1
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Doyle LM, Bienenmann RLM, Gericke R, Xu S, Farquhar ER, Que L, McDonald AR. Preparation and characterization of Mn IIMn III complexes with relevance to class Ib ribonucleotide reductases. J Inorg Biochem 2024; 257:112583. [PMID: 38733704 DOI: 10.1016/j.jinorgbio.2024.112583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Revised: 04/26/2024] [Accepted: 04/30/2024] [Indexed: 05/13/2024]
Abstract
The Mn2 complex [MnII2(TPDP)(O2CPh)2](BPh4) (1, TPDP = 1,3-bis(bis(pyridin-2-ylmethyl)amino)propan-2-ol, Ph =phenyl) was prepared and subsequently characterized via single-crystal X-ray diffraction, X-ray absorption, electronic absorption, and infrared spectroscopies, and mass spectrometry. 1 was prepared in order to explore its properties as a structural and functional mimic of class Ib ribonucleotide reductases (RNRs). 1 reacted with superoxide anion (O2•-) to generate a peroxido-MnIIMnIII complex, 2. The electronic absorption and electron paramagnetic resonance (EPR) spectra of 2 were similar to previously published peroxido-MnIIMnIII species. Furthermore, X-ray near edge absorption structure (XANES) studies indicated the conversion of a MnII2 core in 1 to a MnIIMnIII state in 2. Treatment of 2 with para-toluenesulfonic acid (p-TsOH) resulted in the conversion to a new MnIIMnIII species, 3, rather than causing O-O bond scission, as previously encountered. 3 was characterized using electronic absorption, EPR, and X-ray absorption spectroscopies. Unlike other reported peroxido-MnIIMnIII species, 3 was capable of oxidative O-H activation, mirroring the generation of tyrosyl radical in class Ib RNRs, however without accessing the MnIIIMnIV state.
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Affiliation(s)
- Lorna M Doyle
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Roel L M Bienenmann
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Robert Gericke
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Shuangning Xu
- Department of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, Minneapolis, 55455 MN, United States
| | - Erik R Farquhar
- Case Western Reserve University Center for Synchrotron Biosciences, National Synchrotron Light Source II, Brookhaven National Laboratory Upton, NY, 11973 New York, United States
| | - Lawrence Que
- Department of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, Minneapolis, 55455 MN, United States
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland.
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2
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Doyle L, Magherusan A, Xu S, Murphy K, Farquhar ER, Molton F, Duboc C, Que L, McDonald AR. Class Ib Ribonucleotide Reductases: Activation of a Peroxido-Mn IIMn III to Generate a Reactive Oxo-Mn IIIMn IV Oxidant. Inorg Chem 2024; 63:2194-2203. [PMID: 38231137 PMCID: PMC10828993 DOI: 10.1021/acs.inorgchem.3c04163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/18/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024]
Abstract
In the postulated catalytic cycle of class Ib Mn2 ribonucleotide reductases (RNRs), a MnII2 core is suggested to react with superoxide (O2·-) to generate peroxido-MnIIMnIII and oxo-MnIIIMnIV entities prior to proton-coupled electron transfer (PCET) oxidation of tyrosine. There is limited experimental support for this mechanism. We demonstrate that [MnII2(BPMP)(OAc)2](ClO4) (1, HBPMP = 2,6-bis[(bis(2 pyridylmethyl)amino)methyl]-4-methylphenol) was converted to peroxido-MnIIMnIII (2) in the presence of superoxide anion that converted to (μ-O)(μ-OH)MnIIIMnIV (3) via the addition of an H+-donor (p-TsOH) or (μ-O)2MnIIIMnIV (4) upon warming to room temperature. The physical properties of 3 and 4 were probed using UV-vis, EPR, X-ray absorption, and IR spectroscopies and mass spectrometry. Compounds 3 and 4 were capable of phenol oxidation to yield a phenoxyl radical via a concerted PCET oxidation, supporting the proposed mechanism of tyrosyl radical cofactor generation in RNRs. The synthetic models demonstrate that the postulated O2/Mn2/tyrosine activation mechanism in class Ib Mn2 RNRs is plausible and provides spectral insights into intermediates currently elusive in the native enzyme.
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Affiliation(s)
- Lorna Doyle
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
| | - Adriana Magherusan
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
| | - Shuangning Xu
- Department
of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Kayleigh Murphy
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
| | - Erik R. Farquhar
- Case
Western Reserve University Center for Synchrotron Biosciences, National
Synchrotron Light Source II, Brookhaven
National Laboratory Upton, New
York 11973, United States
| | - Florian Molton
- CNRS
UMR 5250, DCM, Univ. Grenoble Alpes, Grenoble F-38000, France
| | - Carole Duboc
- CNRS
UMR 5250, DCM, Univ. Grenoble Alpes, Grenoble F-38000, France
| | - Lawrence Que
- Department
of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Aidan R. McDonald
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
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3
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Kumar R, Keshri R, Prodhan K, Shaikh K, Draksharapu A. A tetranuclear Mn-diamond core complex as a functional mimic of both catechol oxidase and phenoxazinone synthase enzymes. Dalton Trans 2023; 52:15412-15419. [PMID: 37226832 DOI: 10.1039/d3dt00761h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Through dioxygen activation, a tetranuclear Mn(II,III,III,II) diamond core, [Mn4(HPTP*)2(μ-O)2(H2O)4](ClO4)4 (1) complex, has been synthesised using a suitably designed septadentate ligand framework (HPTP*H = 1,3-bis(bis((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)amino)propan-2-ol). The newly prepared complex 1 was characterised using multiple spectroscopic techniques and X-ray crystallography. 1 exhibits excellent catalytic oxidation reactivity for the model substrates, namely, 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-aminophenol, efficiently mimicking the enzymes catechol oxidase and phenoxazinone synthase, respectively. Remarkably, we employed aerial oxygen to catalyze the oxidation of these model substrates, 3,5-DTBC and 2-aminophenol, with turnover numbers of 835 and 14, respectively. A tetranuclear Mn-diamond core complex that mimics both catechol oxidase and phenoxazinone synthase could pave the way for further research into its potential as a multi-enzymatic functional mimic.
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Affiliation(s)
- Rakesh Kumar
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur - 208016, India.
| | - Rahul Keshri
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur - 208016, India.
| | - Koushik Prodhan
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur - 208016, India.
| | - Kanchan Shaikh
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur - 208016, India.
| | - Apparao Draksharapu
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur - 208016, India.
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4
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Battistella B, Lohmiller T, Cula B, Hildebrandt P, Kuhlmann U, Dau H, Mebs S, Ray K. A New Thiolate-Bound Dimanganese Cluster as a Structural and Functional Model for Class Ib Ribonucleotide Reductases. Angew Chem Int Ed Engl 2023; 62:e202217076. [PMID: 36583430 DOI: 10.1002/anie.202217076] [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: 11/20/2022] [Revised: 12/24/2022] [Accepted: 12/29/2022] [Indexed: 12/31/2022]
Abstract
In class Ib ribonucleotide reductases (RNRs) a dimanganese(II) cluster activates superoxide (O2 ⋅- ) rather than dioxygen (O2 ), to access a high valent MnIII -O2 -MnIV species, responsible for the oxidation of tyrosine to tyrosyl radical. In a biomimetic approach, we report the synthesis of a thiolate-bound dimanganese complex [MnII 2 (BPMT)(OAc)2 ](ClO)4 (BPMT=(2,6-bis{[bis(2-pyridylmethyl)amino]methyl}-4-methylthiophenolate) (1) and its reaction with O2 ⋅- to form a [(BPMT)MnO2 Mn]2+ complex 2. Resonance Raman investigation revealed the presence of an O-O bond in 2, while EPR analysis displayed a 16-line St =1/2 signal at g=2 typically associated with a MnIII MnIV core, as detected in class Ib RNRs. Unlike all other previously reported Mn-O2 -Mn complexes, generated by O2 ⋅- activation at Mn2 centers, 2 proved to be a capable electrophilic oxidant in aldehyde deformylation and phenol oxidation reactions, rendering it one of the best structural and functional models for class Ib RNRs.
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Affiliation(s)
- Beatrice Battistella
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
| | - Thomas Lohmiller
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany.,EPR4Energy Joint Lab, Department Spins in Energy Conversion and Quantum Information Science, Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 16, 12489, Berlin, Germany
| | - Beatrice Cula
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
| | - Peter Hildebrandt
- Institut für Chemie, Fakultät II, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Uwe Kuhlmann
- Institut für Chemie, Fakultät II, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Holger Dau
- Institut für Physik, Freie Universität zu Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Stefan Mebs
- Institut für Physik, Freie Universität zu Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Kallol Ray
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489, Berlin, Germany
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5
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Yadav O, Ansari M, Ansari A. Electronic structures, bonding aspects and spectroscopic parameters of homo/hetero valent bridged dinuclear transition metal complexes. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 278:121331. [PMID: 35597159 DOI: 10.1016/j.saa.2022.121331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/25/2022] [Accepted: 04/27/2022] [Indexed: 06/15/2023]
Abstract
Bridged dinuclear metal complexes have fascinated scientists worldwide, and remarkable success has been achieved to unravel the electronic structures, structure-function relationship, coordination environments, and fine mechanistic details of the enzymes owing to the repercussion of biomimetic studies carried out on dinuclear model systems. Molecular level study of these systems integrated with spectroscopic study helps in gaining deep insights about structural and electronic aspects of natural enzymatic systems. Considering the same, here first time we report DFT study on bridged non-heme metal complexes based on N-Et-HPTB ligand system containing homovalent (MIIMII); {[(MnII)2(O2CCH3)(N-Et-HPTB)]2+; Species I), [(FeII)2(O2CCH3)(N-Et-HPTB)]2+; Species II), [(CoII)2(O2CCH3)(N-Et-HPTB)]2+; Species III)} and heterovalent (MIIIMII): {[(MnIII)(MnII)(O2)(N-Et-HPTB)]2+; Species Ia) [(FeIII)(FeII)(O2)(N-Et-HPTB)]2+; Species IIa) and [(CoIII)(CoII)(O2)(N-Et-HPTB)]2+; Species IIIa)} dinuclear metal centres. Bridging oxygen bears a significant spin density which may prompt important chemical reactions involving activation of bonds like C-H/O-H/N-H etc. TD-DFT calculations for UV-Visible absorption have been carried out to further shed light on structural-functional and electronic structures of these dinuclear species. Studying these dinuclear species may be a good starting point for the study of active sites of the bimetallic centre of dinuclear enzymes and thus may serve as fascinating spectroscopic models. Further, FMO analysis, MEP mapping, and NBO calculations were employed to analyze bonding aspects predict theoretical reactivity behaviour and any kind of stabilizing interactions present in the reported species.
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Affiliation(s)
- Oval Yadav
- Department of Chemistry, Central University of Haryana, Mahendergarh 123031, India
| | - Mursaleem Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Pawai 400076, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Mahendergarh 123031, India.
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6
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Sun J, Yin Y, Li W, Jin O, Na N. CHEMICAL REACTION MONITORING BY AMBIENT MASS SPECTROMETRY. MASS SPECTROMETRY REVIEWS 2022; 41:70-99. [PMID: 33259644 DOI: 10.1002/mas.21668] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 10/16/2020] [Accepted: 10/22/2020] [Indexed: 06/12/2023]
Abstract
Chemical reactions conducted in different media (liquid phase, gas phase, or surface) drive developments of versatile techniques for the detection of intermediates and prediction of reasonable reaction pathways. Without sample pretreatment, ambient mass spectrometry (AMS) has been applied to obtain structural information of reactive molecules that differ in polarity and molecular weight. Commercial ion sources (e.g., electrospray ionization, atmospheric pressure chemical ionization, and direct analysis in real-time) have been reported to monitor substrates and products by offline reaction examination. While the interception or characterization of reactive intermediates with short lifetime are still limited by the offline modes. Notably, online ionization technologies, with high tolerance to salt, buffer, and pH, can achieve direct sampling and ionization of on-going reactions conducted in different media (e.g., liquid phase, gas phase, or surface). Therefore, short-lived intermediates could be captured at unprecedented timescales, and the reaction dynamics could be studied for mechanism examinations without sample pretreatments. In this review, via various AMS methods, chemical reaction monitoring and mechanism elucidation for different classifications of reactions have been reviewed. The developments and advances of common ionization methods for offline reaction monitoring will also be highlighted.
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Affiliation(s)
- Jianghui Sun
- Key Laboratory of Radiopharmaceuticals Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, People's Republic of China
| | - Yiyan Yin
- Key Laboratory of Radiopharmaceuticals Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, People's Republic of China
| | - Weixiang Li
- Key Laboratory of Radiopharmaceuticals Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, People's Republic of China
| | - Ouyang Jin
- Key Laboratory of Radiopharmaceuticals Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, People's Republic of China
| | - Na Na
- Key Laboratory of Radiopharmaceuticals Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, People's Republic of China
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7
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Synthesis, crystal structure and magnetic properties of a pentanuclear Mn(III) cluster with 1,2,4-triazole based Schiff base ligand. Inorganica Chim Acta 2020. [DOI: 10.1016/j.ica.2020.119461] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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9
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Bedin M, Agarwala H, Marx J, Schünemann V, Ott S, Thapper A. Synthesis and properties of a heterobimetallic iron-manganese complex and its comparison with homobimetallic analogues. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2019.03.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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10
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11
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Magherusan AM, Kal S, Nelis DN, Doyle LM, Farquhar ER, Que L, McDonald AR. A Mn II Mn III -Peroxide Complex Capable of Aldehyde Deformylation. Angew Chem Int Ed Engl 2019; 58:5718-5722. [PMID: 30830996 DOI: 10.1002/anie.201900717] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 02/27/2019] [Indexed: 11/07/2022]
Abstract
Ribonucleotide reductases (RNRs) are essential enzymes required for DNA synthesis. In class Ib Mn2 RNRs superoxide (O2 .- ) was postulated to react with the MnII 2 core to yield a MnII MnIII -peroxide moiety. The reactivity of complex 1 ([MnII 2 (O2 CCH3 )2 (BPMP)](ClO4 ), where HBPMP=2,6-bis{[(bis(2-pyridylmethyl)amino]methyl}-4-methylphenol) towards O2 .- was investigated at -90 °C, generating a metastable species, 2. The electronic absorption spectrum of 2 displayed features (λmax =440, 590 nm) characteristic of a MnII MnIII -peroxide species, representing just the second example of such. Electron paramagnetic resonance and X-ray absorption spectroscopies, and mass spectrometry supported the formulation of 2 as a MnII MnIII -peroxide complex. Unlike all other previously reported Mn2 -peroxides, which were unreactive, 2 proved to be a capable oxidant in aldehyde deformylation. Our studies provide insight into the mechanism of O2 -activation in Class Ib Mn2 RNRs, and the highly reactive intermediates in their catalytic cycle.
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Affiliation(s)
- Adriana M Magherusan
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Subhasree Kal
- Department of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN, 55455, USA
| | - Daniel N Nelis
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Lorna M Doyle
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Erik R Farquhar
- Case Western Reserve University Centre for Synchrotron Biosciences, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Lawrence Que
- Department of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN, 55455, USA
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
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12
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Bikas R, Shahmoradi E, Reinoso S, Emami M, Lezama L, Sanchiz J, Noshiranzadeh N. The effect of the orientation of the Jahn–Teller distortion on the magnetic interactions of trinuclear mixed-valence Mn(ii)/Mn(iii) complexes. Dalton Trans 2019; 48:13799-13812. [DOI: 10.1039/c9dt01652j] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The effect of the orientation of the Jahn–Teller distortion on the magnetic interactions in two new mixed-valence trinuclear Mn(iii)–Mn(ii)–Mn(iii) complexes has been investigated.
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Affiliation(s)
- Rahman Bikas
- Department of Chemistry
- Faculty of Science
- Imam Khomeini International University
- 34148-96818 Qazvin
- Iran
| | - Elaheh Shahmoradi
- Department of Chemistry
- Faculty of Science
- University of Zanjan
- 45371-38791 Zanjan
- Iran
| | - Santiago Reinoso
- Institute for Advanced Materials (InaMat)
- Universidad Pública de Navarra
- 31006 Pamplona
- Spain
| | - Marzieh Emami
- Department of Chemistry
- Faculty of Science
- University of Zanjan
- 45371-38791 Zanjan
- Iran
| | - Luis Lezama
- Departamento de Química Inorgánica
- Facultad de Ciencia y Tecnología
- Universidad del País Vasco UPV/EHU
- 48080 Bilbao
- Spain
| | - Joaquín Sanchiz
- Department of Chemistry
- Faculty of Science
- Instituto de Materiales y Nanotecnología
- University of La Laguna
- 38206 Tenerife
| | - Nader Noshiranzadeh
- Department of Chemistry
- Faculty of Science
- University of Zanjan
- 45371-38791 Zanjan
- Iran
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13
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Magherusan AM, Nelis DN, Twamley B, McDonald AR. Catechol oxidase activity of comparable dimanganese and dicopper complexes. Dalton Trans 2018; 47:15555-15564. [PMID: 30345446 DOI: 10.1039/c8dt01378k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthetic Cu complexes have been widely investigated as model systems for catechol oxidase enzymes. The catechol oxidase reactivity of Mn complexes has been less explored, and the effect of metal substitution in catecholase mimics has not been explored. A series of Mn and Cu complexes supported by the same poly-benzimidazole ligand framework have been synthesised and investigated in catecholase activity in acetonitrile medium using 3,5-di-tert-butylcatechol (3,5-DTBC) as a substrate. The Cu complexes proved to be good catechol oxidase mimics with moderate kcat values (∼45 h-1). The kinetic parameters for Mn complexes exhibited lower kcat values (∼8-40 h-1) when compared to the Cu complexes. Our findings demonstrate that later transition metals supported by relatively electron rich ligands yield the highest kcat values for catechol oxidation.
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Affiliation(s)
- Adriana M Magherusan
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland.
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14
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Costa RO, Ferreira SS, Pereira CA, Harmer JR, Noble CJ, Schenk G, Franco RWA, Resende JALC, Comba P, Roberts AE, Fernandes C, Horn A. A New Mixed-Valence Mn(II)Mn(III) Compound With Catalase and Superoxide Dismutase Activities. Front Chem 2018; 6:491. [PMID: 30456211 PMCID: PMC6231112 DOI: 10.3389/fchem.2018.00491] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 09/26/2018] [Indexed: 12/17/2022] Open
Abstract
The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand H2BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, [Mn(III)(μ-HBPClNOL)(μ-BPClNOL)Mn(II)(Cl)](ClO4)·2H2O, 1, in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand H2BPClNOL, a phenoxide and an alkoxide group. In the solid state, this mixed valence dinuclear unit is connected to its neighbors through chloro bridges. Magnetic measurements indicated the presence of ferromagnetic [J = +0.076(13) cm−1] and antiferromagnetic [J = −5.224(13) cm−1] interactions. The compound promotes O2•- dismutation in aqueous solution (IC50 = 0.370 μmol dm−3, kcat = 3.6x106 M−1 s−1). EPR studies revealed that a high-valent Mn(III)-O-Mn(IV) species is involved in the superoxide dismutation catalytic cycle. Complex 1 shows catalase activity only in the presence of a base, e.g., piperazine or triethylamine. Kinetic studies were carried out in the presence of piperazine and employing two different methods, resulting in kcat values of 0.58 ± 0.03 s−1 (detection of O2 production employing a Clark electrode) and 2.59 ± 0.12 s−1 (H2O2 consuption recorded via UV-Vis). EPR and ESI-(+)-MS studies indicate that piperazine induces the oxidation of 1, resulting in the formation of the catalytically active Mn(III)-O-Mn(IV) species.
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Affiliation(s)
- Rafael O Costa
- Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | | | - Crystiane A Pereira
- Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Jeffrey R Harmer
- Centre for Advanced Imaging, University of Queensland, Brisbane, QLD, Australia
| | - Christopher J Noble
- Centre for Advanced Imaging, University of Queensland, Brisbane, QLD, Australia
| | - Gerhard Schenk
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, Australia
| | - Roberto W A Franco
- Laboratório de Ciências Físicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Jackson A L C Resende
- Instituto de Ciências Exatas e da Terra, Campus Universitário do Araguaia, Universidade Federal do Mato Grosso, Barra do Garças, Brazil
| | - Peter Comba
- Anorganisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.,Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Heidelberg, Germany
| | - Asha E Roberts
- Anorganisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany.,Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Heidelberg, Germany
| | - Christiane Fernandes
- Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Adolfo Horn
- Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
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15
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Denler MC, Wijeratne GB, Rice DB, Colmer HE, Day VW, Jackson TA. Mn III-Peroxo adduct supported by a new tetradentate ligand shows acid-sensitive aldehyde deformylation reactivity. Dalton Trans 2018; 47:13442-13458. [PMID: 30183042 PMCID: PMC6176719 DOI: 10.1039/c8dt02300j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The new tetradentate L7BQ ligand (L7BQ = 1,4-di(quinoline-8-yl)-1,4-diazepane) has been synthesized and shown to support MnII and MnIII-peroxo complexes. X-ray crystallography of the [MnII(L7BQ)(OTf)2] complex shows a monomeric MnII center with the L7BQ ligand providing four donor nitrogen atoms in the equatorial field, with two triflate ions bound in the axial positions. When this species is treated with H2O2 and Et3N at -40 °C, a MnIII-peroxo adduct, [MnIII(O2)(L7BQ)]+ is formed. The formation of this new intermediate is supported by a variety of spectroscopic techniques, including electronic absorption, Mn K-edge X-ray absorption and electron paramagnetic resonance methods. Evaluation of extended X-ray absorption fine structure data for [MnIII(O2)(L7BQ)]+ resolved Mn-O bond distances of 1.85 Å, which are on the short end of those previously reported for crystallographically characterized MnIII-peroxo adducts. An analysis of the X-ray pre-edge region of [MnIII(O2)(L7BQ)]+ revealed a large pre-edge area of 20.8 units. Time-dependent density functional theory computations indicate that the pre-edge intensity is due to Mn 4p-3d mixing caused by geometric distortions from centrosymmetry induced by both the peroxo and L7BQ ligands. The reactivity of [MnIII(O2)(L7BQ)]+ towards aldehydes was assessed through reaction with cyclohexanecarboxaldehyde and 2-phenylpropionaldehyde. From these experiments, it was determined that [MnIII(O2)(L7BQ)]+ only reacts with aldehydes in the presence of acid. Specifically, the addition of cyclohexanecarboxylic acid to [MnIII(O2)(L7BQ)]+ converts the MnIII-peroxo adduct to a new intermediate that could be responsible for the observed aldehyde deformylation activity. These observations underscore the challenges in identifying the reactive metal species in aldehyde deformylation reactions.
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Affiliation(s)
- Melissa C Denler
- The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
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