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Panda S, Phan H, Dunietz EM, Brueggemeyer MT, Hota PK, Siegler MA, Jose A, Bhadra M, Solomon EI, Karlin KD. Intramolecular Phenolic H-Atom Abstraction by a N 3ArOH Ligand-Supported (μ-η 2:η 2-Peroxo)dicopper(II) Species Relevant to the Active Site Function of oxy-Tyrosinase. J Am Chem Soc 2024; 146:14942-14947. [PMID: 38775712 PMCID: PMC11193493 DOI: 10.1021/jacs.4c04402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Synthetic side-on peroxide-bound dicopper(II) (SP) complexes are important for understanding the active site structure/function of many copper-containing enzymes. This work highlights the formation of new {CuII(μ-η2:η2-O22-)CuII} complexes (with electronic absorption and resonance Raman (rR) spectroscopic characterization) using tripodal N3ArOH ligands at -135 °C, which spontaneously participate in intramolecular phenolic H-atom abstraction (HAA). This results in the generation of bis(phenoxyl radical)bis(μ-OH)dicopper(II) intermediates, substantiated by their EPR/UV-vis/rR spectroscopic signatures and crystal structural determination of a diphenoquinone dicopper(I) complex derived from ligand para-C═C coupling. The newly observed chemistry in these ligand-Cu systems is discussed with respect to (a) our Cu-MeAN (tridentate N,N,N',N',N″-pentamethyldipropylenetriamine)-derived model SP species, which was unreactive toward exogenous monophenol addition (J. Am. Chem. Soc. 2012, 134, 8513-8524), emphasizing the impact of intramolecularly tethered ArOH groups, and (b) recent advances in understanding the mechanism of action of the tyrosinase (Ty) enzyme.
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Affiliation(s)
- Sanjib Panda
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Hai Phan
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Eleanor M Dunietz
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | | | - Pradip Kumar Hota
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Anex Jose
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Mayukh Bhadra
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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2
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Wang MM, Nguyen TVT, Waser J. Activation of aminocyclopropanes via radical intermediates. Chem Soc Rev 2022; 51:7344-7357. [PMID: 35938356 DOI: 10.1039/d2cs00090c] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aminocyclopropanes are versatile building blocks for accessing high value-added nitrogen-containing products. To control ring-opening promoted by ring strain, the Lewis acid activation of donor-acceptor substituted systems is now well established. Over the last decade, alternative approaches have emerged proceeding via the formation of radical intermediates, alleviating the need for double activation of the cyclopropanes. This tutorial review summarizes key concepts and recent progress in ring-opening transformations of aminocyclopropanes via radical intermediates, divided into formal cycloadditions and 1,3-difunctionalizations.
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Affiliation(s)
- Ming-Ming Wang
- Laboratory of Catalysis and Organic Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland. .,Department of Chemical Biology, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
| | - Tin V T Nguyen
- Laboratory of Catalysis and Organic Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
| | - Jerome Waser
- Laboratory of Catalysis and Organic Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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3
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Broadband Dielectric Spectroscopic Detection of Ethanol: A Side-by-Side Comparison of ZnO and HKUST-1 MOFs as Sensing Media. CHEMOSENSORS 2022. [DOI: 10.3390/chemosensors10070241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The most common gas sensors are based on chemically induced changes in electrical resistivity and necessarily involve making imperfect electrical contacts to the sensing materials, which introduce errors into the measurements. We leverage thermal- and chemical-induced changes in microwave propagation characteristics (i.e., S-parameters) to compare ZnO and surface-anchored metal–organic-framework (HKUST-1 MOF) thin films as sensing materials for detecting ethanol vapor, a typical volatile organic compound (VOC), at low temperatures. We show that the microwave propagation technique can detect ethanol at relatively low temperatures (<100 °C), and afford new mechanistic insights that are inaccessible with the traditional dc-resistance-based measurements. In addition, the metrological technique avoids the inimical measurand distortions due to parasitic electrical effects inherent in the conductometric volatile organic compound detection.
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5
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Askari MS, Effaty F, Gennarini F, Orio M, Le Poul N, Ottenwaelder X. Tuning Inner-Sphere Electron Transfer in a Series of Copper/Nitrosoarene Adducts. Inorg Chem 2020; 59:8678-8689. [PMID: 32073833 DOI: 10.1021/acs.inorgchem.9b03175] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A series of copper/nitrosoarene complexes was created that mimics several steps in biomimetic O2 activation by copper(I). The reaction of the copper(I) complex of N,N,N',N'-tetramethypropylenediamine with a series of para-substituted nitrosobenzene derivatives leads to adducts in which the nitrosoarene (ArNO) is reduced by zero, one, or two electrons, akin to the isovalent species dioxygen, superoxide, and peroxide, respectively. The geometric and electronic structures of these adducts were characterized by means of X-ray diffraction, vibrational analysis, ultraviolet-visible spectroscopy, NMR, electrochemistry, and density functional theory (DFT) calculations. The bonding mode of the NO moiety depends on the oxidation state of the ArNO moiety: κN for ArNO, mononuclear η2-NO and dinuclear μ-η2:η1 for ArNO•-, and dinuclear μ-η2:η2 for ArNO2-. 15N isotopic labeling confirms the reduction state by measuring the NO stretching frequency (1392 cm-1 for κN-ArNO, 1226 cm-1 for η2-ArNO•-, 1133 cm-1 for dinuclear μ-η2:η1-ArNO•-, and 875 cm-1 for dinuclear μ-η2:η2 for ArNO2-). The 15N NMR signal disappears for the ArNO•- species, establishing a unique diagnostic for the radical state. Electrochemical studies indicate reduction waves that are consistent with one-electron reduction of the adducts and are compared with studies performed on Cu-O2 analogues. DFT calculations were undertaken to confirm our experimental findings, notably to establish the nature of the charge-transfer transitions responsible for the intense green color of the complexes. In fine, this family of complexes is unique in that it walks through three redox states of the ArNO moiety while keeping the metal and its supporting ligand the same. This work provides snapshots of the reactivity of the toxic nitrosoarene molecules with the biologically relevant Cu(I) ion.
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Affiliation(s)
- Mohammad S Askari
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Farshid Effaty
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Federica Gennarini
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H4B 1R6, Canada.,Laboratoire de Chimie, Électrochimie Moléculaires et Chimie Analytique, UMR, CNRS 6521, Université de Bretagne Occidentale, Brest 29238, France
| | - Maylis Orio
- Aix Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille 13007, France
| | - Nicolas Le Poul
- Laboratoire de Chimie, Électrochimie Moléculaires et Chimie Analytique, UMR, CNRS 6521, Université de Bretagne Occidentale, Brest 29238, France
| | - Xavier Ottenwaelder
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H4B 1R6, Canada
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6
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Sokolova OO, Bower JF. Selective Carbon–Carbon Bond Cleavage of Cyclopropylamine Derivatives. Chem Rev 2020; 121:80-109. [DOI: 10.1021/acs.chemrev.0c00166] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Olga O. Sokolova
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - John F. Bower
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
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Naveen P, Vijaya Pandiyan B, Anu D, Dallemer F, Kolandaivel P, Prabhakaran R. A pseudo trinuclear nickel–sodium complex containing tris(8‐methyl‐2‐oxo‐quinolidineamino ethylamine): Synthesis, spectral characterization, X‐ray crystallography and in vitrobiological evaluations. Appl Organomet Chem 2020. [DOI: 10.1002/aoc.5605] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- P. Naveen
- Department of ChemistryBharathiar University Coimbatore 641 046 India
| | | | - D. Anu
- Department of ChemistryBharathiar University Coimbatore 641 046 India
| | - F. Dallemer
- LaboratoireChimie Provence‐CNRS, UMR7246Université of Aix‐Marseille, Campus Scientifique de Saint‐Jérôme, Avenue Escadrille Normandie‐Niemen F‐13397 Marseille Cedex 20 France
| | - P. Kolandaivel
- Department of PhysicsBharathiar University Coimbatore 641046 India
| | - R. Prabhakaran
- Department of ChemistryBharathiar University Coimbatore 641 046 India
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Grimm ML, Suleman NK, Hancock AN, Spencer JN, Dudding T, Rowshanpour R, Castagnoli N, Tanko JM. Stereoelectronic and Resonance Effects on the Rate of Ring Opening of N-Cyclopropyl-Based Single Electron Transfer Probes. J Am Chem Soc 2020; 142:2640-2652. [PMID: 31913031 DOI: 10.1021/jacs.9b12617] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N-Cyclopropyl-N-methylaniline (5) is a poor probe for single electron transfer (SET) because the corresponding radical cation undergoes cyclopropane ring opening with a rate constant of only 4.1 × 104 s-1, too slow to compete with other processes such as radical cation deprotonation. The sluggish rate of ring opening can be attributed to either (i) a resonance effect in which the spin and charge of the radical cation in the ring-closed form is delocalized into the phenyl ring, and/or (ii) the lowest energy conformation of the SET product (5•+) does not meet the stereoelectronic requirements for cyclopropane ring opening. To resolve this issue, a new series of N-cyclopropylanilines were designed to lock the cyclopropyl group into the required bisected conformation for ring opening. The results reveal that the rate constant for ring opening of radical cations derived from 1'-methyl-3',4'-dihydro-1'H-spiro[cyclopropane-1,2'-quinoline] (6) and 6'-chloro-1'-methyl-3',4'-dihydro-1'H-spiro[cyclopropane-1,2'-quinoline] (7) are 3.5 × 102 s-1 and 4.1 × 102 s-1, effectively ruling out the stereoelectronic argument. In contrast, the radical cation derived from 4-chloro-N-methyl-N-(2-phenylcyclopropyl)aniline (8) undergoes cyclopropane ring opening with a rate constant of 1.7 × 108 s-1, demonstrating that loss of the resonance energy associated with the ring-closed form of these N-cyclopropylanilines can be amply compensated by incorporation of a radical-stabilizing phenyl substituent on the cyclopropyl group. Product studies were performed, including a unique application of EC-ESI/MS (Electrochemistry/ElectroSpray Ionization Mass Spectrometry) in the presence of 18O2 and H218O to elucidate the mechanism of ring opening of 7•+ and trapping of the resulting distonic radical cation.
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Affiliation(s)
- Michelle L Grimm
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - N Kamrudin Suleman
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - Amber N Hancock
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - Jared N Spencer
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - Travis Dudding
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - Rozhin Rowshanpour
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - Neal Castagnoli
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
| | - James M Tanko
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24060 , United States
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9
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Ryan MC, Whitmire LD, McCann SD, Stahl SS. Copper/TEMPO Redox Redux: Analysis of PCET Oxidation of TEMPOH by Copper(II) and the Reaction of TEMPO with Copper(I). Inorg Chem 2019; 58:10194-10200. [PMID: 31283193 DOI: 10.1021/acs.inorgchem.9b01326] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Copper salts and organic aminoxyls, such as TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), are versatile catalysts for aerobic alcohol oxidation. Previous reports in the literature contain conflicting proposals concerning the redox interactions that take place between copper(I) and copper(II) salts with the aminoxyl and hydroxylamine species, TEMPO and TEMPOH, respectively. Here, we reinvestigate these reactions in an effort to resolve the conflicting claims in the literature. Under anaerobic conditions, CuIIX2 salts [X = acetate (OAc), trifluoroacetate (TFA), and triflate (OTf)] are shown to promote the rapid proton-coupled oxidation of TEMPOH to TEMPO: CuIIX2 + TEMPOH → CuIX + TEMPO + HX. In the reaction with acetate, however, slow reoxidation of CuIOAc occurs. This process requires both TEMPO and HOAc and coincides with the reduction of TEMPO to 2,2,6,6-tetramethylpiperidine. Analogous reactivity is not observed with trifluoroacetate and triflate species. Overall, the facility of the proton-coupled oxidation of TEMPOH by CuII salts suggests that this process could contribute to catalyst regeneration under aerobic oxidation conditions.
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Affiliation(s)
- Michael C Ryan
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Lauren D Whitmire
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Scott D McCann
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Shannon S Stahl
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
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10
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Quist DA, Ehudin MA, Karlin KD. Unprecedented direct cupric-superoxo conversion to a bis- μ-oxo dicopper(III) complex and resulting oxidative activity. Inorganica Chim Acta 2019; 485:155-161. [PMID: 30988551 PMCID: PMC6461407 DOI: 10.1016/j.ica.2018.10.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Investigations of small molecule copper-dioxygen chemistry can and have provided fundamental insights into enzymatic processes (e.g., copper metalloenzyme dioxygen binding geometries and their associated spectroscopy and substrate reactivity). Strategically designing copper-binding ligands has allowed for insight into properties that favor specific (di)copper-dioxygen species. Herein, the tetradentate tripodal TMPA-based ligand (TMPA = tris((2-pyridyl)methyl)amine) possessing a methoxy moiety in the 6-pyridyl position on one arm (OCH3TMPA) was investigated. This system allows for a trigonal bipyramidal copper(II) geometry as shown by the UV-vis and EPR spectra of the cupric complex [(OCH3TMPA)CuII(OH2)](ClO4)2. Cyclic voltammetry experiments determined the reduction potential of this copper(II) species to be -0.35 V vs. Fc+/0 in acetonitrile, similar to other TMPA-derivatives bearing sterically bulky 6-pyridyl substituents. The copper-dioxygen reactivity is also analogous to these TMPA-derivatives, affording a bis-μ-oxo dicopper(III) complex, [{(OCH3TMPA)CuIII}2(O2-)2]2+, upon oxygenation of the copper(I) complex [(OCH3TMPA)CuI](B(C6F5)4) at cryogenic temperatures in 2-methyltetrahydrofuran. This highly reactive intermediate is capable of oxidizing phenolic substrates through a net hydrogen atom abstraction. However, after bubbling of the precursor copper(I) complex with dioxygen at very low temperatures (-135 °C), a cupric superoxide species, [(OCH3TMPA)CuII(O2 •-)]+, is initially formed before slowly converting to [{(OCH3TMPA)CuIII}2(O2-)2]2+. This appears to be the first instance of the direct conversion of a cupric superoxide to a bis-μ-oxo dicopper(III) species in copper(I)-dioxygen chemistry.
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Affiliation(s)
- David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Melanie A. Ehudin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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11
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Large TAG, Mahadevan V, Keown W, Stack TDP. Selective Oxidation of Exogenous Substrates by a Bis-Cu(III) Bis-Oxide Complex: Mechanism and Scope. Inorganica Chim Acta 2018; 486:782-792. [PMID: 31485082 DOI: 10.1016/j.ica.2018.11.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Cu(III)2(μ-O)2 bis-oxides (O) form spontaneously by direct oxygenation of nitrogen-chelated Cu(I) species and constitute a diverse class of versatile 2e-/2H+ oxidants, but while these species have attracted attention as biomimetic models for dinuclear Cu enzymes, reactivity is typically limited to intramolecular ligand oxidation, and systems exhibiting synthetically useful reactivity with exogenous substrates are limited. O tmpd (TMPD = N 1 , N 1 , N 3 , N 3 -tetramethylpropane-1,3-diamine) presents an exception, readily oxidizing a diverse array of exogenous substrates, including primary alcohols and amines selectively over their secondary counterparts in good yields. Mechanistic and DFT analyses suggest substrate oxidation proceeds through initial axial coordination, followed by rate limiting rotation to position the substrate in the Cu(III) equatorial plane, whereupon rapid deprotonation and oxidation by net hydride transfer occurs. Together, the results suggest the selectivity and broad substrate scope unique to O tmpd are best attributed to the combination of ligand flexibility, limited steric demands, and ligand oxidative stability. In keeping with the absence of rate limiting C-H scission, O tmpd exhibits a marked insensitivity to the strength of the substrate Cα-H bond, readily oxidizing benzyl alcohol and 1 octanol at near identical rates.
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Affiliation(s)
- Tao A G Large
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | | | - William Keown
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - T Daniel P Stack
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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12
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Naveen P, Dallemer F, Butcher R, Prabhakaran R. New Ru(II) complexes containing tris(2-pyridylmethyl)amine. Synthesis, structural, CT-DNA/albumin interaction, anti-oxidant and cytotoxicity studies. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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13
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Elwell CE, Gagnon NL, Neisen BD, Dhar D, Spaeth AD, Yee GM, Tolman WB. Copper-Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity. Chem Rev 2017; 117:2059-2107. [PMID: 28103018 PMCID: PMC5963733 DOI: 10.1021/acs.chemrev.6b00636] [Citation(s) in RCA: 445] [Impact Index Per Article: 63.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A longstanding research goal has been to understand the nature and role of copper-oxygen intermediates within copper-containing enzymes and abiological catalysts. Synthetic chemistry has played a pivotal role in highlighting the viability of proposed intermediates and expanding the library of known copper-oxygen cores. In addition to the number of new complexes that have been synthesized since the previous reviews on this topic in this journal (Mirica, L. M.; Ottenwaelder, X.; Stack, T. D. P. Chem. Rev. 2004, 104, 1013-1046 and Lewis, E. A.; Tolman, W. B. Chem. Rev. 2004, 104, 1047-1076), the field has seen significant expansion in the (1) range of cores synthesized and characterized, (2) amount of mechanistic work performed, particularly in the area of organic substrate oxidation, and (3) use of computational methods for both the corroboration and prediction of proposed intermediates. The scope of this review has been limited to well-characterized examples of copper-oxygen species but seeks to provide a thorough picture of the spectroscopic characteristics and reactivity trends of the copper-oxygen cores discussed.
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Affiliation(s)
- Courtney E Elwell
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - Nicole L Gagnon
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - Benjamin D Neisen
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - Debanjan Dhar
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - Andrew D Spaeth
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - Gereon M Yee
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
| | - William B Tolman
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant St. SE, Minneapolis, Minnesota 55455, United States
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14
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Rassadin VA, Six Y. Ring-opening, cycloaddition and rearrangement reactions of nitrogen-substituted cyclopropane derivatives. Tetrahedron 2016. [DOI: 10.1016/j.tet.2016.06.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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15
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Gildner PG, DeAngelis A, Colacot TJ. Palladium-Catalyzed N-Arylation of Cyclopropylamines. Org Lett 2016; 18:1442-5. [PMID: 26934493 DOI: 10.1021/acs.orglett.6b00377] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Peter G. Gildner
- Johnson Matthey
Catalysis and Chiral
Technologies, 2001 Nolte Drive, West Deptford, New Jersey 08066, United States
| | - Andrew DeAngelis
- Johnson Matthey
Catalysis and Chiral
Technologies, 2001 Nolte Drive, West Deptford, New Jersey 08066, United States
| | - Thomas J. Colacot
- Johnson Matthey
Catalysis and Chiral
Technologies, 2001 Nolte Drive, West Deptford, New Jersey 08066, United States
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16
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Kafentzi MC, Orio M, Réglier M, Yao S, Kuhlmann U, Hildebrandt P, Driess M, Simaan AJ, Ray K. Changing the chemical and physical properties of high valent heterobimetallic bis-(μ-oxido) Cu–Ni complexes by ligand effects. Dalton Trans 2016; 45:15994-16000. [DOI: 10.1039/c6dt02391f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two new heterobimetallic [LNiO2Cu(RPY2)]+ (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R = indane, 3a or R = Me, 3b) complexes have been spectroscopically trapped at low temperatures.
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Affiliation(s)
| | - Maylis Orio
- Aix Marseille Univ
- CNRS
- Centrale Marseille
- iSm2
- Marseille
| | | | - Shenglai Yao
- Department of Chemistry
- Technische Universität Berlin
- 10623 Berlin
- Germany
| | - Uwe Kuhlmann
- Department of Chemistry
- Technische Universität Berlin
- 10623 Berlin
- Germany
| | - Peter Hildebrandt
- Department of Chemistry
- Technische Universität Berlin
- 10623 Berlin
- Germany
| | - Matthias Driess
- Department of Chemistry
- Technische Universität Berlin
- 10623 Berlin
- Germany
| | | | - Kallol Ray
- Department of Chemistry
- Humboldt-Universität zu Berlin
- 12489 Berlin
- Germany
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17
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Da Silva JCS, Pennifold RCR, Harvey JN, Rocha WR. A radical rebound mechanism for the methane oxidation reaction promoted by the dicopper center of a pMMO enzyme: a computational perspective. Dalton Trans 2016; 45:2492-504. [DOI: 10.1039/c5dt02638e] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Hydrogen Atom Transfer (HAT) promoted by a triplet state of the bis-oxoCu2(iii) core generates a new radical rebound mechanism for the hydroxylation of methane catalyzed by the binuclear copper site of a pMMO enzyme.
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Affiliation(s)
- Júlio C. S. Da Silva
- BioMat: Biomaterial Modeling Group
- Departamento de Química Fundamental
- CCEN
- Universidade Federal de Pernambuco
- Cidade Universitária
| | | | | | - Willian R. Rocha
- LQC-MM: Laboratório de Química Computacional e Modelagem Molecular
- Departamento de Química
- ICEX
- Universidade Federal de Minas Gerais
- Belo Horizonte
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18
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Saracini C, Ohkubo K, Suenobu T, Meyer GJ, Karlin KD, Fukuzumi S. Laser-Induced Dynamics of Peroxodicopper(II) Complexes Vary with the Ligand Architecture. One-Photon Two-Electron O2 Ejection and Formation of Mixed-Valent Cu(I)Cu(II)-Superoxide Intermediates. J Am Chem Soc 2015; 137:15865-74. [PMID: 26651492 DOI: 10.1021/jacs.5b10177] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Photoexcitation of end-on trans-μ-1,2-peroxodicopper(II) complex [(tmpa)2Cu(II)2(O2)](2+) (1) (λmax = 525 and 600 nm) and side-on μ-η(2):η(2)-peroxodicopper(II) complexes [(N5)Cu(II)2(O2)](2+) (2) and [(N3)Cu(II)2(O2)](2+) (3) at -80 °C in acetone led to one-photon two-electron peroxide-to-dioxygen oxidation chemistry (O2(2-) + hν → O2 + 2e(-)). Interestingly, light excitation of 2 and 3 (having side-on μ-η(2):η(2)-peroxo ligation) led to release of dioxygen, while photoexcitation of 1 (having an end-on trans-1,2-peroxo geometry) did not, even though spectroscopic studies revealed that both reactions proceeded through previously unknown mixed-valent superoxide species: [Cu(II)(O2(•-))Cu(I)](2+) (λmax = 685-740 nm). For 1, this intermediate underwent further fast intramolecular electron transfer to yield an "O2-caged" dicopper(I) adduct, Cu(I)2-O2, and a barrierless stepwise back electron transfer to regenerate 1 occurred. Femtosecond laser excitation of 2 and 3 under the same conditions still led to [Cu(II)(O2(•-))Cu(I)](2+) intermediates that, instead, underwent O2 release with a quantum yield of 0.14 ± 0.1 for 3. Such remarkable differences in reaction pathways likely result from the well-known ligand-derived stability of 2 and 3 vs 1 indicated by ligand-Cu(II/I) redox potentials; (N5)Cu(I) and (N3)Cu(I) complexes are far more stable than (tmpa)Cu(I) species. The fast Cu(I)2/O2 rebinding kinetics was also measured after photoexcitation of 2 and 3, with the results closely tracking those known for the dicopper proteins hemocyanin and tyrosinase, for which the synthetic dicopper(I) precursors [(N5)Cu(I)2](2+) and [(N3)Cu(I)2](2+) and their dioxygen adducts serve as models. The biological relevance of the present findings is discussed, including the potential impact on the solar water splitting process.
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Affiliation(s)
- Claudio Saracini
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Kei Ohkubo
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Suita, Osaka 565-0871, Japan.,Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea
| | - Tomoyoshi Suenobu
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Suita, Osaka 565-0871, Japan
| | - Gerald J Meyer
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Kenneth D Karlin
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Shunichi Fukuzumi
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Suita, Osaka 565-0871, Japan.,Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea.,Faculty of Science and Engineering, Meijo University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Nagoya, Aichi 468-0073, Japan
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19
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Washington C, Maxwell J, Stevenson J, Malone G, Lowe EW, Zhang Q, Wang G, McIntyre NR. Mechanistic studies of the tyrosinase-catalyzed oxidative cyclocondensation of 2-aminophenol to 2-aminophenoxazin-3-one. Arch Biochem Biophys 2015; 577-578:24-34. [PMID: 25982123 DOI: 10.1016/j.abb.2015.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/20/2015] [Accepted: 04/21/2015] [Indexed: 10/23/2022]
Abstract
Tyrosinase (EC 1.14.18.1) catalyzes the monophenolase and diphenolase reaction associated with vertebrate pigmentation and fruit/vegetable browning. Tyrosinase is an oxygen-dependent, dicopper enzyme that has three states: Emet, Eoxy, and Edeoxy. The diphenolase activity can be carried out by both the met and the oxy states of the enzyme while neither mono- nor diphenolase activity results from the deoxy state. In this study, the oxidative cyclocondensation of 2-aminophenol (OAP) to the corresponding 2-aminophenoxazin-3-one (APX) by mushroom tyrosinase was investigated. Using a combination of various steady- and pre-steady state methodologies, we have investigated the kinetic and chemical mechanism of this reaction. The kcat for OAP is 75 ± 2s(-1), K(OAP)M = 1.8 ± 0.2mM, K(O2)M =25 ± 4 μM with substrates binding in a steady-state preferred fashion. Stopped flow and global analysis support a model where OAP preferentially binds to the oxy form over the met (k7 ≫ k1). For the met form, His269 and His61 are the proposed bases, while the oxy form uses the copper-peroxide and His61 for the sequential deprotonation of anilinic and phenolic hydrogens. Solvent KIEs show proton transfer to be increasingly rate limiting for kcat/K(OAP)M as [O2] → 0 μM (1.38 ± 0.06) decreasing to 0.83 ± 0.03 as [O2] → ∞ reflecting a partially rate limiting μ-OH bond cleavage (E met) and formation (E oxy) following protonation in the transition state. The coupling and cyclization reactions of o-quinone imine and OAP pass through a phenyliminocyclohexadione intermediate to APX, forming at a rate of 6.91 ± 0.03 μM(-1)s(-1) and 2.59E-2 ± 5.31E-4s(-1). Differences in reactivity attributed to the anilinic moiety of OAP with o-diphenols are discussed.
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Affiliation(s)
- Courtney Washington
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA
| | - Jamere Maxwell
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA
| | - Joenathan Stevenson
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA
| | - Gregory Malone
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA
| | - Edward W Lowe
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Qiang Zhang
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA
| | - Guangdi Wang
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA
| | - Neil R McIntyre
- Division of Mathematical and Physical Sciences, Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, USA.
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20
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Lee JY, Karlin KD. Elaboration of copper-oxygen mediated C-H activation chemistry in consideration of future fuel and feedstock generation. Curr Opin Chem Biol 2015; 25:184-93. [PMID: 25756327 DOI: 10.1016/j.cbpa.2015.02.014] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 02/12/2015] [Accepted: 02/16/2015] [Indexed: 12/21/2022]
Abstract
To contribute solutions to current energy concerns, improvements in the efficiency of dioxygen mediated C-H bond cleavage chemistry, for example, selective oxidation of methane to methanol, could minimize losses in natural gas usage or produce feedstocks for fuels. Oxidative C-H activation is also a component of polysaccharide degradation, potentially affording alternative biofuels from abundant biomass. Thus, an understanding of active-site chemistry in copper monooxygenases, those activating strong C-H bonds is briefly reviewed. Then, recent advances in the synthesis-generation and study of various copper-oxygen intermediates are highlighted. Of special interest are cupric-superoxide, Cu-hydroperoxo and Cu-oxy complexes. Such investigations can contribute to an enhanced future application of C-H oxidation or oxygenation processes using air, as concerning societal energy goals.
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Affiliation(s)
- Jung Yoon Lee
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA.
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21
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Liu CC, Lin TS, Chan SI, Mou CY. A room temperature catalyst for toluene aliphatic C–H bond oxidation: Tripodal tridentate copper complex immobilized in mesoporous silica. J Catal 2015. [DOI: 10.1016/j.jcat.2014.12.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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22
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Kotani H, Kaida S, Ishizuka T, Sakaguchi M, Ogura T, Shiota Y, Yoshizawa K, Kojima T. Formation and characterization of a reactive chromium(v)-oxo complex: mechanistic insight into hydrogen-atom transfer reactions. Chem Sci 2015; 6:945-955. [PMID: 29560181 PMCID: PMC5811151 DOI: 10.1039/c4sc02285h] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/17/2014] [Indexed: 12/27/2022] Open
Abstract
A mononuclear Cr(v)-oxo complex, [CrV(O)(6-COO--tpa)](BF4)2 (1; 6-COO--tpa = N,N-bis(2-pyridylmethyl)-N-(6-carboxylato-2-pyridylmethyl)amine) was prepared through the reaction of a Cr(iii) precursor complex with iodosylbenzene as an oxidant. Characterization of 1 was achieved using ESI-MS spectrometry, electron paramagnetic resonance, UV-vis, and resonance Raman spectroscopies. The reduction potential (Ered) of 1 was determined to be 1.23 V vs. SCE in acetonitrile based on analysis of the electron-transfer (ET) equilibrium between 1 and a one-electron donor, [RuII(bpy)3]2+ (bpy = 2,2'-bipyridine). The reorganization energy (λ) of 1 was also determined to be 1.03 eV in ET reactions from phenol derivatives to 1 on the basis of the Marcus theory of ET. The smaller λ value in comparison with that of an Fe(iv)-oxo complex (2.37 eV) is caused by the small structural change during ET due to the dπ character of the electron-accepting LUMO of 1. When benzyl alcohol derivatives (R-BA) with different oxidation potentials were employed as substrates, corresponding aldehydes were obtained as the 2e--oxidized products in moderate yields as determined from 1H NMR and GC-MS measurements. One-step UV-vis spectral changes were observed in the course of the oxidation reactions of BA derivatives by 1 and a kinetic isotope effect (KIE) was observed in the oxidation reactions for deuterated BA derivatives at the benzylic position as substrates. These results indicate that the rate-limiting step is a concerted proton-coupled electron transfer (PCET) from substrate to 1. In sharp contrast, in the oxidation of trimethoxy-BA (Eox = 1.22 V) by 1, trimethoxy-BA radical cation was observed by UV-vis spectroscopy. Thus, it was revealed that the mechanism of the oxidation reaction changed from one-step PCET to stepwise ET-proton transfer (ET/PT), depending on the redox potentials of R-BA.
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Affiliation(s)
- Hiroaki Kotani
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
| | - Suzue Kaida
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
| | - Tomoya Ishizuka
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
| | - Miyuki Sakaguchi
- Graduate School of Life Science , University of Hyogo , Kouto , Hyogo 678-1297 , Japan
| | - Takashi Ogura
- Graduate School of Life Science , University of Hyogo , Kouto , Hyogo 678-1297 , Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering , Kyushu University , Motooka , Nishi-Ku , Fukuoka 819-0395 , Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering , Kyushu University , Motooka , Nishi-Ku , Fukuoka 819-0395 , Japan
- Elements Strategy Initiative for Catalysts & Batteries , Kyoto University , Nishikyo-ku , Kyoto 615-8520 , Japan
| | - Takahiko Kojima
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
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23
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Meesala Y, Wu HL, Koteswararao B, Kuo TS, Lee WZ. Aerobic Oxidative Coupling of 2-Naphthol Derivatives Catalyzed by a Hexanuclear Bis(μ-hydroxo)copper(II) Catalyst. Organometallics 2014. [DOI: 10.1021/om500403k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Yedukondalu Meesala
- Department
of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, R.O.C
| | - Hsyueh-Liang Wu
- Department
of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, R.O.C
| | - Bommisetti Koteswararao
- Center
for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Ting-Shen Kuo
- Instrumentation
Center, Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, R.O.C
| | - Way-Zen Lee
- Department
of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, R.O.C
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24
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Wang Y, Bauer JO, Strohmann C, Kumar K. A Bioinspired Catalytic Oxygenase Cascade to Generate Complex Oxindoles. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201403415] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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25
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Wang Y, Bauer JO, Strohmann C, Kumar K. A Bioinspired Catalytic Oxygenase Cascade to Generate Complex Oxindoles. Angew Chem Int Ed Engl 2014; 53:7514-8. [DOI: 10.1002/anie.201403415] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 04/08/2014] [Indexed: 12/26/2022]
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26
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Zheng B, Liu H, Feng J, Zhang J. Effect of coordination sphere of the copper center and Cu―Cu distance on catechol oxidase and nuclease activities of the copper complexes. Appl Organomet Chem 2014. [DOI: 10.1002/aoc.3138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Bin Zheng
- State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of New Drug Design, School of Pharmacy; East China University of Science and Technology; Shanghai 200237 People's Republic of China
| | - Hui Liu
- State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of New Drug Design, School of Pharmacy; East China University of Science and Technology; Shanghai 200237 People's Republic of China
| | - Jie Feng
- State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of New Drug Design, School of Pharmacy; East China University of Science and Technology; Shanghai 200237 People's Republic of China
| | - Jingyan Zhang
- State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of New Drug Design, School of Pharmacy; East China University of Science and Technology; Shanghai 200237 People's Republic of China
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27
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Weisser F, Hohloch S, Plebst S, Schweinfurth D, Sarkar B. Ruthenium complexes of tripodal ligands with pyridine and triazole arms: subtle tuning of thermal, electrochemical, and photochemical reactivity. Chemistry 2014; 20:781-93. [PMID: 24403171 DOI: 10.1002/chem.201303640] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 10/30/2013] [Indexed: 01/02/2023]
Abstract
Electrochemical and photochemical bond-activation steps are important for a variety of chemical transformations. We present here four new complexes, [Ru(L(n) )(dmso)(Cl)]PF6 (1-4), where L(n) is a tripodal amine ligand with 4-n pyridylmethyl arms and n-1 triazolylmethyl arms. Structural comparisons show that the triazoles bind closer to the Ru center than the pyridines. For L(2) , two isomers (with respect to the position of the triazole arm, equatorial or axial), trans-2sym and trans-2un , could be separated and compared. The increase in the number of the triazole arms in the ligand has almost no effect on the Ru(II) /Ru(III) oxidation potentials, but it increases the stability of the RuSdmso bond. Hence, the oxidation waves become more reversible from trans-1 to trans-4, and whereas the dmso ligand readily dissociates from trans-1 upon heating or irradiation with UV light, the RuS bond of trans-4 remains perfectly stable under the same conditions. The strength of the RuS bond is not only influenced by the number of triazole arms but also by their position, as evidenced by the difference in redox behavior and reactivity of the two isomers, trans-2sym and trans-2un . A mechanistic picture for the electrochemical, thermal, and photochemical bond activation is discussed with data from NMR spectroscopy, cyclic voltammetry, and spectroelectrochemistry.
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Affiliation(s)
- Fritz Weisser
- Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstraße 34-36, 14195 Berlin (Germany), Fax: (+49) 30-838-53310
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28
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Haack P, Kärgel A, Greco C, Dokic J, Braun B, Pfaff FF, Mebs S, Ray K, Limberg C. Access to a Cu(II)-O-Cu(II) motif: spectroscopic properties, solution structure, and reactivity. J Am Chem Soc 2013; 135:16148-60. [PMID: 24134722 PMCID: PMC3946511 DOI: 10.1021/ja406721a] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We report a complex with a rare Cu(II)-O-Cu(II) structural motif that is stable at room temperature, which allows its in-depth characterization by a variety of spectroscopic methods. Interest in such compounds is fueled by the recent discovery that a Cu(II)-O-Cu(II) species on the surface of Cu-ZSM-5 is capable of oxidizing methane to methanol, and this in turn ties into mechanistic discussions on the methane oxidation at the dicopper site within the particulate methane monooxygenase. For the synthesis of our Cu2O complex we have developed a novel, neutral ligand system, FurNeu, exhibiting two N-(N',N'-dimethylaminoethyl)(2-pyridylmethyl)amino binding pockets connected by a dibenzofuran spacer. The reaction of FurNeu with CuCl yielded [FurNeu](Cu2(μ-Cl))(CuCl2), 1, demonstrating the geometric potential of the ligand to stabilize Cu-X-Cu moieties. A Cu(I) precursor with weakly coordinating anions was chosen in the next step, namely [Cu(NCCH3)4]OTf, which led to the formation of [FurNeu](Cu(NCCH3))2(OTf)2, 3. Treatment of 3 with O2 or PhIO led to identical green solutions, whose UV-vis spectra were markedly different from the one displayed by [FurNeu](Cu)2(OTf)4, 4, prepared independently from FurNeu and Cu(OTf)2. Further investigations including PhIO consumption experiments, NMR and UV-vis spectroscopy, HR-ESI mass spectrometry, and protonation studies led to the identification of the green product as [FurNeu](Cu2(μ-O))(OTf)2, 5. DOSY NMR spectroscopy confirmed its monomeric character. Over longer periods of time 5 decomposes to give [Cu(picoloyl)2], formed through an oxidative N-dealkylation reaction followed by further oxidation of the ligand. Due to its slow decomposition reaction, all attempts to crystallize 5 failed. However, its structure in solution could be determined by EXAFS analysis in combination with DFT calculations, which revealed a Cu-O-Cu angle that amounts to 105.17°. Moreover, TDDFT calculations helped to rationalize the UV-vis absorptions of 5. The reactivity of complex 5 with 2,4-di-tert-butylphenol, DTBP, was also investigated; the initially formed biphenol product, TBBP, was found to further react in the presence of excessive O2 to yield 2,4,7,9-tetra-tert-butyloxepino[2,3-b]benzofuran, TBOBF, via an intermediate diphenoquinone. It turned out that 5, or its precursor 3, can even be employed as a catalyst for the oxidation of DTBP to TBBP or for the oxidation of TBBP to TBOBF.
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Affiliation(s)
- Peter Haack
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Anne Kärgel
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Claudio Greco
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | | | - Beatrice Braun
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Florian F. Pfaff
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Stefan Mebs
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Kallol Ray
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Christian Limberg
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
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29
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Schweinfurth D, Khusniyarov MM, Bubrin D, Hohloch S, Su CY, Sarkar B. Tuning spin-spin coupling in quinonoid-bridged dicopper(II) complexes through rational bridge variation. Inorg Chem 2013; 52:10332-9. [PMID: 24010410 DOI: 10.1021/ic400955c] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bridged metal complexes [{Cu(tmpa)}2(μ-L(1)-2H)](ClO4)2 (1), [{Cu(tmpa)}2(μ-L(2)-2H)](ClO4)2 (2), [{Cu(tmpa)}2(μ-L(3)-2H)](BPh4)2 (3), and [{Cu(tmpa)}2(μ-L(4)-2H)](ClO4)2 (4) (tmpa = tris(2-pyridylmethyl)amine, L(1) = chloranilic acid, L(2) = 2,5-dihydroxy-1,4-benzoquinone, L(3) = (2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, L(4) = azophenine) were synthesized from copper(II) salts, tmpa, and the bridging quinonoid ligands in the presence of a base. X-ray structural characterization of the complexes showed a distorted octahedral environment around the copper(II) centers for the complexes 1-3, the donors being the nitrogen atoms of tmpa, and the nitrogen or oxygen donors of the bridging quinones. In contrast, the copper(II) centers in 4 display a distorted square-pyramidal coordination, where one of the pyridine arms of each tmpa remains uncoordinated. Bond-length analyses within the bridging ligand exhibit localization of the double bonds inside the bridge for 1-3. In contrast, complete delocalization of double bonds within the bridging ligand is observed for 4. Temperature-dependent magnetic susceptibility measurements on the complexes reveal an antiferromagnetic coupling between the copper(II) ions. The strength of antiferromagnetic coupling was observed to depend on the energy of the HOMO of the bridging quinone ligands, with exchange coupling constants J in the range between -23.2 and -0.6 cm(-1) and the strength of antiferromagnetic coupling of 4 > 3 > 2 > 1. Broken-symmetry density functional theory calculations (DFT) revealed that the orientation of magnetic orbitals in 1 and 2 is different than that in 3 and 4, and this results in two different exchange pathways. These results demonstrate how bridge-mediated spin-spin coupling in quinone-bridged metal complexes can be strongly tuned by a rational design of the bridging ligand employing the [O] for [NR] isoelectronic analogy.
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Affiliation(s)
- David Schweinfurth
- Institut für Chemie und Biochemie, Freie Universität Berlin , Fabeckstrasse 34-36, D-14195, Berlin, Germany
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30
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Hyvl J, Agrawal D, Pohl R, Suri M, Glorius F, Schröder D. Electrospray Ionization Mass Spectrometry Reveals an Unexpected Coupling Product in the Copper-Promoted Synthesis of Pyrazoles. Organometallics 2013. [DOI: 10.1021/om3010417] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jakub Hyvl
- Institute of Organic Chemistry
and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo Náměstí 2, 16610 Prague 6, Czech
Republic
| | - Divya Agrawal
- Institute of Organic Chemistry
and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo Náměstí 2, 16610 Prague 6, Czech
Republic
- Organic Chemistry and Biochemistry, Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Radek Pohl
- Institute of Organic Chemistry
and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo Náměstí 2, 16610 Prague 6, Czech
Republic
| | - Mamta Suri
- Organisch-Chemisches
Institut, International NRW Graduate School of Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Frank Glorius
- Organisch-Chemisches
Institut, International NRW Graduate School of Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Detlef Schröder
- Institute of Organic Chemistry
and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo Náměstí 2, 16610 Prague 6, Czech
Republic
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31
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Lionetti D, Day MW, Agapie T. Metal-Templated Ligand Architectures for Trinuclear Chemistry: Tricopper Complexes and Their O 2 Reactivity. Chem Sci 2012; 4:785-790. [PMID: 23539341 DOI: 10.1039/c2sc21758a] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
A trinucleating framework was assmbled by templation of a heptadentate ligand around yttrium and lanthanides. The generated complexes orient three sets of two or three N-donors each for binding additional metal centers. Addition of three equivalents of copper(I) leads to the formation of tricopper(I) species. Reactions with dioxygen at low temperatures generate species whose spectroscopic features are consistent with a μ3,μ3-dioxo-tricopper complex. Reactivity studies were performed with a variety of substrates. The dioxo-tricopper species deprotonates weak acids, undergoes oxygen atom transfer with one equivalent of triphenylphosphine to yield triphenylphosphine oxide, and abstracts two hydrogen atom equivalents from tetramethylpiperidine-N-hydroxide (TEMPO-H). Thiophenols reduce the oxygenated species to a CuI3 complex and liberate two equivalents of disulfide, consistent with a four-electron four-proton process.
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Affiliation(s)
- Davide Lionetti
- Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd. MC 127-72, Pasadena, CA 91125, USA
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Schweinfurth D, Demeshko S, Khusniyarov MM, Dechert S, Gurram V, Buchmeiser MR, Meyer F, Sarkar B. Capped-Tetrahedrally Coordinated Fe(II) and Co(II) Complexes Using a “Click”-Derived Tripodal Ligand: Geometric and Electronic Structures. Inorg Chem 2012; 51:7592-7. [DOI: 10.1021/ic300392e] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- David Schweinfurth
- Institut für
Anorganische
Chemie, Universität Stuttgart, Pfaffenwaldring
55, D-70550, Stuttgart, Germany
| | - Serhiy Demeshko
- Institut für Anorganische
Chemie, Georg-August Universität Göttingen, Tammanstrasse 4, D-37077, Göttingen, Germany
| | - Marat M. Khusniyarov
- Department Chemie und Pharmazie, Friedrich-Alexander Universität Erlangen-Nürnberg, Egerlandstrasse 1, D-91058, Erlangen, Germany
| | - Sebastian Dechert
- Institut für Anorganische
Chemie, Georg-August Universität Göttingen, Tammanstrasse 4, D-37077, Göttingen, Germany
| | | | - Michael R. Buchmeiser
- Institut für Polymerchemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550,
Stuttgart, Germany
| | - Franc Meyer
- Institut für Anorganische
Chemie, Georg-August Universität Göttingen, Tammanstrasse 4, D-37077, Göttingen, Germany
| | - Biprajit Sarkar
- Institut für
Anorganische
Chemie, Universität Stuttgart, Pfaffenwaldring
55, D-70550, Stuttgart, Germany
- Institut für Chemie und
Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstrasse 34-36, D-14195, Berlin, Germany
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Structure/function correlations among coupled binuclear copper proteins through spectroscopic and reactivity studies of NspF. Proc Natl Acad Sci U S A 2012; 109:10793-7. [PMID: 22711806 DOI: 10.1073/pnas.1208718109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The terminal step of 4-hydroxy-3-nitrosobenzamide biosynthesis in Streptomyces murayamaensis is performed by NspF, a mono-oxygenase that converts o-aminophenols to the corresponding nitroso product (hydroxyanilinase activity). Previous biochemical characterization of the resting form of NspF suggested that this enzyme belonged to the coupled binuclear copper enzyme (CBC) family. Another member of this enzyme family, tyrosinase, is able to mono-oxygenate monophenols (monophenolase activity) but not o-aminophenols. To gain insight into the unique reactivity of NspF, we have generated and characterized the oxy form of its active site. The observation of spectral features identical to those of oxy-tyrosinase indicates that oxy-NspF contains a Cu(2)O(2) core where peroxide is coordinated in a μ-η(2):η(2) mode, confirming that NspF is a CBC enzyme. This oxy form is found to react with monophenols, indicating that, like tyrosinase, NspF also possesses monophenolase activity. A comparison of the two electrophilic mechanisms for the monophenolase and hydroxyanilinase activity indicates a large geometric change between their respective transition states. The potential for specific interactions between the protein pocket and the substrate in each transition state is discussed within the context of the differential reactivity of this family of enzymes with equivalent μ-η(2):η(2) peroxy bridged coupled binuclear copper active sites.
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Park GY, Qayyum MF, Woertink J, Hodgson KO, Hedman B, Narducci Sarjeant AA, Solomon EI, Karlin KD. Geometric and electronic structure of [{Cu(MeAN)}2(μ-η2:η2(O2(2-)))]2+ with an unusually long O-O bond: O-O bond weakening vs activation for reductive cleavage. J Am Chem Soc 2012; 134:8513-24. [PMID: 22571744 DOI: 10.1021/ja300674m] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Certain side-on peroxo-dicopper(II) species with particularly low ν(O-O) (710-730 cm(-1)) have been found in equilibrium with their bis-μ-oxo-dicopper(III) isomer. An issue is whether such side-on peroxo bridges are further activated for O-O cleavage. In a previous study (Liang, H.-C., et al. J. Am. Chem. Soc.2002, 124, 4170), we showed that oxygenation of the three-coordinate complex [Cu(I)(MeAN)](+) (MeAN = N-methyl-N,N-bis[3-(dimethylamino)propyl]amine) leads to a low-temperature stable [{Cu(II)(MeAN)}(2)(μ-η(2):η(2)-O(2)(2-))](2+) peroxo species with low ν(O-O) (721 cm(-1)), as characterized by UV-vis absorption and resonance Raman (rR) spectroscopies. Here, this complex has been crystallized as its SbF(6)(-) salt, and an X-ray structure indicates the presence of an unusually long O-O bond (1.540(5) Å) consistent with the low ν(O-O). Extended X-ray absorption fine structure and rR spectroscopic and reactivity studies indicate the exclusive formation of [{Cu(II)(MeAN)}(2)(μ-η(2):η(2)-O(2)(2-))](2+) without any bis-μ-oxo-dicopper(III) isomer present. This is the first structure of a side-on peroxo-dicopper(II) species with a significantly long and weak O-O bond. DFT calculations show that the weak O-O bond results from strong σ donation from the MeAN ligand to Cu that is compensated by a decrease in the extent of peroxo to Cu charge transfer. Importantly, the weak O-O bond does not reflect an increase in backbonding into the σ* orbital of the peroxide. Thus, although the O-O bond is unusually weak, this structure is not further activated for reductive cleavage to form a reactive bis-μ-oxo dicopper(III) species. These results highlight the necessity of understanding electronic structure changes associated with spectral changes for correlations to reactivity.
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Affiliation(s)
- Ga Young Park
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
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35
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Comba P, Haaf C, Helmle S, Karlin KD, Pandian S, Waleska A. Dioxygen reactivity of new bispidine-copper complexes. Inorg Chem 2012; 51:2841-51. [PMID: 22332786 DOI: 10.1021/ic2019296] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The reactivity of copper complexes of three different second-generation bispidine-based ligands (bispidine = 3,7-diazabicyclo[3.3.1]nonane; mono- and bis-tetradentate; exclusively tertiary amine donors) with dioxygen [(reversible) binding of dioxygen by copper(I)] is reported. The UV-vis, electrospray ionization mass spectrometry, electron paramagnetic resonance, and vibrational spectra (resonance Raman) of the dioxygen adducts indicate that, depending on the ligand and reaction conditions, several different species (mono- and dinuclear, superoxo, peroxo, and hydroperoxo), partially in equilibrium with each other, are formed. Minor changes in the ligand structure and/or experimental conditions (solvent, temperature, relative concentrations) allow switching between the different forms. With one of the ligands, an end-on peroxodicopper(II) complex and a mononuclear hydroperoxocopper(II) complex could be characterized. With another ligand, reversible dioxygen binding was observed, leading to a metastable superoxocopper(II) complex. The amount of dioxygen involved in the reversible binding to Cu(I) was determined quantitatively. The mechanism of dioxygen binding as well as the preference of each of the three ligands for a particular dioxygen adduct is discussed on the basis of a computational (density functional theory) analysis.
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Affiliation(s)
- Peter Comba
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270, D-69120 Heidelberg, Germany.
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36
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Reversible dioxygen binding and arene hydroxylation reactions: Kinetic and thermodynamic studies involving ligand electronic and structural variations. Inorganica Chim Acta 2012; 389:138-150. [PMID: 23420124 DOI: 10.1016/j.ica.2012.01.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Copper-dioxygen interactions are of intrinsic importance in a wide range of biological and industrial processes. Here, we present detailed kinetic/thermodynamic studies on the O(2)-binding and arene hydroxylation reactions of a series of xylyl-bridged binuclear copper(I) complexes, where the effects of ligand electronic and structural elements on these reactions are investigated. Ligand 4-pyridyl substituents influence the reversible formation of side-on bound μ-η(2):η(2)-peroxodicopper(II) complexes, with stronger donors leading to more rapid formation and greater thermodynamic stability of product complexes [Cu(II) (2)((R)XYL)(O(2) (2-))](2+). An interaction of the latter with the xylyl π-system is indicated. Subsequent peroxo electrophilic attack on the arene leads to C-H activation and oxygenation with hydroxylated products [Cu(II) (2)((R)XYLO(2-))((-)OH)](2+) being formed. A related unsymmetrical binucleating ligand was also employed. Its corresponding O(2)-adduct [Cu(II) (2)(UN)(O(2) (2-))](2+) is more stable, but primarily because the subsequent decay by hydroxylation is in a relative sense slower. The study emphasizes how ligand electronic effects can and do influence and tune copper(I)-dioxygen complex formation and subsequent reactivity.
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37
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Siluvai GS, Vargheese B, Murthy NN. H2O2 reactivity of a dinuclear copper(II) complex incorporating a constrained binucleating polyaminopyridyl ligand and a phosphodiester coligand. Inorganica Chim Acta 2011. [DOI: 10.1016/j.ica.2011.04.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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38
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Bidentate guanidine ligands with ethylene spacer in copper-dioxygen chemistry: Structural characterization of bis(μ-hydroxo) dicopper complexes. Inorganica Chim Acta 2011. [DOI: 10.1016/j.ica.2011.02.061] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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39
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Takahashi A, Kurahashi T, Fujii H. Redox Potentials of Oxoiron(IV) Porphyrin π-Cation Radical Complexes: Participation of Electron Transfer Process in Oxygenation Reactions. Inorg Chem 2011; 50:6922-8. [DOI: 10.1021/ic102564e] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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40
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Weisser F, Huebner R, Schweinfurth D, Sarkar B. Energy-Level Tailoring in a Series of Redox-Rich Quinonoid-Bridged Diruthenium Complexes Containing Tris(2-pyridylmethyl)amine as a Co-Ligand. Chemistry 2011; 17:5727-36. [DOI: 10.1002/chem.201003253] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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41
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Zhang L, Ang GY, Chiba S. Copper-Catalyzed Benzylic C−H Oxygenation under an Oxygen Atmosphere via N-H Imines as an Intramolecular Directing Group. Org Lett 2011; 13:1622-5. [DOI: 10.1021/ol200425c] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Line Zhang
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Gim Yean Ang
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Shunsuke Chiba
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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42
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Lucas HR, Meyer GJ, Karlin KD. CO and O2 binding to pseudo-tetradentate ligand-copper(I) complexes with a variable N-donor moiety: kinetic/thermodynamic investigation reveals ligand-induced changes in reaction mechanism. J Am Chem Soc 2011; 132:12927-40. [PMID: 20726586 DOI: 10.1021/ja104107q] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The kinetics, thermodynamics, and coordination dynamics are reported for O(2) and CO 1:1 binding to a series of pseudo-tetradentate ligand-copper(I) complexes ((D)LCu(I)) to give Cu(I)/O(2) and Cu(I)/CO product species. Members of the (D)LCu(I) series possess an identical tridentate core structure where the cuprous ion binds to the bispicolylamine (L) fragment. (D)L also contains a fourth variable N-donor moiety {D = benzyl (Bz); pyridyl (Py); imidazolyl (Im); dimethylamino (NMe(2)); (tert-butylphenyl)pyridyl (TBP); quinolyl (Q)}. The structural characteristics of (D)LCu(I)-CO and (D)LCu(I) are detailed, with X-ray crystal structures reported for (TBP)LCu(I)-CO, (Bz)LCu(I)-CO, and (Q)LCu(I). Infrared studies (solution and solid-state) confirm that (D)LCu(I)-CO possess the same four-coordinate core structure in solution with the variable D moiety "dangling", i.e., not coordinated to the copper(I) ion. Other trends observed for the present series appear to derive from the degree to which the D-group interacts with the cuprous ion center. Electrochemical studies reveal close similarities of behavior for (Im)LCu(I) and (NMe(2))LCu(I) (as well as for (TBP)LCu(I) and (Q)LCu(I)), which relate to the O(2) binding kinetics and thermodynamics. Equilibrium CO binding data (K(CO), ΔH°, ΔS°) were obtained by conducting UV-visible spectrophotometric CO titrations, while CO binding kinetics and thermodynamics (k(CO), ΔH(double dagger), ΔS(double dagger)) were measured through variable-temperature (193-293 K) transient absorbance laser flash photolysis experiments, λ(ex) = 355 nm. Carbon monoxide dissociation rate constants (k(-CO)) and corresponding activation parameters (ΔH(double dagger), ΔS(double dagger)) have also been obtained. CO binding to (D)LCu(I) follows an associative mechanism, with the increased donation from D leading to higher k(CO) values. Unlike observations from previous work, the K(CO) values increased as the k(CO) and k(-CO) values declined; the latter decreased at a faster rate. By using the "flash-and-trap" method (λ(ex) = 355 nm, 188-218 K), the kinetics and thermodynamics (k(O(2)), ΔH(double dagger), ΔS(double dagger)) for O(2) binding to (NMe(2))LCu(I) and (Im)LCu(I) were measured and compared to those for (Py)LCu(I). A surprising change in the O(2) binding mechanism was deduced from the thermodynamic ΔS(double dagger) values observed, associative for (Py)LCu(I) but dissociative for (NMe(2))LCu(I) and (Im)LCu(I); these results are interpreted as arising from a difference in the timing of electron transfer from copper(I) to O(2) as this molecule coordinates and a tetrahydrofuran (THF) solvent molecule dissociates. The change in mechanism was not simply related to alterations in (D)LCu(II/I) geometries or the order in which O(2) and THF coordinate. The equilibrium O(2) binding constant (K(O(2)), ΔH°, ΔS°) and O(2) dissociation rate constants (k(-O(2)), ΔH(double dagger), ΔS(double dagger)) were also determined. Overall the results demonstrate that subtle changes in the coordination environment, as occur over time through evolution in nature or through controlled ligand design in synthetic systems, dictate to a critically detailed level the observed chemistry in terms of reaction kinetics, structure, and reactivity, and thus function. Results reported here are also compared to relevant copper and/or iron biological systems and analogous synthetic ligand-copper systems.
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Affiliation(s)
- Heather R Lucas
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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43
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Warren JJ, Tronic TA, Mayer JM. Thermochemistry of proton-coupled electron transfer reagents and its implications. Chem Rev 2010; 110:6961-7001. [PMID: 20925411 PMCID: PMC3006073 DOI: 10.1021/cr100085k] [Citation(s) in RCA: 1193] [Impact Index Per Article: 85.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Jeffrey J. Warren
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
| | - Tristan A. Tronic
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
| | - James M. Mayer
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
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44
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Hanson SK, Baker RT, Gordon JC, Scott BL, Silks LAP, Thorn DL. Mechanism of alcohol oxidation by dipicolinate vanadium(V): unexpected role of pyridine. J Am Chem Soc 2010; 132:17804-16. [PMID: 21121665 DOI: 10.1021/ja105739k] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dipicolinate vanadium(V) alkoxide complexes (dipic)V(V)(O)(OR) (OR = isopropoxide (1), n-butanoxide (2), cyclobutanoxide (3), and α-tert-butylbenzylalkoxide (4)) react with pyridine to afford vanadium(IV) and 0.5 equiv of an aldehyde or ketone product. The role of pyridine in the reaction has been investigated. Both NMR and X-ray crystallography experiments indicate that pyridine coordinates to 1, which is in equilibrium with (dipic)V(V)(O)(O(i)Pr)(pyr) (1-Pyr). Kinetic studies of the alcohol oxidation suggest a pathway where the rate-limiting step is bimolecular and involves attack of pyridine on the C-H bond of the isopropoxide ligand of 1 or 1-Pyr. The oxidations of mechanistic probes cyclobutanol and α-tert-butylbenzylalcohol support a two-electron pathway proceeding through a vanadium(III) intermediate. The alcohol oxidation reaction is promoted by more basic pyridines and facilitated by electron-withdrawing substituents on the dipicolinate ligand. The involvement of base in the elementary alcohol oxidation step observed for the dipicolinate system is an unprecedented mechanism for vanadium-mediated alcohol oxidation and suggests new ways to tune reactivity and selectivity of vanadium catalysts.
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Affiliation(s)
- Susan K Hanson
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, United States.
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45
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Roberts KM, Jones JP. Anilinic N-oxides support cytochrome P450-mediated N-dealkylation through hydrogen-atom transfer. Chemistry 2010; 16:8096-107. [PMID: 20521282 DOI: 10.1002/chem.201000185] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mechanism of N-dealkylation mediated by cytochrome P450 (P450) has long been studied and argued as either a single electron transfer (SET) or a hydrogen atom transfer (HAT) from the amine to the oxidant of the P450, the reputed iron-oxene. In our study, tertiary anilinic N-oxides were used as oxygen surrogates to directly generate a P450-mediated oxidant that is capable of N-dealkylating the dimethylaniline derived from oxygen donation. These surrogates were employed to probe the generated reactive oxygen species and the subsequent mechanism of N-dealkylation to distinguish between the HAT and SET mechanisms. In addition to the expected N-demethylation of the product aniline, 2,3,4,5,6-pentafluoro-N,N-dimethylaniline N-oxide (PFDMAO) was found to be capable of N-dealkylating both N,N-dimethylaniline (DMA) and N-cyclopropyl-N-methylaniline (CPMA). Rate comparisons of the N-demethylation of DMA supported by PFDMAO show a 27-fold faster rate than when supported by N,N-dimethylaniline N-oxide (DMAO). Whereas intermolecular kinetic isotope effects were masked, intramolecular measurements showed values reflective of those seen previously in DMAO- and the native NADPH/O(2)-supported systems (2.33 and 2.8 for the N-demethylation of PFDMA and DMA from the PFDMAO system, respectively). PFDMAO-supported N-dealkylation of CPMA led to the ring-intact product N-cyclopropylaniline (CPA), similar to that seen with the native system. The formation of CPA argues against a SET mechanism in favor of a P450-like HAT mechanism. We suggest that the similarity of KIEs, in addition to the formation of the ring-intact CPA, argues for a similar mechanism of Compound I (Cpd I) formation followed by HAT for N-dealkylation by the native and N-oxide-supported systems and demonstrate the ability of the N-oxide-generated oxidant to act as an accurate mimic of the native P450 oxidant.
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Affiliation(s)
- Kenneth M Roberts
- Department of Chemistry, Washington State University, PO BOX 644630, Pullman, WA 99164-4630, USA
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Toluene and ethylbenzene aliphatic C-H bond oxidations initiated by a dicopper(II)-mu-1,2-peroxo complex. J Am Chem Soc 2010; 131:3230-45. [PMID: 19216527 DOI: 10.1021/ja807081d] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
With an anisole-containing polypyridylamine potential tetradentate ligand (O)L, a mu-1,2-peroxo-dicopper(II) complex [{(O)LCu(II)}(2)(O(2)(2-))](2+) forms from the reaction of the mononuclear compound [Cu(I)((O)L)(MeCN)]B(C(6)F(5))(4) ((O)LCu(I)) with O(2) in noncoordinating solvents at -80 degrees C. Thermal decay of this peroxo complex in the presence of toluene or ethylbenzene leads to rarely seen C-H activation chemistry; benzaldehyde and acetophenone/1-phenylethanol mixtures, respectively, are formed. Experiments with (18)O(2) confirm that the oxygen source in the products is molecular O(2) and deuterium labeling experiments indicate k(H)/k(D) = 7.5 +/- 1 for the toluene oxygenation. The O(2)-reaction of [Cu(I)((Bz)L)(CH(3)CN)](+) ((Bz)LCu(I)) leads to a dicopper(III)-bis-mu-oxo species [{(Bz)LCu(III)}(2)(mu-O(2-))(2)](2+) at -80 degrees C, and from such solutions, very similar toluene oxygenation chemistry occurs. Ligand (Bz)L is a tridentate chelate, possessing the same moiety found in (O)L, but without the anisole O-atom donor. In these contexts, the nature of the oxidant species in or derived from [{(O)LCu(II)}(2)(O(2)(2-))](2+) is discussed and likely mechanisms of reaction initiated by toluene H-atom abstraction chemistry are detailed. To confirm the structural formulations of the dioxygen-adducts, UV-vis and resonance Raman spectroscopic studies have been carried out and these results are reported and compared to previously described systems including [{Cu(II)((Py)L)}(2)(O(2))](2+) ((Py)L = TMPA = tris(2-methylpyridyl)amine). Using (L)Cu(I), CO-binding properties (i.e., nu(C-O) values) along with electrochemical property comparisons, the relative donor abilities of (O)L, (Bz)L, and (Py)L are assessed.
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47
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Chiba S, Zhang L, Lee JY. Copper-Catalyzed Synthesis of Azaspirocyclohexadienones from α-Azido-N-arylamides under an Oxygen Atmosphere. J Am Chem Soc 2010; 132:7266-7. [DOI: 10.1021/ja1027327] [Citation(s) in RCA: 190] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shunsuke Chiba
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Line Zhang
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Jian-Yuan Lee
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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48
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Halime Z, Kieber-Emmons MT, Qayyum MF, Mondal B, Gandhi T, Puiu SC, Chufán EE, Sarjeant AAN, Hodgson KO, Hedman B, Solomon EI, Karlin KD. Heme-copper-dioxygen complexes: toward understanding ligand-environmental effects on the coordination geometry, electronic structure, and reactivity. Inorg Chem 2010; 49:3629-45. [PMID: 20380465 PMCID: PMC2893725 DOI: 10.1021/ic9020993] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nature of the ligand is an important aspect of controlling the structure and reactivity in coordination chemistry. In connection with our study of heme-copper-oxygen reactivity relevant to cytochrome c oxidase dioxygen-reduction chemistry, we compare the molecular and electronic structures of two high-spin heme-peroxo-copper [Fe(III)O(2)(2-)Cu(II)](+) complexes containing N(4) tetradentate (1) or N(3) tridentate (2) copper ligands. Combining previously reported and new resonance Raman and EXAFS data coupled to density functional theory calculations, we report a geometric structure and more complete electronic description of the high-spin heme-peroxo-copper complexes 1 and 2, which establish mu-(O(2)(2-)) side-on to the Fe(III) and end-on to Cu(II) (mu-eta(2):eta(1)) binding for the complex 1 but side-on/side-on (mu-eta(2):eta(2)) mu-peroxo coordination for the complex 2. We also compare and summarize the differences and similarities of these two complexes in their reactivity toward CO, PPh(3), acid, and phenols. The comparison of a new X-ray structure of mu-oxo complex 2a with the previously reported 1a X-ray structure, two thermal decomposition products respectively of 2 and 1, reveals a considerable difference in the Fe-O-Cu angle between the two mu-oxo complexes ( angleFe-O-Cu = 178.2 degrees in 1a and angleFe-O-Cu = 149.5 degrees in 2a). The reaction of 2 with 1 equiv of an exogenous nitrogen-donor axial base leads to the formation of a distinctive low-temperature-stable, low-spin heme-dioxygen-copper complex (2b), but under the same conditions, the addition of an axial base to 1 leads to the dissociation of the heme-peroxo-copper assembly and the release of O(2). 2b reacts with phenols performing H-atom (e(-) + H(+)) abstraction resulting in O-O bond cleavage and the formation of high-valent ferryl [Fe(IV)=O] complex (2c). The nature of 2c was confirmed by a comparison of its spectroscopic features and reactivity with those of an independently prepared ferryl complex. The phenoxyl radical generated by the H-atom abstraction was either (1) directly detected by electron paramagnetic resonance spectroscopy using phenols that produce stable radicals or (2) indirectly detected by the coupling product of two phenoxyl radicals.
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Affiliation(s)
- Zakaria Halime
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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49
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Affiliation(s)
- Ahmet Gunay
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Klaus H. Theopold
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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Yao S, Xiong Y, Vogt M, Grützmacher H, Herwig C, Limberg C, Driess M. O-O bond activation in heterobimetallic peroxides: synthesis of the peroxide [LNi(mu,eta2:eta2-O2)K] and its conversion into a bis(mu-hydroxo) nickel zinc complex. Angew Chem Int Ed Engl 2010; 48:8107-10. [PMID: 19768826 DOI: 10.1002/anie.200903772] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Shenglai Yao
- Technische Universität Berlin, Institute of Chemistry: Metalorganics and Inorganic Materials, Sekr. C2, Strasse des 17. Juni 135, 10623 Berlin, Germany
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