1
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DeLucia AA, Olshansky L. Carboxylate Shift Dynamics in Biomimetic Co 2(μ-OH) 2 Complexes. Inorg Chem 2024; 63:1109-1118. [PMID: 38170989 DOI: 10.1021/acs.inorgchem.3c03470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Carboxylate shift mechanisms provide low-energy pathways to accommodate changes in oxidation state and coordination number required during catalysis in metalloenzyme active sites. These processes are challenging to observe in their native enzymes and molecular models can provide insight into their mechanistic details. We report here the direct observation of a carboxylate shift reaction in biomimetic yet structurally stable dicobalt complexes featuring both monodentate and bridging acetate ligands, as well as intramolecular hydrogen-bonding interactions. Subjecting the series of complexes [Co2(μ-OH)2(μ-1,3-OAc)(κ-OAc)2(pyR)4]PF6 ([1R]PF6, OAc = acetate, pyR = pyridine with para-R substituents: OMe, H, or CN) to a Lewis acid triggers conversion of a monodentate acetate to a μ-1,3 bridging mode, forming [Co2(μ-OH)2(μ-1,3-OAc)2(pyR)4]2+ ([2R]2+). [2R]2+ is susceptible to solvent binding, affording [Co2(μ-OH)2(μ-1,3-OAc)(κ-OAc)(MeCN)(pyR)4]2+ ([3R]2+) in MeCN. These reaction products and intermediates were isolated and characterized in the solid state by isotopic labeling and Fourier transform infrared (FTIR) spectroscopy, as well as by X-ray diffraction. The kinetics of the formation and decay of [1R]+, [2R]2+, and [3R]2+ were also examined in situ by 1H-NMR spectroscopy to provide a kinetic model for the carboxylate shift reaction. The rate constants extracted from global fit analyses of these reactions increase with increasing electron donation from R. Leveraging robust diamagnetic CoIII complexes, these studies provide mechanistic details of carboxylate shift reactivity and highlight the utility of ligand dynamicity in mediating the transient formation of unstable metal complexes.
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Affiliation(s)
- Alyssa A DeLucia
- Department of Chemistry, Center for Biophysics and Quantitative Biology, Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3028, United States
| | - Lisa Olshansky
- Department of Chemistry, Center for Biophysics and Quantitative Biology, Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3028, United States
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2
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Lee KHK, Aebersold L, Peralta JE, Abboud KA, Christou G. Synthesis, Structure, and Magnetic Properties of an Fe 36 Dimethylarsinate Cluster: The Largest "Ferric Wheel". Inorg Chem 2022; 61:17256-17267. [PMID: 36251497 DOI: 10.1021/acs.inorgchem.2c02841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis and characterization of a high-nuclearity FeIII/O/arsinate cluster is reported within the salt [Fe36O12(OH)6(O2AsMe2)63(O2CH)3(H2O)6](NO3)12 (1). The compound was prepared from the reaction of Fe(NO3)3·9H2O, dimethylarsinic acid (Me2AsO2H), and triethylamine in a 1:2:4 molar ratio in acetonitrile. The Fe36 cation of 1 is an unprecedented structural type consisting of nine Fe4 butterfly units of two types, three {FeIII4(μ3-O)2} units A, and six {FeIII4(μ3-O)(μ3-OH)} units B, linked by multiple bridging Me2AsO2- groups into an Fe36 triangular wheel/loop with C3 crystallographic and D3 virtual symmetry that looks like a guitar plectrum. The unusual structure has been rationalized on the basis of the different curvatures of units A and B, the presence of intra-Fe36 hydrogen bonding, and the tendency of Me2AsO2- groups to favor μ3-bridging modes. The cations stack into supramolecular nanotubes parallel to the crystallographic c axis and contain badly disordered solvent and NO3- anions. The cation of 1 is the highest-nuclearity "ferric wheel" to date and also the highest-nuclearity Fe/O cluster of any structural type with a single contiguous Fe/O core. Variable-temperature direct-current magnetic susceptibility data and alternating-current in-phase magnetic susceptibility data indicate that the cation of 1 possesses an S = 0 ground state and dominant antiferromagnetic interactions. The Fe2 pairwise Ji,j couplings were estimated by the combined use of a magnetostructural correlation for high-nuclearity FeIII/oxo clusters and density functional theory calculations using broken-symmetry methods and the Green's function approach. The three methods gave satisfyingly similar Ji,j values and allowed the identification of spin-frustration effects and the resulting relative spin-vector alignments and thus rationalization of the S = 0 ground state of the cation.
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Affiliation(s)
- Kenneth Hong Kit Lee
- Department of Chemistry, University of Florida, Gainesville, Florida32611-7200, United States
| | - Lucas Aebersold
- Department of Physics and Science of Advanced Materials, Central Michigan University, Mount Pleasant, Michigan48859, United States
| | - Juan E Peralta
- Department of Physics and Science of Advanced Materials, Central Michigan University, Mount Pleasant, Michigan48859, United States
| | - Khalil A Abboud
- Department of Chemistry, University of Florida, Gainesville, Florida32611-7200, United States
| | - George Christou
- Department of Chemistry, University of Florida, Gainesville, Florida32611-7200, United States
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Hale AR, Lott ME, Peralta JE, Foguet-Albiol D, Abboud KA, Christou G. Magnetic Properties of High-Nuclearity Fe x-oxo ( x = 7, 22, 24) Clusters Analyzed by a Multipronged Experimental, Computational, and Magnetostructural Correlation Approach. Inorg Chem 2022; 61:11261-11276. [PMID: 35816698 DOI: 10.1021/acs.inorgchem.2c01371] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis, structure, and magnetic properties of three related iron(III)-oxo clusters are reported, [Fe7O3(O2CPh)9(mda)3(H2O)] (1), [Fe22O14(OH)3(O2CMe)21(mda)6](ClO4)2 (2), and [Fe24O15(OH)4(OEt)(O2CMe)21(mda)7](ClO4)2 (3), where mdaH2 is N-methyldiethanolamine. 1 was prepared from the reaction of [Fe3O(O2CPh)6(H2O)3](NO3) with mdaH2 in a 1:2 ratio in MeCN, whereas 2 and 3 were prepared from the reaction of FeCl3/NaO2CMe/mdaH2 in a 2:∼13:2 ratio and FeCl3/NaO2CMe/mdaH2/pyridine in a 2:∼13:2:25 ratio, respectively, both in EtOH. The core of 1 consists of a central octahedral FeIII ion held within a nonplanar Fe6 loop by three μ3-O2- and three μ2-RO- arms from the three mda2- chelates. The cores of the cations of 2 and 3 consist of an A:B:A three-layer topology, in which a central Fe6 (2) or Fe8 (3) layer B is sandwiched between two Fe8 layers A. The A layers structurally resemble 1 with the additional Fe added at the center to retain virtual C3 symmetry. The central Fe6 layer B of 2 consists of a {Fe4(μ4-O)2(μ3-OH)2}6+ cubane with an Fe on either side attached to cubane O2- ions, whereas that of 3 has the same cubane but with an {Fe3(μ3-O)(μ-OH)} unit attached on one side and a single Fe on the other. Variable-temperature dc and ac magnetic susceptibility studies revealed dominant antiferromagnetic coupling in all complexes leading to ground-state spins of S = 5/2 for 1 and S = 0 for 2 and 3. All Fe2 pairwise exchange parameters (Jij) for 1-3 were estimated by two independent methods: density functional theory (DFT) calculations using broken symmetry methods and a magnetostructural correlation previously developed for high-nuclearity FeIII/O complexes. The two approaches gave satisfyingly similar Jij values, and the latter allowed rationalization of the experimental ground states by identification of the spin frustration effects operative and the resultant relative spin vector alignments at each FeIII ion.
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Affiliation(s)
- Ashlyn R Hale
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Unites States
| | - Megan E Lott
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Unites States
| | - Juan E Peralta
- Department of Physics and Science of Advanced Materials, Central Michigan University, Mount Pleasant, Michigan 48859, United States
| | - Dolos Foguet-Albiol
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Unites States
| | - Khalil A Abboud
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Unites States
| | - George Christou
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, Unites States
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Hale AR, Aebersold LE, Peralta JE, Foguet-Albiol D, Abboud KA, Christou G. Analysis of spin frustration in an FeIII7 cluster using a combination of computational, experimental, and magnetostructural correlation methods. Polyhedron 2022. [DOI: 10.1016/j.poly.2022.116045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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5
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Balamurugan M, Suresh E, Palaniandavar M. μ-Oxo-bridged diiron(iii) complexes of tripodal 4N ligands as catalysts for alkane hydroxylation reaction using m-CPBA as an oxidant: substrate vs. self hydroxylation. RSC Adv 2021; 11:21514-21526. [PMID: 35478792 PMCID: PMC9034113 DOI: 10.1039/d1ra03135j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 05/28/2021] [Indexed: 11/23/2022] Open
Abstract
A series of non-heme μ-oxo-bridged dinuclear iron(iii) complexes of the type [Fe2(μ-O)(L1–L6)2Cl2]Cl21–6 have been isolated and their catalytic activity towards oxidative transformation of alkanes into alcohols has been studied using m-choloroperbenzoic acid (m-CPBA) as an oxidant. All the complexes were characterized by CHN, electrochemical, and UV-visible spectroscopic techniques. The molecular structures of 2 and 5 have been determined successfully by single crystal X-ray diffraction analysis and both possesses octahedral coordination geometry and each iron atom is coordinated by four nitrogen atoms of the 4N ligand and a bridging oxygen. The sixth position of each octahedron is coordinated by a chloride ion. The (μ-oxo)diiron(iii) core is linear in 2 (Fe–O–Fe, 180.0°), whereas it is non-linear (Fe–O–Fe, 161°) in 5. All the diiron(iii) complexes show quasi-reversible one electron transfer in the cyclic voltammagram and catalyze the hydroxylation of alkanes like cyclohexane, adamantane with m-CPBA as an oxidant. In acetonitrile solution, adding excess m-CPBA to the diiron(iii) complex 2 without chloride ions leads to intramolecular hydroxylation reaction of the oxidant. Interestingly, 2 catalyzes alkane hydroxylation in the presence of chloride ions, but intramolecular hydroxylation in the absence of chloride ions. The observed selectivity for cyclohexane (A/K, 5–7) and adamantane (3°/2°, 9–18) suggests the involvement of high-valent iron–oxo species rather than freely diffusing radicals in the catalytic reaction. Moreover, 4 oxidizes (A/K, 7) cyclohexane very efficiently up to 513 TON while 5 oxidizes adamantane with good selectivity (3°/2°, 18) using m-CPBA as an oxidant. The electronic effects of ligand donors dictate the efficiency and selectivity of catalytic hydroxylation of alkanes. The ligand stereoelectronic effect of diiron(iii) complexes determines the efficiency and selectivity of catalytic alkane hydroxylation with m-CPBA as an oxidant.![]()
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Affiliation(s)
- Mani Balamurugan
- School of Chemistry, Bharathidasan University Tiruchirappalli 620 024 Tamil Nadu India
| | - Eringathodi Suresh
- Analytical Science Discipline, Central Salt and Marine Chemicals Research Institute Bhavnagar 364 002 India
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6
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Harrowfield J, Thuéry P. Dipodal, Tripodal, and Discoidal Coordination Modes of Kemp's Triacid Anions. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.201901249] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jack Harrowfield
- ISIS, Université de Strasbourg 8 allée Gaspard Monge 67083 Strasbourg France
| | - Pierre Thuéry
- CEA, CNRS, NIMBE Université Paris‐Saclay 91191 Gif‐sur‐Yvette France
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7
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Hofmann AJ, Jandl C, Hess CR. Structural Differences and Redox Properties of Unsymmetric Diiron PDIxCy Complexes. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.201901173] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Andreas J. Hofmann
- Department of Chemistry and Catalysis Research Center Technische Universität München Lichtenbergstraße 4 85748 Garching Germany
| | - Christian Jandl
- Department of Chemistry and Catalysis Research Center Technische Universität München Lichtenbergstraße 4 85748 Garching Germany
| | - Corinna R. Hess
- Department of Chemistry and Catalysis Research Center Technische Universität München Lichtenbergstraße 4 85748 Garching Germany
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8
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Singh AP, Joshi RP, Abboud KA, Peralta JE, Christou G. Molecular spin frustration in mixed-chelate Fe5 and Fe6 oxo clusters with high ground state spin values. Polyhedron 2020. [DOI: 10.1016/j.poly.2019.114182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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9
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Lehnert N, Fujisawa K, Camarena S, Dong HT, White CJ. Activation of Non-Heme Iron-Nitrosyl Complexes: Turning Up the Heat. ACS Catal 2019. [DOI: 10.1021/acscatal.9b03219] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Kiyoshi Fujisawa
- Department of Chemistry, Ibaraki University, Mito 310-8512, Japan
| | - Stephanie Camarena
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Hai T. Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Corey J. White
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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10
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Ganguly T, Das A, Majumdar A. Iron(II) Mediated Desulfurization of Organosulfur Substrates Produces Nonheme Diiron(II)-hydrosulfides. Inorg Chem 2019; 58:9998-10011. [DOI: 10.1021/acs.inorgchem.9b01144] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tuhin Ganguly
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India
| | - Ayan Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India
| | - Amit Majumdar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India
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11
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Kuter D, Suárez L, Dodd EL, Noll BC, Stephens PW, Bohle DS. Hydrating the Bispropionate Notch in Malaria Pigment: A New Structural Motif in the Iron(III)(deuteroporphyrin) Dimer. Chemistry 2019; 25:4373-4378. [PMID: 30499153 DOI: 10.1002/chem.201805116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Indexed: 11/11/2022]
Abstract
Treating deuterohemin, chloro(deuteroporphyrinato)iron(III), with a non-coordinating base in DMSO/methanol allows for the isolation of [(deuteroporphyrinato)iron(III)]2 , deuterohematin anhydride (DHA), an analogue of malaria pigment, the natural product of heme detoxification by malaria. The structure of DHA obtained from this solvent system has been solved by X-ray powder diffraction analysis and displays many similarities, yet important structural differences, to malaria pigment. Most notably, a water molecule of solvation occupies a notch created by the propionate side chains and stabilizes a markedly bent propionate ligand coordinated with a long Fe-O bond, and a carboxylate cluster associated with water molecules is generated. Together, these features account for its increased solubility and more open structure, with an increased porphyrin-porphyrin separation. The IR spectroscopic signature associated with this structure also accounts for the strong IR band at 1587 cm-1 seen for many amorphous preparations of synthetic malaria pigment, and it is proposed that stabilizing these structures may be a new objective for antimalarial drugs. The important role of the vinyl substituents in this biochemistry is further demonstrated by the structure of deuterohemin obtained by single-crystal X-ray diffraction analysis.
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Affiliation(s)
- David Kuter
- Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, H3A 0B8, Canada.,Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, Stellenbosch, 7602, South Africa
| | - Liliana Suárez
- Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, H3A 0B8, Canada
| | - Erin L Dodd
- Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, H3A 0B8, Canada
| | - Bruce C Noll
- Bruker-AXS, 5465 E Cheryl Pkwy, Fitchburg, WI, 53711, USA
| | - Peter W Stephens
- Department of Physics and Astronomy, State University of New York, Stony Brook, Stony Brook, New York, 11794-3800, USA
| | - D Scott Bohle
- Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, H3A 0B8, Canada
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12
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A growing family of O2 activating dinuclear iron enzymes with key catalytic diiron(III)-peroxo intermediates: Biological systems and chemical models. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2016.05.014] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Mitchell KJ, Abboud KA, Christou G. Magnetostructural Correlation for High-Nuclearity Iron(III)/Oxo Complexes and Application to Fe5, Fe6, and Fe8 Clusters. Inorg Chem 2016; 55:6597-608. [DOI: 10.1021/acs.inorgchem.6b00769] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kylie J. Mitchell
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Khalil A. Abboud
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - George Christou
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
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14
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Zheng D, Wang N, Wang M, Ding S, Ma C, Darensbourg MY, Hall MB, Sun L. Intramolecular Iron-Mediated C–H Bond Heterolysis with an Assist of Pendant Base in a [FeFe]-Hydrogenase Model. J Am Chem Soc 2014; 136:16817-23. [DOI: 10.1021/ja5078014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Dehua Zheng
- State
Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research
Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, People’s Republic of China
| | - Ning Wang
- Department of Chemistry, Texas A&M University, College Station, Texas 77845, United States
- School
of Chemistry and Chemical Engineering, Henan University of Technology, Zhengzhou 450001, People’s Republic of China
| | - Mei Wang
- State
Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research
Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, People’s Republic of China
| | - Shengda Ding
- Department of Chemistry, Texas A&M University, College Station, Texas 77845, United States
| | - Chengbing Ma
- State
Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Fuzhou 350002, People’s Republic of China
| | | | - Michael B. Hall
- Department of Chemistry, Texas A&M University, College Station, Texas 77845, United States
| | - Licheng Sun
- State
Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research
Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, People’s Republic of China
- Department
of Chemistry, KTH Royal Institute of Technology, Stockholm 10044, Sweden
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15
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Janssen FFBJ, Peters LCJM, Schlebos PPJ, Smits JMM, de Gelder R, Rowan AE. Uncorrelated Dynamical Processes in Tetranuclear Carboxylate Clusters Studied by Variable-Temperature 1H NMR Spectroscopy. Inorg Chem 2013; 52:13004-13. [DOI: 10.1021/ic401522v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Femke F. B. J. Janssen
- Institute for Molecules and
Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Laurens C. J. M. Peters
- Institute for Molecules and
Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Paul P. J. Schlebos
- Institute for Molecules and
Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Jan M. M. Smits
- Institute for Molecules and
Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - René de Gelder
- Institute for Molecules and
Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Alan E. Rowan
- Institute for Molecules and
Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
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16
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Ye S, Riplinger C, Hansen A, Krebs C, Bollinger JM, Neese F. Electronic structure analysis of the oxygen-activation mechanism by Fe(II)- and α-ketoglutarate (αKG)-dependent dioxygenases. Chemistry 2012; 18:6555-67. [PMID: 22511515 PMCID: PMC3955955 DOI: 10.1002/chem.201102829] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Indexed: 11/09/2022]
Abstract
α-Ketoglutarate (αKG)-dependent nonheme iron enzymes utilize a high-spin (HS) ferrous center to couple the activation of oxygen to the decarboxylation of the cosubstrate αKG to yield succinate and CO(2), and to generate a high-valent ferryl species that then acts as an oxidant to functionalize the target C-H bond. Herein a detailed analysis of the electronic-structure changes that occur in the oxygen activation by this enzyme was performed. The rate-limiting step, which is identical on the septet and quintet surfaces, is the nucleophilic attack of the distal O atom of the O(2) adduct on the carbonyl group in αKG through a bicyclic transition state ((5, 7) TS1). Due to the different electronic structures in (5, 7) TS1, the decay of (7)TS1 leads to a ferric oxyl species, which undergoes a rapid intersystem crossing to form the ferryl intermediate. By contrast, a HS ferrous center ligated by a peroxosuccinate is obtained on the quintet surface following (5)TS1. Thus, additional two single-electron transfer steps are required to afford the same Fe(IV)-oxo species. However, the triplet reaction channel is catalytically irrelevant. The biological role of αKG played in the oxygen-activation reaction is dual. The αKG LUMO (C=O π*) serves as an electron acceptor for the nucleophilic attack of the superoxide monoanion. On the other hand, the αKG HOMO (C1-C2 σ) provides the second and third electrons for the further reduction of the superoxide. In addition to density functional theory, high-level ab initio calculations have been used to calculate the accurate energies of the critical points on the alternative potential-energy surfaces. Overall, the results delivered by the ab initio calculations are largely parallel to those obtained with the B3LYP density functional, thus lending credence to our conclusions.
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Affiliation(s)
- Shengfa Ye
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Christoph Riplinger
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Andreas Hansen
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
| | - Carsten Krebs
- Department of Chemistry Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park, Pennsylvania 16802 (USA)
| | - J. Martin Bollinger
- Department of Chemistry Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park, Pennsylvania 16802 (USA)
| | - Frank Neese
- Max-Plank Institute for Bioinorganic Chemistry Stiftstrasse 34–36 45470 Mülheim an der Ruhr (Germany)
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17
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Takemura Y, Okui Y, Kure B, Nakajima T, Tanase T, Mikuriya M, Takahashi M. Octanuclear iron(III) complexes supported by Kemp’s tricarboxylate ligands. Inorganica Chim Acta 2011. [DOI: 10.1016/j.ica.2011.09.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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18
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Do LH, Lippard SJ. Evolution of strategies to prepare synthetic mimics of carboxylate-bridged diiron protein active sites. J Inorg Biochem 2011; 105:1774-85. [PMID: 22113107 PMCID: PMC3232320 DOI: 10.1016/j.jinorgbio.2011.08.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 08/08/2011] [Accepted: 08/11/2011] [Indexed: 10/17/2022]
Abstract
We present a comprehensive review of research conducted in our laboratory in pursuit of the long-term goal of reproducing the structures and reactivity of carboxylate-bridged diiron centers used in biology to activate dioxygen for the conversion of hydrocarbons to alcohols and related products. This article describes the evolution of strategies devised to achieve these goals and illustrates the challenges in getting there. Particular emphasis is placed on controlling the geometry and coordination environment of the diiron core, preventing formation of polynuclear iron clusters, maintaining the structural integrity of model complexes during reactions with dioxygen, and tuning the ligand framework to stabilize desired oxygenated diiron species. Studies of the various model systems have improved our understanding of the electronic and physical characteristics of carboxylate-bridged diiron units and their reactivity toward molecular oxygen and organic moieties. The principles and lessons that have emerged from these investigations will guide future efforts to develop more sophisticated diiron protein model complexes.
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Affiliation(s)
- Loi H. Do
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139. U.S.A
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139. U.S.A
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Jones MB, Hardcastle KI, Hagen KS, MacBeth CE. Oxygen Activation and Intramolecular C–H Bond Activation by an Amidate-Bridged Diiron(II) Complex. Inorg Chem 2011; 50:6402-4. [DOI: 10.1021/ic2007183] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matthew B. Jones
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | | | - Karl S. Hagen
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Cora E. MacBeth
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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Bochevarov AD, Friesner RA, Lippard SJ. The prediction of Fe Mössbauer parameters by the density functional theory: a benchmark study. J Chem Theory Comput 2010; 6:3735-3749. [PMID: 21258606 PMCID: PMC3023914 DOI: 10.1021/ct100398m] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We report the performance of eight density functionals (B3LYP, BPW91, OLYP, O3LYP, M06, M06-2X, PBE, and SVWN5) in two Gaussian basis sets (Wachters and Partridge-1 on iron atoms; cc-pVDZ on the rest of atoms) for the prediction of the isomer shift (IS) and the quadrupole splitting (QS) parameters of Mössbauer spectroscopy. Two sources of geometry (density functional theory-optimized and X-ray) are used. Our data set consists of 31 iron-containing compounds (35 signals), the Mössbauer spectra of which were determined at liquid helium temperature and where the X-ray geometries are known. Our results indicate that the larger and uncontracted Partridge-1 basis set produces slightly more accurate linear correlations of electronic density used for the prediction of IS and noticeably more accurate results for the QS parameter. We confirm and discuss the earlier observation of Noodleman and co-workers that different oxidation states of iron produce different IS calibration lines. The B3LYP and O3LYP functionals have the lowest errors for either IS or QS. BPW91, OLYP, PBE, and M06 have a mixed success whereas SVWN5 and M06-2X demonstrate the worst performance. Finally, our calibrations and conclusions regarding the best functional to compute the Mössbauer characteristics are applied to candidate structures for the peroxo and Q intermediates of the enzyme methane monooxygenase hydroxylase (MMOH), and compared to experimental data in the literature.
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Cho DW, Parthasarathi R, Pimentel AS, Maestas GD, Park HJ, Yoon UC, Dunaway-Mariano D, Gnanakaran S, Langan P, Mariano PS. Nature and Kinetic Analysis of Carbon−Carbon Bond Fragmentation Reactions of Cation Radicals Derived from SET-Oxidation of Lignin Model Compounds. J Org Chem 2010; 75:6549-62. [DOI: 10.1021/jo1012509] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dae Won Cho
- Department of Chemistry and
Chemical Biology, University of New Mexico, Albuquerque, New Mexico
87131
| | | | - Adam S. Pimentel
- Department of Chemistry and
Chemical Biology, University of New Mexico, Albuquerque, New Mexico
87131
| | - Gabriel D. Maestas
- Department of Chemistry and
Chemical Biology, University of New Mexico, Albuquerque, New Mexico
87131
| | - Hea Jung Park
- Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea
| | - Ung Chan Yoon
- Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea
| | - Debra Dunaway-Mariano
- Department of Chemistry and
Chemical Biology, University of New Mexico, Albuquerque, New Mexico
87131
| | - S. Gnanakaran
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
| | - Paul Langan
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
| | - Patrick S. Mariano
- Department of Chemistry and
Chemical Biology, University of New Mexico, Albuquerque, New Mexico
87131
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Pirngruber GD, Frunz L, Lüchinger M. The characterisation and catalytic properties of biomimetic metal–peptide complexes immobilised on mesoporous silica. Phys Chem Chem Phys 2009; 11:2928-38. [DOI: 10.1039/b819678h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Comparative Fe and Zn K-edge X-ray absorption spectroscopic study of the ferroxidase centres of human H-chain ferritin and bacterioferritin from Desulfovibrio desulfuricans. J Biol Inorg Chem 2008; 14:35-49. [DOI: 10.1007/s00775-008-0422-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Accepted: 08/12/2008] [Indexed: 10/21/2022]
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24
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Lozan V, Kersting B. Macrocyclic Nickel(II) Complexes Coligated by Hydrosulfide and Hexasulfide Ions: Syntheses, Structures, and Magnetic Properties of [NiII2L(μ-SH)]+ and [{LNiII2}2(μ-S6)]2+. Inorg Chem 2008; 47:5386-93. [DOI: 10.1021/ic8003432] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vasile Lozan
- Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany
| | - Berthold Kersting
- Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany
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25
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Characterization and Properties of Non-Heme Iron Peroxo Complexes. STRUCTURE AND BONDING 2007. [DOI: 10.1007/3-540-46592-8_6] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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26
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Paredes-García V, Venegas-Yazigi D, Latorre R, Spodine E. Electronic properties of mixed valence iron(II,III) dinuclear complexes with carboxylate bridges. Polyhedron 2006. [DOI: 10.1016/j.poly.2006.01.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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27
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Kato M, Tanase T, Mikuriya M. Dinuclear Copper(II) Complexes with {Cu2(μ-hydroxo)bis(μ-carboxylato)}+ Cores and Their Reactions with Sugar Phosphate Esters: A Substrate Binding Model of Fructose-1,6-bisphosphatase. Inorg Chem 2006; 45:2925-41. [PMID: 16562948 DOI: 10.1021/ic051942d] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reactions of CuX2.nH2O with the biscarboxylate ligand XDK (H2XDK = m-xylenediamine bis(Kemp's triacid imide)) in the presence of N-donor auxiliary ligands yielded a series of dicopper(II) complexes, [Cu2(mu-OH)(XDK)(L)2]X (L = N,N,N',N'-tetramethylethylenediamine (tetmen), X = NO3 (1a), Cl (1b); L = N,N,N'-trimethylethylenediamine (tmen), X = NO3 (2a), Cl (2b); L =2,2'-bipyridine (bpy), X = NO3 (3); L = 1,10-phenanthroline (phen), X = NO3 (4); L = 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), X = NO3 (5); L = 4-methyl-1,10-phenanthroline (Mephen), X = NO3 (6)). Complexes 1-6 were characterized by X-ray crystallography (Cu...Cu = 3.1624(6)-3.2910(4) A), and the electrochemical and magnetic properties were also examined. Complexes 3 and 4 readily reacted with diphenyl phosphoric acid (HDPP) or bis(4-nitrophenyl) phosphoric acid (HBNPP) to give [Cu2(mu-phosphate)(XDK)(L)2]NO3 (L = bpy, phosphate = DPP (11); L = phen, phosphate = DPP (12), BNPP (13)), where the phsophate diester bridges the two copper ions in a mu-1,3-O,O' bidentate fashion (Cu...Cu = 4.268(3)-4.315(1) A). Complexes 4 and 6 with phen and Mephen have proven to be good precursors to accommodate a series of sugar monophosphate esters (Sugar-P) onto the biscarboxylate-bridged dicopper centers, yielding [Cu2(mu-Sugar-P)(XDK)(L)2] (Sugar-P = alpha-D-Glc-1-P (23a and b), D-Glc-6-P (24a and b), D-Man-6-P (25a), D-Fru-6-P (26a and b); L = phen (a), Mephen (b)) and [Cu2(mu-Gly-n-P)(XDK)(Mephen)2] (Gly-n-P = glycerol n-phosphate; n = 2 (21), 3 (22)), where Glc, Man, and Fru are glucose, mannose, and fructose, respectively. The structure of [Cu2(mu-MNPP)(XDK)(phen)2(CH3OH)] (20) was characterized as a reference compound (H2MNPP = 4-nitrophenyl phosphoric acid). Complexes 4 and 6 also reacted with d-fructose 1,6-bisphosphate (D-Fru-1,6-P2) to afford the tetranuclear copper(II) complexes formulated as [Cu4(mu-D-Fru-1,6-P2)(XDK)2(L)4] (L = phen (27a), Mephen (27b)). The detailed structure of 27a was determined by X-ray crystallography to involve two different tetranuclear complexes with alpha- and beta-anomers of D-Fru-1,6-P2, [Cu4(mu-alpha-D-Fru-1,6-P2)(XDK)2(phen)4] and [Cu4(mu-beta-D-Fru-1,6-P2)(XDK)2(phen)4], in which the D-Fru-1,6-P2 tetravalent anion bridges the two [Cu2(XDK)(phen)2]2+ units through the C1 and C6 phosphate groups in a mu-1,3-O,O' bidentate fashion (Cu...Cu = 4.042(2)-4.100(2) A). Notably, the structure with alpha-D-Fru-1,6-P2 demonstrated the presence of a strong hydrogen bond between the C2 hydroxyl group and the C1 phosphate oxygen atom, which may support the previously proposed catalytic mechanism in the active site of fructose-1,6-bisphosphatase.
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Affiliation(s)
- Merii Kato
- Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoya-higashi-machi, Nara 630-8285, Japan
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Carson EC, Lippard SJ. Synthesis, characterization, and preliminary oxygenation studies of benzyl- and ethyl-substituted pyridine ligands of carboxylate-rich diiron(II) complexes. Inorg Chem 2006; 45:828-36. [PMID: 16411721 PMCID: PMC2505187 DOI: 10.1021/ic051471v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study benzyl and ethyl groups were appended to pyridine and aniline ancillary ligands in diiron(II) complexes of the type [Fe(2)(mu-O(2)CAr(R))(2)(O(2)CAr(R))(2)(L)(2)], where (-)O(2)CAr(R) is a sterically hindered terphenyl carboxylate, 2,6-di(p-tolyl)- or 2,6-di(p-fluorophenyl)benzoate (R = Tol or 4-FPh, respectively). These crystallographically characterized compounds were prepared as analogues of the diiron(II) center in the hydroxylase component of soluble methane monooxygenase (MMOH). The use of 2-benzylpyridine (2-Bnpy) yielded doubly bridged [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-Bnpy)(2)] (1) and [Fe(2)(mu-O(2)CAr(4)(-)(FPh))(2)(O(2)CAr(4)(-)(FPh))(2)(2-Bnpy)(2)] (4), whereas tetra-bridged [Fe(2)(mu-O(2)CAr(Tol))(4)(4-Bnpy)(2)] (3) resulted when 4-benzylpyridine (4-Bnpy) was employed. Similarly, 2-(4-chlorobenzyl)pyridine (2-(4-ClBn)py) and 2-benzylaniline (2-Bnan) were employed as N-donor ligands to prepare [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-(4-ClBn)py)(2)] (2) and [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-Bnan)(2)] (5). The placement of the substituent on the pyridine ring had no effect on the geometry of the diiron(II) compounds isolated when 2-, 3-, or 4-ethylpyridine (2-, 3-, or 4-Etpy) was introduced as the ancillary nitrogen ligand. The isolated [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-Etpy)] (6), [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(3-Etpy)] (7), [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(4-Etpy)] (8), and [Fe(2)(mu-O(2)CAr(4)(-FPh))(2)(O(2)CAr(4)(-)(FPh))(2)(2-Etpy)(2)] (9) complexes all contain doubly bridged metal centers. The oxygenation of compounds 1-9 was studied by GC-MS and NMR analysis of the organic fragments following decomposition of the product complexes. Hydrocarbon fragment oxidation occurred for compounds in which the substrate moiety was in close proximity to the diiron center. The extent of oxidation depended upon the exact makeup of the ligand set.
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Affiliation(s)
- Emily C Carson
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Carson EC, Lippard SJ. Dioxygen-initiated oxidation of heteroatomic substrates incorporated into ancillary pyridine ligands of carboxylate-rich diiron(II) complexes. Inorg Chem 2006; 45:837-48. [PMID: 16411722 PMCID: PMC2505175 DOI: 10.1021/ic051476s] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Progress toward the development of functional models of the carboxylate-bridged diiron active site in soluble methane monooxygenase is described in which potential substrates are introduced as substituents on bound pyridine ligands. Pyridine ligands incorporating a thiol, sulfide, sulfoxide, or phosphine moiety were allowed to react with the preassembled diiron(II) complex [Fe(2)(mu-O(2)CAr(R))(2)(O(2)CAr(R))(2)(THF)(2)], where (-)O(2)CAr(R) is a sterically hindered 2,6-di(p-tolyl)- or 2,6-di(p-fluorophenyl)benzoate (R = Tol or 4-FPh). The resulting diiron(II) complexes were characterized crystallographically. Triply and doubly bridged compounds [Fe(2)(mu-O(2)CAr(Tol))(3)(O(2)CAr(Tol))(2-MeSpy)] (4) and [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-MeS(O)py)(2)] (5) resulted when 2-methylthiopyridine (2-MeSpy) and 2-pyridylmethylsulfoxide (2-MeS(O)py), respectively, were employed. Another triply bridged diiron(II) complex, [Fe(2)(mu-O(2)CAr(4)(-)(FPh))(3)-(O(2)CAr(4)(-)(FPh))(2-Ph(2)Ppy)] (3), was obtained containing 2-diphenylphosphinopyridine (2-Ph(2)Ppy). The use of 2-mercaptopyridine (2-HSpy) produced the mononuclear complex [Fe(O(2)CAr(Tol))(2)(2-HSpy)(2)] (6a). Together with that of previously reported [Fe(2)(mu-O(2)CAr(Tol))(3)(O(2)CAr(Tol))(2-PhSpy)] (2) and [Fe(2)(mu-O(2)CAr(Tol))(3)(O(2)CAr(Tol))(2-Ph(2)Ppy)] (1), the dioxygen reactivity of these iron(II) complexes was investigated. A dioxygen-dependent intermediate (6b) formed upon exposure of 6a to O(2), the electronic structure of which was probed by various spectroscopic methods. Exposure of 4 and 5 to dioxygen revealed both sulfide and sulfoxide oxidation. Oxidation of 3 in CH(2)Cl(2) yields [Fe(2)(mu-OH)(2)(mu-O(2)CAr(4)(-)(FPh))(O(2)CAr(4)(-FPh))(3)(OH(2))(2-Ph(2)P(O)py)] (8), which contains the biologically relevant {Fe(2)(mu-OH)(2)(mu-O(2)CR)}(3+) core. This reaction is sensitive to the choice of carboxylate ligands, however, since the p-tolyl analogue 1 yielded a hexanuclear species, 7, upon oxidation.
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Affiliation(s)
- Emily C. Carson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Kryatov SV, Rybak-Akimova EV, Schindler S. Kinetics and Mechanisms of Formation and Reactivity of Non-heme Iron Oxygen Intermediates. Chem Rev 2005; 105:2175-226. [PMID: 15941212 DOI: 10.1021/cr030709z] [Citation(s) in RCA: 313] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
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Shan X, Que L. Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species. Proc Natl Acad Sci U S A 2005; 102:5340-5. [PMID: 15802473 PMCID: PMC556236 DOI: 10.1073/pnas.0409640102] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reaction of [Fe(2)(mu-OH)(2)(6-Me(3)-TPA)(2)](2+) (1) [6-Me(3)-TPA, Tris(6-methyl-2-pyridylmethyl)amine] with O(2) in CH(2)Cl(2) at -80 degrees C gives rise to two new intermediates, 2 and 3, before the formation of previously characterized [Fe(2)(O)(O(2))(6-Me(3)-TPA)(2)](2+) (4) that allow the oxygenation reaction to be monitored one electron-transfer step at a time. Raman evidence assigns 2 and 3 as a diiron-superoxo species and a diiron-peroxo species, respectively. Intermediate 2 exhibits its nu(O-O) at 1,310 cm(-1) with a -71-cm(-1) (18)O isotope shift. A doublet peak pattern for the (16)O(18)O isotopomer of 2 in mixed-isotope Raman experiments strongly suggests that the superoxide ligand of 2 is bound end-on. This first example of a nonheme iron-superoxo intermediate exhibits the highest frequency nu(O-O) yet observed for a biomimetic metal-dioxygen adduct. The bound superoxide of 2, unlike the bound peroxide of 4, is readily reduced by 2,4-di-tert-butylphenol via a proton-coupled electron-transfer mechanism, emphasizing that metal-superoxo species may serve as oxidants in oxygen activation mechanisms of metalloenzymes. The discovery of intermediates 2 and 3 allows us to dissect the initial steps of dioxygen binding at a diiron center leading to its activation for substrate oxidation.
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Affiliation(s)
- Xiaopeng Shan
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, MN 55455, USA
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Onoda A, Haruna H, Yamamoto H, Takahashi K, Kozuki H, Okamura TA, Ueyama N. Proton-Driven Conformational Switch of a Cyclohexyl Skeleton Coupled with NH···O Hydrogen-Bond Formation. European J Org Chem 2005. [DOI: 10.1002/ejoc.200400385] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Kryatov SV, Taktak S, Korendovych IV, Rybak-Akimova EV, Kaizer J, Torelli S, Shan X, Mandal S, MacMurdo VL, Mairata i Payeras A, Que L. Dioxygen Binding to Complexes with FeII2(μ-OH)2 Cores: Steric Control of Activation Barriers and O2-Adduct Formation. Inorg Chem 2004; 44:85-99. [PMID: 15627364 DOI: 10.1021/ic0485312] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of complexes with [Fe(II)(2)(mu-OH)(2)] cores has been synthesized with N3 and N4 ligands and structurally characterized to serve as models for nonheme diiron(II) sites in enzymes that bind and activate O(2). These complexes react with O(2) in solution via bimolecular rate-limiting steps that differ in rate by 10(3)-fold, depending on ligand denticity and steric hindrance near the diiron center. Low-temperature trapping of a (mu-oxo)(mu-1,2-peroxo)diiron(III) intermediate after O(2) binding requires sufficient steric hindrance around the diiron center and the loss of a proton (presumably that of a hydroxo bridge or a yet unobserved hydroperoxo intermediate). The relative stability of these and other (mu-1,2-peroxo)diiron(III) intermediates suggests that these species may not be on the direct pathway for dioxygen activation.
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Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, Massachusetts 02155, USA
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Wei PP, Skulan AJ, Mitić N, Yang YS, Saleh L, Bollinger JM, Solomon EI. Electronic and spectroscopic studies of the non-heme reduced binuclear iron sites of two ribonucleotide reductase variants: comparison to reduced methane monooxygenase and contributions to O2 reactivity. J Am Chem Soc 2004; 126:3777-88. [PMID: 15038731 DOI: 10.1021/ja0374731] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Circular dichroism (CD), magnetic circular dichroism (MCD), and variable-temperature variable-field (VTVH) MCD have been used to probe the biferrous active site of two variants of ribonucleotide reductase. The aspartate to glutamate substitution (R2-D84E) at the binuclear iron site modifies the endogenous ligand set of ribonucleotide reductase to match that of the binuclear center in the hydroxylase component of methane monooxygenase (MMOH). The crystal structure of chemically reduced R2-D84E suggests that the active-site structure parallels that of MMOH. However, CD, MCD, and VTVH MCD data combined with spin-Hamiltonian analysis of reduced R2-D84E indicate a different coordination environment relative to reduced MMOH, with no mu-(1,1)(eta(1),eta(2)) carboxylate bridge. To further understand the variations in geometry of the active site, which lead to differences in reactivity, density functional theory (DFT) calculations have been carried out to identify active-site structures for R2-wt and R2-D84E consistent with these spectroscopic data. The effects of varying the ligand set, positions of bound and free waters, and additional protein constraints on the geometry and energy of the binuclear site of both R2-wt and variant R2s are also explored to identify the contributions to their structural differences and their relation to reduced MMOH.
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Affiliation(s)
- Pin-Pin Wei
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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Kryatov SV, Chavez FA, Reynolds AM, Rybak-Akimova EV, Que L, Tolman WB. Mechanistic Studies on the Formation and Reactivity of Dioxygen Adducts of Diiron Complexes Supported by Sterically Hindered Carboxylates. Inorg Chem 2004; 43:2141-50. [PMID: 15018538 DOI: 10.1021/ic049976t] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dioxygen activation by enzymes such as methane monooxygenase, ribonucleotide reductase, and fatty acid desaturases occurs at a nonheme diiron active site supported by two histidines and four carboxylates, typically involving a (peroxo)diiron(III,III) intermediate in an early step of the catalytic cycle. Biomimetic tetracarboxylatodiiron(II,II) complexes with the familiar "paddlewheel" topology comprising sterically bulky o-dixylylbenzoate ligands with pyridine, 1-methylimidazole, or THF at apical sites readily react with O(2) to afford thermally labile peroxo intermediates that can be trapped and characterized spectroscopically at low temperatures (193 K). Cryogenic stopped-flow kinetic analysis of O(2) adduct formation carried out for the three complexes reveals that dioxygen binds to the diiron(II,II) center with concentration dependences and activation parameters indicative of a direct associative pathway. The pyridine and 1-methylimidazole intermediates decay by self-decomposition. However, the THF intermediate decays much faster by oxygen transfer to added PPh(3), the kinetics of which has been studied with double mixing experiments in a cryogenic stopped-flow apparatus. The results show that the decay of the THF intermediate is kinetically controlled by the dissociation of a THF ligand, a conclusion supported by the observation of saturation kinetic behavior with respect to PPh(3), inhibition by added THF, and invariant saturation rate constants for the oxidation of various phosphines. It is proposed that the proximity of the reducing substrate to the peroxide ligand on the diiron coordination sphere facilitates the oxygen-atom transfer. This unique investigation of the reaction of an O(2) adduct of a biomimetic tetracarboxylatodiiron(II,II) complex provides a synthetic precedent for understanding the electrophilic reactivity of like adducts in the active sties of nonheme diiron enzymes.
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Affiliation(s)
- Sergey V Kryatov
- Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, MA 02155, USA
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37
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Tshuva EY, Lippard SJ. Synthetic Models for Non-Heme Carboxylate-Bridged Diiron Metalloproteins: Strategies and Tactics. Chem Rev 2004; 104:987-1012. [PMID: 14871147 DOI: 10.1021/cr020622y] [Citation(s) in RCA: 536] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Edit Y Tshuva
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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38
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Gavrilova AL, Bosnich B. Principles of Mononucleating and Binucleating Ligand Design. Chem Rev 2004; 104:349-83. [PMID: 14871128 DOI: 10.1021/cr020604g] [Citation(s) in RCA: 455] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anna L Gavrilova
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, USA
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39
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Beck A, Barth A, Hübner E, Burzlaff N. Bis(pyrazol-1-yl)acetates as Tripodal Heteroscorpionate Ligands in Iron Chemistry: Syntheses and Structures of Iron(II) and Iron(III) Complexes with bpza, bdmpza, and bdtbpza Ligands. Inorg Chem 2003; 42:7182-8. [PMID: 14577787 DOI: 10.1021/ic034097c] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molecular structure of the previously reported species "[Fe(bdtbpza)Cl]" has been revealed by X-ray structure determination to be a ferrous dimer [Fe(bdtbpza)Cl](2) (2c) [bdtbpza = bis(3,5-di-tert-butylpyrazol-1-yl)acetate]. The syntheses of ferrous 2:1 complexes [Fe(bpza)(2)] (3a) and [Fe(bdtbpza)(2)] (3c) as well as ferric 1:1 complexes [NEt(4)][Fe(bpza)Cl(3)] (4a) and [NEt(4)][Fe(bdmpza)Cl(3)] (4b) [bpza = bis(pyrazol-1-yl)acetate, bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] are reported. Complexes 3a, previously reported [Fe(bdmpza)(2)] (3b), and 3c are high-spin. No spin crossover to the low-spin state was observed in the temperature range of 5-350 K. 4a and 4b are synthesized in one step and in high yield from [NEt(4)](2)[Cl(3)FeOFeCl(3)]. 4a and 4b are iron(III) high-spin complexes. Crystallographic information: 2c (C(24)H(39)ClFeN(4)O(2).CH(2)Cl(2).CH(3)CN) is triclinic, P1, a = 12.171(16) A, b = 12.851(14) A, c = 13.390(13) A, alpha = 98.61(9) degrees, beta = 113.51(11) degrees, gamma = 108.10(5) degrees, Z = 2; 3a (C(8)H(7)Fe(0.5)N(4)O(2)) is monoclinic, P2(1)/n, a = 7.4784(19) A, b = 7.604(3) A, c = 16.196(4) A, beta = 95.397(9) degrees, Z = 4; 3c (C(24)H(39)Fe(0.5)N(4)O(2)) is monoclinic, P2(1)/n, a = 9.939(6) A, b = 18.161(10) A, c = 13.722(8) A, beta = 97.67(7) degrees, Z = 4; 4b (C(20)H(35)Cl(3)FeN(5)O(2)) is monoclinic, C2/c, a = 30.45(6) A, b = 12.33(2) A, c = 16.17(3) A, beta = 118.47(5) degrees, Z = 8.
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Affiliation(s)
- Alexander Beck
- Fachbereich Chemie, Universität Konstanz, Fach M728, D-78457 Konstanz, Germany
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40
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Bhatia SC, Ravi N. A Mössbauer study of the interaction of chitosan and D-glucosamine with iron and its relevance to other metalloenzymes. Biomacromolecules 2003; 4:723-7. [PMID: 12741790 DOI: 10.1021/bm020131n] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interaction of iron with water-soluble polymer chitosan and monomer d-glucosamine is investigated by Mössbauer spectroscopy. The 4.2 K Mössbauer spectrum of Fe-water-soluble chitosan complex indicates the presence of a magnetic pattern and a quadrupole doublet, and analysis of the spectral data leads to the conclusion that an Fe(II) state is partially stabilized in this system. Fe-glucosamine (monomer of chitosan) complex, on the other hand, clearly stabilizes the Fe(II) state in the acidic pH range as evidenced from the isomer shift extracted from the Mössbauer spectra. The oxidation state of the metal ion in the complex is found to be pH dependent. Indirect evidence supporting the involvement of amino group in the bonding with the metal ion is discussed. From the analysis of the experimental data under varying experimental conditions, it is concluded that the metal ion in the complex is at least tetracoordinated and at most hexacoordinated with O/N ligands of the polymer or monomer and thus corroborates the bonding scheme proposed earlier.
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Affiliation(s)
- Subhash C Bhatia
- Department of Chemistry, Morehouse College, Atlanta, Georgia 30314, USA
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41
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Jensen MP, Lange SJ, Mehn MP, Que EL, Que L. Biomimetic aryl hydroxylation derived from alkyl hydroperoxide at a nonheme iron center. Evidence for an Fe(IV)=O oxidant. J Am Chem Soc 2003; 125:2113-28. [PMID: 12590539 DOI: 10.1021/ja028478l] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many nonheme iron-dependent enzymes activate dioxygen to catalyze hydroxylations of arene substrates. Key features of this chemistry have been developed from complexes of a family of tetradentate tripodal ligands obtained by modification of tris(2-pyridylmethyl)amine (TPA) with single alpha-arene substituents. These included the following: -C(6)H(5) (i.e., 6-PhTPA), L(1); -o-C(6)H(4)D, o-d(1)-L(1); -C(6)D(5), d(5)-L(1); -m-C(6)H(4)NO(2), L(2); -m-C(6)H(4)CF(3), L(3); -m-C(6)H(4)Cl, L(4); -m-C(6)H(4)CH(3), L(5); -m-C(6)H(4)OCH(3), L(6); -p-C(6)H(4)OCH(3), L(7). Additionally, the corresponding ligand with one alpha-phenyl and two alpha-methyl substituents (6,6-Me(2)-6-PhTPA, L(8)) was also synthesized. Complexes of the formulas [(L(1))Fe(II)(NCCH(3))(2)](ClO(4))(2), [(L(n)())Fe(II)(OTf)(2)] (n = 1-7, OTf = (-)O(3)SCF(3)), and [(L(8))Fe(II)(OTf)(2)](2) were obtained and characterized by (1)H NMR and UV-visible spectroscopies and by X-ray diffraction in the cases of [(L(1))Fe(II)(NCCH(3))(2)](ClO(4))(2), [(L(6))Fe(II)(OTf)(2)], and [(L(8))Fe(II)(OTf)(2)](2). The complexes react with tert-butyl hydroperoxide ((t)()BuOOH) in CH(3)CN solutions to give iron(III) complexes of ortho-hydroxylated ligands. The product complex derived from L(1) was identified as the solvated monomeric complex [(L(1)O(-))Fe(III)](2+) in equilibrium with its oxo-bridged dimer [(L(1)O(-))(2)Fe(III)(2)(mu(2)-O)](2+), which was characterized by X-ray crystallography as the BPh(4)(-) salt. The L(8) product was also an oxo-bridged dimer, [(L(8)O(-))(2)Fe(III)(2)(mu(2)-O)](2+). Transient intermediates were observed at low temperature by UV-visible spectroscopy, and these were characterized as iron(III) alkylperoxo complexes by resonance Raman and EPR spectroscopies for L(1) and L(8). [(L(1))Fe(II)(OTf)(2)] gave rise to a mixture of high-spin (S = 5/2) and low-spin (S = 1/2) Fe(III)-OOR isomers in acetonitrile, whereas both [(L(1))Fe(OTf)(2)] in CH(2)Cl(2) and [(L(8))Fe(OTf)(2)](2) in acetonitrile afforded only high-spin intermediates. The L(1) and L(8) intermediates both decomposed to form respective phenolate complexes, but their reaction times differed by 3 orders of magnitude. In the case of L(1), (18)O isotope labeling indicated that the phenolate oxygen is derived from the terminal peroxide oxygen via a species that can undergo partial exchange with exogenous water. The iron(III) alkylperoxo intermediate is proposed to undergo homolytic O-O bond cleavage to yield an oxoiron(IV) species as an unobserved reactive intermediate in the hydroxylation of the pendant alpha-aryl substituents. The putative homolytic chemistry was confirmed by using 2-methyl-1-phenyl-2-propyl hydroperoxide (MPPH) as a probe, and the products obtained in the presence and in the absence of air were consistent with formation of alkoxy radical (RO(*)). Moreover, when one ortho position was labeled with deuterium, no selectivity was observed between hydroxylation of the deuterated and normal isotopomeric ortho sites, but a significant 1,2-deuterium shift ("NIH shift") occurred. These results provide strong mechanistic evidence for a metal-centered electrophilic oxidant, presumably an oxoiron(IV) complex, in these arene hydroxylations and support participation of such a species in the mechanisms of the nonheme iron- and pterin-dependent aryl amino acid hydroxylases.
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Affiliation(s)
- Michael P Jensen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA
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42
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43
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Lee D, Lippard SJ. Modeling dioxygen-activating centers in non-heme diiron enzymes: carboxylate shifts in diiron(II) complexes supported by sterically hindered carboxylate ligands. Inorg Chem 2002; 41:2704-19. [PMID: 12005495 DOI: 10.1021/ic020186y] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
General synthetic routes are described for a series of diiron(II) complexes supported by sterically demanding carboxylate ligands 2,6-di(p-tolyl)benzoate (Ar(Tol)CO(2)(-)) and 2,6-di(4-fluorophenyl)benzoate (Ar(4-FPh)CO(2)(-)). The interlocking nature of the m-terphenyl units in self-assembled [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (L = C(5)H(5)N (4); 1-MeIm (5)) promotes the formation of coordination geometries analogous to those of the non-heme diiron cores in the enzymes RNR-R2 and Delta 9D. Magnetic susceptibility and Mössbauer studies of 4 and 5 revealed properties consistent with weak antiferromagnetic coupling between the high-spin iron(II) centers. Structural studies of several derivatives obtained by ligand substitution reactions demonstrated that the [Fe(2)(O(2)CAr')(4)L(2)] (Ar' = Ar(Tol); Ar(4-FPh)) module is geometrically flexible. Details of ligand migration within the tetracarboxylate diiron core, facilitated by carboxylate shifts, were probed by solution variable-temperature (19)F NMR spectroscopic studies of [Fe(2)(mu-O(2)CAr(4-FPh))(2)-(O(2)CAr(4-FPh))(2)(THF)(2)] (8) and [Fe(2)(mu-O(2)CAr(4-FPh))(4)(4-(t)BuC(5)H(4)N)(2)] (12). Dynamic motion in the primary coordination sphere controls the positioning of open sites and regulates the access of exogenous ligands, processes that also occur in non-heme diiron enzymes during catalysis.
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Affiliation(s)
- Dongwhan Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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44
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Fokin AA, Schreiner PR. Selective alkane transformations via radicals and radical cations: insights into the activation step from experiment and theory. Chem Rev 2002; 102:1551-94. [PMID: 11996544 DOI: 10.1021/cr000453m] [Citation(s) in RCA: 306] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrey A Fokin
- Department of Organic Chemistry, Kiev Polytechnic Institute, 37 Pobedy Avenue, 03056 Kiev, Ukraine.
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45
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Wasser IM, de Vries S, Moënne-Loccoz P, Schröder I, Karlin KD. Nitric oxide in biological denitrification: Fe/Cu metalloenzyme and metal complex NO(x) redox chemistry. Chem Rev 2002; 102:1201-34. [PMID: 11942794 DOI: 10.1021/cr0006627] [Citation(s) in RCA: 355] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ian M Wasser
- Department of Chemistry, The Johns Hopkins University, Charles and 34th Streets, Baltimore, MD 21218, USA
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46
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Aguirre F, Husband J, Thompson CJ, Stringer KL, Metz RB. Electronic spectroscopy of intermediates involved in the conversion of methane to methanol by FeO+. J Chem Phys 2002. [DOI: 10.1063/1.1448489] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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47
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Lee D, Hung PL, Spingler B, Lippard SJ. Sterically hindered carboxylate ligands support water-bridged dimetallic centers that model features of metallohydrolase active sites. Inorg Chem 2002; 41:521-31. [PMID: 11825079 DOI: 10.1021/ic0107431] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis and characterization of carboxylate-bridged dimetallic complexes are described. By using m-terphenyl-derived carboxylate ligands, a series of dicobalt(II), dicobalt(III), dinickel(II), and dizinc(II) complexes were synthesized. The compounds are [Co(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (1), [Co(2)(mu-OH(2))(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (2a-c), [Co(2)(mu-OH)(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (3), [Ni(2)(mu-O(2)CAr(Tol))(4)L(2)] (4), [Ni(2)(mu-HO...H)(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (5), and [Zn(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)L(2)] (6), where Ar(Tol)CO(2)H = 2,6-di(p-tolyl)benzoic acid and L = pyridine, THF, or N,N-dibenzylethylenediamine. Structural analysis of these complexes revealed that additional bridging ligands can be readily accommodated within the [M(2)(mu-O(2)CAr(Tol))(2)](2+) core, allowing a wide distribution of M...M distances from 2.5745(6) to 4.0169(9) A. Unprecedented bridging units [M(2)(mu-OH(2))(2)(mu-O(2)CR)(2)](n+) and [M(2)(mu-HO...H)(2)(mu-O(2)CR)(2)](n+) were identified in 2a-c and 5, respectively, in which strong hydrogen bonding accommodates shifts of protons from bridging water molecules toward the dangling oxygen atoms of terminal monodentate carboxylate groups. Such a proton shift along the O...H...O coordinate attenuates the donor ability of the anionic carboxylate ligand, which can translate into increased Lewis acidity at the metal centers. Such double activation of bridging water molecules by a Lewis acidic metal center and a metal-bound general base may facilitate the reactivity of metallohydrolases such as methionine aminopeptidase (MAP).
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Affiliation(s)
- Dongwhan Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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48
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Mizoguchi TJ, Kuzelka J, Spingler B, DuBois JL, Davydov RM, Hedman B, Hodgson KO, Lippard SJ. Synthesis and spectroscopic studies of non-heme diiron(III) species with a terminal hydroperoxide ligand: models for hemerythrin. Inorg Chem 2001; 40:4662-73. [PMID: 11511213 DOI: 10.1021/ic010076b] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two compounds, [Fe2(mu-OH)(mu-Ph4DBA)(TMEDA)2(OTf)] (4) and [Fe2(mu-OH)(mu-Ph4DBA)(DPE)2(OTf)] (7), where Ph4DBA(2-) is the dinucleating bis(carboxylate) ligand dibenzofuran-4,6-bis(diphenylacetate), have been prepared as synthetic models for the dioxygen-binding non-heme diiron protein hemerythrin (Hr). X-ray crystallography reveals that, in the solid state, these compounds contain the asymmetric coordination environment found at the diiron center in the reduced form of the protein, deoxyHr. Mössbauer spectra of the models (4, delta = 1.21(2), DeltaE(Q) = 2.87(2) mm s(-1); 7, delta(av) = 1.23(1), DeltaE(Qav) = 2.79(1) mm s(-1)) and deoxyHr (delta = 1.19, DeltaE(Q) = 2.81 mm s(-1)) are also in good agreement. Oxygenation of the diiron(II) complexes dissolved in CH2Cl2 containing 3 equiv of N-MeIm (4) or neat EtCN (7) at -78 degrees C affords a red-orange solution with optical bands at 336 nm (7300 M(-1) cm(-1)) and 470 nm (2600 M(-1) cm(-1)) for 4 and at 334 nm (6400 M(-1) cm(-1)) and 484 nm (2350 M(-1) cm(-1)) for 7. These spectra are remarkably similar to that of oxyHr, 330 nm (6800 M(-1) cm(-1)) and 500 nm (2200 M(-1) cm(-1)). The electron paramagnetic resonance (EPR) spectrum of the cryoreduced, mixed-valence dioxygen adduct of 7 displays properties consistent with a (mu-oxo)diiron(II,III) core. An investigation of 7 and its dioxygen-bound adduct by extended X-ray absorption fine structure (EXAFS) spectroscopy indicates that the oxidized species contains a (mu-oxo)diiron(III) core with iron-ligand distances in agreement with those expected for oxide, carboxylate, and amine/hydroperoxide donor atoms. The analogous cobalt complex [Co2(mu-OH)(mu-Ph4DBA)(TMEDA)2(OTf)] (6) was synthesized and structurally characterized, but it was unreactive toward dioxygen.
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Affiliation(s)
- T J Mizoguchi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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49
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Tanase T, Inukai H, Onaka T, Kato M, Yano S, Lippard SJ. Trinuclear Zn(II) and Cu(II) homo and heterotrimetallic complexes involving D-glucopyranosyl and biscarboxylate bridging ligands. A substrate binding model of xylose isomerases. Inorg Chem 2001; 40:3943-53. [PMID: 11466052 DOI: 10.1021/ic001419t] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reactions of MCl(2).nH(2)O with N,N'-bis(D-glucopyranosyl)-1,4,7-triazacyclononane ((D-Glc)(2)-tacn), which was formed from D-glucose and 1,4,7-triazacyclononane (tacn) in situ, afforded a series of mononuclear divalent metal complexes with two beta-D-glucopyranosyl moieties, [M((D-Glc)(2)-tacn)Cl]Cl (M = Zn (11), Cu (12), Ni (13), Co (14)). Complexes 11-14 were characterized by analytical and spectroscopic measurements and X-ray crystallography and were found to have a distorted octahedral M(II) center ligated by the pentacoordinate N-glycoside ligand, (beta-D-glucopyranosyl)(2)-tacn, and a chloride anion. Each D-glucose moiety is tethered to the metal center through the beta-N-glycosidic bond with tacn and additionally coordinated via the C-2 hydroxyl group, resulting in a lambda-gauche five-membered chelate ring. When L-rhamnose (6-deoxy-L-mannose) was used instead of D-glucose, the nickel(II) complex with two beta-L-rhamnopyranosyl moieties, [Ni((D-Man)(2)-tacn)(MeOH)]Cl(2) (15), was obtained and characterized by an X-ray analysis. Reactions of 11 (M = Zn) with [Zn(XDK)(H(2)O)] (21) or [Cu(XDK)(py)(2)] (22) (H(2)XDK = m-xylylenediamine bis(Kemp's triacid imide)) yielded homo and heterotrimetallic complexes formulated as [Zn(2)M'((D-Glc)(2)-tacn)(2)(XDK)]Cl(2) (M' = Zn (31), Cu (32)). The similar reactions of 12 (M = Cu) with complex 21 or 22 afforded [Cu(2)M'((D-Glc)(2)-tacn)(2)(XDK)]Cl(2) (M' = Cu (33), Zn (34)). An X-ray crystallographic study revealed that complexes 31 and 34 have either Zn(II)(3) or Cu(II)Zn(II)Cu(II) trimetallic centers bridged by two carboxylate groups of XDK and two D-glucopyranosyl residues. The M...M' separations are 3.418(3)-3.462(3) A (31) and 3.414(1)-3.460(1) A (34), and the M...M'...M angles are 155.18(8) degrees (31) and 161.56(6) degrees (34). The terminal metal ions are octahedrally coordinated by the (D-Glc)(2)-tacn ligand through three nitrogen atoms of tacn, two oxygen atoms of the C-2 hydroxyl groups of the carbohydrates, and a carboxylate oxygen atom of XDK ligand. The central metal ions sit in a distorted octahedral environment ligated by four oxygen atoms of the carbohydrate residues in the (D-Glc)(2)-tacn ligands and two carboxylate oxygen atoms of XDK. The deprotonated beta-D-glucopyranosyl unit at the C-2 hydroxyl group bridges the terminal and central ions with the C-2 mu-alkoxo group, with the C-1 N-glycosidic amino and the C-3 hydroxyl groups coordinating to each metal center. Complexes 31-34 are the first examples of metal complexes in which D-glucose units act as bridging ligands. These structures could be very useful substrate binding models of xylose or glucose isomerases, which promote D-glucose D-fructose isomerization by using divalent dimetallic centers bridged by a glutamate residue.
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Affiliation(s)
- T Tanase
- Department of Chemistry, Faculty of Science, Nara Women's University, Nara-shi, Nara 630-8285, Japan.
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50
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Kryatov SV, Rybak-Akimova EV, MacMurdo VL, Que L. A mechanistic study of the reaction between a diiron(II) complex [FeII(2)(mu-OH)2(6-Me3-TPA)2](2+) and O2 to form a diiron(III) peroxo complex. Inorg Chem 2001; 40:2220-8. [PMID: 11327894 DOI: 10.1021/ic001300k] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A kinetic study of the reaction between a diiron(II) complex [Fe(II)(2)(mu-OH)(2)(6-Me(3)-TPA)(2)](2+) 1, where 6-Me(3)-TPA = tris(6-methyl-2-pyridylmethyl)amine, and dioxygen is presented. A diiron(III) peroxo complex [Fe(III)(2)(mu-O)(mu-O(2))(6-Me(3)-TPA)(2)](2+) 2 forms quantitatively in dichloromethane at temperatures from -80 to -40 degrees C. The reaction is first order in [Fe(II)(2)] and [O(2)], with the activation parameters DeltaH(double dagger) = 17 +/- 2 kJ mol(-1) and DeltaS(double dagger) = -175 +/- 20 J mol(-1) K(-1). The reaction rate is not significantly influenced by the addition of H(2)O or D(2)O. The reaction proceeds faster in more polar solvents (acetone and acetonitrile), but the yield of 2 is not quantitative in these solvents. Complex 1 reacts with NO at a rate about 10(3) faster than with O(2). The mechanistic analysis suggests an associative rate-limiting step for the oxygenation of 1, similar to that for stearoyl-ACP Delta(9)-desaturase, but distinct from the probable dissociative pathway of methane monoxygenase. An eta(1)-superoxo Fe(II)Fe(III) species is a likely steady-state intermediate during the oxygenation of complex 1.
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Affiliation(s)
- S V Kryatov
- Department of Chemistry, Tufts University, Medford, MA 02155, USA
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