1
|
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.
Collapse
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
| |
Collapse
|
2
|
Libman A, Ben-Lulu M, Gaster E, Bera R, Shames AI, Shaashua O, Vershinin V, Torubaev Y, Pappo D. Multicopper Clusters Enable Oxidative Phenol Macrocyclization (OxPM) of Peptides. J Am Chem Soc 2023; 145:21002-21011. [PMID: 37721386 DOI: 10.1021/jacs.3c06978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
The biosynthesis of glycopeptide antibiotics such as vancomycin and other biologically active biaryl-bridged and diaryl ether-linked macrocyclic peptides includes key enzymatic oxidative phenol macrocyclization(s) of linear precursors. However, a simple and step-economical biomimetic version of this transformation remains underdeveloped. Here, we report highly efficient conditions for preparing biaryl-bridged and diaryl ether-linked macrocyclic peptides based on multicopper(II) clusters. The selective syntheses of ring models of vancomycin and the arylomycin cyclic core illustrate the potential of this technology to facilitate the assembly of complex antibiotic macrocyclic peptides, whose syntheses are considered highly challenging. The unprecedented ability of multicopper(II) clusters to chelate tethered diphenols and promote intramolecular over intermolecular coupling reactions demonstrates that copper clusters can catalyze redox transformations that cannot be accessed by smaller metal catalysts.
Collapse
Affiliation(s)
- Anna Libman
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Mor Ben-Lulu
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Eden Gaster
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Ratnadeep Bera
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Alexander I Shames
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Omer Shaashua
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Vlada Vershinin
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Yury Torubaev
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Doron Pappo
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| |
Collapse
|
3
|
Alayoglu P, Chang T, Lorenzo Ocampo MV, Murray LJ, Chen YS, Mankad NP. Metal Site-Specific Electrostatic Field Effects on a Tricopper(I) Cluster Probed by Resonant Diffraction Anomalous Fine Structure (DAFS). Inorg Chem 2023; 62:15267-15276. [PMID: 37651726 DOI: 10.1021/acs.inorgchem.3c02472] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Studies of multinuclear metal complexes are greatly enhanced by resonant diffraction measurements, which probe X-ray absorption profiles of crystallographically independent metal sites within a cluster. In particular, X-ray diffraction anomalous fine structure (DAFS) analysis provides data that can be interpreted akin to site-specific XANES, allowing for differences in metal K-edge resonances to be deconvoluted even for different metal sites within a homometallic system. Despite the prevalence of Cu-containing clusters in biology and energy science, DAFS has yet to be used to analyze multicopper complexes of any type until now. Here, we report an evaluation of trends using a series of strategically chosen Cu(I) and Cu(II) complexes to determine how energy dependencies of anomalous scattering factors are impacted by coordination geometry, ligand shell, cluster nuclearity, and oxidation state. This calibration data is used to analyze a formally tricopper(I) complex that was found by DAFS to be site-differentiated due to the unsymmetrical influence on different Cu sites of the electrostatic field from a proximal K+ cation.
Collapse
Affiliation(s)
- Pinar Alayoglu
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, Illinois 60607, United States
| | - Tieyan Chang
- ChemMatCARS, The University of Chicago, Argonne, Illinois 60439, United States
| | - M Victoria Lorenzo Ocampo
- Center for Catalysis and Florida Center for Heterocyclic Chemistry, Department of Chemistry, University of Florida, Gainesville, Florida 32611 United States
| | - Leslie J Murray
- Center for Catalysis and Florida Center for Heterocyclic Chemistry, Department of Chemistry, University of Florida, Gainesville, Florida 32611 United States
| | - Yu-Sheng Chen
- ChemMatCARS, The University of Chicago, Argonne, Illinois 60439, United States
| | - Neal P Mankad
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, Illinois 60607, United States
| |
Collapse
|
4
|
He X, Iliescu A, Yang T, Arguilla MQ, Chen T, Kulik HJ, Dincă M. Reversible O-O Bond Scission and O 2 Evolution at MOF-Supported Tetramanganese Clusters. J Am Chem Soc 2023. [PMID: 37471064 DOI: 10.1021/jacs.3c05374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
The scission of the O-O bond in O2 during respiration and the formation of the O-O bond during photosynthesis are the engines of aerobic life. Likewise, the reduction of O2 and the oxidation of reduced oxygen species to form O2 are indispensable components for emerging renewable technologies, including energy storage and conversion, yet discrete molecule-like systems that promote these fundamental reactions are rare. Herein, we report a square-planar tetramanganese cluster formed by self-assembly within a metal-organic framework that reversibly reduces O2 by four electrons, facilitating the interconversion between molecular O2 and metal-oxo species. The tetranuclear cluster spontaneously cleaves the O-O bond of O2 at room temperature to generate a tetramanganese-bis(μ2-oxo) species, which, in turn, is competent for O-O bond reformation and O2 evolution at elevated temperatures, enabled by the head-to-head orientation of two oxo species. This study demonstrates the viability of four-electron interconversion between molecular O2 and metal-oxo species and highlights the importance of site isolation for achieving multi-electron chemistry at polynuclear metal clusters.
Collapse
Affiliation(s)
- Xin He
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Andrei Iliescu
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Tzuhsiung Yang
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Maxx Q Arguilla
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Tianyang Chen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Heather J Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Mircea Dincă
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| |
Collapse
|
5
|
Interplay of electronic and geometric structure on Cu phenanthroline, bipyridine and derivative complexes, synthesis, characterization, and reactivity towards oxygen. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.214943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
6
|
Jian J, Liao J, Zhou M, Yao M, Chen Y, Liang X, Liu C, Tong Q. Enhanced Photoelectrochemical Water Splitting of Black Silicon Photoanode with pH‐Dependent Copper‐Bipyridine Catalysts. Chemistry 2022; 28:e202201520. [DOI: 10.1002/chem.202201520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Indexed: 11/12/2022]
Affiliation(s)
- Jing‐Xin Jian
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| | - Jia‐Xin Liao
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| | - Mu‐Han Zhou
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| | - Ming‐Ming Yao
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| | - Yi‐Jing Chen
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| | - Xi‐Wen Liang
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| | - Chao‐Ping Liu
- Department of Physics Shantou University Shantou Guangdong 515063 P. R. China
| | - Qing‐Xiao Tong
- Department of Chemistry Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province and Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention Shantou University Shantou Guangdong 515063 P. R. China
| |
Collapse
|
7
|
Zhang W, Moore CE, Zhang S. Multiple Proton-Coupled Electron Transfers at a Tricopper Cluster: Modeling the Reductive Regeneration Process in Multicopper Oxidases. J Am Chem Soc 2022; 144:1709-1717. [PMID: 35044761 DOI: 10.1021/jacs.1c10948] [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
Metal clusters in enzymes carry out the life-sustaining reactions by accumulating multiple redox equivalents in a narrow potential range. This redox potential leveling effect commonly observed in Nature has yet to be reproduced with synthetic metal clusters. Herein, we employ a fully encapsulated synthetic tricopper complex to model the three-electron two-proton reductive regeneration of fully reduced trinuclear copper cluster CuICuICuI(μ2-OH2) (FR) from native intermediate CuIICuIICuII(μ3-O) (NI) in multicopper oxidases (MCOs). The tricopper cluster can access four oxidation states (I,I,I to II,II,II) and four protonation states ([Cu3(μ3-O)]LH, [Cu3(μ3-OH)]L, [Cu3(μ3-OH)]LH, and [Cu3(μ3-OH2)]L, where LH denotes the protonated ligand), allowing mechanistic investigation of proton-coupled electron transfer (PCET) relevant to MCOs. Seven tricopper complexes with discrete oxidation and protonation states were characterized with spectroscopy or X-ray single-crystal diffraction. A stepwise electron transfer-proton transfer (ET-PT) mechanism is established for the reduction of CuIICuIICuII(μ3-O)LH to CuIICuIICuI(μ3-OH)L, while a stepwise PT-ET mechanism is determined for the reduction of CuIICuICuI(μ3-OH)LH to CuICuICuI(μ2-OH2)L. The switch-over from ET-PT to PT-ET mechanism showcases that the tricopper complex can adopt different PCET mechanisms to circumvent high-barrier proton transfer steps. Overall, three-electron two-proton reduction occurs within a narrow potential range of 170 mV, exemplifying the redox potential leveling effect of secondary proton relays in delivering multiple redox equivalents at metal clusters.
Collapse
Affiliation(s)
- Weiyao Zhang
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Curtis E Moore
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Shiyu Zhang
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| |
Collapse
|
8
|
Zhong X, Bouchey CJ, Kabir E, Tolman WB. Using a monocopper-superoxo complex to prepare multicopper-peroxo species relevant to proposed enzyme intermediates. J Inorg Biochem 2021; 222:111498. [PMID: 34120095 PMCID: PMC9835715 DOI: 10.1016/j.jinorgbio.2021.111498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 05/29/2021] [Accepted: 05/29/2021] [Indexed: 01/16/2023]
Abstract
With the goal of generating a (peroxo)tricopper species analogous to the Peroxy Intermediate proposed for multicopper oxidases, solutions of the copper-superoxide complex [K(Krypt)][LCuO2] (L = N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide, Krypt = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) were reacted with the dicopper(I) complex [(TPBN)Cu2(MeCN)2][PF6]2 at -70 °C (TPBN = N,N,N',N'-tetrakis-(2-pyridylmethyl)-1,4-diaminobutane). A metastable intermediate formed, which on the basis of UV-vis, EPR, and resonance Raman spectroscopy was proposed to derive from reaction of two equivalents of the copper-superoxide with one equivalent of the dicopper(I) complex to yield a complex with two (peroxo)dicopper moieties rather than the desired (peroxo)tricopper PI model. A similar intermediate formed upon reaction of [K(Krypt)][LCuO2] with [(BPMA)Cu(MeCN)][PF6] (BPMA = N,N-bis(2-pyridylmethyl)-methyl-amine), which contained the same donor set as provided by TPBN. Comparison of resonance Raman data and consideration of structural preferences for LCuX species led to hypothesis of a μ-η1:η2-peroxo structure for both intermediates.
Collapse
Affiliation(s)
- Xinzhe Zhong
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, MO 63130-4899, United States of America
| | - Caitlin J. Bouchey
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, MO 63130-4899, United States of America,Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455, United States of America
| | - Evanta Kabir
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, MO 63130-4899, United States of America
| | - William B. Tolman
- Department of Chemistry, Washington University in St. Louis, One Brookings Hall, Campus Box 1134, St. Louis, MO 63130-4899, United States of America,Corresponding author. (W.B. Tolman)
| |
Collapse
|
9
|
Wang Q, Brooks SH, Liu T, Tomson NC. Tuning metal-metal interactions for cooperative small molecule activation. Chem Commun (Camb) 2021; 57:2839-2853. [PMID: 33624638 PMCID: PMC8274379 DOI: 10.1039/d0cc07721f] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cluster complexes have attracted interest for decades due to their promise of drawing analogies to metallic surfaces and metalloenzyme active sites, but only recently have chemists started to develop ligand scaffolds that are specifically designed to support multinuclear transition metal cores. Such ligands not only hold multiple metal centers in close proximity but also allow for fine-tuning of their electronic structures and surrounding steric environments. This Feature Article highlights ligand designs that allow for cooperative small molecule activation at cluster complexes, with a particular focus on complexes that contain metal-metal bonds. Two useful ligand-design elements have emerged from this work: a degree of geometric flexibility, which allows for novel small molecule activation modes, and the use of redox-active ligands to provide electronic flexibility to the cluster core. The authors have incorporated these factors into a unique class of dinucleating macrocycles (nPDI2). Redox-active fragments in nPDI2 mimic the weak-overlap covalent bonding that is characteristic of M-M interactions, and aliphatic linkers in the ligand backbone provide geometric flexibility, allowing for interconversion between a range of geometries as the dinuclear core responds to the requirements of various small molecule substrates. The union of these design elements appears to be a powerful combination for analogizing critical aspects of heterogeneous and metalloenzyme catalysts.
Collapse
Affiliation(s)
- Qiuran Wang
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | |
Collapse
|
10
|
Zhang W, Moore CE, Zhang S. Encapsulation of tricopper cluster in a synthetic cryptand enables facile redox processes from Cu ICu ICu I to Cu IICu IICu II states. Chem Sci 2020; 12:2986-2992. [PMID: 34164067 PMCID: PMC8179370 DOI: 10.1039/d0sc05441k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
One-pot reaction of tris(2-aminoethyl)amine (TREN), [CuI(MeCN)4]PF6, and paraformaldehyde affords a mixed-valent [TREN4CuIICuICuI(μ3-OH)](PF6)3 complex. The macrocyclic azacryptand TREN4 contains four TREN motifs, three of which provide a bowl-shape binding pocket for the [Cu3(μ3-OH)]3+ core. The fourth TREN caps on top of the tricopper cluster to form a cryptand, imposing conformational constraints and preventing solvent interaction. Contrasting the limited redox capability of synthetic tricopper complexes reported so far, [TREN4CuIICuICuI(μ3-OH)](PF6)3 exhibits several reversible single-electron redox events. The distinct electrochemical behaviors of [TREN4CuIICuICuI(μ3-OH)](PF6)3 and its solvent-exposed analog [TREN3CuIICuIICuII(μ3-O)](PF6)4 suggest that isolation of tricopper core in a cryptand enables facile electron transfer, allowing potential application of synthetic tricopper complexes as redox catalysts. Indeed, the fully reduced [TREN4CuICuICuI(μ3-OH)](PF6)2 can reduce O2 under acidic conditions. The geometric constraints provided by the cryptand are reminiscent of Nature's multicopper oxidases (MCOs). For the first time, a synthetic tricopper cluster was isolated and fully characterized at CuICuICuI (4a), CuIICuICuI (4b), and CuIICuIICuI (4c) states, providing structural and spectroscopic models for many intermediates in MCOs. Fast electron transfer rates (105 to 106 M-1 s-1) were observed for both CuICuICuI/CuIICuICuI and CuIICuICuI/CuIICuIICuI redox couples, approaching the rapid electron transfer rates of copper sites in MCO.
Collapse
Affiliation(s)
- Weiyao Zhang
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH USA
| | - Curtis E Moore
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH USA
| | - Shiyu Zhang
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH USA
| |
Collapse
|
11
|
Brazeau SEN, Doerrer LH. Cu(i)-O 2 oxidation reactions in a fluorinated all-O-donor ligand environment. Dalton Trans 2019; 48:4759-4768. [PMID: 30869674 DOI: 10.1039/c8dt05028g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Investigation of Cu-O2 oxidation reactivity is important in biological and anthropogenic chemistry. Zeolites are one of the most promising Cu/O based oxidation catalysts for development of industrial-scale CH4 to CH3OH conversion. Their oxidation mechanisms are not well understood, however, highlighting the importance of the investigation of molecular Cu(i)-O2 reactivity with O-donor complexes. Herein, we give an overview of the synthesis, structural properties, and O2 reactivity of three different series of O-donor fluorinated Cu(i) alkoxides: K[Cu(OR)2], [(Ph3P)Cu(μ-OR)2Cu(PPh3)], and K[(R3P)Cu(pinF)], in which OR = fluorinated monodentate alkoxide ligands and pinF = perfluoropinacolate. This breadth allowed for the exploration of the influence of the denticity of the ligand, coordination number, the presence of phosphine, and KF/O interactions on their O2 reactivity. KF/O interactions were required to activate O2 in the monodentate-ligand-only family, whereas these connections did not affect O2 activation in the bidentate complexes, potentially due to the presence of phosphine. Both families formed trisanionic, trinuclear cores of the form {Cu3(μ3-O)2}3-. Intramolecular and intermolecular substrate oxidation were also explored and found to be influenced by the fluorinated ligand. Namely, {Cu3(μ3-O)2}3- from K[Cu(OR)2] could perform both monooxygenase reactivity and oxidase catalysis, whereas those from K[(R3P)Cu(pinF)] could only perform oxidase catalysis.
Collapse
Affiliation(s)
- Sarah E N Brazeau
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA.
| | | |
Collapse
|
12
|
Abstract
Multimetallic cofactors supported by weak-field donors frequently function as reaction centers in metalloproteins, and many of these cofactors catalyze small molecule activation (e.g., N2, O2, CO2) with prominent roles in geochemical element cycles or detoxification. Notable examples include the iron-molybdenum cofactor of the molybdenum-dependent nitrogenases, which catalyze N2 fixation, and the NiFe4S4 cluster and the Mo(O)SCu site in various carbon monoxide dehydrogenases. The prevailing proposed reaction mechanisms for these multimetallic cofactors relies on a cooperative pathway, in which the oxidation state changes are distributed over the aggregate coupled with orbital overlap between the substrate and more than one metal ion within the cluster. Such cooperativity has also been proposed for chemical transformations at the surfaces of heterogeneous catalysts. However, the design details that afford cooperative effects and allow such reactivity to be harnessed effectively in homogeneous synthetic systems remain unclear. Relatedly, hydride donors ligated to these metal cluster cofactors are suggested as precursors to the state that reacts with substrates; here too, however, the reactivity of hydride-decorated clusters supported by weak-field ligands is underexplored. Inspired by the reactivity potential of multimetallic assemblies evidenced in biological systems, approaches to design, synthesize, and evaluate reactivity of polynuclear metal compounds have been actively explored. In a similar vein to the templating function afforded by enzyme active sites, a carefully engineered organic ligand can be employed to control metal nuclearity of the complex and the local coordination environment of each metal center. This Account presents our efforts within this field, beginning with ligand design considerations followed by a survey of observed small molecule activation by trimetallic cyclophanates. We highlight the distinct reactivity outcomes accessed by multimetallic compounds as compared to aggregates that assemble in reaction mixtures from monometallic precursors. Contributing to the opportunity for programmed cooperativity in these designed multimetallic compounds, the cyclophane also dictates the orientation of substrate binding and metal-substrate interactions, which has a prominent influence on reactivity. For example, the dinitrogen-tricopper(I) cyclophanate reacts with dioxygen with markedly different results as compared to monocopper compounds. As an unexpected outcome, one series of tricopper compounds were discovered to be competent catalysts for carbon dioxide reduction to oxalate-a formally one-electron process-hinting at an inherently broader reaction scope for weak-field clusters at lowering the barrier for one-electron pathways as well as multielectron redox transformations. Further reflecting the role of the ligand in tuning reactivity, the trimetallic trihydride cluster compounds, [M3(μ-H)3]3+ (M = FeII, CoII, ZnII), demonstrate substrate specificity for CO2 over various other unsaturated molecules and surprising stability toward water. This series reflects the role of the local environment of a shallow ligand pocket to control substrate access. Summed together, the systems described here evidence the anticipated cooperative reactivity accessed in designed multimetallic species vs self-assembled monometallic systems (e.g., O2 activation and O atom transfer) as well as control of substrate access by seemingly subtle structural effects. Indeed, future efforts aim to interrogate the limits of cooperativity in these systems as well as the role of ligand dynamics and sterics on reactivity.
Collapse
Affiliation(s)
- Ricardo B. Ferreira
- Center for Catalysis and Florida Center for Heterocyclic Chemistry, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Leslie J. Murray
- Center for Catalysis and Florida Center for Heterocyclic Chemistry, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| |
Collapse
|
13
|
Brazeau SEN, Norwine EE, Hannigan SF, Orth N, Ivanović-Burmazović I, Rukser D, Biebl F, Grimm-Lebsanft B, Praedel G, Teubner M, Rübhausen M, Liebhäuser P, Rösener T, Stanek J, Hoffmann A, Herres-Pawlis S, Doerrer LH. Dual oxidase/oxygenase reactivity and resonance Raman spectra of {Cu3O2} moiety with perfluoro-t-butoxide ligands. Dalton Trans 2019; 48:6899-6909. [DOI: 10.1039/c9dt00516a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A mechanism for the formation of O-donor trinuclear {Cu3O2} moiety is reported.
Collapse
Affiliation(s)
| | | | | | - Nicole Orth
- Department Chemie und Pharmazie
- Lehrstuhl für Bioanorganische Chemie
- Friedrich Alexander Universität Erlangen-Nürnberg
- 91058 Erlangen
- Germany
| | - Ivana Ivanović-Burmazović
- Department Chemie und Pharmazie
- Lehrstuhl für Bioanorganische Chemie
- Friedrich Alexander Universität Erlangen-Nürnberg
- 91058 Erlangen
- Germany
| | - Dieter Rukser
- Institut für Nanostruktur- und Festkörperphysik
- Universität Hamburg
- 22761 Hamburg
- Germany
| | - Florian Biebl
- Institut für Nanostruktur- und Festkörperphysik
- Universität Hamburg
- 22761 Hamburg
- Germany
| | | | - Gregor Praedel
- Institut für Nanostruktur- und Festkörperphysik
- Universität Hamburg
- 22761 Hamburg
- Germany
| | - Melissa Teubner
- Institut für Nanostruktur- und Festkörperphysik
- Universität Hamburg
- 22761 Hamburg
- Germany
| | - Michael Rübhausen
- Institut für Nanostruktur- und Festkörperphysik
- Universität Hamburg
- 22761 Hamburg
- Germany
| | | | - Thomas Rösener
- Institut für Anorganische Chemie
- RWTH Aachen University
- 52074 Aachen
- Germany
| | - Julia Stanek
- Institut für Anorganische Chemie
- RWTH Aachen University
- 52074 Aachen
- Germany
| | - Alexander Hoffmann
- Institut für Anorganische Chemie
- RWTH Aachen University
- 52074 Aachen
- Germany
| | | | | |
Collapse
|