1
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Gupta K, Datta A. An activity-based fluorescent sensor with a penta-coordinate N-donor binding site detects Cu ions in living systems. Chem Commun (Camb) 2023; 59:8282-8285. [PMID: 37318277 DOI: 10.1039/d3cc02201c] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
An activity-based sensor afforded a 63 times fluorescence-enhancement with Cu2+/Cu+ ions and could image Cu2+/Cu+ in living cells and in a multicellular organism. The sensor functioned only in the presence of ambient dioxygen and glutathione, and the characterization of intermediates and products hinted toward a sensing mechanism involving a CuII hydroperoxo species.
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Affiliation(s)
- Kunika Gupta
- Department of Chemical Sciences, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Ankona Datta
- Department of Chemical Sciences, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai-400005, India.
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2
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Roy M, Nath AK, Pal I, Dey SG. Second Sphere Interactions in Amyloidogenic Diseases. Chem Rev 2022; 122:12132-12206. [PMID: 35471949 DOI: 10.1021/acs.chemrev.1c00941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amyloids are protein aggregates bearing a highly ordered cross β structural motif, which may be functional but are mostly pathogenic. Their formation, deposition in tissues and consequent organ dysfunction is the central event in amyloidogenic diseases. Such protein aggregation may be brought about by conformational changes, and much attention has been directed toward factors like metal binding, post-translational modifications, mutations of protein etc., which eventually affect the reactivity and cytotoxicity of the associated proteins. Over the past decade, a global effort from different groups working on these misfolded/unfolded proteins/peptides has revealed that the amino acid residues in the second coordination sphere of the active sites of amyloidogenic proteins/peptides cause changes in H-bonding pattern or protein-protein interactions, which dramatically alter the structure and reactivity of these proteins/peptides. These second sphere effects not only determine the binding of transition metals and cofactors, which define the pathology of some of these diseases, but also change the mechanism of redox reactions catalyzed by these proteins/peptides and form the basis of oxidative damage associated with these amyloidogenic diseases. The present review seeks to discuss such second sphere modifications and their ramifications in the etiopathology of some representative amyloidogenic diseases like Alzheimer's disease (AD), type 2 diabetes mellitus (T2Dm), Parkinson's disease (PD), Huntington's disease (HD), and prion diseases.
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Affiliation(s)
- Madhuparna Roy
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Arnab Kumar Nath
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Ishita Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Somdatta Ghosh Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
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3
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Theoretical perspective on mononuclear copper-oxygen mediated C–H and O–H activations: A comparison between biological and synthetic systems. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(21)63974-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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4
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Quek SY, Debnath S, Laxmi S, van Gastel M, Krämer T, England J. Sterically Stabilized End-On Superoxocopper(II) Complexes and Mechanistic Insights into Their Reactivity with O-H, N-H, and C-H Substrates. J Am Chem Soc 2021; 143:19731-19747. [PMID: 34783549 DOI: 10.1021/jacs.1c07837] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Instability of end-on superoxocopper(II) complexes, with respect to conversion to peroxo-bridged dicopper(II) complexes, has largely constrained their study to very low temperatures. This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of bulky ligands, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support copper(I) complexes that react with O2 to yield [CuII(η1-O2•-)(Ar3-TMPA)]+ species, which are stable against dimerization at all temperatures. Binding of O2 saturates at subambient temperatures and can be reversed by warming. The onset of oxygenation for the Ar = tpb and dpb systems is observed at 25 °C, and all three [CuII(η1-O2•-)(Ar3-TMPA)]+ complexes are stable against self-decay at temperatures of ≤-20 °C. This provides a wide temperature window for study of these complexes, which was exploited by performing extensive reaction kinetics measurements for [CuII(η1-O2•-)(tpb3-TMPA)]+ using a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2) versus oxidation potentials (Eox) for a range of phenols, construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicate that reaction with all substrates proceeds via H atom transfer (HAT), reaction with the phenols proceeds with significant charge transfer, and full tunneling of both H and D atoms occurs in the case of 1,2-diphenylhydrazine and 4-methoxy-2,6-di-tert-butylphenol. Oxidation of C-H bonds proved to be kinetically challenging, and whereas [CuII(η1-O2•-)(tpb3-TMPA)]+ can oxidize moderately strong O-H and N-H bonds, it is only able to oxidize very weak C-H bonds.
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Affiliation(s)
- Sebastian Y Quek
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Suman Debnath
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Shoba Laxmi
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Maurice van Gastel
- Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr D-45470, Germany
| | - Tobias Krämer
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare W23 F2H6, Ireland.,Hamilton Institute, Maynooth University, Maynooth, Co. Kildare W23 F2H6, Ireland
| | - Jason England
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.,Department of Chemistry, University of Lincoln, Lincoln LN6 7TW, U.K
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5
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Berthonnaud L, Esmieu C, Mallet-Ladeira S, Hureau C. Solid-state and solution characterizations of [(TMPA)Cu(II)(SO 3)] and [(TMPA)Cu(II)(S 2O 3)] complexes: Application to sulfite and thiosulfate fast detection. J Inorg Biochem 2021; 225:111601. [PMID: 34597885 DOI: 10.1016/j.jinorgbio.2021.111601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/03/2021] [Accepted: 09/09/2021] [Indexed: 10/20/2022]
Abstract
Sulfite (SO32-) and thiosulfate (S2O32-) ions are used as food preservative and antichlor agent respectively. To detect low levels of such anions we used Cu(II) complex of the Tris-Methyl Pyridine Amine (TMPA) ligand, denoted L. Formation of [LCu(SO3)] (1) and [LCu(S2O3)] (2) in solution were monitored using UV-Vis, EPR and cyclic voltammetry, while the solid-state X-ray structures of both complexes were solved. In addition, we also evaluated the pH range in which the complexes are stable, and the anions binding affinity values for the [LCu(solvent)]2+ (3) parent complex. As a matter of illustration, we determined the sulfite content in a commercial crystal sugar.
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Affiliation(s)
- Léonie Berthonnaud
- LCC-CNRS, Université de Toulouse, CNRS, Toulouse, France; Division of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, Japan
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6
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Sarkar S, Kim M, Lee H. Catecholase Activities of Copper(
II
) Complexes With
N
4
Ligands. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Shuranjan Sarkar
- Department of Chemistry and Green‐Nano Research Center Kyungpook National University Daegu 41566 Republic of Korea
- Chemistry Division Bangladesh Jute Research Institute Dhaka 1207 Bangladesh
| | - Minyoung Kim
- Department of Chemistry and Green‐Nano Research Center Kyungpook National University Daegu 41566 Republic of Korea
| | - Hong‐In Lee
- Department of Chemistry and Green‐Nano Research Center Kyungpook National University Daegu 41566 Republic of Korea
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7
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Morimoto Y, Kawai M, Nakanishi A, Sugimoto H, Itoh S. Controlling the Reactivity of Copper(II) Acylperoxide Complexes. Inorg Chem 2021; 60:8554-8565. [PMID: 33848148 DOI: 10.1021/acs.inorgchem.1c00475] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The redox state of the metallomonooxygenases is finely tuned by imposing specific coordination environments on the metal center to reduce the activation energy for the generation of active-oxygen species and subsequent substrate oxygenation reactions. In this study, copper(II) complexes supported by a series of linear tetradentate ligands consisting of a rigid 6-, 7-, or 8-membered cyclic diamine with two pyridylmethyl (-CH2Py) side arms (L6Pym2, L7Pym2, and L8Pym2) are employed to examine the effects of the coordination environment on the reactivity of their acylperoxide adduct complexes. The UV-vis and electron paramagnetic resonance spectroscopic data indicate that the ligand-field splitting between the dx2-y2 and dz2 orbitals of the starting copper(II) complexes increase with an increase of the ring size of the diamine moiety (L6Pym2 → L7Pym2 → L8Pym2). In the reaction of these copper(II) complexes with m-chloroperbenzoic acid (m-CPBA), the L6Pym2 complex gives a stable m-CPBA adduct complex, whereas the L7Pym2 and L8Pym2 complexes are immediately converted to the corresponding m-chlorobenzoic acid (m-CBA) adducts, indicating that the reactivity of the copper(II) acylperoxide complexes largely depends on the coordination environment induced by the supporting ligands. Density functional theory (DFT) calculations on the m-CPBA adduct complexes show that the ligand-field-splitting energy increases with an increase of the ring size of the diamine moiety, as in the case of the starting copper(II) complexes, which enhances the reactivity of the m-CPBA adduct complexes. The reasons for such different reactivities of the m-CPBA adduct complexes are evaluated by using DFT calculations.
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Affiliation(s)
- Yuma Morimoto
- Department of Molecular Chemistry, Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Makito Kawai
- Department of Molecular Chemistry, Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Aya Nakanishi
- Department of Molecular Chemistry, Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hideki Sugimoto
- Department of Molecular Chemistry, Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shinobu Itoh
- Department of Molecular Chemistry, Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
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8
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Guo M, Lee YM, Fukuzumi S, Nam W. Biomimetic metal-oxidant adducts as active oxidants in oxidation reactions. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.213807] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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9
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Nath AK, Ghatak A, Dey A, Dey SG. Intermediates involved in serotonin oxidation catalyzed by Cu bound Aβ peptides. Chem Sci 2020; 12:1924-1929. [PMID: 34163956 PMCID: PMC8179298 DOI: 10.1039/d0sc06258h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The degradation of neurotransmitters is a hallmark feature of Alzheimer's disease (AD). Copper bound Aβ peptides, invoked to be involved in the pathology of AD, are found to catalyze the oxidation of serotonin (5-HT) by H2O2. A combination of EPR and resonance Raman spectroscopy reveals the formation of a Cu(ii)–OOH species and a dimeric, EPR silent, Cu2O2 bis-μ-oxo species under the reaction conditions. The Cu(ii)–OOH species, which can be selectively formed in the presence of excess H2O2, is the reactive intermediate responsible for 5-HT oxidation. H2O2 produced by the reaction of O2 with reduced Cu(i)–Aβ species can also oxidize 5-HT. Both these pathways are physiologically relevant and may be involved in the observed decay of neurotransmitters as observed in AD patients. The mononuclear copper hydroperoxo species (Cu(ii)–OOH) of Cu–Aβ is the active oxidant responsible for serotonin oxidation by Cu–Aβ in the presence of physiologically relevant oxidants like O2 and H2O2, which can potentially cause oxidative degradation of neurotransmitters, a marker of Alzheimer's disease.![]()
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Affiliation(s)
- Arnab Kumar Nath
- Indian Association for the Cultivation of Science 2A & 2B, Raja S. C. Mullick Road, Jadavpur Kolkata 700032 India
| | - Arnab Ghatak
- Indian Association for the Cultivation of Science 2A & 2B, Raja S. C. Mullick Road, Jadavpur Kolkata 700032 India
| | - Abhishek Dey
- Indian Association for the Cultivation of Science 2A & 2B, Raja S. C. Mullick Road, Jadavpur Kolkata 700032 India
| | - Somdatta Ghosh Dey
- Indian Association for the Cultivation of Science 2A & 2B, Raja S. C. Mullick Road, Jadavpur Kolkata 700032 India
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10
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Mononuclear copper(II) complexes containing a macrocyclic ditopic ligand: Synthesis, structures and properties. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2019.119081] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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11
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Will J, Würtele C, Becker J, Walter O, Schindler S. Synthesis, crystal structures and reactivity towards dioxygen of copper(I) complexes with tripodal aliphatic amine ligands. Polyhedron 2019. [DOI: 10.1016/j.poly.2019.07.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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12
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Oh H, Ching WM, Kim J, Lee WZ, Hong S. Hydrogen Bond-Enabled Heterolytic and Homolytic Peroxide Activation within Nonheme Copper(II)-Alkylperoxo Complexes. Inorg Chem 2019; 58:12964-12974. [DOI: 10.1021/acs.inorgchem.9b01898] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Hana Oh
- Department of Chemistry, Sookmyung Women’s University, Seoul 04310, Korea
| | - Wei-Min Ching
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan
- Instrumental Center, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Jin Kim
- Western Seoul Centre, Korea Basic Science Institute, Seoul 03759, Republic of Korea
| | - Way-Zen Lee
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Seungwoo Hong
- Department of Chemistry, Sookmyung Women’s University, Seoul 04310, Korea
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13
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Singh N, Botcha NK, Jones TM, Ertem MZ, Niklas J, Farquhar ER, Poluektov OG, Mukherjee A. Reactivity of bio-inspired Cu(II) (N2/Py2) complexes with peroxide at room temperature. J Inorg Biochem 2019; 197:110674. [DOI: 10.1016/j.jinorgbio.2019.03.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 03/05/2019] [Accepted: 03/18/2019] [Indexed: 12/01/2022]
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14
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Kim B, Jeong D, Ohta T, Cho J. Nucleophilic reactivity of a copper(II)-hydroperoxo complex. Commun Chem 2019. [DOI: 10.1038/s42004-019-0187-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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15
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Nag SS, Mukherjee G, Barman P, Sastri CV. Influence of induced steric on the switchover reactivity of mononuclear Cu(II)-alkylperoxo complexes. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2018.09.087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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16
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Adam SM, Wijeratne GB, Rogler PJ, Diaz DE, Quist DA, Liu JJ, Karlin KD. Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function. Chem Rev 2018; 118:10840-11022. [PMID: 30372042 PMCID: PMC6360144 DOI: 10.1021/acs.chemrev.8b00074] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.
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Affiliation(s)
- Suzanne M. Adam
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Gayan B. Wijeratne
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Patrick J. Rogler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Daniel E. Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jeffrey J. Liu
- 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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17
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Paria S, Ohta T, Morimoto Y, Sugimoto H, Ogura T, Itoh S. Structure and Reactivity of Copper Complexes Supported by a Bulky Tripodal N
4
Ligand: Copper(I)/Dioxygen Reactivity and Formation of a Hydroperoxide Copper(II) Complex. Z Anorg Allg Chem 2018. [DOI: 10.1002/zaac.201800083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Sayantan Paria
- Department of Material and Life Science Division of Advanced Science and Biotechnology Graduate School of Engineering Osaka University 2‐1 Yamada‐oka 565–0871 Osaka Suita Japan
- Graduate School of Life Science Department of Chemistry Indian Institute of Technology Delhi Hauz Khas 110016 New Delhi India
| | - Takehiro Ohta
- Picobiology Institute Graduate School of Life Science University of Hyogo RSC‐UH LP Center 679–5148 Hyogo Koto 1‐1‐1, Sayo‐cho, Sayo‐gun Japan
| | - Yuma Morimoto
- Department of Material and Life Science Division of Advanced Science and Biotechnology Graduate School of Engineering Osaka University 2‐1 Yamada‐oka 565–0871 Osaka Suita Japan
| | - Hideki Sugimoto
- Department of Material and Life Science Division of Advanced Science and Biotechnology Graduate School of Engineering Osaka University 2‐1 Yamada‐oka 565–0871 Osaka Suita Japan
| | - Takashi Ogura
- Picobiology Institute Graduate School of Life Science University of Hyogo RSC‐UH LP Center 679–5148 Hyogo Koto 1‐1‐1, Sayo‐cho, Sayo‐gun Japan
| | - Shinobu Itoh
- Department of Material and Life Science Division of Advanced Science and Biotechnology Graduate School of Engineering Osaka University 2‐1 Yamada‐oka 565–0871 Osaka Suita Japan
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18
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Trammell R, See YY, Herrmann AT, Xie N, Díaz DE, Siegler MA, Baran PS, Garcia-Bosch I. Decoding the Mechanism of Intramolecular Cu-Directed Hydroxylation of sp 3 C-H Bonds. J Org Chem 2017; 82:7887-7904. [PMID: 28654755 PMCID: PMC5792191 DOI: 10.1021/acs.joc.7b01069] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The use of copper in directed C-H oxidation has been relatively underexplored. In a seminal example, Schönecker showed that copper and O2 promoted the hydroxylation of steroid-containing ligands. Recently, Baran (J. Am. Chem. Soc. 2015, 137, 13776) improved the reaction conditions to oxidize similar substrates with excellent yields. In both reports, the involvement of Cu2O2 intermediates was suggested. In this collaborative article, we studied the hydroxylation mechanism in great detail, resulting in the overhaul of the previously accepted mechanism and the development of improved reaction conditions. Extensive experimental evidence (spectroscopic characterization, kinetic analysis, intermolecular reactivity, and radical trap experiments) is provided to support each of the elementary steps proposed and the hypothesis that a key mononuclear LCuII(OOR) intermediate undergoes homolytic O-O cleavage to generate reactive RO• species, which are responsible for key C-H hydroxylation within the solvent cage. These key findings allowed the oxidation protocol to be reformulated, leading to improvements of the reaction cost, practicability, and isolated yield.
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Affiliation(s)
- Rachel Trammell
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
| | - Yi Yang See
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Aaron T. Herrmann
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Nan Xie
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
| | - Daniel E. Díaz
- Johns Hopkins University, Baltimore, Maryland 21218, United States
| | | | - Phil S. Baran
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Isaac Garcia-Bosch
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
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19
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Neisen BD, Gagnon NL, Dhar D, Spaeth AD, Tolman WB. Formally Copper(III)-Alkylperoxo Complexes as Models of Possible Intermediates in Monooxygenase Enzymes. J Am Chem Soc 2017; 139:10220-10223. [PMID: 28722408 DOI: 10.1021/jacs.7b05754] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Reaction of [NBu4][LCuIIOH] with excess ROOH (R = cumyl or tBu) yielded [NBu4][LCuIIOOR], the reversible one-electron oxidation of which generated novel species with [CuOOR]2+ cores (formally CuIIIOOR), identified by spectroscopy and theory for the case R = cumyl. This species reacts with weak O-H bonds in TEMPO-H and 4-dimethylaminophenol (NMe2PhOH), the latter yielding LCu(OPhNMe2), which was also prepared independently. With the identification of [CuOOR]2+ complexes, the first precedent for this core in enzymes is provided, with implications for copper monooxygenase mechanisms.
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Affiliation(s)
- Benjamin D Neisen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Nicole L Gagnon
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Debanjan Dhar
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Andrew D Spaeth
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - William B Tolman
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
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20
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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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21
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Kim B, Jeong D, Cho J. Nucleophilic reactivity of copper(ii)–alkylperoxo complexes. Chem Commun (Camb) 2017; 53:9328-9331. [DOI: 10.1039/c7cc03965d] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Copper(ii)–alkylperoxo adducts, [Cu(CHDAP)(OOR)]+ (CHDAP = N,N′-dicyclohexyl-2,11-diaza[3,3](2,6)pyridinophane; R = C(CH3)2Ph and tBu), perform aldehyde deformylation (i.e., nucleophilic reactivity) under the stoichiometric reaction conditions.
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Affiliation(s)
- Bohee Kim
- Department of Emerging Materials Science
- DGIST
- Daegu 42988
- Korea
| | - Donghyun Jeong
- Department of Emerging Materials Science
- DGIST
- Daegu 42988
- Korea
| | - Jaeheung Cho
- Department of Emerging Materials Science
- DGIST
- Daegu 42988
- Korea
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22
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Zerk TJ, Martinez M, Bernhardt PV. A Kinetico-Mechanistic Study on CuII Deactivators Employed in Atom Transfer Radical Polymerization. Inorg Chem 2016; 55:9848-9857. [DOI: 10.1021/acs.inorgchem.6b01700] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Timothy J. Zerk
- School
of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
| | - Manuel Martinez
- Departament
de Química Inorgànica i Orgànica, Secció
de Química Inorgànica, Universitat de Barcelona, Martí
i Franquès 1-11, E-08028 Barcelona, Spain
| | - Paul V. Bernhardt
- School
of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
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23
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Chaloner L, Khomutovskaya A, Thomas F, Ottenwaelder X. Supramolecular control of monooxygenase reactivity in a copper(ii) cryptate. Dalton Trans 2016; 45:11109-19. [DOI: 10.1039/c6dt00490c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We report on the formation and self-decomposition of Cu(ii)–hydroperoxo intermediates with a cryptand ligand. The second coordination sphere of the cryptand steers the oxidative reactivity of the intermediates towards the formation of an unprecedented N-oxide.
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Affiliation(s)
- L. Chaloner
- Department of Chemistry and Biochemistry
- Concordia University
- Montreal
- Canada
| | - A. Khomutovskaya
- Department of Chemistry and Biochemistry
- Concordia University
- Montreal
- Canada
| | - F. Thomas
- Équipe de Chimie Inorganique Redox
- Département de Chimie Moléculaire
- Université Joseph Fourier
- Cedex 9
- France
| | - X. Ottenwaelder
- Department of Chemistry and Biochemistry
- Concordia University
- Montreal
- Canada
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24
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Paria S, Ohta T, Morimoto Y, Ogura T, Sugimoto H, Fujieda N, Goto K, Asano K, Suzuki T, Itoh S. Generation, Characterization, and Reactivity of a Cu(II)-Alkylperoxide/Anilino Radical Complex: Insight into the O-O Bond Cleavage Mechanism. J Am Chem Soc 2015; 137:10870-3. [PMID: 26291639 DOI: 10.1021/jacs.5b04104] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The reaction of [Cu(I)(TIPT3tren) (CH3CN)]ClO4 (1) and cumene hydroperoxide (C6H5C(CH3)2OOH, ROOH) at -60 °C in CH2Cl2 gave a Cu(II)-alkylperoxide/anilino radical complex 2, the formation of which was confirmed by UV-vis, resonance Raman, EPR, and CSI-mass spectroscopy. The mechanism of formation of 2, as well as its reactivity, has been explored.
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Affiliation(s)
- Sayantan Paria
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University , 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Takehiro Ohta
- Picobiology Institute, Graduate School of Life Science, University of Hyogo , RSC-UH LP Center, Koto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Yuma Morimoto
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University , 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Takashi Ogura
- Picobiology Institute, Graduate School of Life Science, University of Hyogo , RSC-UH LP Center, Koto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Hideki Sugimoto
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University , 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Nobutaka Fujieda
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University , 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Kei Goto
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology , 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Kaori Asano
- Comprehensive Analysis Center, The Institute of Scientific and Industrial Research (ISIR), Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0057, Japan
| | - Takeyuki Suzuki
- Comprehensive Analysis Center, The Institute of Scientific and Industrial Research (ISIR), Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0057, Japan
| | - Shinobu Itoh
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University , 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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25
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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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26
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Kim S, Ginsbach JW, Lee JY, Peterson RL, Liu JJ, Siegler MA, Sarjeant AA, Solomon EI, Karlin KD. Amine oxidative N-dealkylation via cupric hydroperoxide Cu-OOH homolytic cleavage followed by site-specific fenton chemistry. J Am Chem Soc 2015; 137:2867-74. [PMID: 25706825 PMCID: PMC4482616 DOI: 10.1021/ja508371q] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Copper(II) hydroperoxide species are significant intermediates in processes such as fuel cells and (bio)chemical oxidations, all involving stepwise reduction of molecular oxygen. We previously reported a Cu(II)-OOH species that performs oxidative N-dealkylation on a dibenzylamino group that is appended to the 6-position of a pyridyl donor of a tripodal tetradentate ligand. To obtain insights into the mechanism of this process, reaction kinetics and products were determined employing ligand substrates with various para-substituent dibenzyl pairs (-H,-H; -H,-Cl; -H,-OMe, and -Cl,-OMe), or with partially or fully deuterated dibenzyl N-(CH2Ph)2 moieties. A series of ligand-copper(II) bis-perchlorate complexes were synthesized, characterized, and the X-ray structures of the -H,-OMe analogue were determined. The corresponding metastable Cu(II)-OOH species were generated by addition of H2O2/base in acetone at -90 °C. These convert (t1/2 ≈ 53 s) to oxidatively N-dealkylated products, producing para-substituted benzaldehydes. Based on the experimental observations and supporting DFT calculations, a reaction mechanism involving dibenzylamine H-atom abstraction or electron-transfer oxidation by the Cu(II)-OOH entity could be ruled out. It is concluded that the chemistry proceeds by rate limiting Cu-O homolytic cleavage of the Cu(II)-(OOH) species, followed by site-specific copper Fenton chemistry. As a process of broad interest in copper as well as iron oxidative (bio)chemistries, a detailed computational analysis was performed, indicating that a Cu(I)OOH species undergoes O-O homolytic cleavage to yield a hydroxyl radical and Cu(II)OH rather than heterolytic cleavage to yield water and a Cu(II)-O(•-) species.
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Affiliation(s)
- Sunghee Kim
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Jake W. Ginsbach
- Department of Chemistry, Stanford University, Stanford, California 94305
| | - Jung Yoon Lee
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Ryan L. Peterson
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Jeffrey J. Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Maxime A. Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Amy A. Sarjeant
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
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27
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Sánchez-Eguía BN, Flores-Alamo M, Orio M, Castillo I. Side-on cupric–superoxo triplet complexes as competent agents for H-abstraction relevant to the active site of PHM. Chem Commun (Camb) 2015; 51:11134-7. [DOI: 10.1039/c5cc02332g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Side-on cupric–superoxo complexes with triplet ground states mimic the active site of PHM and are capable of H-abstraction.
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Affiliation(s)
| | - M. Flores-Alamo
- Facultad de Química
- División de Estudios de Posgrado
- Universidad Nacional Autónoma de México
- México DF
- Mexico
| | - M. Orio
- Laboratoire de Spectrochimie Infrarouge et Raman
- Université des Sciences et Technologies de Lille
- 59655 Villeneuve d'Ascq Cedex
- France
- Institut des Sciences Moléculaires de Marseille
| | - I. Castillo
- Instituto de Química
- Universidad Nacional Autónoma de México
- México DF
- Mexico
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28
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Hossain MM, Tseng MC, Lee CR, Shyu SG. Synthesis, Structure, and Reactivity of [Cu(phen)2]ClO2: Aerobic Oxidation of Cl-to ClO2-at Room Temperature. Eur J Inorg Chem 2013. [DOI: 10.1002/ejic.201301287] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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29
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Yu WF, Meng XG, Peng X, Li XH, Liu Y. Selective oxidation of Mandelic acids catalyzed by copper (II) complexes. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.molcata.2013.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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30
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Kim S, Saracini C, Siegler MA, Drichko N, Karlin KD. Coordination chemistry and reactivity of a cupric hydroperoxide species featuring a proximal H-bonding substituent. Inorg Chem 2012; 51:12603-5. [PMID: 23153187 DOI: 10.1021/ic302071e] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
At -90 °C in acetone, a stable hydroperoxo complex [(BA)Cu(II)OOH](+) (2) (BA, a tetradentate N(4) ligand possessing a pendant -N(H)CH(2)C(6)H(5) group) is generated by reacting [(BA)Cu(II)(CH(3)COCH(3))](2+) with only 1 equiv of H(2)O(2)/Et(3)N. The exceptional stability of 2 is ascribed to internal H-bonding. Species 2 is also generated in a manner not previously known in copper chemistry, by adding 1.5 equiv of H(2)O(2) (no base) to the cuprous complex [(BA)Cu(I)](+). The broad implications for this finding are discussed. Species 2 slowly converts to a μ-1,2-peroxodicopper(II) analogue (3) characterized by UV-vis and resonance Raman spectroscopies. Unlike a close analogue not possessing internal H-bonding, 2 affords no oxidative reactivity with internal or external substrates. However, 2 can be protonated to release H(2)O(2), but only with HClO(4), while 1 equiv Et(3)N restores 2.
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Affiliation(s)
- Sunghee Kim
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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31
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Tano T, Sugimoto H, Fujieda N, Itoh S. Heterolytic Alkyl Hydroperoxide O-O Bond Cleavage by Copper(I) Complexes. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201200555] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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32
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Chaloner L, Askari MS, Kutteh A, Schindler S, Ottenwaelder X. Formation and Reactivity of a Biomimetic Hydroperoxocopper(II) Cryptate. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201100080] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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33
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Tano T, Ertem MZ, Yamaguchi S, Kunishita A, Sugimoto H, Fujieda N, Ogura T, Cramer CJ, Itoh S. Reactivity of copper(II)-alkylperoxo complexes. Dalton Trans 2011; 40:10326-36. [PMID: 21808769 DOI: 10.1039/c1dt10656b] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Copper(II) complexes 1a and 1b, supported by tridentate ligand bpa [bis(2-pyridylmethyl)amine] and tetradentate ligand tpa [tris(2-pyridylmethyl)amine], respectively, react with cumene hydroperoxide (CmOOH) in the presence of triethylamine in CH(3)CN to provide the corresponding copper(II) cumylperoxo complexes 2a and 2b, the formation of which has been confirmed by resonance Raman and ESI-MS analyses using (18)O-labeled CmOOH. UV-vis and ESR spectra as well as DFT calculations indicate that 2a has a 5-coordinate square-pyramidal structure involving CmOO(-) at an equatorial position and one solvent molecule at an axial position at low temperature (-90 °C), whereas a 4-coordinate square-planar structure that has lost the axial solvent ligand is predominant at higher temperatures (above 0 °C). Complex 2b, on the other hand, has a typical trigonal bipyramidal structure with the tripodal tetradentate tpa ligand, where the cumylperoxo ligand occupies an axial position. Both cumylperoxo copper(II) complexes 2a and 2b are fairly stable at ambient temperature, but decompose at a higher temperature (60 °C) in CH(3)CN. Detailed product analyses and DFT studies indicate that the self-decomposition involves O-O bond homolytic cleavage of the peroxo moiety; concomitant hydrogen-atom abstraction from the solvent is partially involved. In the presence of 1,4-cyclohexadiene (CHD), the cumylperoxo complexes react smoothly at 30 °C to give benzene as one product. Detailed product analyses and DFT studies indicate that reaction with CHD involves concerted O-O bond homolytic cleavage and hydrogen-atom abstraction from the substrate, with the oxygen atom directly bonded to the copper(II) ion (proximal oxygen) involved in the C-H bond activation step.
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Affiliation(s)
- Tetsuro Tano
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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