine, CA 92697
| | | | - Michael T Green
- Department of Chemistry, University of California Irvine, CA 92697;
- Department of Molecular Biosciences and Biochemistry, University of California Irvine, CA 92697
| | - A S Borovik
- Department of Chemistry, University of California Irvine, CA 92697;
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35
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Wu S, Kaur J, Karl TA, Tian X, Barham JP. Synthetic Molecular Photoelectrochemistry: New Frontiers in Synthetic Applications, Mechanistic Insights and Scalability. Angew Chem Int Ed Engl 2021; 61:e202107811. [PMID: 34478188 PMCID: PMC9303540 DOI: 10.1002/anie.202107811] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Indexed: 11/11/2022]
Abstract
Synthetic photoelectrochemistry (PEC) is receiving increasing attention as a new frontier for the generation and handling of reactive intermediates. PEC permits selective single‐electron transfer (SET) reactions in a much greener way and broadens the redox window of possible transformations. Herein, the most recent contributions are reviewed, demonstrating exciting new opportunities, namely, the combination of PEC with other reactivity paradigms (hydrogen‐atom transfer, radical polar crossover, energy transfer sensitization), scalability up to multigram scale, novel selectivities in SET super‐oxidations/reductions and the importance of precomplexation to temporally enable excited radical ion catalysis.
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Affiliation(s)
- Shangze Wu
- University of Regensburg: Universitat Regensburg, Fakultät für Chemie und Pharmazie, GERMANY
| | - Jaspreet Kaur
- University of Regensburg: Universitat Regensburg, Fakultät für Chemie und Pharmazie, GERMANY
| | - Tobias A Karl
- University of Regensburg: Universitat Regensburg, Fakultät für Chemie und Pharmazie, GERMANY
| | - Xianhai Tian
- University of Regensburg: Universitat Regensburg, Fakultät für Chemie und Pharmazie, GERMANY
| | - Joshua Philip Barham
- Universitat Regensburg, Fakultat fur Chemie und Pharmazie, Universität Regensburg, Fakultät für Chemie und Pharmazie, 93040, Regensburg, GERMANY
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36
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Engbers S, Trifonova EA, Hess KM, Vries F, Klein JEMN. Synthesis of a Sterically Encumbered Pincer Au(III)−OH Complex. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Silène Engbers
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Evgeniya A. Trifonova
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Kristopher M. Hess
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Folkert Vries
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Johannes E. M. N. Klein
- Molecular Inorganic Chemistry Stratingh Institute for Chemistry Faculty of Science and Engineering University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
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37
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Liu H, Shen Q. Well-defined organometallic Copper(III) complexes: Preparation, characterization and reactivity. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.213923] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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38
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Wu T, Musgrove J, Siegler MA, Garcia-Bosch I. Mononuclear and Dinuclear Copper Complexes of Tridentate Redox-active Ligands with Tunable H-bonding Donors: Structure, Spectroscopy and H + /e - Reactivity. Chem Asian J 2021; 16:1608-1618. [PMID: 33929787 DOI: 10.1002/asia.202100286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 04/29/2021] [Indexed: 11/06/2022]
Abstract
In this research article, we describe the synthesis and characterization of mononuclear and dinuclear Cu complexes bound by a family of tridentate redox-active ligands with tunable H-bonding donors. The mononuclear Cu-anion complexes were oxidized to the corresponding "high-valent" intermediates by oxidation of the redox-active ligand. These species were capable of oxidizing phenols with weak O-H bonds via H-atom abstraction. Thermodynamic analysis of the H-atom abstractions, which included reduction potential measurements, pKa determination and kinetic studies, revealed that modification of the anion coordinated to the Cu and changes in the H-bonding donor did not lead to major differences in the reactivity of the "high-valent" CuY complexes (Y: hydroxide, phenolate and acetate), which indicated that the tridentate ligand scaffold acts as the H+ and e- acceptor.
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Affiliation(s)
- Tong Wu
- Department of Chemistry, Southern Methodist University, Dallas, Texas, 75275, United States
| | - Justin Musgrove
- Department of Chemistry, Southern Methodist University, Dallas, Texas, 75275, United States
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Isaac Garcia-Bosch
- Department of Chemistry, Southern Methodist University, Dallas, Texas, 75275, United States
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40
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Wu W, De Hont JT, Parveen R, Vlaisavljevich B, Tolman WB. Sulfur-Containing Analogues of the Reactive [CuOH] 2+ Core. Inorg Chem 2021; 60:5217-5223. [PMID: 33733755 DOI: 10.1021/acs.inorgchem.1c00216] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
With the aim of drawing comparisons to the highly reactive complex LCuOH (L = bis(2,6-diisopropylphenylcarboxamido)pyridine), the complexes [Bu4N][LCuSR] (R = H or Ph) were prepared, characterized by spectroscopy and X-ray crystallography, and oxidized at low temperature to generate the species assigned as LCuSR on the basis of spectroscopy and theory. Consistent with the smaller electronegativity of S versus O, redox potentials for the LCuSR-/0 couples were ∼50 mV lower than for LCuOH-/0, and the rates of the proton-coupled electron transfer reactions of LCuSR with anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine at -80 °C were significantly slower (by more than 100 times) than the same reaction of LCuOH. Density functional theory (DFT) and time-dependent DFT calculations on LCuZ (Z = OH, SH, SPh) revealed subtle differences in structural and UV-visible parameters. Further comparison to complexes with Z = F, Cl, and Br using complete active space (CAS) self-consistent field and localized orbital CAS configuration interaction calculations along with a valence-bond-like interpretation of the wave functions showed differences with previously reported results ( J. Am. Chem. Soc. 2020, 142, 8514), and argue for a consistent electronic structure across the entire series of complexes, rather than a change in the nature of the ligand field arrangement for Z = F.
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Affiliation(s)
- Wen Wu
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
| | - Jacqui Tehranchi De Hont
- Department of Chemistry, University of Minnesota, 207 Pleasant Avenue SE, Minneapolis, Minnesota 55455, United States
| | - Riffat Parveen
- University of South Dakota, 414 E. Clark Street, Vermillion, South Dakota 57069, United States
| | - Bess Vlaisavljevich
- University of South Dakota, 414 E. Clark Street, Vermillion, South Dakota 57069, United States
| | - William B Tolman
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
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41
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Schröder GC, O’Dell WB, Swartz PD, Meilleur F. Preliminary results of neutron and X-ray diffraction data collection on a lytic polysaccharide monooxygenase under reduced and acidic conditions. Acta Crystallogr F Struct Biol Commun 2021; 77:128-133. [PMID: 33830078 PMCID: PMC8034432 DOI: 10.1107/s2053230x21002399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 03/02/2021] [Indexed: 11/10/2022] Open
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper-center enzymes that are involved in the oxidative cleavage of the glycosidic bond in crystalline cellulose and other polysaccharides. The LPMO reaction is initiated by the addition of a reductant and oxygen to ultimately form an unknown activated copper-oxygen species that is responsible for polysaccharide-substrate H-atom abstraction. Given the sensitivity of metalloproteins to radiation damage, neutron protein crystallography provides a nondestructive technique for structural characterization while also informing on the positions of H atoms. Neutron cryo-crystallography permits the trapping of catalytic intermediates, thereby providing insight into the protonation states and chemical nature of otherwise short-lived species in the reaction mechanism. To characterize the reaction-mechanism intermediates of LPMO9D from Neurospora crassa, a cryo-neutron diffraction data set was collected from an ascorbate-reduced crystal. A second neutron diffraction data set was collected at room temperature from an LPMO9D crystal exposed to low-pH conditions to probe the protonation states of ionizable groups involved in catalysis under acidic conditions.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - William B. O’Dell
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Paul D. Swartz
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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42
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Krishnan VM, Shopov DY, Bouchey CJ, Bailey WD, Parveen R, Vlaisavljevich B, Tolman WB. Structural Characterization of the [CuOR] 2+ Core. J Am Chem Soc 2021; 143:3295-3299. [PMID: 33621089 DOI: 10.1021/jacs.0c13470] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Formal Cu(III) complexes bearing an oxygen-based auxiliary ligand ([CuOR]2+, R = H or CH2CF3) were stabilized by modulating the donor character of supporting ligand LY (LY = 4-Y, N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide, Y = H or OMe) and/or the basicity of the auxiliary ligand, enabling the first characterization of these typically highly reactive cores by NMR spectroscopy and X-ray crystallography. Enhanced lifetimes in solution and slowed rates of PCET with a phenol substrate were observed. NMR spectra corroborate the S = 0 ground states of the complexes, and X-ray structures reveal shortened Cu-ligand bond distances that match well with theory.
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Affiliation(s)
- V Mahesh Krishnan
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
| | - Dimitar Y Shopov
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
| | - Caitlin J Bouchey
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
| | - Wilson D Bailey
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
| | - Riffat Parveen
- University of South Dakota, 414 E. Clark Street, Vermillion, South Dakota 57069, United States
| | - Bess Vlaisavljevich
- University of South Dakota, 414 E. Clark Street, Vermillion, South Dakota 57069, United States
| | - William B Tolman
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, Missouri 63130-4899, United States
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43
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Charette BJ, Ziller JW, Heyduk AF. Metal-Ion Influence on Ligand-Centered Hydrogen-Atom Transfer. Inorg Chem 2021; 60:1579-1589. [PMID: 33434022 DOI: 10.1021/acs.inorgchem.0c02981] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ligand-centered hydrogen-atom-transfer (HAT) reactivity was examined for a family of group 10 metal complexes containing a tridentate pincer ligand derived from bis(2-mercapto-p-tolyl)amine, [SNS]H3. Six new metal complexes of palladium and platinum were synthesized with the [SNS] ligand platform in different redox and protonation states to complete the group 10 series previously reported with nickel. The HAT reactivity was examined for this family of nickel, palladium, and platinum complexes to determine the impact of a metal ion on the ligand-centered reactivity. Thermodynamic measurements revealed that N-H bond dissociation free energies increased by approximately 10 kcal mol-1 along the series Ni < Pd < Pt driven by changes to both the redox potential and pKa of the ligand. Kinetic analyses for all three metal complexes suggest that the barrier to the HAT reactivity is primarily entropic rather than enthalpic for this system.
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Affiliation(s)
- Bronte J Charette
- Department of Chemistry, University of California at Irvine (UCI), Irvine, California 92677-2025, United States
| | - Joseph W Ziller
- Department of Chemistry, University of California at Irvine (UCI), Irvine, California 92677-2025, United States
| | - Alan F Heyduk
- Department of Chemistry, University of California at Irvine (UCI), Irvine, California 92677-2025, United States
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Brandt A, RanguMagar AB, Szwedo P, Wayland HA, Parnell CM, Munshi P, Ghosh A. Highly economical and direct amination of sp 3 carbon using low-cost nickel pincer catalyst. RSC Adv 2021; 11:1862-1874. [PMID: 35424101 PMCID: PMC8693581 DOI: 10.1039/d0ra09639c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 12/07/2020] [Indexed: 11/21/2022] Open
Abstract
Developing more efficient routes to achieve C-N bond coupling is of great importance to industries ranging from products in pharmaceuticals and fertilizers to biomedical technologies and next-generation electroactive materials. Over the past decade, improvements in catalyst design have moved synthesis away from expensive metals to newer inexpensive C-N cross-coupling approaches via direct amine alkylation. For the first time, we report the use of an amide-based nickel pincer catalyst (1) for direct alkylation of amines via activation of sp3 C-H bonds. The reaction was accomplished using a 0.2 mol% catalyst and no additional activating agents other than the base. Upon optimization, it was determined that the ideal reaction conditions involved solvent dimethyl sulfoxide at 110 °C for 3 h. The catalyst demonstrated excellent reactivity in the formation of various imines, intramolecularly cyclized amines, and substituted amines with a turnover number (TON) as high as 183. Depending on the base used for the reaction and the starting amines, the catalyst demonstrated high selectivity towards the product formation. The exploration into the mechanism and kinetics of the reaction pathway suggested the C-H activation as the rate-limiting step, with the reaction second-order overall, holding first-order behavior towards the catalyst and toluene substrate.
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Affiliation(s)
- Andrew Brandt
- Department of Chemistry, University of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA +1 501 569 8838 +1 501 569 8827
| | - Ambar B RanguMagar
- Department of Chemistry, University of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA +1 501 569 8838 +1 501 569 8827
| | - Peter Szwedo
- Department of Chemistry, University of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA +1 501 569 8838 +1 501 569 8827
| | - Hunter A Wayland
- Department of Chemistry, University of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA +1 501 569 8838 +1 501 569 8827
| | - Charlette M Parnell
- Department of Chemistry, University of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA +1 501 569 8838 +1 501 569 8827
| | - Pradip Munshi
- Research Center, Reliance Industries Limited Vadodara Gujarat 391346 India +91 265 261 6066
| | - Anindya Ghosh
- Department of Chemistry, University of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA +1 501 569 8838 +1 501 569 8827
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Abstract
High-valent oxocobalt(IV) species have been invoked as key intermediates in oxidative catalysis, but investigations into the chemistry of proton-coupled redox reactions of such species have been limited. Herein, the reactivity of an established water oxidation catalyst, [Co4O4(OAc)4(py)4][PF6], toward H-atom abstraction reactions is described. Mechanistic analyses and density functional theory (DFT) calculations support a concerted proton-electron transfer (CPET) pathway in which the high energy intermediates formed in stepwise pathways are bypassed. Natural bond orbital (NBO) calculations point to cooperative donor-acceptor σ interactions at the transition state, whereby the H-atom of the substrate is transferred to an orbital delocalized over a Co3(μ3-O) fragment. The mechanistic insights provide design principles for the development of catalytic C-H activation processes mediated by a multimetallic oxo metal cluster.
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Gericke R, Doyle LM, Farquhar ER, McDonald AR. Oxo-Free Hydrocarbon Oxidation by an Iron(III)-Isoporphyrin Complex. Inorg Chem 2020; 59:13952-13961. [PMID: 32955871 DOI: 10.1021/acs.inorgchem.0c01618] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metal-halides that perform proton coupled electron-transfer (PCET) oxidation are an important new class of high-valent oxidant. In investigating metal-dihalides, we reacted [FeIII(Cl)(T(OMe)PP)] (1, T(OMe)PP = meso-tetra(4-methoxyphenyl)porphyrinyl) with (dichloroiodo)benzene. An FeIII-meso-chloro-isoporphyrin complex [FeIII(Cl)2(T(OMe)PP-Cl)] (2) was obtained. 2 was characterized by electronic absorption, 1H NMR, EPR, and X-ray absorption spectroscopies and mass spectrometry with support from computational analyses. 2 was reacted with a series of hydrocarbon substrates. The measured kinetic data exhibited a nonlinear behavior, whereby the oxidation followed a hydrogen-atom-transfer (HAT) PCET mechanism. The meso-chlorine atom was identified as the HAT agent. In one case, a halogenated product was identified by mass spectrometry. Our findings demonstrate that oxo-free hydrocarbon oxidation with heme systems is possible and show the potential for iron-dihalides in oxidative hydrocarbon halogenation.
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Affiliation(s)
- Robert Gericke
- School of Chemistry, College Green, Trinity College Dublin, The University of Dublin, Dublin 2 D02 PN40, Ireland
| | - Lorna M Doyle
- School of Chemistry, College Green, Trinity College Dublin, The University of Dublin, Dublin 2 D02 PN40, Ireland
| | - Erik R Farquhar
- National Synchrotron Light Source II, Brookhaven National Laboratory, Case Western Reserve University Center for Synchrotron Biosciences, Upton, New York 11973, United States
| | - Aidan R McDonald
- School of Chemistry, College Green, Trinity College Dublin, The University of Dublin, Dublin 2 D02 PN40, Ireland
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9,10-Dihydroanthracene auto-photooxidation efficiently triggered photo-catalytic oxidation of organic compounds by molecular oxygen under visible light. MOLECULAR CATALYSIS 2020. [DOI: 10.1016/j.mcat.2020.111127] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Brander S, Horvath I, Ipsen JØ, Peciulyte A, Olsson L, Hernández-Rollán C, Nørholm MHH, Mossin S, Leggio LL, Probst C, Thiele DJ, Johansen KS. Biochemical evidence of both copper chelation and oxygenase activity at the histidine brace. Sci Rep 2020; 10:16369. [PMID: 33004835 PMCID: PMC7529816 DOI: 10.1038/s41598-020-73266-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/15/2020] [Indexed: 12/22/2022] Open
Abstract
Lytic polysaccharide monooxygenase (LPMO) and copper binding protein CopC share a similar mononuclear copper site. This site is defined by an N-terminal histidine and a second internal histidine side chain in a configuration called the histidine brace. To understand better the determinants of reactivity, the biochemical and structural properties of a well-described cellulose-specific LPMO from Thermoascus aurantiacus (TaAA9A) is compared with that of CopC from Pseudomonas fluorescens (PfCopC) and with the LPMO-like protein Bim1 from Cryptococcus neoformans. PfCopC is not reduced by ascorbate but is a very strong Cu(II) chelator due to residues that interacts with the N-terminus. This first biochemical characterization of Bim1 shows that it is not redox active, but very sensitive to H2O2, which accelerates the release of Cu ions from the protein. TaAA9A oxidizes ascorbate at a rate similar to free copper but through a mechanism that produce fewer reactive oxygen species. These three biologically relevant examples emphasize the diversity in how the proteinaceous environment control reactivity of Cu with O2.
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Affiliation(s)
- Søren Brander
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1958, Frederiksberg, Denmark
| | - Istvan Horvath
- Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Johan Ø Ipsen
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg, Denmark
| | - Ausra Peciulyte
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Lisbeth Olsson
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Cristina Hernández-Rollán
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Morten H H Nørholm
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Susanne Mossin
- Centre for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, 2100, Copenhagen Ø, Denmark
| | - Corinna Probst
- Department of Biochemistry, Pharmacology and Cancer Biology and Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Dennis J Thiele
- Department of Biochemistry, Pharmacology and Cancer Biology and Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Katja S Johansen
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1958, Frederiksberg, Denmark. .,Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden.
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Larsson ED, Dong G, Veryazov V, Ryde U, Hedegård ED. Is density functional theory accurate for lytic polysaccharide monooxygenase enzymes? Dalton Trans 2020; 49:1501-1512. [PMID: 31922155 DOI: 10.1039/c9dt04486h] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The lytic polysaccharide monooxygenase (LPMO) enzymes boost polysaccharide depolymerization through oxidative chemistry, which has fueled the hope for more energy-efficient production of biofuel. We have recently proposed a mechanism for the oxidation of the polysaccharide substrate (E. D. Hedegård and U. Ryde, Chem. Sci., 2018, 9, 3866-3880). In this mechanism, intermediates with superoxide, oxyl, as well as hydroxyl (i.e. [CuO2]+, [CuO]+ and [CuOH]2+) cores were involved. These complexes can have both singlet and triplet spin states, and both spin-states may be important for how LPMOs function during catalytic turnover. Previous calculations on LPMOs have exclusively been based on density functional theory (DFT). However, different DFT functionals are known to display large differences for spin-state splittings in transition-metal complexes, and this has also been an issue for LPMOs. In this paper, we study the accuracy of DFT for spin-state splittings in superoxide, oxyl, and hydroxyl intermediates involved in LPMO turnover. As reference we employ multiconfigurational perturbation theory (CASPT2).
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Affiliation(s)
- Ernst D Larsson
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE-221 00 Lund, Sweden.
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Li Y, Fan W, Zhang Z, Xie X, Xiang S, Huang D. Copper(II)-hydroxide facilitated C-C bond formation: the carboxamido pyridine system versus the methylimino pyridine system. Dalton Trans 2020; 49:12189-12196. [PMID: 32930687 DOI: 10.1039/d0dt02288h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A copper(ii)-hydroxide-induced carbon-carbon bond formation reaction is explored with the synthesis of an asymmetric carboxamido-methylimino pyridine Cu(i) complex of [CuI(py(N-C[double bond, length as m-dash]O)(N[double bond, length as m-dash]C-C)ph2Me2)2]- (12). Two imine-methyl groups are coupled to form a bridged C-C bond (N[double bond, length as m-dash]C-C-C-C[double bond, length as m-dash]N) at the methyl positions with the reduction of two Cu2+ center ions to Cu+. The reaction is checked with three dicarboxamido pyridine [CuII-OH] complexes, with which dinuclear Cu(i) complexes of [Cu2(py(N-C[double bond, length as m-dash]O)2ph2R2)2]2- (R = methyl (3), methyl and allyl (6)) and trinuclear [CuII-CuI-CuII] complex of [Cu3(⊂20-py(N-C[double bond, length as m-dash]O)2ph2dienMe3)2]+ (9) are obtained. The reactivities of the [CuII-L] (L = DMF, OH-) complexes in dicarboxamido pyridine, carboxamido-methylimino pyridine and dimethylimino pyridine systems are discussed in terms of the electron delocalization properties of ligands. A cooperative metal-ligand (Cu2+ and enamide ligand) interaction is proposed based on the characterization of ligated Cu(ii) intermediates with the techniques of X-ray crystallography, UV-vis spectroscopy, cyclic voltammogram, EPR spectroscopy, and DFT calculations.
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Affiliation(s)
- Yinghua Li
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
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