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Abstract
The oxidation of alcohols to the corresponding carbonyl products is an important organic transformation and the products are used in a variety of applications. The development of catalytic methods for selective alcohol oxidation have garnered significant attention in an attempt to find a more sustainable method without any limitations. Copper, in combination with 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) and supported by organic ligands, have emerged as the most effective catalysts for selective alcohol oxidation and these catalyst systems are frequently compared to galactose oxidase (GOase). The efficiency of GOase has led to extensive research to mimic the active sites of these enzymes, leading to a variety of Cu/TEMPO· catalyst systems being reported over the years. The mechanistic pathway by which Cu/TEMPO· catalyst systems operate has been investigated by several research groups, which led to partially contradicting mechanistic description. Due to the disadvantages and limitations of employing TEMPO· as co-catalyst, alternative nitroxyl radicals or in situ formed radicals, as co-catalysts, have been successfully evaluated in alcohol oxidation. Herein we discuss the development and mechanistic elucidation of Cu/TEMPO· catalyst systems as biomimetic alcohol oxidation catalysts.
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102
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Li J, Koto T, Davis I, Liu A. Probing the Cys-Tyr Cofactor Biogenesis in Cysteine Dioxygenase by the Genetic Incorporation of Fluorotyrosine. Biochemistry 2019; 58:2218-2227. [PMID: 30946568 DOI: 10.1021/acs.biochem.9b00006] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cysteine dioxygenase (CDO) is a nonheme iron enzyme that adds two oxygen atoms from dioxygen to the sulfur atom of l-cysteine. Adjacent to the iron site of mammalian CDO, there is a post-translationally generated Cys-Tyr cofactor, whose presence substantially enhances the oxygenase activity. The formation of the Cys-Tyr cofactor in CDO is an autocatalytic process, and it is challenging to study by traditional techniques because the cross-linking reaction is a side, uncoupled, single-turnover oxidation buried among multiple turnovers of l-cysteine oxygenation. Here, we take advantage of our recent success in obtaining a purely uncross-linked human CDO due to site-specific incorporation of 3,5-difluoro-l-tyrosine (F2-Tyr) at the cross-linking site through the genetic code expansion strategy. Using EPR spectroscopy, we show that nitric oxide (•NO), an oxygen surrogate, similarly binds to uncross-linked F2-Tyr157 CDO as in wild-type human CDO. We determined X-ray crystal structures of uncross-linked F2-Tyr157 CDO and mature wild-type CDO in complex with both l-cysteine and •NO. These structural data reveal that the active site cysteine (Cys93 in the human enzyme), rather than the generally expected tyrosine (i.e., Tyr157), is well-aligned to be oxidized should the normal oxidation reaction uncouple. This structure-based understanding is further supported by a computational study with models built on the uncross-linked ternary complex structure. Together, these results strongly suggest that the first target to oxidize during the iron-assisted Cys-Tyr cofactor biogenesis is Cys93. Based on these data, a plausible reaction mechanism implementing a cysteine radical involved in the cross-link formation is proposed.
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Affiliation(s)
- Jiasong Li
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Teruaki Koto
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Ian Davis
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
| | - Aimin Liu
- Department of Chemistry , University of Texas at San Antonio , San Antonio , Texas 78249 , United States
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103
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Skatova AA, Bazyakina NL, Fedushkin IL, Piskunov AV, Druzhkov NO, Cherkasov AV. Mononuclear gallium complexes with the redox-active dmp-bian ligand (dmp-bian is 1,2-bis[(2,6-dimethylphenyl)imino]acenaphthene): synthesis and reactions with alkynes. Russ Chem Bull 2019. [DOI: 10.1007/s11172-019-2383-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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104
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Kundu BK, Ranjan R, Mukherjee A, Mobin SM, Mukhopadhyay S. Mannich base Cu(II) complexes as biomimetic oxidative catalyst. J Inorg Biochem 2019; 195:164-173. [PMID: 30954693 DOI: 10.1016/j.jinorgbio.2019.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/23/2019] [Accepted: 03/28/2019] [Indexed: 11/16/2022]
Abstract
Galactose Oxidase (GOase) and catechol oxidase (COase) are the metalloenzymes of copper having monomeric and dimeric sites of coordination, respectively. This paper summarizes the results of our studies on the structural, spectral and catalytic properties of new mononuclear copper (II) complexes [CuL(OAc)] (1), and [CuL2] (2), (HL = 2,4‑dichloro‑6‑{[(2'‑dimethyl‑aminoethyl)methylamino]methyl}‑phenol) which can mimic the functionalities of the metalloenzymes GOase and COase. The structure of the compounds has been elucidated by X-ray crystallography and the mimicked Cu(II) catalysts were further characterized by EPR. These mimicked models were used for GOase and COase catalysis. The GOase catalytic results were identified by GC-MS and, analyzed by HPLC at room temperature. The conversion of benzyl alcohol to benzaldehyde were significant in presence of a strong base, Bu4NOMe in comparison to the neutral medium. Apart from that, despite of being monomeric in nature, both the homogeneous catalysts are very prone to participate in COase mimicking oxidation reaction. Nevertheless, during COase catalysis, complex 1 was found to convert 3,5‑ditertarybutyl catechol (3,5-DTBC) to 3,5‑ditertarybutyl quinone (3,5-DTBQ) having greater rate constant, kcat or turn over number (TON) value over complex 2. The generation of reactive intermediates during COase catalysis were accounted by electrospray ionization mass spectrometry (ESI-MS). Through mechanistic approach, we found that H2O2 is the byproduct for both the GOase and COase catalysis, thus, confirming the generation of reactive oxygen species during catalysis. Notably, complex 1 having mono-ligand coordinating atmosphere has superior catalytic activity for both cases in comparison to complex 2, that is having di-ligand environment.
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Affiliation(s)
- Bidyut Kumar Kundu
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India
| | - Rishi Ranjan
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India
| | | | - Shaikh M Mobin
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India
| | - Suman Mukhopadhyay
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India; Discipline of Biosciences and Biomedical Engineering, School of Engineering, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India.
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105
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Chen J, Guo X, Zhu M, Chen C, Li D. Polysaccharide monooxygenase-catalyzed oxidation of cellulose to glucuronic acid-containing cello-oligosaccharides. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:42. [PMID: 30858879 PMCID: PMC6391835 DOI: 10.1186/s13068-019-1384-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/20/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND Polysaccharide monooxygenases (PMOs) play an important role in the enzymatic degradation of cellulose. They have been demonstrated to able to C6-oxidize cellulose to produce C6-hexodialdoses. However, the biological function of C6 oxidation of PMOs remains unknown. In particular, it is unclear whether C6-hexodialdoses can be further oxidized to uronic acid (glucuronic acid-containing oligosaccharides). RESULTS A PMO gene, Hipmo1, was isolated from Humicola insolens and expressed in Pichia pastoris. This PMO (HiPMO1), belonging to the auxiliary activity 9 (AA9) family, was shown to able to cleave cellulose to yield non-oxidized and oxidized cello-oligosaccharides. The enzyme oxidizes C6 positions in cellulose to form glucuronic acid-containing cello-oligosaccharides, followed by hydrolysis with beta-glucosidase and beta-glucuronidase to yield glucose, glucuronic acid, and saccharic acid. This indicates that HiPMO1 can catalyze C6 oxidation of hydroxyl groups of cellulose to carboxylic groups. CONCLUSIONS HiPMO1 oxidizes C6 of cellulose to form glucuronic acid-containing cello-oligosaccharides followed by hydrolysis with beta-glucosidase and beta-glucuronidase to yield glucose, glucuronic acid, and saccharic acid, and even possibly by beta-eliminative cleavage to produce unsaturated cello-oligosaccharides. This study provides a new mechanism for cellulose cleavage by C6 oxidation of HiPMO1.
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Affiliation(s)
- Jinyin Chen
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Xiuna Guo
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Min Zhu
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Chen Chen
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Duochuan Li
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
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106
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van der Vlugt JI. Radical-Type Reactivity and Catalysis by Single-Electron Transfer to or from Redox-Active Ligands. Chemistry 2019; 25:2651-2662. [PMID: 30084211 PMCID: PMC6471147 DOI: 10.1002/chem.201802606] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Indexed: 12/12/2022]
Abstract
Controlled ligand-based redox-activity and chemical non-innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand-to-substrate single-electron transfer as a relatively new mode of operation to exploit ligand-centered reactivity and catalysis based thereon.
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Affiliation(s)
- Jarl Ivar van der Vlugt
- Bio-Inspired Homogeneous and Supramolecular Catalysis Groupvan ‘t Hoff Institute for Molecular SciencesUniversity of AmsterdamScience Park 9041098 XHAmsterdamNetherlands
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107
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Lee J, Ju M, Cho OH, Kim Y, Nam KT. Tyrosine-Rich Peptides as a Platform for Assembly and Material Synthesis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2019; 6:1801255. [PMID: 30828522 PMCID: PMC6382316 DOI: 10.1002/advs.201801255] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/27/2018] [Indexed: 05/27/2023]
Abstract
The self-assembly of biomolecules can provide a new approach for the design of functional systems with a diverse range of hierarchical nanoarchitectures and atomically defined structures. In this regard, peptides, particularly short peptides, are attractive building blocks because of their ease of establishing structure-property relationships, their productive synthesis, and the possibility of their hybridization with other motifs. Several assembling peptides, such as ionic-complementary peptides, cyclic peptides, peptide amphiphiles, the Fmoc-peptide, and aromatic dipeptides, are widely studied. Recently, studies on material synthesis and the application of tyrosine-rich short peptide-based systems have demonstrated that tyrosine units serve as not only excellent assembly motifs but also multifunctional templates. Tyrosine has a phenolic functional group that contributes to π-π interactions for conformation control and efficient charge transport by proton-coupled electron-transfer reactions in natural systems. Here, the critical roles of the tyrosine motif with respect to its electrochemical, chemical, and structural properties are discussed and recent discoveries and advances made in tyrosine-rich short peptide systems from self-assembled structures to peptide/inorganic hybrid materials are highlighted. A brief account of the opportunities in design optimization and the applications of tyrosine peptide-based biomimetic materials is included.
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Affiliation(s)
- Jaehun Lee
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Misong Ju
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Ouk Hyun Cho
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Younghye Kim
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Ki Tae Nam
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
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108
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Gordon JB, Vilbert AC, Siegler MA, Lancaster KM, Moënne-Loccoz P, Goldberg DP. A Nonheme Thiolate-Ligated Cobalt Superoxo Complex: Synthesis and Spectroscopic Characterization, Computational Studies, and Hydrogen Atom Abstraction Reactivity. J Am Chem Soc 2019; 141:3641-3653. [PMID: 30776222 DOI: 10.1021/jacs.8b13134] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The synthesis and characterization of a Co(II) dithiolato complex Co(Me3TACN)(S2SiMe2) (1) are reported. Reaction of 1 with O2 generates a rare thiolate-ligated cobalt-superoxo species Co(O2)(Me3TACN)(S2SiMe2) (2) that was characterized spectroscopically and structurally by resonance Raman, EPR, and X-ray absorption spectroscopies as well as density functional theory. Metal-superoxo species are proposed to S-oxygenate metal-bound thiolate donors in nonheme thiol dioxygenases, but 2 does not lead to S-oxygenation of the intramolecular thiolate donors and does not react with exogenous sulfur donors. However, complex 2 is capable of oxidizing the O-H bonds of 2,2,6,6-tetramethylpiperidin-1-ol derivatives via H atom abstraction. Complementary proton-coupled electron-transfer reactivity is seen for 2 with separated proton/reductant pairs. The reactivity studies indicate that 2 can abstract H atoms from weak X-H bonds with bond dissociation free energy (BDFE) ≤ 70 kcal mol-1. DFT calculations predict that the putative Co(OOH) product has an O-H BDFE = 67 kcal mol-1, which matches the observed pattern of reactivity seen for 2. These data provide new information regarding the selectivity of S-oxygenation versus H atom abstraction in thiolate-ligated nonheme metalloenzymes that react with O2.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Avery C Vilbert
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Maxime A Siegler
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Pierre Moënne-Loccoz
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239-3098 , United States
| | - David P Goldberg
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
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109
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Saund SS, Goldschmid SL, Ng K, Stewart V, Siegler MA, Thoi VS. Exploring ligand non-innocence of coordinatively-versatile diamidodipyrrinato cobalt complexes. Chem Commun (Camb) 2019; 55:1825-1828. [PMID: 30672518 DOI: 10.1039/c8cc08674e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The non-innocence of diamidodipyrrin is explored in a series of cobaltous complexes with novel binding motifs. By varying the coordination modes, a reversible one-electron reduction is remarkably shifted by nearly 200 mV in a single metal-ligand platform. Our study illustrates a new strategy for modifying the redox activity of porphyrin-like scaffolds.
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Affiliation(s)
- Simran S Saund
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
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110
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Glaser T. A dinucleating ligand system with varying terminal donor functions but without bridging donor functions: Design, synthesis, and applications for diiron complexes. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2018.09.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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111
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Trammell R, Rajabimoghadam K, Garcia-Bosch I. Copper-Promoted Functionalization of Organic Molecules: from Biologically Relevant Cu/O 2 Model Systems to Organometallic Transformations. Chem Rev 2019; 119:2954-3031. [PMID: 30698952 DOI: 10.1021/acs.chemrev.8b00368] [Citation(s) in RCA: 157] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Copper is one of the most abundant and less toxic transition metals. Nature takes advantage of the bioavailability and rich redox chemistry of Cu to carry out oxygenase and oxidase organic transformations using O2 (or H2O2) as oxidant. Inspired by the reactivity of these Cu-dependent metalloenzymes, chemists have developed synthetic protocols to functionalize organic molecules under enviormentally benign conditions. Copper also promotes other transformations usually catalyzed by 4d and 5d transition metals (Pd, Pt, Rh, etc.) such as nitrene insertions or C-C and C-heteroatom coupling reactions. In this review, we summarized the most relevant research in which copper promotes or catalyzes the functionalization of organic molecules, including biological catalysis, bioinspired model systems, and organometallic reactivity. The reaction mechanisms by which these processes take place are discussed in detail.
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Affiliation(s)
- Rachel Trammell
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
| | | | - Isaac Garcia-Bosch
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
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112
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Eijsink VGH, Petrovic D, Forsberg Z, Mekasha S, Røhr ÅK, Várnai A, Bissaro B, Vaaje-Kolstad G. On the functional characterization of lytic polysaccharide monooxygenases (LPMOs). BIOTECHNOLOGY FOR BIOFUELS 2019; 12:58. [PMID: 30923566 PMCID: PMC6423801 DOI: 10.1186/s13068-019-1392-0] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/06/2019] [Indexed: 05/02/2023]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are abundant in nature and best known for their role in the enzymatic conversion of recalcitrant polysaccharides such as chitin and cellulose. LPMO activity requires an oxygen co-substrate, which was originally thought to be O2, but which may also be H2O2. Functional characterization of LPMOs is not straightforward because typical reaction mixtures will promote side reactions, including auto-catalytic inactivation of the enzyme. For example, despite some recent progress, there is still limited insight into the kinetics of the LPMO reaction. Recent discoveries concerning the role of H2O2 in LPMO catalysis further complicate the picture. Here, we review commonly used methods for characterizing LPMOs, with focus on benefits and potential pitfalls, rather than on technical details. We conclude by pointing at a few key problems and potential misconceptions that should be taken into account when interpreting existing data and planning future experiments.
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Affiliation(s)
- Vincent G. H. Eijsink
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Dejan Petrovic
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Zarah Forsberg
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Sophanit Mekasha
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Åsmund K. Røhr
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Anikó Várnai
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Bastien Bissaro
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
| | - Gustav Vaaje-Kolstad
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), PO Box 5003, 1432 Ås, Norway
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113
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Zheng J, Liu Z, Jin X, Dang Y. Unveiling the mechanism and regioselectivity of iron-dipyrrinato-catalyzed intramolecular C(sp3)–H amination of alkyl azides. Catal Sci Technol 2019. [DOI: 10.1039/c8cy02479k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism of iron-catalyzed C(sp3)–H amination was established, in which regioselectivity arose from both radical stability and ring strain.
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Affiliation(s)
- Jia Zheng
- Department of Chemistry
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences
- Tianjin University, and Collaborative Innovation Center of Chemical Science and Engineering
- Tianjin 300072
- China
| | - Zheyuan Liu
- Department of Chemistry
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences
- Tianjin University, and Collaborative Innovation Center of Chemical Science and Engineering
- Tianjin 300072
- China
| | - Xiaojiao Jin
- Department of Chemistry
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences
- Tianjin University, and Collaborative Innovation Center of Chemical Science and Engineering
- Tianjin 300072
- China
| | - Yanfeng Dang
- Department of Chemistry
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences
- Tianjin University, and Collaborative Innovation Center of Chemical Science and Engineering
- Tianjin 300072
- China
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114
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Safaei E, Balaghi SE, Chiang L, Clarke RM, Martelino D, Webb MI, Wong EWY, Savard D, Walsby CJ, Storr T. Stabilization of different redox levels of a tridentate benzoxazole amidophenoxide ligand when bound to Co(iii) or V(v). Dalton Trans 2019; 48:13326-13336. [DOI: 10.1039/c9dt02865j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The electronic structure of Co and V complexes of a tridentate benzoxazole-containing aminophenol ligand NNOH2 were characterized by both experimental and theoretical methods.
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Affiliation(s)
- Elham Safaei
- Department of Chemistry
- College of Science
- Shiraz University
- Shiraz
- Iran
| | | | - Linus Chiang
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Ryan M. Clarke
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Diego Martelino
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Michael I. Webb
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Edwin W. Y. Wong
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Didier Savard
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Charles J. Walsby
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Tim Storr
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
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115
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Rajabimoghadam K, Darwish Y, Bashir U, Pitman D, Eichelberger S, Siegler MA, Garcia-Bosch I. Tunable intramolecular multicenter H-bonding interactions in first-row metal complexes bearing bidentate redox-active ligands. J COORD CHEM 2019; 72:1346-1357. [PMID: 34113052 DOI: 10.1080/00958972.2019.1624728] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In this research article, we report the synthesis and structural characterization of a family of first-row metal complexes bearing redox-active ligands with tunable H-bonding donors. We observed that these coordination complexes can adopt three different geometries and that they are stabilized by intramolecular multicenter H-bonding interactions, which are systematically modified by changing the metal ion (Co, Ni, Cu, Zn), the ligand scaffold (variations in the diamine and ureanyl substituents used) and the solvent of crystallization.
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Affiliation(s)
| | - Yousef Darwish
- Department of Chemistry, Southern Methodist University, Dallas, TX, USA
| | - Umyeena Bashir
- Department of Chemistry, Southern Methodist University, Dallas, TX, USA
| | - Dylan Pitman
- Department of Chemistry, Southern Methodist University, Dallas, TX, USA
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116
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Hu Y, Wang M, Li P, Li H, Wang L. A Highly Efficient Copper‐Catalyzed C(sp2)−H Alkoxylation of the Benzamide Enabled by A Bidendate Directing Group. ASIAN J ORG CHEM 2018. [DOI: 10.1002/ajoc.201800664] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Yu Hu
- Department of ChemistryHuaibei Normal University, Huaibei Anhui 235000 P.R. China
| | - Min Wang
- Department of ChemistryHuaibei Normal University, Huaibei Anhui 235000 P.R. China
| | - Pinhua Li
- Department of ChemistryHuaibei Normal University, Huaibei Anhui 235000 P.R. China
| | - Hongji Li
- Department of ChemistryHuaibei Normal University, Huaibei Anhui 235000 P.R. China
| | - Lei Wang
- State Key Laboratory of Organometallic ChemistryShanghai Institute of Organic Chemistry Shanghai 200032 People's Republic of China
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117
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Rajabimoghadam K, Darwish Y, Bashir U, Pitman D, Eichelberger S, Siegler MA, Swart M, Garcia-Bosch I. Catalytic Aerobic Oxidation of Alcohols by Copper Complexes Bearing Redox-Active Ligands with Tunable H-Bonding Groups. J Am Chem Soc 2018; 140:16625-16634. [PMID: 30400740 DOI: 10.1021/jacs.8b08748] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In this research article, we describe the structure, spectroscopy, and reactivity of a family of copper complexes bearing bidentate redox-active ligands that contain H-bonding donor groups. Single-crystal X-ray crystallography shows that these tetracoordinate complexes are stabilized by intramolecular H-bonding interactions between the two ligand scaffolds. Interestingly, the Cu complexes undergo multiple reversible oxidation-reduction processes associated with the metal ion (CuI, CuII, CuIII) and/or the o-phenyldiamido ligand (L2-, L•-, L). Moreover, some of the CuII complexes catalyze the aerobic oxidation of alcohols to aldehydes (or ketones) at room temperature. Our extensive mechanistic analysis suggests that the dehydrogenation of alcohols occurs via an unusual reaction pathway for galactose oxidase model systems, in which O2 reduction occurs concurrently with substrate oxidation.
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Affiliation(s)
| | - Yousef Darwish
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
| | - Umyeena Bashir
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
| | - Dylan Pitman
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
| | - Sidney Eichelberger
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
| | - Maxime A Siegler
- Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Marcel Swart
- ICREA , Pg. Lluís Companys 23 , 08010 Barcelona , Spain.,IQCC , University of Girona , Campus Montilivi (Ciències) , Girona , Spain
| | - Isaac Garcia-Bosch
- Department of Chemistry , Southern Methodist University , Dallas , Texas 75275 , United States
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118
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Abeyawardhane DL, Fernández RD, Heitger DR, Crozier MK, Wolver JC, Lucas HR. Copper Induced Radical Dimerization of α-Synuclein Requires Histidine. J Am Chem Soc 2018; 140:17086-17094. [DOI: 10.1021/jacs.8b08947] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
| | - Ricardo D. Fernández
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Denver R. Heitger
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Madeleine K. Crozier
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Julia C. Wolver
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Heather R. Lucas
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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119
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Mondal S, Bera S, Maity S, Ghosh P. Orthometalated N-(Benzophenoxazine)- o-aminophenol: Phenolato versus Phenoxyl States. ACS OMEGA 2018; 3:13323-13334. [PMID: 31458047 PMCID: PMC6645054 DOI: 10.1021/acsomega.8b01983] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 10/03/2018] [Indexed: 06/10/2023]
Abstract
The molecular and electronic structures of the orthometalated ruthenium(III) and osmium(III) complexes of N-(benzophenoxazine)-o-aminophenol (OXLH2) that exhibits versatile redox activities are reported. The redox chemistry of OXLH2 is remarkably different from that of N-(aryl)-o-aminophenol (APLH2). The study established that OXLH2 is redox noninnocent and is a precursor of a phenoxyl radical. One of the C-H bonds of OXLH2 is activated by ions, and OXLH2 reveals three different redox states as dianionic phenolato (OXL2-), monoanionic phenoxyl radical (OXL•-), and zwitterionic phenoxium cation (OXL±) states. The reaction of OXLH2 with [RuII(PPh3)3Cl2] in boiling toluene in air affords an orthometalated OXL2- complex of ruthenium(III), trans-[(OXL2-)RuIII(PPh3)2(Cl)] (1), whereas the similar reaction with [OsII(PPh3)3Br2] yields an orthometalated OXL•- complex, cis-[(OXL•-)OsIII(PPh3)Br2] (2). 1 and 2 exhibit ligand-based reversible redox waves due to OXL•-/OXL2-, OXL±/OXL•-, and MIII/MII couples. The 1 + ion is a OXL•- complex of ruthenium(III). 2 - exhibits temperature-dependent valence tautomerism due to [OsII(OXL•-) ↔ OsIII(OXL2-)] equilibrium. 2 2- is a OXL2- complex of osmium(II), while 1 2+ and 2 + are OXL± complexes of metal(III). 2 is an oxidant and effective catalyst for oxidation of 3,5-di-tert-butylcatechol to the corresponding quinone, and the turnover number is 119.7 h-1. The UV-vis-NIR absorption spectrum of 1 displays an NIR band at 800 nm due to an intra-ligand-charge-transfer transition, which is absent in 2 incorporating a OXL•- radical. The molecular and electronic structures of 1 and 2 and their oxidized and reduced analogues were confirmed by single-crystal X-ray crystallography, variable-temperature electron paramagnetic resonance spectroscopy, spectroelectrochemical measurements, and density functional theory calculations.
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Affiliation(s)
| | | | | | - Prasanta Ghosh
- E-mail: . Phone: +91-33-2428-7347. Fax: +91-33-2477-3597
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120
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Piskunov AV, Pashanova KI, Bogomyakov AS, Smolyaninov IV, Starikov AG, Fukin GK. Cobalt complexes with hemilabile o-iminobenzoquinonate ligands: a novel example of redox-induced electron transfer. Dalton Trans 2018; 47:15049-15060. [PMID: 30303221 DOI: 10.1039/c8dt02733a] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The tetracoordinated square-planar CoIII complex (imSQC(O)Ph)CoIII(APC(O)Ph) (1) bearing a radical anion and the closed-shell o-amidophenolate forms of the functionalized o-aminophenol H2LC(O)Ph were synthesized. The intermediate spin state (SCo = 1) CoIII center was found for compound 1. The cyclic voltammogram of derivative 1 contains two oxidative processes and one reductive redox process as well as an additional multi-electron wave at high negative potentials above -2 V, which can involve both the ligand and metal center. One-electron oxidation of 1 by silver triflate produces the [(imSQC(O)Ph)CoII(imQC(O)Ph)]OTf·2toluene (2) derivative with the trigonal prismatic coordination environment of the metal arising from the additional coordination of -C(O)Ph hemilabile groups. This is a first example of a trigonal prismatic coordination polyhedron in cobalt-based complexes featuring o-iminobenzoquinone ligands. The trigonal prismatic geometry achieved by the unique flexibility of the ligand allows metal-to-ligand redox-induced electron transfer (RIET). Chemical oxidation of complex 1 promotes the reduction of CoIII to CoII in compound 2 due to the redox-active nature of o-iminobenzoquinonate ligands. Remarkably, this is the first example of RIET in cobalt-based derivatives with this type of ligand. The oxidative states of the ligands and cobalt ion in both complexes were unequivocally established according to the X-ray data collection by using the utility of "metric oxidation state" (MOS). The spin states of the metal centers were unambiguously determined by density functional theory. The strong antiferromagnetic exchange via metal-ligand interactions is dominant in compounds 1 and 2, giving the doublet (S = 1/2) and triplet (S = 1) ground spin state, respectively.
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Affiliation(s)
- Alexandr V Piskunov
- G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Laboratory of Organoelement Compounds, 49 Tropinina Street, 603137, Nizhny Novgorod, Russian Federation.
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121
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Sarkar P, Mukherjee C. A non-innocent pincer H 3L ONS ligand and its corresponding octahedral low-spin Fe(iii) complex formation via ligand-centric homolytic S-S bond scission. Dalton Trans 2018; 47:13337-13341. [PMID: 30207350 DOI: 10.1039/c8dt02763c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the presence of FeCl3 and Et3N, a ligand H4Ldtda(AP) underwent S-S bond cleavage and generated a pincer non-innocent H3LONS ligand, which formed a homoleptic, six-coordinate, low-spin Fe(iii) complex (1). The complex comprised two 2-iminobenzosemiquinone (1-) π-radicals and one thiyl π-radical.
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Affiliation(s)
- Prasenjit Sarkar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
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122
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Khan FF, Klein J, Priego JL, Sarkar B, Jiménez-Aparicio R, Lahiri GK. Questions of Noninnocence and Ease of Azo Reduction in Diruthenium Frameworks with a 1,8-Bis((E)-phenyldiazenyl)naphthalene-2,7-dioxido Bridge. Inorg Chem 2018; 57:12800-12810. [DOI: 10.1021/acs.inorgchem.8b01996] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Farheen Fatima Khan
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Johannes Klein
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstraße 34-36, D-14195 Berlin, Germany
| | - José Luis Priego
- Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Biprajit Sarkar
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstraße 34-36, D-14195 Berlin, Germany
| | - Reyes Jiménez-Aparicio
- Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Goutam Kumar Lahiri
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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123
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Kundu S, Dutta D, Maity S, Weyhermüller T, Ghosh P. Proton-Coupled Oxidation of a Diarylamine: Amido and Aminyl Radical Complexes of Ruthenium(II). Inorg Chem 2018; 57:11948-11960. [DOI: 10.1021/acs.inorgchem.8b01401] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Suman Kundu
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
| | - Debarpan Dutta
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
| | - Suvendu Maity
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
| | - Thomas Weyhermüller
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Prasanta Ghosh
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
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124
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Colomban C, Philouze C, Molton F, Leconte N, Thomas F. Copper(II) complexes of N3O ligands as models for galactose oxidase: Effect of variation of steric bulk of coordinated phenoxyl moiety on the radical stability and spectroscopy. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.09.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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125
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Chiang L, Wasinger EC, Shimazaki Y, Young V, Storr T, Stack TDP. Electronic Structure and Reactivity Studies of a Nonsymmetric One-Electron Oxidized Cu II Bis-phenoxide Complex. Inorganica Chim Acta 2018; 481:151-158. [PMID: 30581226 PMCID: PMC6301013 DOI: 10.1016/j.ica.2017.09.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The tetradentate mixed imino/amino phenoxide ligand (N-(3,5-di-tert-butylsalicylidene)-N'-(2-hydroxyl-3,5-di-tert-butylbenzyl))-trans-1,2-cyclohexanediamine (salalen) was complexed with CuII, and the resulting Cu complex (2) was characterized by a number of experimental techniques and theoretical calculations. Two quasi-reversible redox processes for 2, as observed by cyclic voltammetry, demonstrated the potential stability of oxidized forms, and also the increased electron-donating ability of the salalen ligand in comparison to the salen analogue. The electronic structure of the one-electron oxidized [2]+ was then studied in detail, and Cu K-edge X-ray Absorption Spectroscopy (XAS) measurements confirmed a CuII-phenoxyl radical complex in solution. Subsequent resonance Raman (rR) and variable temperature 1H NMR studies, coupled with theoretical calculations, showed that [2• ]+ is a triplet (S = 1) CuII-phenoxyl radical species, with localization of the radical on the more electron-rich aminophenoxide. Attempted isolation of X-ray quality crystals of [2• ]+ afforded [2H]+, with a protonated phenol bonded to CuII, and an additional H-bonding interaction with the SbF6 - counterion. Stoichiometric reaction of dilute solutions of [2• ]+ with benzyl alcohol showed that the complex reacted in a similar manner as the oxidized CuII-salen analogue, and does not exhibit a substrate-binding pre-equilibrium as observed for the oxidized bisaminophenoxide CuII-salan derivative.
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Affiliation(s)
- Linus Chiang
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Erik C Wasinger
- Department of Chemistry and Biochemistry, California State University, Chico, CA 95928, USA
| | - Yuichi Shimazaki
- College of Science, Ibaraki University. Bunkyo, Mito, 310-8512, Japan
| | - Victor Young
- Department of Chemistry, The University of Minnesota, Minneapolis, MN 55455, USA
| | - Tim Storr
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| | - T Daniel P Stack
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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126
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Eckshtain-Levi M, Lavi R, Arora H, Orio M, Benisvy L. Tuning the locus of oxidation in Cu-diamido-diphenoxo complexes: From Cu(III) to Cu(II)-phenoxyl radical. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.09.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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127
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128
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Paul GC, Das K, Maity S, Begum S, Srivastava HK, Mukherjee C. Geometry-Driven Iminosemiquinone Radical to Cu(II) Electron Transfer and Stabilization of an Elusive Five-Coordinate Cu(I) Complex: Synthesis, Characterization, and Reactivity with KO2. Inorg Chem 2018; 58:1782-1793. [DOI: 10.1021/acs.inorgchem.8b01931] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ganesh Chandra Paul
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Kanu Das
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Suvendu Maity
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
| | - Samiyara Begum
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Hemant Kumar Srivastava
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Chandan Mukherjee
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
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129
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Mews NM, Hörner G, Schubert H, Berkefeld A. Tuning of Thiyl/Thiolate Complex Near-Infrared Chromophores of Platinum through Geometrical Constraints. Inorg Chem 2018; 57:9670-9682. [PMID: 29561154 DOI: 10.1021/acs.inorgchem.8b00122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The chemistry of radical-ligand complexes of the transition metals has developed into a vibrant field of research that spans from fundamental studies on the relationship between the chemical and electronic structures to applications in catalysis and functional materials chemistry. In general, fine-tuning of the relevant properties relies on an increasingly diversifying pool of radical-proligand structures. Surprisingly, the variability of the conformational freedom and the number of distinct bonding modes supported by many radical proligands is limited. This work reports on the angular constraints and relative geometric alignment of metal and ligand orbitals as key parameters that render a series of chemically similar thiyl/thiolate complexes of platinum(II) electronically and spectroscopically distinct. The use of conformational flexible thiophenols as primary ligand scaffolds is essential to establishing a defined radical-ligand [(areneS)2PtII]•+ core whose electronic structure is modulated by a series of auxiliary coligands at platinum.
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Affiliation(s)
- Nicole M Mews
- Institut für Anorganische Chemie , Eberhard Karls Universität Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Gerald Hörner
- Institut für Chemie, Quantenchemie und Bioanorganische Chemie , Technische Universität (TU) Berlin , Straße des 17 Juni 135 , 10623 Berlin , Germany
| | - Hartmut Schubert
- Institut für Anorganische Chemie , Eberhard Karls Universität Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Andreas Berkefeld
- Institut für Anorganische Chemie , Eberhard Karls Universität Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
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130
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Mondol R, Otten E. Reactivity of Two-Electron-Reduced Boron Formazanate Compounds with Electrophiles: Facile N-H/N-C Bond Homolysis Due to the Formation of Stable Ligand Radicals. Inorg Chem 2018; 57:9720-9727. [PMID: 29446931 PMCID: PMC6106049 DOI: 10.1021/acs.inorgchem.8b00079] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
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The reactivity of
a boron complex with a redox-active formazanate ligand, LBPh2 [L = PhNNC(p-tol)NNPh], was studied. Two-electron
reduction of this main-group complex generates the stable, nucleophilic
dianion [LBPh2]2–, which reacts with
the electrophiles BnBr and H2O to form products that derive
from ligand benzylation and protonation, respectively. The resulting
complexes are anionic boron analogues of leucoverdazyls. N–C
and N–H bond homolysis of these compounds was studied by exchange
NMR spectroscopy and kinetic experiments. The weak N–C and
N–H bonds in these systems derive from the stability of the
resulting borataverdazyl radical, in which the unpaired electron is
delocalized over the four N atoms in the ligand backbone. We thus
demonstrate the ability of this system to take up two electrons and
an electrophile (E+ = Bn+, H+) in
a process that takes place on the organic ligand. In addition, we
show that the [2e–/E+] stored on the
ligand can be converted to E• radicals, reactivity
that has implications in energy storage applications such as hydrogen
evolution. A boron complex with a redox-active
formazanate ligand in its two-electron-reduced state is shown to react
with electrophiles (BnBr and H+). The resulting “borataleucoverdazyl”
products have weak N−C and N−H bonds; homolytic cleavage
reactions lead to stable ligand-based radicals. Thus, the accumulation
of [2e−/E+] on the formazanate ligand
and conversion to E• radicals are demonstrated,
and their potential relevance in energy-related electrocatalysis (e.g.,
proton reduction) is discussed.
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Affiliation(s)
- Ranajit Mondol
- Stratingh Institute for Chemistry , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands
| | - Edwin Otten
- Stratingh Institute for Chemistry , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands
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131
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Storr T, Mukherjee R. Preface for the Forum on Applications of Metal Complexes with Ligand-Centered Radicals. Inorg Chem 2018. [DOI: 10.1021/acs.inorgchem.8b02171] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Tim Storr
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Rabindranath Mukherjee
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
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132
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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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133
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Bhadra M, Lee JYC, Cowley RE, Kim S, Siegler MA, Solomon EI, Karlin KD. Intramolecular Hydrogen Bonding Enhances Stability and Reactivity of Mononuclear Cupric Superoxide Complexes. J Am Chem Soc 2018; 140:9042-9045. [PMID: 29957998 PMCID: PMC6217813 DOI: 10.1021/jacs.8b04671] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
[(L)CuII(O2•-)]+ (i.e., cupric-superoxo) complexes, as the first and/or key reactive intermediates in (bio)chemical Cu-oxidative processes, including in the monooxygenases PHM and DβM, have been systematically stabilized by intramolecular hydrogen bonding within a TMPA ligand-based framework. Also, gradual strengthening of ligand-derived H-bonding dramatically enhances the [(L)CuII(O2•-)]+ reactivity toward hydrogen-atom abstraction (HAA) of phenolic O-H bonds. Spectroscopic properties of the superoxo complexes and their azido analogues, [(L)CuII(N3-)]+, also systematically change as a function of ligand H-bonding capability.
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Affiliation(s)
- Mayukh Bhadra
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jung Yoon C. Lee
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Ryan E. Cowley
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Sunghee Kim
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Maxime A. Siegler
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Kenneth D. Karlin
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
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134
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Hunter CD, Guo T, Daskhan G, Richards MR, Cairo CW. Synthetic Strategies for Modified Glycosphingolipids and Their Design as Probes. Chem Rev 2018; 118:8188-8241. [DOI: 10.1021/acs.chemrev.8b00070] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Carmanah D. Hunter
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Tianlin Guo
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Gour Daskhan
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Michele R. Richards
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Christopher W. Cairo
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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135
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Cleavage of a carbon-fluorine bond by an engineered cysteine dioxygenase. Nat Chem Biol 2018; 14:853-860. [PMID: 29942080 PMCID: PMC6103799 DOI: 10.1038/s41589-018-0085-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 05/04/2018] [Indexed: 11/08/2022]
Abstract
Cysteine dioxygenase (CDO) plays an essential role in sulfur metabolism by regulating homeostatic levels of cysteine. Human CDO contains a post-translationally generated Cys93-Tyr157 cross-linked cofactor. Here, we investigated this Cys-Tyr cross-linking by incorporating unnatural tyrosines in place of Tyr157 via a genetic method. The catalytically active variants were obtained with a thioether bond between Cys93 and the halogen-substituted Tyr157, and we determined the crystal structures of both wild-type and engineered CDO variants in the purely uncross-linked form and with a mature cofactor. Along with mass spectrometry and 19F NMR, these data indicated that the enzyme could catalyze oxidative C-F or C-Cl bond cleavage, resulting in a substantial conformational change of both Cys93 and Tyr157 during cofactor assembly. These findings provide insights into the mechanism of Cys-Tyr cofactor biogenesis and may aid the development of bioinspired aromatic carbon-halogen bond activation.
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136
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Jia X, Peng P, Cui J, Xin N, Huang X. Four N,O-Bidentate-Chelated Ligand-Tunable Copper(II) Complexes: Synthesis, Structural Characterization and Exceptional Catalytic Properties for Chan-Lam Coupling Reactions. ASIAN J ORG CHEM 2018. [DOI: 10.1002/ajoc.201800153] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Xuefeng Jia
- Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, School of Chemical and Material Science; Shanxi Normal University; Linfen, Shanxi Province 041004 China
| | - Pai Peng
- Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, School of Chemical and Material Science; Shanxi Normal University; Linfen, Shanxi Province 041004 China
| | - Jing Cui
- Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, School of Chemical and Material Science; Shanxi Normal University; Linfen, Shanxi Province 041004 China
| | - Nana Xin
- Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology; School of Chemistry & Chemical Engineering; Liaocheng University; Liaocheng Shandong Province 252059 China
| | - Xianqiang Huang
- Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology; School of Chemistry & Chemical Engineering; Liaocheng University; Liaocheng Shandong Province 252059 China
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137
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Jiao Y, Tang B, Zhang Y, Xu J, Wang Z, Zhang X. Highly Efficient Supramolecular Catalysis by Endowing the Reaction Intermediate with Adaptive Reactivity. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201713351] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Yang Jiao
- Key Lab of Organic Optoelectronics & Molecular Engineering Department of Chemistry Tsinghua University Beijing 100084 China
| | - Bohan Tang
- Key Lab of Organic Optoelectronics & Molecular Engineering Department of Chemistry Tsinghua University Beijing 100084 China
| | - Yucheng Zhang
- Key Lab of Organic Optoelectronics & Molecular Engineering Department of Chemistry Tsinghua University Beijing 100084 China
| | - Jiang‐Fei Xu
- Key Lab of Organic Optoelectronics & Molecular Engineering Department of Chemistry Tsinghua University Beijing 100084 China
| | - Zhiqiang Wang
- Key Lab of Organic Optoelectronics & Molecular Engineering Department of Chemistry Tsinghua University Beijing 100084 China
| | - Xi Zhang
- Key Lab of Organic Optoelectronics & Molecular Engineering Department of Chemistry Tsinghua University Beijing 100084 China
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138
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Jiao Y, Tang B, Zhang Y, Xu JF, Wang Z, Zhang X. Highly Efficient Supramolecular Catalysis by Endowing the Reaction Intermediate with Adaptive Reactivity. Angew Chem Int Ed Engl 2018; 57:6077-6081. [PMID: 29644773 DOI: 10.1002/anie.201713351] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Indexed: 12/17/2022]
Abstract
A new strategy of highly efficient supramolecular catalysis is developed by endowing the reaction intermediate with adaptive reactivity. The supramolecular catalyst, prepared by host-guest complexation between 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and cucurbit[7]uril (CB[7]), was used for biphasic oxidation of alcohols. Cationic TEMPO+ , the key intermediate, was stabilized by the electrostatic effect of CB[7] in aqueous phase, thus promoting the formation of TEMPO+ and inhibiting side reactions. Moreover, through the migration into the organic phase, TEMPO+ was separated from CB[7] and recovered the high reactivity to drive a fast oxidation of substrates. The adaptive reactivity of TEMPO+ induced an integral optimization of the catalytic cycle and greatly improved the conversion of the reaction. This work highlights the unique advantages of dynamic noncovalent interactions on modulating the activity of reaction intermediates, which may open new horizons for supramolecular catalysis.
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Affiliation(s)
- Yang Jiao
- Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Bohan Tang
- Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Yucheng Zhang
- Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Jiang-Fei Xu
- Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Zhiqiang Wang
- Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Xi Zhang
- Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, China
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139
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Lecarme L, Kochem A, Chiang L, Moutet J, Berthiol F, Philouze C, Leconte N, Storr T, Thomas F. Electronic Structure and Reactivity of One-Electron-Oxidized Copper(II) Bis(phenolate)–Dipyrrin Complexes. Inorg Chem 2018; 57:9708-9719. [DOI: 10.1021/acs.inorgchem.8b00044] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Lauréline Lecarme
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Amélie Kochem
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Linus Chiang
- Department of Chemistry, University of the Fraser Valley, Abbotsford, British Columbia V2S 7M8, Canada
| | - Jules Moutet
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Florian Berthiol
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Christian Philouze
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Nicolas Leconte
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
| | - Tim Storr
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Fabrice Thomas
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, B.P. 53, 38041 Grenoble Cedex 9, France
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140
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Kojima T, Ogishima F, Nishibu T, Kotani H, Ishizuka T, Okajima T, Nozawa S, Shiota Y, Yoshizawa K, Ohtsu H, Kawano M, Shiga T, Oshio H. Intermediate-Spin Iron(III) Complexes Having a Redox-Noninnocent Macrocyclic Tetraamido Ligand. Inorg Chem 2018; 57:9683-9695. [DOI: 10.1021/acs.inorgchem.8b00037] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Takahiko Kojima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
- CREST, Japan Science and Technology Agency, 4 Chome-1-8, Kawaguchi, Honcho, Saitama 332-0012, Japan
| | - Fumiya Ogishima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Takahisa Nishibu
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Hiroaki Kotani
- 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
| | - Toshihiro Okajima
- Kyushu Synchrotron Light Research Center, 8-7 Yayoigaoka, Tosu, Saga 841-0005, Japan
| | - Shunsuke Nozawa
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- CREST, Japan Science and Technology Agency, 4 Chome-1-8, Kawaguchi, Honcho, Saitama 332-0012, Japan
- Institute for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Hiroyoshi Ohtsu
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Masaki Kawano
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Takuya Shiga
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Hiroki Oshio
- 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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141
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Tanimoto R, Yamada K, Suzuki S, Kozaki M, Okada K. Group 11 Metal Complexes Coordinated by the (Nitronyl Nitroxide)-2-ide Radical Anion: Facile Oxidation of Stable Radicals Controlled by Metal-Carbon Bonds in Radical-Metalloids. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201800038] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Ryu Tanimoto
- Graduate School of Science; Osaka City University; 558-8585 Osaka Osaka Prefecture Japan
| | - Kiyomi Yamada
- Graduate School of Science; Osaka City University; 558-8585 Osaka Osaka Prefecture Japan
| | - Shuichi Suzuki
- Graduate School of Science; Osaka City University; 558-8585 Osaka Osaka Prefecture Japan
| | - Masatoshi Kozaki
- Graduate School of Science; Osaka City University; 558-8585 Osaka Osaka Prefecture Japan
| | - Keiji Okada
- Graduate School of Science; Osaka City University; 558-8585 Osaka Osaka Prefecture Japan
- The Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA); 558-8585 Osaka Osaka Prefecture Japan
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142
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Erxleben A. Transition metal salen complexes in bioinorganic and medicinal chemistry. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.06.060] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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143
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Jehdaramarn A, Pornsuwan S, Chumsaeng P, Phomphrai K, Sangtrirutnugul P. Effects of appended hydroxyl groups and ligand chain length on copper coordination and oxidation activity. NEW J CHEM 2018. [DOI: 10.1039/c7nj03113k] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effects of appended hydroxyl groups and the chain length of a series of (imino)pyridine ligands on copper coordination and copper-catalyzed aerobic oxidation of alcohols were investigated.
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Affiliation(s)
- Attawit Jehdaramarn
- Center of Excellence for Innovation in Chemistry (PERCH-CIC)
- Department of Chemistry
- Faculty of Science
- Mahidol University
- Bangkok
| | - Soraya Pornsuwan
- Center of Excellence for Innovation in Chemistry (PERCH-CIC)
- Department of Chemistry
- Faculty of Science
- Mahidol University
- Bangkok
| | - Phongnarin Chumsaeng
- Center of Excellence for Innovation in Chemistry (PERCH-CIC)
- Department of Chemistry
- Faculty of Science
- Mahidol University
- Bangkok
| | - Khamphee Phomphrai
- Department of Materials Science and Engineering
- School of Molecular Science and Engineering
- Vidyasirimedhi Institute of Science and Technology (VISTEC)
- Wangchan
- Thailand
| | - Preeyanuch Sangtrirutnugul
- Center of Excellence for Innovation in Chemistry (PERCH-CIC)
- Department of Chemistry
- Faculty of Science
- Mahidol University
- Bangkok
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144
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Xie J, Lo PK, Lam CS, Lau KC, Lau TC. A hydrogen-atom transfer mechanism in the oxidation of alcohols by [FeO4]2− in aqueous solution. Dalton Trans 2018; 47:240-245. [DOI: 10.1039/c7dt03830e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxidation of alcohols by [FeO4]2− in aqueous solution is found to proceed via a hydrogen atom transfer (HAT) mechanism based on deuterium isotope effects, correlation between rate constants and bond dissociation energies (BDEs) and DFT calculations.
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Affiliation(s)
- Jianhui Xie
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- School of Chemistry and Chemical Engineering
- Hefei University of Technology
- Hefei 230009
- P. R. China
| | - Po-Kam Lo
- Department of Chemistry
- City University of Hong Kong
- Hong Kong
- People's Republic of China
| | - Chow-Shing Lam
- Department of Chemistry
- City University of Hong Kong
- Hong Kong
- People's Republic of China
| | - Kai-Chung Lau
- Department of Chemistry
- City University of Hong Kong
- Hong Kong
- People's Republic of China
| | - Tai-Chu Lau
- Department of Chemistry
- City University of Hong Kong
- Hong Kong
- People's Republic of China
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145
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van Leest NP, Epping RF, van Vliet KM, Lankelma M, van den Heuvel EJ, Heijtbrink N, Broersen R, de Bruin B. Single-Electron Elementary Steps in Homogeneous Organometallic Catalysis. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2018. [DOI: 10.1016/bs.adomc.2018.07.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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146
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Chen C, Chen J, Geng Z, Wang M, Liu N, Li D. Regioselectivity of oxidation by a polysaccharide monooxygenase from Chaetomium thermophilum. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:155. [PMID: 29991963 PMCID: PMC5987470 DOI: 10.1186/s13068-018-1156-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 05/29/2018] [Indexed: 05/15/2023]
Abstract
BACKGROUND Polysaccharide monooxygenases (PMOs) of the auxiliary activity 9 (AA9) family have been reported to oxidize C1, C4, and C6 positions in cellulose. However, currently no direct evidence exists that PMOs oxidize C6 positions in cellulose, and molecular mechanism of C1, C4 and C6 oxidation is unclear. RESULTS In this study, a PMO gene (Ctpmo1) belonging to AA9 was isolated from Chaetomium thermophilum and successfully expressed and correctly processed in Pichia pastoris. A simple and effective chemical method of using Br2 to oxidize CtPMO1 reaction products was developed to directly identify C4- and C6-oxidized products by matrix-assisted laser desorption/ionization-time-of-flight tandem mass spectrometry (MALDI-TOF-MS). The PMO (CtPMO1) cleaves phosphoric acid-swollen cellulose (PASC) and celloheptaose, resulting in the formation of oxidized and nonoxidized oligosaccharides. Product identification shows that the enzyme can oxidize C1, C4, and C6 in PASC and cello-oligosaccharides. Mutagenesis of the aromatic residues Tyr27, His64, His157 and residue Tyr206 on the flat surface of CtPMO1 was carried out using site-directed mutagenesis to form the mutated enzymes Y27A, H64A, H157A, and Y206A. It was demonstrated that Y27A retained complete activity of C1, C4, and C6 oxidation on cellulose; Y206A retained partial activity of C1 and C4 oxidation but completely lost activity of C6 oxidation on cellulose; H64A almost completely lost activity of C1, C4, and C6 oxidation on cellulose; and H157A completely lost activity of C1, C4, and C6 oxidation on cellulose. CONCLUSIONS This finding provides direct and molecular evidence for C1, C4, especially C6 oxidation by lytic polysaccharide monooxygenase. CtPMO1 oxidizes not only C1 and C4 but also C6 positions in cellulose. The aromatic acid residues His64, His157 and residue Tyr206 on CtPMO1 flat surface are involved in activity of C1, C4, C6 oxidation.
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Affiliation(s)
- Chen Chen
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Jinyin Chen
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Zhigang Geng
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Meixia Wang
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Ning Liu
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
| | - Duochuan Li
- Department of Mycology, Shandong Agricultural University, Taian, 271018 Shandong China
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147
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Mustieles Marín I, Cheisson T, Singh-Chauhan R, Herrero C, Cordier M, Clavaguéra C, Nocton G, Auffrant A. Electronic Structures of Mono-Oxidized Copper and Nickel Phosphasalen Complexes. Chemistry 2017; 23:17940-17953. [PMID: 28980736 DOI: 10.1002/chem.201703390] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Indexed: 11/11/2022]
Abstract
Non-innocent ligands render the determination of the electronic structure in metal complexes difficult. As such, a combination of experimental techniques and quantum chemistry are required to correctly elucidate them. This paper deals with the one-electron oxidation of copper(II) and nickel(II) complexes featuring a phosphasalen ligand (Psalen), which differs from salen analogues by the presence of iminophosphorane groups (P=N) instead of imines. Various experimental techniques (X-ray diffraction, cyclic voltammetry, NMR, EPR, and UV/Vis spectroscopies, and magnetic measurements) as well as quantum chemical calculations were used to define the electronic structure of the oxidized complexes. These can be modified by a small change in the ligand structure, that is, the replacement of a tert-butyl group by a methoxy on the phenoxide ring. The different techniques have allowed quantifying the amount of spin density located on the metal center and on the Psalen ligands. All complexes were found to possess a multi-configurational ground state, in which the ratio of the +II versus +III oxidation state of the metal center, and therefore the phenolate versus phenoxyl radical ligand character, varies upon the substituents. The tert-butyl group favors a strong localization on the metal center whereas with the methoxy group the metallic configurations decrease and the ligand configurations increase. The importance of the geometrical considerations compared with the electronic substituent effect is highlighted by the differences observed between the solid-state (EPR, magnetic measurements) and solution characterizations (EPR and NMR data).
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Affiliation(s)
- Irene Mustieles Marín
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France
| | - Thibault Cheisson
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France
| | - Rohit Singh-Chauhan
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France
| | - Christian Herrero
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS-Univ. Paris-Sud, Univ. Paris Saclay, 91405, Orsay Cedex, France
| | - Marie Cordier
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France
| | - Carine Clavaguéra
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France.,Laboratoire de Chimie Physique, CNRS-Université Paris-Sud, Université Paris-Saclay, 15 avenue Jean Perrin, 91405, Orsay, France
| | - Grégory Nocton
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France
| | - Audrey Auffrant
- LCM, CNRS-Ecole polytechnique, Université Paris-Saclay, 91128, Palaiseau Cedex, France
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148
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Rational Engineering of a Flavoprotein Oxidase for Improved Direct Oxidation of Alcohols to Carboxylic Acids. Molecules 2017; 22:molecules22122205. [PMID: 29231859 PMCID: PMC6149797 DOI: 10.3390/molecules22122205] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 12/06/2017] [Accepted: 12/08/2017] [Indexed: 11/25/2022] Open
Abstract
The oxidation of alcohols to the corresponding carbonyl or carboxyl compounds represents a convenient strategy for the selective introduction of electrophilic carbon centres into carbohydrate-based starting materials. The O2-dependent oxidation of prim-alcohols by flavin-containing alcohol oxidases often yields mixtures of aldehyde and carboxylic acid, which is due to “over-oxidation” of the aldehyde hydrate intermediate. In order to directly convert alcohols into carboxylic acids, rational engineering of 5-(hydroxymethyl)furfural oxidase was performed. In an attempt to improve the binding of the aldehyde hydrate in the active site to boost aldehyde-oxidase activity, two active-site residues were exchanged for hydrogen-bond-donating and -accepting amino acids. Enhanced over-oxidation was demonstrated and Michaelis–Menten kinetics were performed to corroborate these findings.
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149
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Characterization of the one-electron oxidized Cu(II)-salen complexes with a side chain aromatic ring: the effect of the indole ring on the Cu(II)-phenoxyl radical species. J Biol Inorg Chem 2017; 23:51-59. [PMID: 29218633 DOI: 10.1007/s00775-017-1508-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 11/09/2017] [Indexed: 10/18/2022]
Abstract
To gain insights into the role of the proximal indole ring in the redox-active metal center as seen in galactose oxidase, we prepared the Cu(II)-salen-type complexes having a pendent indol-3-ylmethyl (1), methyl (2) or benzyl (3) group substituted on the ethylenediamine moiety and investigated the structures and redox properties by various physicochemical methods and theoretical calculations. Neutral complexes 1, 2, and 3 showed no significant difference in the UV-Vis-NIR and EPR spectra. One-electron oxidation of 1, 2, and 3 by addition of 1 equiv. of thianthrenyl radical gave [1]SbCl 6 , [2]SbCl 6 , and [3]SbCl 6 , respectively, which could be assigned to relatively localized phenoxyl radical species. The cyclic and differential pulse voltammograms of [1]SbCl 6 showed two redox waves with a large separation between the first and second redox potentials compared with the separations observed for [2]SbCl 6 and [3]SbCl 6 . This suggests that [1]SbCl 6 is more stabilized than [2]SbCl 6 and [3]SbCl 6 . The NIR band of [1]SbCl 6 showed a larger blue shift than that of [2]SbCl 6 and [3]SbCl 6 . The EPR spectrum of [2]SbCl 6 exhibited an intense signal at the g value of 2 due to partial disproportionation to form the EPR active two-electron oxidized complex [2] 2+ , while the EPR intensity of [1]SbCl 6 was much weaker than that of [2]SbCl 6 . These results indicate that the pendent indole moiety stabilizes the Cu(II)-phenoxyl radical in [1]SbCl 6 most probably by stacking with the phenoxyl moiety, which is further supported by DFT calculations.
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150
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