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Depenbrock F, Limpke T, Stammler A, Oldengott J, Bögge H, Glaser T. Increasing the electron donation in a dinucleating ligand family: molecular and electronic structures in a series of Co IICo II complexes. Dalton Trans 2024; 53:9554-9567. [PMID: 38771300 DOI: 10.1039/d4dt00877d] [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
We have developed a family of dinucleating ligands with varying terminal donors to generate dinuclear peroxo and high-valent complexes and to correlate their stabilities and reactivities with their molecular and electronic structures as a function of the terminal donors. It appears that the electron-donating ability of the terminal donors is an important handle for controlling these stabilities and reactivities. Here, we present the synthesis of a new dinucleating ligand with potentially strong donating terminal imidazole donors. As CoII ions are sensitive to variations in donor strength in terms of coordination number, magnetism, UV-Vis-NIR spectra, redox potentials, we probe the electron donation ability of this new ligand in CoIICoII complexes in comparison to the parent CoIICoII complexes with terminal pyridine donors and we synthesize the analogous CoIICoII complexes with terminal 6-methylpyridines and methoxy-substituted pyridines. The molecular structures show indeed strong variations in coordination numbers and bond lengths. These differences in the molecular structures are reflected in the magnetic properties and in the d-d transitions demonstrating that the molecular structures remain intact upon dissolution. The redox potentials are analyzed with respect to the electron donation ability and are the only handle to observe an effect of the methoxy-substituted pyridines. All data taken together show the following order of electron donating ability for the terminal donors: 6-methylpyridines ≪ pyridines < methoxy-substituted pyridines ≪ imidazoles.
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Affiliation(s)
- Felix Depenbrock
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
| | - Thomas Limpke
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
| | - Anja Stammler
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
| | - Jan Oldengott
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
| | - Hartmut Bögge
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
| | - Thorsten Glaser
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
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2
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Stoichiometric Alkane and Aldehyde Hydroxylation Reactions Mediated by In Situ Generated Iron(III)-Iodosylbenzene Adduct. Molecules 2023; 28:molecules28041855. [PMID: 36838842 PMCID: PMC9958819 DOI: 10.3390/molecules28041855] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/06/2023] [Accepted: 02/14/2023] [Indexed: 02/18/2023] Open
Abstract
Previously synthesized and spectroscopically characterized mononuclear nonheme, low-spin iron(III)-iodosylbenzene complex bearing a bidentate pyridyl-benzimidazole ligands has been investigated in alkane and aldehyde oxidation reactions. The in situ generated Fe(III) iodosylbenzene intermediate is a reactive oxidant capable of activating the benzylic C-H bond of alkane. Its electrophilic character was confirmed by using substituted benzaldehydes and a modified ligand framework containing electron-donating (Me) substituents. Furthermore, the results of kinetic isotope experiments (KIE) using deuterated substrate indicate that the C-H activation can be interpreted through a tunneling-like HAT mechanism. Based on the results of the kinetic measurements and the relatively high KIE values, we can conclude that the activation of the C-H bond mediated by iron(III)-iodosylbenzene adducts is the rate-determining step.
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3
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Röhs FLB, Dammers S, Stammler A, Oldengott J, Bögge H, Bill E, Glaser T. Dinuclear Diferrous Complexes of a Bis(tetradentate) Dinucleating Ligand: Influence of the Exogenous Ligands on the Molecular and Electronic Structures. Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202200177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Susanne Dammers
- Bielefeld University: Universitat Bielefeld Fakultät für Chemie GERMANY
| | - Anja Stammler
- Bielefeld University: Universitat Bielefeld Fakultät für Chemie GERMANY
| | - Jan Oldengott
- Bielefeld University: Universitat Bielefeld Fakultät für Chemie GERMANY
| | - Hartmut Bögge
- Bielefeld University: Universitat Bielefeld Fakultät für Chemie GERMANY
| | - Eckhard Bill
- Mulheimer Max-Planck-Institute: Max-Planck-Institut fur chemische Energiekonversion Max-Planck-Institut für Chemische Energiekonversion GERMANY
| | - Thorsten Glaser
- Bielefeld University: Universitat Bielefeld Department of Chemistry Universitätsstr. 24 33615 Bielefeld GERMANY
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4
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Walleck S, Zimmermann TP, Hachmeister H, Pilger C, Huser T, Katz S, Hildebrandt P, Stammler A, Bögge H, Bill E, Glaser T. Generation of a μ-1,2-hydroperoxo Fe IIIFe III and a μ-1,2-peroxo Fe IVFe III Complex. Nat Commun 2022; 13:1376. [PMID: 35296656 PMCID: PMC8927127 DOI: 10.1038/s41467-022-28894-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 02/17/2022] [Indexed: 12/05/2022] Open
Abstract
μ-1,2-Peroxo-diferric intermediates (P) of non-heme diiron enzymes are proposed to convert upon protonation either to high-valent active species or to activated P′ intermediates via hydroperoxo-diferric intermediates. Protonation of synthetic μ-1,2-peroxo model complexes occurred at the μ-oxo and not at the μ-1,2-peroxo bridge. Here we report a stable μ-1,2-peroxo complex {FeIII(μ-O)(μ-1,2-O2)FeIII} using a dinucleating ligand and study its reactivity. The reversible oxidation and protonation of the μ-1,2-peroxo-diferric complex provide μ-1,2-peroxo FeIVFeIII and μ-1,2-hydroperoxo-diferric species, respectively. Neither the oxidation nor the protonation induces a strong electrophilic reactivity. Hence, the observed intramolecular C-H hydroxylation of preorganized methyl groups of the parent μ-1,2-peroxo-diferric complex should occur via conversion to a more electrophilic high-valent species. The thorough characterization of these species provides structure-spectroscopy correlations allowing insights into the formation and reactivities of hydroperoxo intermediates in diiron enzymes and their conversion to activated P′ or high-valent intermediates. Iron coordination complexes can be used to gain insight on biologically relevant iron-oxygen compounds generated in iron metalloenzymes. Here, the authors characterise a μ-1,2-hydroperoxo FeIIIFeIII and a μ-1,2-peroxo FeIVFeIII, and study their reactivity in C-H activation.
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Affiliation(s)
- Stephan Walleck
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Thomas Philipp Zimmermann
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Henning Hachmeister
- Biomolekulare Photonik, Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Christian Pilger
- Biomolekulare Photonik, Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Thomas Huser
- Biomolekulare Photonik, Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Sagie Katz
- Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Anja Stammler
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Hartmut Bögge
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470, Mülheim an der Ruhr, Germany
| | - Thorsten Glaser
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany.
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5
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Lee JL, Biswas S, Sun C, Ziller JW, Hendrich MP, Borovik AS. Bioinspired Di-Fe Complexes: Correlating Structure and Proton Transfer over Four Oxidation States. J Am Chem Soc 2022; 144:4559-4571. [PMID: 35192354 DOI: 10.1021/jacs.1c12888] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Metalloproteins with active sites containing di-Fe cores exhibit diverse chemical reactivity that is linked to the precise transfer of protons and electrons which directly involve the di-Fe units. The redox conversions are commonly corroborated by spectroscopic methods, but the associated structural changes are often difficult to assess, particularly those related to proton movements. This report describes the development of di-Fe complexes in which the movements of protons and electrons are pinpointed during the stepwise oxidation of a di-FeII species to one with an FeIIIFeIV core. Complex formation was promoted using the phosphinic amido tripodal ligand [poat]3- (N,N',N″-[nitrilotris(ethane-2,1-diyl)]tris(P,P-diphenylphosphinic amido)) that provided dynamic coordination spheres that assisted in regulating both electron and proton transfer processes. Oxidation of an [FeII-(μ-OH)-FeIII] complex led to the corresponding di-FeIII species containing a hydroxido bridge that was not stable at room temperature and converted to a species containing an oxido bridging ligand and protonation of one phosphinic amido group to form [Hpoat]2-. Deprotonation led to a new species with an [FeIII-(μ-O)-FeIII] core that could be further oxidized to its FeIIIFeIV analogue. Reactions with phenols suggest homolytic cleavage of the O-H bond to give products that are consistent with the initial formation of a phenoxyl radical─spectroscopic studies indicated that the electron is transferred to the FeIV center, and the proton is initially transferred to the more sterically hindered oxido ligand but then relocates to [poat]3-. These findings offer new mechanistic insights related to the stability of and the reactions performed by di-Fe enzymes.
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Affiliation(s)
- Justin L Lee
- Department of Chemistry, University of California,1102 Natural Sciences II, Irvine, California 92697, United States
| | - Saborni Biswas
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Chen Sun
- Department of Chemistry, University of California,1102 Natural Sciences II, Irvine, California 92697, United States
| | - Joseph W Ziller
- Department of Chemistry, University of California,1102 Natural Sciences II, Irvine, California 92697, United States
| | - Michael P Hendrich
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - A S Borovik
- Department of Chemistry, University of California,1102 Natural Sciences II, Irvine, California 92697, United States
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6
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N,N-bis(2-quinolinylmethyl)benzylamine. MOLBANK 2021. [DOI: 10.3390/m1208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
N,N-bis(2-quinolinylmethyl)benzylamine (1) was synthesized under basic conditions from a pseudo-three-component reaction between benzylamine and two molecules of 2-(quinolinylmethyl)chloride, resulting in the formation of two N–C bonds in a single step. Compound (1) crystallizes in the triclinic system of the P-1 space group. The unit cell comprises a dimer of 1, in which the monomers are linked by two complementary hydrogen bonds between N1 and H′1–C′1 of another molecule. The dimers form chains along the a-axis through intermolecular interactions between the N′2 acceptor atoms and C″17 donors from molecules in the nearest neighboring dimer. These interactions form extended sheets of the dimers of 1, along the ab plane. The quinolinylmeth-2-yl groups of 1 lie in almost orthogonal planes and their N1/2(q) donor atoms are away from the apical amino N3 atom.
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7
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Török P, Unjaroen D, Viktória Csendes F, Giorgi M, Browne WR, Kaizer J. A nonheme peroxo-diiron(III) complex exhibiting both nucleophilic and electrophilic oxidation of organic substrates. Dalton Trans 2021; 50:7181-7185. [PMID: 34019062 PMCID: PMC8168641 DOI: 10.1039/d1dt01502h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The complex [FeIII2(μ-O2)(L3)4(S)2]4+ (L3 = 2-(4-thiazolyl)benzimidazole, S = solvent) forms upon reaction of [FeII(L3)2] with H2O2 and is a functional model of peroxo-diiron intermediates invoked during the catalytic cycle of oxidoreductases. The spectroscopic properties of the complex are in line with those of complexes formed with N-donor ligands. [FeIII2(μ-O2)(L3)4(S)2]4+ shows both nucleophilic (aldehydes) and electrophilic (phenol, N,N-dimethylanilines) oxidative reactivity and unusually also electron transfer oxidation. A bidentate ligand based iron complex shows nucleophillic and electrophillice reactivity in the oxidation of organic substrates.![]()
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Affiliation(s)
- Patrik Török
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8200 Veszprém, Hungary.
| | - Duenpen Unjaroen
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
| | - Flóra Viktória Csendes
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8200 Veszprém, Hungary.
| | - Michel Giorgi
- Aix-Marseille Université, FR1739, Spectropole, Campus St Jérome, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France
| | - Wesley R Browne
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
| | - József Kaizer
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8200 Veszprém, Hungary.
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8
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Kripli B, Szávuly M, Csendes FV, Kaizer J. Functional models of nonheme diiron enzymes: reactivity of the μ-oxo-μ-1,2-peroxo-diiron(iii) intermediate in electrophilic and nucleophilic reactions. Dalton Trans 2020; 49:1742-1746. [PMID: 31967142 DOI: 10.1039/c9dt04551a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The reactivity of the previously reported peroxo-adduct [FeIII2(μ-O)(μ-1,2-O2)(IndH)2(solv)2]2+ (1) (IndH = 1,3-bis(2-pyridyl-imino)isoindoline) has been investigated in nucleophilic (e.g., deformylation of alkyl and aryl alkyl aldehydes) and electrophilic (e.g. oxidation of phenols) stoichiometric reactions as biomimics of ribonucleotide reductase (RNR-R2) and aldehyde deformylating oxygenase (ADO) enzymes. Based on detailed kinetic and mechanistic studies, we have found further evidence for the ambiphilic behaviour of the peroxo intermediates proposed for diferric oxidoreductase enzymes.
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Affiliation(s)
- Balázs Kripli
- Department of Chemistry, University of Pannonia, H-8201 Veszprém, Hungary.
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9
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Banerjee S, Draksharapu A, Crossland PM, Fan R, Guo Y, Swart M, Que L. Sc 3+-Promoted O-O Bond Cleavage of a (μ-1,2-Peroxo)diiron(III) Species Formed from an Iron(II) Precursor and O 2 to Generate a Complex with an Fe IV2(μ-O) 2 Core. J Am Chem Soc 2020; 142:4285-4297. [PMID: 32017545 DOI: 10.1021/jacs.9b12081] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Soluble methane monooxygenase (sMMO) carries out methane oxidation at 4 °C and under ambient pressure in a catalytic cycle involving the formation of a peroxodiiron(III) intermediate (P) from the oxygenation of the diiron(II) enzyme and its subsequent conversion to Q, the diiron(IV) oxidant that hydroxylates methane. Synthetic diiron(IV) complexes that can serve as models for Q are rare and have not been generated by a reaction sequence analogous to that of sMMO. In this work, we show that [FeII(Me3NTB)(CH3CN)](CF3SO3)2 (Me3NTB = tris((1-methyl-1H-benzo[d]imidazol-2-yl)methyl)amine) (1) reacts with O2 in the presence of base, generating a (μ-1,2-peroxo)diiron(III) adduct with a low O-O stretching frequency of 825 cm-1 and a short Fe···Fe distance of 3.07 Å. Even more interesting is the observation that the peroxodiiron(III) complex undergoes O-O bond cleavage upon treatment with the Lewis acid Sc3+ and transforms into a bis(μ-oxo)diiron(IV) complex, thus providing a synthetic precedent for the analogous conversion of P to Q in the catalytic cycle of sMMO.
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Affiliation(s)
- Saikat Banerjee
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Apparao Draksharapu
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Patrick M Crossland
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Ruixi Fan
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Marcel Swart
- ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain.,IQCC and Department of Chemistry, University of Girona, 17003 Girona, Spain
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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10
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Kripli B, Csendes FV, Török P, Speier G, Kaizer J. Stoichiometric Aldehyde Deformylation Mediated by Nucleophilic Peroxo-diiron(III) Complex as a Functional Model of Aldehyde Deformylating Oxygenase. Chemistry 2019; 25:14290-14294. [PMID: 31448834 DOI: 10.1002/chem.201903727] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Indexed: 11/11/2022]
Abstract
The reactivity of the previously reported peroxo adduct [FeIII 2 (μ-O2 )(MeBzim-Py)4 (CH3 CN)2 ]4+ (1) (MeBzim-Py=2-(2'-pyridyl)-N-methylbenzimidazole) towards aldehyde substrates including phenylacetaldehyde (PAA), hydrocinnamaldehyde (HCA), propionaldehyde (PA), 2-phenylpropionaldehyde (PPA), cyclohexanecarboxaldehyde (CCA), and para-substituted benzaldehydes (benzoyl chlorides) has been investigated. Complex 1 proved to be a nucleophilic oxidant in aldehyde deformylation reaction. These models, including detailed kinetic and mechanistic studies, may serve as the first biomimics of aldehyde deformylating oxygenase (ADO) enzymes.
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Affiliation(s)
- Balázs Kripli
- Department of Chemistry, University of Pannonia, 8201, Veszprém, Hungary
| | | | - Patrik Török
- Department of Chemistry, University of Pannonia, 8201, Veszprém, Hungary
| | - Gábor Speier
- Department of Chemistry, University of Pannonia, 8201, Veszprém, Hungary
| | - József Kaizer
- Department of Chemistry, University of Pannonia, 8201, Veszprém, Hungary
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11
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YAGUCHI R, FURUTACHI H, SHIROTSUKI S, ZHANG X, ISHIKAWA T, AKINE S, TOSHA T, FUJINAMI S, SUZUKI M, KITAGAWA T. Synthesis and Crystal Structure of the Bis(μ-hydroxo)diiron(II) Complex with Tridentate Ligands Having a Sterically Bulky Imidazolyl Group. X-RAY STRUCTURE ANALYSIS ONLINE 2019. [DOI: 10.2116/xraystruct.35.27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Reiko YAGUCHI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Hideki FURUTACHI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Sanae SHIROTSUKI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Xi ZHANG
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Takanao ISHIKAWA
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Shigehisa AKINE
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University
| | | | - Shuhei FUJINAMI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Masatatsu SUZUKI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Teizo KITAGAWA
- Picobiology Institute, Graduate School of Life Science, University of Hyogo
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12
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Muthuramalingam S, Maheshwaran D, Velusamy M, Mayilmurugan R. Regioselective oxidative carbon-oxygen bond cleavage catalysed by copper(II) complexes: A relevant model study for lytic polysaccharides monooxygenases activity. J Catal 2019. [DOI: 10.1016/j.jcat.2019.03.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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13
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SEKINO M, FURUTACHI H, TASAKI K, ISHIKAWA T, FUJINAMI S, AKINE S, SAKATA Y, SUZUKI M, NOMURA T, OGURA T, KITAGAWA T. Crystal Structure of Bis(μ-hydroxo)diiron(II) Complex with a Dinucleating Ligand Having a Butyl Linker. X-RAY STRUCTURE ANALYSIS ONLINE 2019. [DOI: 10.2116/xraystruct.35.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Mio SEKINO
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Hideki FURUTACHI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Kyosuke TASAKI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Takanao ISHIKAWA
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Shuhei FUJINAMI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Shigehisa AKINE
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University
| | - Yoko SAKATA
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Masatatsu SUZUKI
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University
| | - Takashi NOMURA
- Picobiology Institute, Graduate School of Life Science, University of Hyogo
| | - Takashi OGURA
- Picobiology Institute, Graduate School of Life Science, University of Hyogo
| | - Teizo KITAGAWA
- Picobiology Institute, Graduate School of Life Science, University of Hyogo
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14
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Jasniewski AJ, Que L. Dioxygen Activation by Nonheme Diiron Enzymes: Diverse Dioxygen Adducts, High-Valent Intermediates, and Related Model Complexes. Chem Rev 2018; 118:2554-2592. [PMID: 29400961 PMCID: PMC5920527 DOI: 10.1021/acs.chemrev.7b00457] [Citation(s) in RCA: 304] [Impact Index Per Article: 50.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A growing subset of metalloenzymes activates dioxygen with nonheme diiron active sites to effect substrate oxidations that range from the hydroxylation of methane and the desaturation of fatty acids to the deformylation of fatty aldehydes to produce alkanes and the six-electron oxidation of aminoarenes to nitroarenes in the biosynthesis of antibiotics. A common feature of their reaction mechanisms is the formation of O2 adducts that evolve into more reactive derivatives such as diiron(II,III)-superoxo, diiron(III)-peroxo, diiron(III,IV)-oxo, and diiron(IV)-oxo species, which carry out particular substrate oxidation tasks. In this review, we survey the various enzymes belonging to this unique subset and the mechanisms by which substrate oxidation is carried out. We examine the nature of the reactive intermediates, as revealed by X-ray crystallography and the application of various spectroscopic methods and their associated reactivity. We also discuss the structural and electronic properties of the model complexes that have been found to mimic salient aspects of these enzyme active sites. Much has been learned in the past 25 years, but key questions remain to be answered.
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Affiliation(s)
- Andrew J. Jasniewski
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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15
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Csonka R, Lakk-Bogáth D, Gömöry Á, Drahos L, Giorgi M, Speier G, Szilágyi RK, Kaizer J. Non-innocent ground state electronic structure of a polynuclear copper complex with picolinate bridges. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.07.065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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16
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Affiliation(s)
- Eike B. Bauer
- University of Missouri - St. Louis; Department of Chemistry and Biochemistry; One University Boulevard St. Louis, MO 63121 USA
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17
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Jasniewski AJ, Komor AJ, Lipscomb JD, Que L. Unprecedented (μ-1,1-Peroxo)diferric Structure for the Ambiphilic Orange Peroxo Intermediate of the Nonheme N-Oxygenase CmlI. J Am Chem Soc 2017; 139:10472-10485. [PMID: 28673082 PMCID: PMC5568637 DOI: 10.1021/jacs.7b05389] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The final step in the biosynthesis of the antibiotic chloramphenicol is the oxidation of an aryl-amine substrate to an aryl-nitro product catalyzed by the N-oxygenase CmlI in three two-electron steps. The CmlI active site contains a diiron cluster ligated by three histidine and four glutamate residues and activates dioxygen to perform its role in the biosynthetic pathway. It was previously shown that the active oxidant used by CmlI to facilitate this chemistry is a peroxo-diferric intermediate (CmlIP). Spectroscopic characterization demonstrated that the peroxo binding geometry of CmlIP is not consistent with the μ-1,2 mode commonly observed in nonheme diiron systems. Its geometry was tentatively assigned as μ-η2:η1 based on comparison with resonance Raman (rR) features of mixed-metal model complexes in the absence of appropriate diiron models. Here, X-ray absorption spectroscopy (XAS) and rR studies have been used to establish a refined structure for the diferric cluster of CmlIP. The rR experiments carried out with isotopically labeled water identified the symmetric and asymmetric vibrations of an Fe-O-Fe unit in the active site at 485 and 780 cm-1, respectively, which was confirmed by the 1.83 Å Fe-O bond observed by XAS. In addition, a unique Fe···O scatterer at 2.82 Å observed from XAS analysis is assigned as arising from the distal O atom of a μ-1,1-peroxo ligand that is bound symmetrically between the irons. The (μ-oxo)(μ-1,1-peroxo)diferric core structure associated with CmlIP is unprecedented among diiron cluster-containing enzymes and corresponding biomimetic complexes. Importantly, it allows the peroxo-diferric intermediate to be ambiphilic, acting as an electrophilic oxidant in the initial N-hydroxylation of an arylamine and then becoming a nucleophilic oxidant in the final oxidation of an aryl-nitroso intermediate to the aryl-nitro product.
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Affiliation(s)
- Andrew J. Jasniewski
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
| | - Anna J. Komor
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
| | - John D. Lipscomb
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
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18
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Jasniewski AJ, Knoot CJ, Lipscomb JD, Que L. A Carboxylate Shift Regulates Dioxygen Activation by the Diiron Nonheme β-Hydroxylase CmlA upon Binding of a Substrate-Loaded Nonribosomal Peptide Synthetase. Biochemistry 2016; 55:5818-5831. [PMID: 27668828 PMCID: PMC5258830 DOI: 10.1021/acs.biochem.6b00834] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The first step in the nonribosomal peptide synthetase (NRPS)-based biosynthesis of chloramphenicol is the β-hydroxylation of the precursor l-p-aminophenylalanine (l-PAPA) catalyzed by the monooxygenase CmlA. The active site of CmlA contains a dinuclear iron cluster that is reduced to the diferrous state (WTR) to initiate O2 activation. However, rapid O2 activation occurs only when WTR is bound to CmlP, the NRPS to which l-PAPA is covalently attached. Here the X-ray crystal structure of WTR is reported, which is very similar to that of the as-isolated diferric enzyme in which the irons are coordinately saturated. X-ray absorption spectroscopy is used to investigate the WTR cluster ligand structure as well as the structures of WTR in complex with a functional CmlP variant (CmlPAT) with and without l-PAPA attached. It is found that formation of the active WTR:CmlPAT-l-PAPA complex converts at least one iron of the cluster from six- to five-coordinate by changing a bidentately bound amino acid carboxylate to monodentate on Fe1. The only bidentate carboxylate in the structure of WTR is E377. The crystal structure of the CmlA variant E377D shows only monodentate carboxylate coordination. Reduced E377D reacts rapidly with O2 in the presence or absence of CmlPAT-l-PAPA, showing loss of regulation. However, this variant fails to catalyze hydroxylation, suggesting that E377 has the dual role of coupling regulation of O2 reactivity with juxtaposition of the substrate and the reactive oxygen species. The carboxylate shift in response to substrate binding represents a novel regulatory strategy for oxygen activation in diiron oxygenases.
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Affiliation(s)
- Andrew J. Jasniewski
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
| | - Cory J. Knoot
- Department of Biochemistry Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
| | - John D. Lipscomb
- Department of Biochemistry Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
- Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455
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19
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Jasniewski AJ, Engstrom LM, Vu VV, Park MH, Que L. X-ray absorption spectroscopic characterization of the diferric-peroxo intermediate of human deoxyhypusine hydroxylase in the presence of its substrate eIF5a. J Biol Inorg Chem 2016; 21:605-18. [PMID: 27380180 PMCID: PMC4990465 DOI: 10.1007/s00775-016-1373-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 06/16/2016] [Indexed: 11/29/2022]
Abstract
Human deoxyhypusine hydroxylase (hDOHH) is an enzyme that is involved in the critical post-translational modification of the eukaryotic translation initiation factor 5A (eIF5A). Following the conversion of a lysine residue on eIF5A to deoxyhypusine (Dhp) by deoxyhypusine synthase, hDOHH hydroxylates Dhp to yield the unusual amino acid residue hypusine (Hpu), a modification that is essential for eIF5A to promote peptide synthesis at the ribosome, among other functions. Purification of hDOHH overexpressed in E. coli affords enzyme that is blue in color, a feature that has been associated with the presence of a peroxo-bridged diiron(III) active site. To gain further insight into the nature of the diiron site and how it may change as hDOHH goes through the catalytic cycle, we have conducted X-ray absorption spectroscopic studies of hDOHH on five samples that represent different species along its reaction pathway. Structural analysis of each species has been carried out, starting with the reduced diferrous state, proceeding through its O2 adduct, and ending with a diferric decay product. Our results show that the Fe⋯Fe distances found for the five samples fall within a narrow range of 3.4-3.5 Å, suggesting that hDOHH has a fairly constrained active site. This pattern differs significantly from what has been associated with canonical dioxygen activating nonheme diiron enzymes, such as soluble methane monooxygenase and Class 1A ribonucleotide reductases, for which the Fe⋯Fe distance can change by as much as 1 Å during the redox cycle. These results suggest that the O2 activation mechanism for hDOHH deviates somewhat from that associated with the canonical nonheme diiron enzymes, opening the door to new mechanistic possibilities for this intriguing family of enzymes.
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Affiliation(s)
- Andrew J Jasniewski
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN, 55455, USA
| | - Lisa M Engstrom
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN, 55455, USA
| | - Van V Vu
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN, 55455, USA
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, Ward 13, District 4, Ho Chi Minh City, Vietnam
| | - Myung Hee Park
- National Institute of Dental and Craniofacial Research, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN, 55455, USA.
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20
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Szávuly MI, Surducan M, Nagy E, Surányi M, Speier G, Silaghi-Dumitrescu R, Kaizer J. Functional models of nonheme diiron enzymes: kinetic and computational evidence for the formation of oxoiron(iv) species from peroxo-diiron(iii) complexes, and their reactivity towards phenols and H2O2. Dalton Trans 2016; 45:14709-18. [PMID: 27283752 DOI: 10.1039/c6dt01598k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reactivity of the previously reported peroxo adducts [Fe2(μ-O2)(L(1))4(CH3CN)2](2+), and [Fe2(μ-O2)(L(2))4(CH3CN)2](2+), (L(1) = 2-(2'-pyridyl)benzimidazole and L(2) = 2-(2'-pyridyl)-N-methylbenzimidazole) towards H2O2 as catalase mimics, and towards various phenols as functional RNR-R2 mimics, is described. Kinetic, mechanistic and computational studies gave direct evidence for the involvement of the (μ-1,2-peroxo)diiron(iii) intermediate in the O-H activation process via formation of low-spin oxoiron(iv) species.
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Affiliation(s)
- Miklós István Szávuly
- Department of Chemistry, University of Pannonia, 8201 Veszprém, Wartha Vince u. 1., Hungary.
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21
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Sekino M, Furutachi H, Tasaki K, Ishikawa T, Mori S, Fujinami S, Akine S, Sakata Y, Nomura T, Ogura T, Kitagawa T, Suzuki M. New mechanistic insight into intramolecular arene hydroxylation initiated by (μ-1,2-peroxo)diiron(III) complexes with dinucleating ligands. Dalton Trans 2016; 45:469-73. [PMID: 26646073 DOI: 10.1039/c5dt04088d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
(μ-1,2-Peroxo)diiron(iii) complexes (-R) with dinucleating ligands (R-L) generated from the reaction of bis(μ-hydroxo)diiron(ii) complexes [Fe2(R-L)(OH)2](2+) (-R) with dioxygen in acetone at -20 °C provide a diiron-centred electrophilic oxidant, presumably diiron(iv)-oxo species, which is involved in aromatic ligand hydroxylation.
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Affiliation(s)
- Mio Sekino
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Hideki Furutachi
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Kyosuke Tasaki
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Takanao Ishikawa
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Shigeki Mori
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Shuhei Fujinami
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Shigehisa Akine
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Yoko Sakata
- Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
| | - Takashi Nomura
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Ako-gun, Hyogo 678-1297, Japan
| | - Takashi Ogura
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Ako-gun, Hyogo 678-1297, Japan
| | - Teizo Kitagawa
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Ako-gun, Hyogo 678-1297, Japan
| | - Masatatsu Suzuki
- Department of Chemistry and Biochemistry, Graduate Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
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22
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Gehring H, Metzinger R, Braun B, Herwig C, Harder S, Ray K, Limberg C. An iron(ii) hydride complex of a ligand with two adjacent β-diketiminate binding sites and its reactivity. Dalton Trans 2016; 45:2989-96. [PMID: 26757878 PMCID: PMC5536248 DOI: 10.1039/c5dt04266f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
After lithiation of PYR-H2 (PYR = [(NC(Me)C(H)C(Me)NC6H3(iPr)2)2(C5H3N)](2-)) - the precursor of an expanded β-diketiminato ligand system with two binding pockets - with KN(TMS)2 the reaction of the resulting potassium salt with FeBr2 led to a dinuclear iron(ii) bromide complex [(PYR)Fe(μ-Br)2Fe] (1). Through treatment with KHBEt3 the bromide ligands could be replaced by hydrides to yield [PYR)Fe2(μ-H)2] (2), a distorted analogue of known β-diketiminato iron hydride complexes, as evidenced by NMR, Mößbauer and X-ray absorption spectroscopy, as well as by its reactivity: for instance, 2 reacts with the proton source lutidinium triflate via protonation of the hydride ligands to form an iron(ii) product [(PYR)Fe2(OTf)2] (4), while CO2 inserts into the Fe-H bonds generating the formate complex [(PYR)Fe2(μ-HCOO)2] (5); in the presence of traces of water partial hydrolysis occurs so that [(PYR)Fe2(μ-OH)(μ-HCOO)] (6) is isolated. Altogether, the iron(ii) chemistry supported by the PYR(2-) ligand is distinctly different from the one of nickel(ii), where both, the arrangement of the two binding pockets and the additional pyridyl donor led to diverging features as compared with the corresponding system based on the parent β-diketiminato ligand.
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Affiliation(s)
- Henrike Gehring
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany.
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23
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Balamurugan M, Suresh E, Palaniandavar M. Non-heme μ-Oxo- and bis(μ-carboxylato)-bridged diiron(iii) complexes of a 3N ligand as catalysts for alkane hydroxylation: stereoelectronic factors of carboxylate bridges determine the catalytic efficiency. Dalton Trans 2016; 45:11422-36. [DOI: 10.1039/c6dt01059h] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The stereoelectronic factors of carboxylate bridges in diiron(iii) complexes determine the efficiency of catalytic alkane hydroxylation with m-CPBA.
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Affiliation(s)
- Mani Balamurugan
- School of Chemistry
- Bharathidasan University
- Tiruchirappalli - 620024
- India
| | - Eringathodi Suresh
- Analytical Science Discipline
- Central Salt and Marine Chemicals Research Institute
- Bhavnagar - 364 002
- India
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24
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Yatabe T, Kikkawa M, Matsumoto T, Urabe K, Robertson A, Nakai H, Ogo S. An Fe-based Model for Metabolism Linking between O 2-reduction and H 2O-oxidation. CHEM LETT 2015. [DOI: 10.1246/cl.150468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Takeshi Yatabe
- Center for Small Molecule Energy, Kyushu University
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
| | - Mitsuhiro Kikkawa
- Center for Small Molecule Energy, Kyushu University
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
| | - Takahiro Matsumoto
- Center for Small Molecule Energy, Kyushu University
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
| | - Keishi Urabe
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
| | - Andrew Robertson
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
| | - Hidetaka Nakai
- Center for Small Molecule Energy, Kyushu University
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
| | - Seiji Ogo
- Center for Small Molecule Energy, Kyushu University
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
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25
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Kakuda S, Rolle C, Ohkubo K, Siegler MA, Karlin KD, Fukuzumi S. Lewis acid-induced change from four- to two-electron reduction of dioxygen catalyzed by copper complexes using scandium triflate. J Am Chem Soc 2015; 137:3330-7. [PMID: 25659416 PMCID: PMC4630010 DOI: 10.1021/ja512584r] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mononuclear copper complexes, [(tmpa)Cu(II)(CH3CN)](ClO4)2 (1, tmpa = tris(2-pyridylmethyl)amine) and [(BzQ)Cu(II)(H2O)2](ClO4)2 (2, BzQ = bis(2-quinolinylmethyl)benzylamine)], act as efficient catalysts for the selective two-electron reduction of O2 by ferrocene derivatives in the presence of scandium triflate (Sc(OTf)3) in acetone, whereas 1 catalyzes the four-electron reduction of O2 by the same reductant in the presence of Brønsted acids such as triflic acid. Following formation of the peroxo-bridged dicopper(II) complex [(tmpa)Cu(II)(O2)Cu(II)(tmpa)](2+), the two-electron reduced product of O2 with Sc(3+) is observed to be scandium peroxide ([Sc(III)(O2(2-))](+)). In the presence of 3 equiv of hexamethylphosphoric triamide (HMPA), [Sc(III)(O2(2-))](+) was oxidized by [Fe(bpy)3](3+) (bpy = 2,2-bipyridine) to the known superoxide species [(HMPA)3Sc(III)(O2(•-))](2+) as detected by EPR spectroscopy. A kinetic study revealed that the rate-determining step of the catalytic cycle for the two-electron reduction of O2 with 1 is electron transfer from Fc* to 1 to give a cuprous complex which is highly reactive toward O2, whereas the rate-determining step with 2 is changed to the reaction of the cuprous complex with O2 following electron transfer from ferrocene derivatives to 2. The explanation for the change in catalytic O2-reaction stoichiometry from four-electron with Brønsted acids to two-electron reduction in the presence of Sc(3+) and also for the change in the rate-determining step is clarified based on a kinetics interrogation of the overall catalytic cycle as well as each step of the catalytic cycle with study of the observed effects of Sc(3+) on copper-oxygen intermediates.
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Affiliation(s)
- Saya Kakuda
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, ALCA (JST), Osaka University, Suita, Osaka 565-0871, Japan
| | - Clarence Rolle
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Kei Ohkubo
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, ALCA (JST), Osaka University, Suita, Osaka 565-0871, Japan
| | - Maxime A. Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Shunichi Fukuzumi
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, ALCA (JST), Osaka University, Suita, Osaka 565-0871, Japan
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26
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Li JL, Jiang L, Wang BW, Tian JL, Gu W, Liu X, Yan SP. Significant differences in the biological activity of mononuclear Cu(ii) and Ni(ii) complexes with the polyquinolinyl ligand. NEW J CHEM 2015. [DOI: 10.1039/c4nj00876f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The difference in the redox activity of metal ions Cu(ii) and Ni(ii) results in some discrepancy in the biological activity of their complexes.
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Affiliation(s)
- Jun-Ling Li
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
| | - Lin Jiang
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
| | - Bi-Wei Wang
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
| | - Jin-Lei Tian
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
| | - Wen Gu
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
| | - Xin Liu
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
| | - Shi-Ping Yan
- Department of Chemistry
- Nankai University
- Tianjin 300071
- People's Republic of China
- Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry
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27
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Kerber WD, Perez KA, Ren C, Siegler MA. Speciation of Ferric Phenoxide Intermediates during the Reduction of Iron(III)−μ-Oxo Dimers by Hydroquinone. Inorg Chem 2014; 53:11507-16. [DOI: 10.1021/ic5014347] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- William D. Kerber
- Department of Chemistry, Bucknell University, Lewisburg, Pennsylvania 17837, United States
| | - Kaitlyn A. Perez
- Department of Chemistry, Bucknell University, Lewisburg, Pennsylvania 17837, United States
| | - Chuqiao Ren
- Department of Chemistry, Bucknell University, Lewisburg, Pennsylvania 17837, United States
| | - Maxime A. Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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28
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Pap JS, Draksharapu A, Giorgi M, Browne WR, Kaizer J, Speier G. Stabilisation of μ-peroxido-bridged Fe(III) intermediates with non-symmetric bidentate N-donor ligands. Chem Commun (Camb) 2014; 50:1326-9. [PMID: 24343416 DOI: 10.1039/c3cc48196d] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The spectroscopic characterisation of the (μ-1,2-peroxido)diiron(iii) species formed transiently upon reaction of [Fe(ii)(NN)3](2+) complexes with H2O2 by UV/vis absorption and resonance Raman spectroscopy is reported. The intermediacy of such species in the disproportionation of H2O2 is demonstrated.
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Affiliation(s)
- József S Pap
- Department of Chemistry, University of Pannonia, H-8200 Veszprém, Hungary.
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29
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Sues PE, Forbes MW, Lough AJ, Morris RH. Ligand-based molecular recognition and dioxygen splitting: an endo epoxide ending. Dalton Trans 2014; 43:4137-45. [PMID: 24458017 DOI: 10.1039/c3dt53495b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The phosphido complex RuCp*(PPh2CH=CHPPh2)(PPh2) (1) was exposed to a number of small molecules and was found to recognize and activate molecular oxygen in an unprecedented fashion: the ruthenium species split O2 in a ligand-based 4-electron reduction to produce an endo epoxide, as well as a phosphinito ligand. Based on XRD data, VT NMR studies, cyclooctene trapping studies, and crossover experiments it was determined that the reaction proceeded through an intramolecular mechanism in which initial oxidation of the phosphido ligand generated an end-on peroxo intermediate. This mechanism was also supported by computational studies and electrochemical experiments. In contrast, an analogue of 1, RuCp*(Ph2P(ortho-C6H4)PPh2)(PPh2) (3), reacted in an intermolecular fashion to generate two phosphinito ligands.
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Affiliation(s)
- Peter E Sues
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
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Kim H, Kang J, Kim KB, Song EJ, Kim C. A highly selective quinoline-based fluorescent sensor for Zn(II). SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 118:883-7. [PMID: 24161851 DOI: 10.1016/j.saa.2013.09.118] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/26/2013] [Accepted: 09/26/2013] [Indexed: 05/21/2023]
Abstract
A quinoline-based simple receptor (bis(2-quinolinylmethyl)benzylamine = 1) as a Zn(2+) selective fluorescent chemosensor showed a large fluorescent enhancement with a blue shift in the presence of Zn(2+) which is attributed to a chelation enhanced fluorescence (CHEF) effect with inhibition of a photoinduced electron transfer (PET) process of 1. In particular, this receptor could clearly distinguish Zn(2+) from Cd(2+). The binding mode of 1 and Zn(2+) was found to be a 1:1 and confirmed by Job plot, (1)H NMR titration and ESI-mass spectrometry analysis.
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Affiliation(s)
- Hyun Kim
- Department of Fine Chemistry, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea
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31
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Stoian SA, Xue G, Bominaar EL, Que L, Münck E. Spectroscopic and theoretical investigation of a complex with an [O═Fe(IV)-O-Fe(IV)═O] core related to methane monooxygenase intermediate Q. J Am Chem Soc 2014; 136:1545-58. [PMID: 24380398 DOI: 10.1021/ja411376u] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Previous efforts to model the diiron(IV) intermediate Q of soluble methane monooxygenase have led to the synthesis of a diiron(IV) TPA complex, 2, with an O=Fe(IV)-O-Fe(IV)-OH core that has two ferromagnetically coupled Sloc = 1 sites. Addition of base to 2 at -85 °C elicits its conjugate base 6 with a novel O═Fe(IV)-O-Fe(IV)═O core. In frozen solution, 6 exists in two forms, 6a and 6b, that we have characterized extensively using Mössbauer and parallel mode EPR spectroscopy. The conversion between 2 and 6 is quantitative, but the relative proportions of 6a and 6b are solvent dependent. 6a has two equivalent high-spin (Sloc = 2) sites, which are antiferromagnetically coupled; its quadrupole splitting (0.52 mm/s) and isomer shift (0.14 mm/s) match those of intermediate Q. DFT calculations suggest that 6a assumes an anti conformation with a dihedral O═Fe-Fe═O angle of 180°. Mössbauer and EPR analyses show that 6b is a diiron(IV) complex with ferromagnetically coupled Sloc = 1 and Sloc = 2 sites to give total spin St = 3. Analysis of the zero-field splittings and magnetic hyperfine tensors suggests that the dihedral O═Fe-Fe═O angle of 6b is ∼90°. DFT calculations indicate that this angle is enforced by hydrogen bonding to both terminal oxo groups from a shared water molecule. The water molecule preorganizes 6b, facilitating protonation of one oxo group to regenerate 2, a protonation step difficult to achieve for mononuclear Fe(IV)═O complexes. Complex 6 represents an intriguing addition to the handful of diiron(IV) complexes that have been characterized.
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Affiliation(s)
- Sebastian A Stoian
- Department of Chemistry, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
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Mikata Y, Kawata K, Takeuchi S, Nakanishi K, Konno H, Itami S, Yasuda K, Tamotsu S, Burdette SC. Isoquinoline-derivatized tris(2-pyridylmethyl)amines as fluorescent zinc sensors with strict Zn2+/Cd2+ selectivity. Dalton Trans 2014; 43:10751-9. [DOI: 10.1039/c4dt01054j] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Lassalle-Kaiser B, Boron TT, Krewald V, Kern J, Beckwith MA, Schroeder H, Alonso-Mori R, Nordlund D, Weng TC, Sokaras D, Neese F, Bergmann U, Yachandra VK, DeBeer S, Pecoraro VL, Yano J. Experimental and computational X-ray emission spectroscopy as a direct probe of protonation states in oxo-bridged Mn(IV) dimers relevant to redox-active metalloproteins. Inorg Chem 2013; 52:12915-22. [PMID: 24161081 PMCID: PMC3867288 DOI: 10.1021/ic400821g] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The protonation state of oxo bridges in nature is of profound importance for a variety of enzymes, including the Mn4CaO5 cluster of photosystem II and the Mn2O2 cluster in Mn catalase. A set of dinuclear bis-μ-oxo-bridged Mn(IV) complexes in different protonation states was studied by Kβ emission spectroscopy to form the foundation for unraveling the protonation states in the native complex. The valence-to-core regions (valence-to-core XES) of the spectra show significant changes in intensity and peak position upon protonation. DFT calculations were performed to simulate the valence-to-core XES spectra and to assign the spectral features to specific transitions. The Kβ(2,5) peaks arise primarily from the ligand 2p to Mn 1s transitions, with a characteristic low energy shoulder appearing upon oxo-bridge protonation. The satellite Kβ" peak provides a more direct signature of the protonation state change, since the transitions originating from the 2s orbitals of protonated and unprotonated μ-oxo bridges dominate this spectral region. The energies of the Kβ" features differ by ~3 eV and thus are well resolved in the experimental spectra. Additionally, our work explores the chemical resolution limits of the method, namely, whether a mixed (μ-O)(μ-OH2) motif can be distinguished from a symmetric (μ-OH)2 one. The results reported here highlight the sensitivity of Kβ valence-to-core XES to single protonation state changes of bridging ligands, and form the basis for further studies of oxo-bridged polymetallic complexes and metalloenzyme active sites. In a complementary paper, the results from X-ray absorption spectroscopy of the same Mn(IV) dimer series are discussed.
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Affiliation(s)
- Benedikt Lassalle-Kaiser
- Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Thaddeus T. Boron
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Vera Krewald
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Jan Kern
- Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Martha A. Beckwith
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Henning Schroeder
- Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | | | - Dennis Nordlund
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Tsu-Chien Weng
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | | | - Frank Neese
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Uwe Bergmann
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Vittal K. Yachandra
- Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Vincent L. Pecoraro
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Junko Yano
- Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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Pap JS, Cranswick MA, Balogh-Hergovich E, Baráth G, Giorgi M, Rohde GT, Kaizer J, Speier G, Que L. An Iron(II)(1,3-bis(2'-pyridylimino)isoindoline) Complex as a Catalyst for Substrate Oxidation with H 2O 2. Evidence for a Transient Peroxodiiron(III) Species. Eur J Inorg Chem 2013; 2013:3858-3866. [PMID: 24587695 PMCID: PMC3935335 DOI: 10.1002/ejic.201300162] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Indexed: 11/06/2022]
Abstract
The complex [Fe(indH)(solvent)3](ClO4)2 (1) has been isolated from the reaction of equimolar amounts of 1,3-bis(2'-pyridylimino)isoindoline (indH) and Fe(ClO4)2 in acetonitrile and characterized by X-ray crystallography and several spectroscopic techniques. It is a suitable catalyst for the oxidation of thioanisoles and benzyl alcohols with H2O2 as the oxidant. Hammett correlations and kinetic isotope effect experiments support the involvement of an electrophilic metal-based oxidant. A metastable green species (2) is observed when 1 is reacted with H2O2 at -40 °C, which has been characterized to have a FeIII(μ-O)(μ-O2)FeIII core on the basis of UV-Vis, electron paramagnetic resonance, resonance Raman, and X-ray absorption spectroscopic data.
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Affiliation(s)
- József S Pap
- Department of Chemistry, University of Pannonia, 8201 Veszprém, Wartha Vince u. 1., Hungary
| | - Matthew A Cranswick
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455, USA
| | - E Balogh-Hergovich
- Department of Chemistry, University of Pannonia, 8201 Veszprém, Wartha Vince u. 1., Hungary
| | - Gábor Baráth
- Department of Chemistry, University of Pannonia, 8201 Veszprém, Wartha Vince u. 1., Hungary
| | - Michel Giorgi
- Aix-Marseille Université, FR1739, Spectropole, Campus St. Jérôme, Avenue Escadrille Normandie-Niemen, 13397 Marseille cedex 20, France
| | - Gregory T Rohde
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455, USA
| | - József Kaizer
- Department of Chemistry, University of Pannonia, 8201 Veszprém, Wartha Vince u. 1., Hungary
| | - Gábor Speier
- Department of Chemistry, University of Pannonia, 8201 Veszprém, Wartha Vince u. 1., Hungary
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455, USA
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35
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Coggins MK, Sun X, Kwak Y, Solomon EI, Rybak-Akimova E, Kovacs JA. Characterization of metastable intermediates formed in the reaction between a Mn(II) complex and dioxygen, including a crystallographic structure of a binuclear Mn(III)-peroxo species. J Am Chem Soc 2013; 135:5631-40. [PMID: 23470101 PMCID: PMC3709604 DOI: 10.1021/ja311166u] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Transition-metal peroxos have been implicated as key intermediates in a variety of critical biological processes involving O2. Because of their highly reactive nature, very few metal-peroxos have been characterized. The dioxygen chemistry of manganese remains largely unexplored despite the proposed involvement of a Mn-peroxo, either as a precursor to, or derived from, O2, in both photosynthetic H2O oxidation and DNA biosynthesis. These are arguably two of the most fundamental processes of life. Neither of these biological intermediates has been observed. Herein we describe the dioxygen chemistry of coordinatively unsaturated [Mn(II)(S(Me2)N4(6-Me-DPEN))] (+) (1), and the characterization of intermediates formed en route to a binuclear mono-oxo-bridged Mn(III) product {[Mn(III)(S(Me2)N4(6-Me-DPEN)]2(μ-O)}(2+) (2), the oxo atom of which is derived from (18)O2. At low-temperatures, a dioxygen intermediate, [Mn(S(Me2)N4(6-Me-DPEN))(O2)](+) (4), is observed (by stopped-flow) to rapidly and irreversibly form in this reaction (k1(-10 °C) = 3780 ± 180 M(-1) s(-1), ΔH1(++) = 26.4 ± 1.7 kJ mol(-1), ΔS1(++) = -75.6 ± 6.8 J mol(-1) K(-1)) and then convert more slowly (k2(-10 °C) = 417 ± 3.2 M(-1) s(-1), ΔH2(++) = 47.1 ± 1.4 kJ mol(-1), ΔS2(++) = -15.0 ± 5.7 J mol(-1) K(-1)) to a species 3 with isotopically sensitive stretches at νO-O(Δ(18)O) = 819(47) cm(-1), kO-O = 3.02 mdyn/Å, and νMn-O(Δ(18)O) = 611(25) cm(-1) consistent with a peroxo. Intermediate 3 releases approximately 0.5 equiv of H2O2 per Mn ion upon protonation, and the rate of conversion of 4 to 3 is dependent on [Mn(II)] concentration, consistent with a binuclear Mn(O2(2-)) Mn peroxo. This was verified by X-ray crystallography, where the peroxo of {[Mn(III)(S(Me2)N4(6-Me-DPEN)]2(trans-μ-1,2-O2)}(2+) (3) is shown to be bridging between two Mn(III) ions in an end-on trans-μ-1,2-fashion. This represents the first characterized example of a binuclear Mn(III)-peroxo, and a rare case in which more than one intermediate is observed en route to a binuclear μ-oxo-bridged product derived from O2. Vibrational and metrical parameters for binuclear Mn-peroxo 3 are compared with those of related binuclear Fe- and Cu-peroxo compounds.
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Affiliation(s)
- Michael K Coggins
- Department of Chemistry, University of Washington, Campus Box 351700 Seattle, Washington 98195-1700, USA
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36
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Sun X, Kryatov SV, Rybak-Akimova EV. Kinetic insights into the reactivity of the intermediates generated from hydrogen peroxide and diiron(III) complex with tris(picolyl)amine (TPA). Dalton Trans 2013; 42:4427-35. [PMID: 23338901 DOI: 10.1039/c2dt32599c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two intermediates (2 and 3) are formed consecutively in the reaction of a diiron(III) complex [Fe(III)(2)(μ-O)(OH)(H(2)O)(TPA)(2)](ClO(4))(3) (TPA = tris(2-pyridylmethyl)amine, tris(picolyl)amine) with H(2)O(2) in CH(3)CN at -40 °C. Low-temperature stopped-flow studies showed that both species are kinetically competent in oxidation of phosphines and phenols. The first intermediate (2) reacts with substrates very rapidly (second-order rate constants reach 10(5)-10(6) M(-1) s(-1) for substituted triarylphosphines and 10(3)-10(5) M(-1) s(-1) for substituted phenols), in keeping with a diiron(IV)-oxo formulation. The second intermediate (3), a mixed-valent Fe(III)Fe(IV) species, is more stable than 2, and reacts with substrates more slowly (second-order rate constants range from 150 to 550 M(-1) s(-1) for triaryl phosphine oxidation, and from 18 to 790 M(-1) s(-1) for phenol oxidation). Reaction rates increase with increasing electron donating abilities of substituents, indicating that both 2 and 3 act as electrophilic oxidants.
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Affiliation(s)
- Xianru Sun
- Department of Chemistry, Tufts University, Medford, MA, USA.
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37
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Frisch JR, McDonnell R, Rybak-Akimova EV, Que L. Factors affecting the carboxylate shift upon formation of nonheme diiron-O2 adducts. Inorg Chem 2013; 52:2627-36. [PMID: 23432330 DOI: 10.1021/ic302543n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several [Fe(II)2(N-EtHPTB)(μ-O2X)](2+) complexes (1·O2X) have been synthesized, where N-EtHPTB is the anion of N,N,N'N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane and O2X is an oxyanion bridge. Crystal structures reveal five-coordinate (μ-alkoxo)diiron(II) cores. These diiron(II) complexes react with O2 at low temperatures in CH2Cl2 (-90 °C) to form blue-green O2 adducts that are best described as triply bridged (μ-η(1):η(1)-peroxo)diiron(III) species (2·O2X). With one exception, all 2·O2X intermediates convert irreversibly to doubly bridged, blue (μ-η(1):η(1)-peroxo)diiron(III) species (3·O2X). Where possible, 2·O2X and 3·O2X intermediates were characterized using resonance Raman spectroscopy, showing respective νO-O values of ∼850 and ∼900 cm(-1). How the steric and electronic properties of O2X affect conversion of 2·O2X to 3·O2X was examined. Stopped-flow analysis reveals that oxygenation kinetics of 1·O2X is unaffected by the nature of O2X, and for the first time, the benzoate analog of 2·O2X (2·O2CPh) is observed.
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Affiliation(s)
- Jonathan R Frisch
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, United States
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38
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Cranswick MA, Meier KK, Shan X, Stubna A, Kaizer J, Mehn MP, Münck E, Que L. Protonation of a peroxodiiron(III) complex and conversion to a diiron(III/IV) intermediate: implications for proton-assisted O-O bond cleavage in nonheme diiron enzymes. Inorg Chem 2012; 51:10417-26. [PMID: 22971084 PMCID: PMC3462276 DOI: 10.1021/ic301642w] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Oxygenation of a diiron(II) complex, [Fe(II)(2)(μ-OH)(2)(BnBQA)(2)(NCMe)(2)](2+) [2, where BnBQA is N-benzyl-N,N-bis(2-quinolinylmethyl)amine], results in the formation of a metastable peroxodiferric intermediate, 3. The treatment of 3 with strong acid affords its conjugate acid, 4, in which the (μ-oxo)(μ-1,2-peroxo)diiron(III) core of 3 is protonated at the oxo bridge. The core structures of 3 and 4 are characterized in detail by UV-vis, Mössbauer, resonance Raman, and X-ray absorption spectroscopies. Complex 4 is shorter-lived than 3 and decays to generate in ~20% yield of a diiron(III/IV) species 5, which can be identified by electron paramagnetic resonance and Mössbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (μ-oxo)(μ-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O-O bond and formation of a high-valent diiron complex, thereby mimicking the steps involved in the formation of intermediate X in the activation cycle of ribonucleotide reductase.
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Affiliation(s)
- Matthew A. Cranswick
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
| | - Katlyn K. Meier
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Xiaopeng Shan
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
| | - Audria Stubna
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Jószef Kaizer
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
| | - Mark P. Mehn
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
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Torapava N, Radkevich A, Persson I, Davydov D, Eriksson L. Formation of a heteronuclear hydrolysis complex in the ThIV–FeIII system. Dalton Trans 2012; 41:4451-9. [DOI: 10.1039/c2dt30058c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Bruijnincx PCA, Buurmans ILC, Huang Y, Juhász G, Viciano-Chumillas M, Quesada M, Reedijk J, Lutz M, Spek AL, Münck E, Bominaar EL, Klein Gebbink RJM. Mono- and dinuclear iron complexes of bis(1-methylimidazol-2-yl)ketone (bik): structure, magnetic properties, and catalytic oxidation studies. Inorg Chem 2011; 50:9243-55. [PMID: 21902227 PMCID: PMC3221465 DOI: 10.1021/ic200332y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The newly synthesized dinuclear complex [Fe(III)(2)(μ-OH)(2)(bik)(4)](NO(3))(4) (1) (bik, bis(1-methylimidazol-2-yl)ketone) shows rather short Fe···Fe (3.0723(6) Å) and Fe-O distances (1.941(2)/1.949(2) Å) compared to other unsupported Fe(III)(2)(μ-OH)(2) complexes. The bridging hydroxide groups of 1 are strongly hydrogen-bonded to a nitrate anion. The (57)Fe isomer shift (δ = 0.45 mm s(-1)) and quadrupole splitting (ΔE(Q) = 0.26 mm s(-1)) obtained from Mössbauer spectroscopy are consistent with the presence of two identical high-spin iron(III) sites. Variable-temperature magnetic susceptibility studies revealed antiferromagnetic exchange (J = 35.9 cm(-1) and H = JS(1)·S(2)) of the metal ions. The optimized DFT geometry of the cation of 1 in the gas phase agrees well with the crystal structure, but both the Fe···Fe and Fe-OH distances are overestimated (3.281 and 2.034 Å, respectively). The agreement in these parameters improves dramatically (3.074 and 1.966 Å) when the hydrogen-bonded nitrate groups are included, reducing the value calculated for J by 35%. Spontaneous reduction of 1 was observed in methanol, yielding a blue [Fe(II)(bik)(3)](2+) species. Variable-temperature magnetic susceptibility measurements of [Fe(II)(bik)(3)](OTf)(2) (2) revealed spin-crossover behavior. Thermal hysteresis was observed with 2, due to a loss of cocrystallized solvent molecules, as monitored by thermogravimetric analysis. The hysteresis disappears once the solvent is fully depleted by thermal cycling. [Fe(II)(bik)(3)](OTf)(2) (2) catalyzes the oxidation of alkanes with t-BuOOH. High selectivity for tertiary C-H bond oxidation was observed with adamantane (3°/2° value of 29.6); low alcohol/ketone ratios in cyclohexane and ethylbenzene oxidation, a strong dependence of total turnover number on the presence of O(2), and a low retention of configuration in cis-1,2-dimethylcyclohexane oxidation were observed. Stereoselective oxidation of olefins with dihydrogen peroxide yielding epoxides was observed under both limiting oxidant and substrate conditions.
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Affiliation(s)
- Pieter C. A. Bruijnincx
- Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Inge L. C. Buurmans
- Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Yuxing Huang
- Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Gergely Juhász
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Marta Viciano-Chumillas
- Leiden Institute of Chemistry, Leiden University, Coordination and Bioinorganic Chemistry Group, P. O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Manuel Quesada
- Leiden Institute of Chemistry, Leiden University, Coordination and Bioinorganic Chemistry Group, P. O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Jan Reedijk
- Leiden Institute of Chemistry, Leiden University, Coordination and Bioinorganic Chemistry Group, P. O. Box 9502, 2300 RA Leiden, The Netherlands
- Department of Chemistry, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
| | - Martin Lutz
- Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Anthony L. Spek
- Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Emile L. Bominaar
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Robertus J. M. Klein Gebbink
- Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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Louka FR, Spell ML, Grebowicz J, Albering JH, Mautner FA, Massoud SS. Coordination chemistry of 1,4-bis[bis(2-pyridylmethyl)aminomethyl]benzene with copper(II). J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2011.03.066] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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42
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Badiei YM, Siegler MA, Goldberg DP. O2 activation by bis(imino)pyridine iron(II)-thiolate complexes. J Am Chem Soc 2011; 133:1274-7. [PMID: 21207980 DOI: 10.1021/ja109923a] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The new iron(II)-thiolate complexes [((iPr)BIP)Fe(II)(SPh)(Cl)] (1) and [((iPr)BIP)Fe(II)(SPh)(OTf)] (2) [BIP = bis(imino)pyridine] were prepared as models for cysteine dioxygenase (CDO), which converts Cys to Cys-SO(2)H at a (His)(3)Fe(II) center. Reaction of 1 and 2 with O(2) leads to Fe-oxygenation and S-oxygenation, respectively. For 1 + O(2), the spectroscopic and reactivity data, including (18)O isotope studies, are consistent with an assignment of an iron(IV)-oxo complex, [((iPr)BIP)Fe(IV)(O)(Cl)](+) (3), as the product of oxygenation. In contrast, 2 + O(2) results in direct S-oxygenation to give a sulfonato product, PhSO(3)(-). The positioning of the thiolate ligand in 1 versus 2 appears to play a critical role in determining the outcome of O(2) activation. The thiolate ligands in 1 and 2 are essential for O(2) reactivity and exhibit an important influence over the Fe(III)/Fe(II) redox potential.
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Affiliation(s)
- Yosra M Badiei
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21212, United States
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Oldenburg PD, Feng Y, Pryjomska-Ray I, Ness D, Que L. Olefin Cis-Dihydroxylation with Bio-Inspired Iron Catalysts. Evidence for an FeII/FeIV Catalytic Cycle. J Am Chem Soc 2010; 132:17713-23. [DOI: 10.1021/ja1021014] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Paul D. Oldenburg
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Yan Feng
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Iweta Pryjomska-Ray
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Daniel Ness
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Liang J, Zhang J, Zhu L, Duarandin A, Young VG, Geacintov N, Canary JW. Structures, metal ion affinities, and fluorescence properties of soluble derivatives of tris((6-phenyl-2-pyridyl)methyl)amine. Inorg Chem 2010; 48:11196-208. [PMID: 19877674 DOI: 10.1021/ic901662z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Metal complexes of tris((6-phenyl-2-pyridyl)methyl)amine (2) have hydrophobic cavities that potentially accommodate small molecules. However, the utility of this attractive motif has been hampered by the poor solubility of such complexes in many common solvents. In this study, two tripodal ligands (3, tris-[6-(3,4,5-trimethoxy-phenyl)-pyridin-2-ylmethyl]-amine, and 4, tris((6-(3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenyl)pyridin-2-yl)methyl)amine) derived from 2 were prepared with enhanced solubility in organic and aqueous solvents. The X-ray crystallographic analyses of selected ligands and complexes revealed that the hydrophobic cavities inside the zinc complexes were retained after derivatization. Fluorescence, nuclear magnetic resonance (NMR), and potentiometric titration studies, which were enabled by the improved solubility, were performed to investigate the binding properties of the soluble ligands (3 and 4) with metal ions such as Zn(2+) and Cu(2+). When saturating quantities of Zn(2+) ions are added to ligand 3 in acetonitrile, the fluorescence emission maximum exhibits a pronounced red shift of approximately 80 nm (from 376 to 457 nm) and is enhanced by a factor of >100 when measured at 520 nm. The fluorescence properties of the Zn(2+) ion-coordinated ligands in the Zn(3) complex are consistent with a charge-transfer character in the excited state, with possible contributions from a planarization of the pyridyl-trimethoxyphenyl groups in the excited state, and from excitonic interactions.
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Affiliation(s)
- Jian Liang
- Department of Chemistry, New York University, New York, New York 10003, USA
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45
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van Eldik R, Hubbard CD. Application of low-temperature rapid-scan techniques in the elucidation of inorganic reaction mechanisms. Coord Chem Rev 2010. [DOI: 10.1016/j.ccr.2009.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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46
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Knight JC, Amoroso AJ, Edwards PG, Prabaharan R, Singh N. The co-ordination chemistry of bis(2,2′-bipyrid-6′-yl)ketone with first row transition metals: The reversible interconversion of a mononuclear complex and a dinuclear hemiketal containing species. Dalton Trans 2010; 39:8925-36. [PMID: 20714623 DOI: 10.1039/c0dt00344a] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- James C Knight
- Department of Chemistry, Cardiff University, PO Box 912, Cardiff, CF10 3TB
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Frisch JR, Vu VV, Martinho M, Münck E, Que L. Characterization of two distinct adducts in the reaction of a nonheme diiron(II) complex with O2. Inorg Chem 2009; 48:8325-36. [PMID: 19610611 DOI: 10.1021/ic900961k] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two [Fe(II)(2)(N-EtHPTB)(mu-O(2)X)](2+) complexes, where N-EtHPTB is the anion of N,N,N'N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane and O(2)X is O(2)PPh(2) (1 x O(2)PPh(2)) or O(2)AsMe(2) (1 x O(2)AsMe(2)), have been synthesized. Their crystal structures both show interiron distances of 3.54 A that arise from a (mu-alkoxo)diiron(II) core supported by an O(2)X bridge. These diiron(II) complexes react with O(2) at low temperatures in MeCN (-40 degrees C) and CH(2)Cl(2) (-60 degrees C) to form long-lived O(2) adducts that are best described as (mu-eta(1):eta(1)-peroxo)diiron(III) species (2 x O(2)X) with nu(O-O) approximately 850 cm(-1). Upon warming to -30 degrees C, 2 x O(2)PPh(2) converts irreversibly to a second (mu-eta(1):eta(1)-peroxo)diiron(III) intermediate (3 x O(2)PPh(2)) with nu(O-O) approximately 900 cm(-1), a value which matches that reported for [Fe(2)(N-EtHPTB)(O(2))(O(2)CPh)](2+) (3 x O(2)CPh) (Dong et al. J. Am. Chem. Soc. 1993, 115, 1851-1859). Mossbauer spectra of 2 x O(2)PPh(2) and 3 x O(2)PPh(2) indicate that the iron centers within each species are antiferromagnetically coupled with J approximately 60 cm(-1), while extended X-ray absorption fine structure analysis reveals interiron distances of 3.25 and 3.47 A for 2 x O(2)PPh(2) and 3 x O(2)PPh(2), respectively. A similarly short interiron distance (3.27 A) is found for 2 x O(2)AsMe(2). The shorter interiron distance associated with 2 x O(2)PPh(2) and 2 x O(2)AsMe(2) is proposed to derive from a triply bridged diiron(III) species with alkoxo (from N-EtHPTB), 1,2-peroxo, and 1,3-O(2)X bridges, while the longer distance associated with 3 x O(2)PPh(2) results from the shift of the O(2)PPh(2) bridge to a terminal position on one iron. The differences in nu(O-O) are also consistent with the different interiron distances. It is suggested that the O...O bite distance of the O(2)X moiety affects the thermal stability of 2 x O(2)X, with the O(2)X having the largest bite distance (O(2)AsMe(2)) favoring the 2 x O(2)X adduct and the O(2)X having the smallest bite distance (O(2)CPh) favoring the 3 x O(2)X adduct. Interestingly, neither 3 x O(2)AsMe(2) nor the benzoate analog of 2 x O(2)X (2 x O(2)Bz) are observed.
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Affiliation(s)
- Jonathan R Frisch
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, USA
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Wane A, Thallaj N, Mandon D. Biomimetic Interaction between FeIIand O2: Effect of the Second Coordination Sphere on O2Binding to FeIIComplexes: Evidence of Coordination at the Metal Centre by a Dissociative Mechanism in the Formation of μ-Oxo Diferric Complexes. Chemistry 2009; 15:10593-602. [DOI: 10.1002/chem.200901350] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Fiedler AT, Shan X, Mehn MP, Kaizer J, Torelli S, Frisch JR, Kodera M, Que L. Spectroscopic and computational studies of (mu-oxo)(mu-1,2-peroxo)diiron(III) complexes of relevance to nonheme diiron oxygenase intermediates. J Phys Chem A 2009; 112:13037-44. [PMID: 18811130 DOI: 10.1021/jp8038225] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
With the goal of gaining insight into the structures of peroxo intermediates observed for oxygen-activating nonheme diiron enzymes, a series of metastable synthetic diiron(III)-peroxo complexes with [Fe(III)(2)(mu-O)(mu-1,2-O(2))] cores has been characterized by X-ray absorption and resonance Raman spectroscopies, EXAFS analysis shows that this basic core structure gives rise to an Fe-Fe distance of approximately 3.15 A; the distance is decreased by 0.1 A upon introduction of an additional carboxylate bridge. In corresponding resonance Raman studies, vibrations arising from both the Fe-O-Fe and the Fe-O-O-Fe units can be observed. Importantly a linear correlation can be discerned between the nu(O-O) frequency of a complex and its Fe-Fe distance among the subset of complexes with [Fe(III)(2)(mu-OR)(mu-1,2-O(2))] cores (R = H, alkyl, aryl, or no substituent). These experimental studies are complemented by a normal coordinate analysis and DFT calculations.
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Affiliation(s)
- Adam T Fiedler
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, Minnesota 55455, USA
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Mandal PC, Bhattacharyya J, Das S, Mukhopadhyay S, Kirschenbaum LJ. Mechanistic studies on the oxidation of pyruvic acid by an oxo-bridged diiron(III,III) complex in aqueous acidic media. Polyhedron 2009. [DOI: 10.1016/j.poly.2009.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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