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Josephy T, Kumar R, Bleher K, Röhs F, Glaser T, Rajaraman G, Comba P. Synthesis, Characterization, and Reactivity of Bispidine-Iron(IV)-Tosylimido Species. Inorg Chem 2024; 63:12109-12119. [PMID: 38875304 DOI: 10.1021/acs.inorgchem.4c01237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2024]
Abstract
Reported are the synthesis and detailed studies of the iron(IV)-tosylimido complexes of two isomeric pentadentate bispidine ligands (bispidines are 3,7-diazabicyclo[3.3.1]nonane derivatives). This completes a series of five tosylimido complexes with comparable pentadentate amine/pyridine ligands, where the corresponding [(L)FeIV═O]2+ oxidants have been studied in detail. The characterization of the two new complexes in solution (UV-vis-NIR, Mössbauer, HR-ESI-MS) shows that these oxidants have an intermediate spin (S = 1) electronic ground state. The reactivities have been studied as oxidants in C-H activation at 1,3-cyclohexadiene and nitrogen atom transfer to thioanisole. For the latter substrate, the entire set of data for the five ligands and for both nitrogen and oxygen atom transfer is now available and the interesting observation is that oxygen atom transfer is, as expected, generally faster than nitrogen atom transfer, with the exception of the two ligands that have four and three pyridine groups oriented parallel to the Fe-O and Fe-N axes. A thorough DFT analysis indicates that this is due to steric effects in the case of the [(L)FeIV═O]2+ species, which are less important in the [(L)FeIV═NTs]2+ compounds due to partial electron transfer from the thioanisole substrate to the iron(IV)-tosylimido oxidant.
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Affiliation(s)
- Thomas Josephy
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270,Heidelberg D-69120, Germany
| | - Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Katharina Bleher
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270,Heidelberg D-69120, Germany
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen 76344, Germany
| | - Fridolin Röhs
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, Bielefeld D-33615, Germany
| | - Thorsten Glaser
- Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, Bielefeld D-33615, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Peter Comba
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270,Heidelberg D-69120, Germany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), Universität Heidelberg, Heidelberg 69120, Germany
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Kubeil M, Neuber C, Starke M, Arndt C, Rodrigues Loureiro L, Hoffmann L, Feldmann A, Bachmann M, Pietzsch J, Comba P, Stephan H. 64Cu tumor labeling with hexadentate picolinic acid-based bispidine immunoconjugates. Chemistry 2024:e202400366. [PMID: 38506263 DOI: 10.1002/chem.202400366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 03/14/2024] [Accepted: 03/18/2024] [Indexed: 03/21/2024]
Abstract
Discussed are two picolinate appended bispidine ligands (3,7-diazabicyclo[3.3.1]nonane derivatives) in comparison with an earlier described bis-pyridine derivative, which are all known to strongly bind CuII. The radiopharmacological characterization of the two isomeric bispidine complexes includes quantitative labeling with 64CuII at ambient conditions with high radiochemical purities and yields (molar activities >200 MBq/nmol). Challenge experiments in presence of EDTA, cyclam, human serum and SOD demonstrate high stability and inertness of the 64Cu-bispidine complexes. Biodistribution studies performed in Wistar rats indicate a rapid renal elimination for both 64Cu-labeled chelates. The bispidine ligand with the picolinate group in N7 position was selected for further biological experiments, and its backbone was therefore substituted with a benzyl-NCS group at C9. Two tumor target modules (TMs), targeting prostate stem cell antigen (PSCA), overexpressed in prostate cancer, and the fibroblast activation protein (FAP) in fibrosarcoma, were selected for thiourea coupling with the NCS-functionalized ligand and lysine residues of TMs. Small animal PET experiments on tumor-bearing mice showed specific accumulation of the 64Cu-labeled TMs in PSCA- and FAP-overexpressing tumors (standardized uptake value (SUV) for PC3: 2.7±0.6 and HT1080: 7.2±1.25) with almost no uptake in wild type tumors.
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Affiliation(s)
- Manja Kubeil
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - Christin Neuber
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - Miriam Starke
- Universität Heidelberg, Anorganisch-Chemisches, Institut INF 270, 69120, Heidelberg, Germany
| | - Claudia Arndt
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
- Mildred Scheel Early Career Center, Faculty of Medicine Carl Gustav Carus, Technische Universiät Dresden, 01307, Dresden, Germany
| | - Liliana Rodrigues Loureiro
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - Lydia Hoffmann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - Anja Feldmann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
- National Center for Tumor Diseases Dresden (NCT/UCC), University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307, Dresden, Germany
- German Cancer Consortium (DKTK), partner site Dresden, and German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany
| | - Michael Bachmann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
- National Center for Tumor Diseases Dresden (NCT/UCC), University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307, Dresden, Germany
- German Cancer Consortium (DKTK), partner site Dresden, and German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
- Technische Universität Dresden, Faculty of Chemistry and Food Chemistry, School of Science, 01069, Dresden, Germany
| | - Peter Comba
- Universität Heidelberg, Anorganisch-Chemisches, Institut INF 270, 69120, Heidelberg, Germany
- Universität Heidelberg, Interdisciplinary Center for Scientific Computing, INF 205, 69120, Heidelberg, Germany
| | - Holger Stephan
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
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Kumar R, Ansari A, Comba P, Rajaraman G. Rebound or Cage Escape? The Role of the Rebound Barrier for the Reactivity of Non-Heme High-Valent Fe IV =O Species. Chemistry 2024; 30:e202303300. [PMID: 37929771 DOI: 10.1002/chem.202303300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/03/2023] [Accepted: 11/06/2023] [Indexed: 11/07/2023]
Abstract
Owing to their high reactivity and selectivity, variations in the spin ground state and a range of possible pathways, high-valent FeIV =O species are popular models with potential bioinspired applications. An interesting example of a structure-reactivity pattern is the detailed study with five nonheme amine-pyridine pentadentate ligand FeIV =O species, including N4py: [(L1 )FeIV =O]2+ (1), bntpen: [(L2 )FeIV =O]2+ (2), py2 tacn: [(L3 )FeIV =O]2+ (3), and two isomeric bispidine derivatives: [(L4 )FeIV =O]2+ (4) and [(L5 )FeIV =O]2+ (5). In this set, the order of increasing reactivity in the hydroxylation of cyclohexane differs from that with cyclohexadiene as substrate. A comprehensive DFT, ab initio CASSCF/NEVPT2 and DLPNO-CCSD(T) study is presented to untangle the observed patterns. These are well reproduced when both activation barriers for the C-H abstraction and the OH rebound are taken into account. An MO, NBO and deformation energy analysis reveals the importance of π(pyr) → π*xz (FeIII -OH) electron donation for weakening the FeIII -OH bond and thus reducing the rebound barrier. This requires that pyridine rings are oriented perpendicularly to the FeIII -OH bond and this is a subtle but crucial point in ligand design for non-heme iron alkane hydroxylation.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Haryana, 123031, India
| | - Peter Comba
- Institute of Inorganic Chemistry &, Interdisciplinary Center for Scientific Computing, Heidelberg University, 69120, Heidelberg, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
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Hädeler J, Velmurugan G, Lauer R, Radhamani R, Keppler F, Comba P. Natural Abiotic Iron-Oxido-Mediated Formation of C 1 and C 2 Compounds from Environmentally Important Methyl-Substituted Substrates. J Am Chem Soc 2023. [PMID: 37930326 DOI: 10.1021/jacs.3c06709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Organic and inorganic volatile compounds containing one carbon atom (C1), such as carbon dioxide, methane, methanol, formaldehyde, carbon monoxide, and chloromethane, are ubiquitous in the environment, are key components in global carbon cycling, play an important role in atmospheric physics and chemistry, e.g., as greenhouse gases, destroy stratospheric and tropospheric ozone, and control the atmospheric oxidation capacity. Up to now, most C1 compounds in the environment were associated with complex metabolic and enzymatic pathways in organisms or to combustion processes of organic matter. We now present compelling evidence that many C1 and C2 compounds have a common origin in methyl groups of methyl-substituted substrates that are cleaved by the iron oxide-mediated formation of methyl radicals. This scenario is derived from experiments with a mechanistically well-studied bispidine-iron-oxido complex as oxidant and dimethyl sulfoxide as the environmentally relevant model substrate and is supported by computational modeling based on density functional theory and ab initio quantum-chemical studies. The exhaustive experimental model studies, also involving extensive isotope labeling, are complemented with the substitution of the bispidine model system by environmentally relevant iron oxides and, finally, a collection of soils with varying iron and organic matter contents. The combination of all data suggests that the iron oxide-mediated formation of methyl radicals from methyl-substituted substrates is a common abiotic source for widespread C1 and C2 compounds in the environment.
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Affiliation(s)
- Jonas Hädeler
- Institut für Geowissenschaften, INF 234-236, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Gunasekaran Velmurugan
- Anorganisch-Chemisches Institut INF 270, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Rebekka Lauer
- Institut für Geowissenschaften, INF 234-236, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Rejith Radhamani
- Anorganisch-Chemisches Institut INF 270, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Frank Keppler
- Institut für Geowissenschaften, INF 234-236, Universität Heidelberg, D-69120 Heidelberg, Germany
- Heidelberg Center for the Environment (HCE), Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Peter Comba
- Anorganisch-Chemisches Institut INF 270, Universität Heidelberg, D-69120 Heidelberg, Germany
- Interdisciplinary Center for Scientific Computing, INF 205, Universität Heidelberg, D-69120 Heidelberg, Germany
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Bleher K, Comba P, Kass D, Ray K, Wadepohl H. Reactivities of iron(IV)-oxido compounds with pentadentate bispidine ligands. J Inorg Biochem 2023; 241:112123. [PMID: 36701984 DOI: 10.1016/j.jinorgbio.2023.112123] [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: 08/30/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 01/11/2023]
Abstract
The FeIVO complexes of bispidines (3,7-diazabicyclo[3.3.1]nonane derivatives) are known to be highly reactive oxidants - with the tetradentate bispidine, the so far most reactive ferryl complex has been reported and two isomeric pentadentate ligands also lead to very reactive high-valent oxidants. With a series of 4 new bispidine derivatives we now try to address the question why the bispidine scaffold in general leads to very reactive oxidants and how this can be tuned by ligand modifications. The study is based on a full structural, spectroscopic and electrochemical analysis of the iron(II) precursors, spectroscopic data of the iron(IV)-oxido complexes, a kinetic analysis of the stoichiometric oxidation of thioanisole by five different bispidine‑iron(IV)-oxido complexes and on product analyses of reactions by the five ferryl oxidants with thioanisole, β-methylstyrene and cis-stilbene as substrates.
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Affiliation(s)
- Katharina Bleher
- Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, D-69120 Heidelberg, Germany
| | - Peter Comba
- Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, D-69120 Heidelberg, Germany; Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), Germany.
| | - Dustin Kass
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor Strasse 2, D-12489 Berlin, Germany
| | - Kallol Ray
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor Strasse 2, D-12489 Berlin, Germany
| | - Hubert Wadepohl
- Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, D-69120 Heidelberg, Germany
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Recent progress in oxidation chemistry of high-valent ruthenium-oxo and osmium-oxo complexes and related species. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lippi M, Wadepohl H, Comba P, Cametti M. A Bispidine based CuII/ZnII Heterobimetallic Coordination Polymer. Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202200221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Martina Lippi
- Politecnico di Milano Department of Chemistry, Materials and Chemical Engineering ITALY
| | - Hubert Wadepohl
- Heidelberg University Interdisciplinary Center of Scientific Computing GERMANY
| | - Peter Comba
- Heidelberg University Anorganisch-Chemisches Institut GERMANY
| | - Massimo Cametti
- Politecnico di Milano Dipartimento di Chimica, Materiali ed Ingegneria Chimica Via Luigi Mancinelli 7 20131 Milano ITALY
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Comba P, Nunn G, Scherz F, Walton PH. Intermediate-spin iron(IV)-oxido species with record reactivity. Faraday Discuss 2022; 234:232-244. [PMID: 35156976 DOI: 10.1039/d1fd00073j] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nonheme iron(IV)-oxido complex trans-N3-[(L1)FeIVO(Cl)]+, where L1 is a derivative of the tetradentate bispidine 2,4-di(pyridine-2-yl)-3,7-diazabicyclo[3.3.1]nonane-1-one, has an S = 1 electronic ground state and is the most reactive nonheme iron model system known so far, of a similar order of reactivity as nonheme iron enzymes (C-H abstraction of cyclohexane, -90 °C (propionitrile), t1/2 = 3.5 s). The reaction with cyclohexane selectively leads to chlorocyclohexane, but "cage escape" at the [(L1)FeIII(OH)(Cl)]+/cyclohexyl radical intermediate lowers the productivity. Ligand field theory is used herein to analyze the d-d transitions of [(L1)FeIVO(X)]n+ (X = Cl-, Br-, MeCN) in comparison with the thoroughly characterized ferryl complex of tetramethylcyclam (TMC = L2; [(L2)FeIVO(MeCN)]2+). The ligand field parameters and d-d transition energies are shown to provide important information on the triplet-quintet gap and its correlation with oxidation reactivity.
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Affiliation(s)
- Peter Comba
- Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, D-69120 Heidelberg, Germany. .,Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), Germany
| | - George Nunn
- Department of Chemistry, University of York, Heslington, YORK, YO10 5DD, UK
| | - Frederik Scherz
- Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, D-69120 Heidelberg, Germany.
| | - Paul H Walton
- Department of Chemistry, University of York, Heslington, YORK, YO10 5DD, UK
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Heck J, Metz F, Buchenau S, Teubner M, Grimm-Lebsanft B, Spaniol TP, Hoffmann A, Rübhausen MA, Herres-Pawlis S. Manipulating electron transfer – the influence of substituents on novel copper guanidine quinolinyl complexes. Chem Sci 2022; 13:8274-8288. [PMID: 35919707 PMCID: PMC9297705 DOI: 10.1039/d2sc02910c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 06/11/2022] [Indexed: 11/21/2022] Open
Abstract
Copper guanidine quinolinyl complexes act as good entatic state models due to their distorted structures leading to a high similarity between Cu(i) and Cu(ii) complexes. For a better understanding of the entatic state principle regarding electron transfer a series of guanidine quinolinyl ligands with different substituents in the 2- and 4-position were synthesized to examine the influence on the electron transfer properties of the corresponding copper complexes. Substituents with different steric or electronic influences were chosen. The effects on the properties of the copper complexes were studied applying different experimental and theoretical methods. The molecular structures of the bis(chelate) copper complexes were examined in the solid state by single-crystal X-ray diffraction and in solution by X-ray absorption spectroscopy and density functional theory (DFT) calculations revealing a significant impact of the substituents on the complex structures. For a better insight natural bond orbital (NBO) calculations of the ligands and copper complexes were performed. The electron transfer was analysed by the determination of the electron self-exchange rates following Marcus theory. The obtained results were correlated with the results of the structural analysis of the complexes and of the NBO calculations. Nelsen's four-point method calculations give a deeper understanding of the thermodynamic properties of the electron transfer. These studies reveal a significant impact of the substituents on the properties of the copper complexes. Copper guanidine quinolinyl complexes act as good entatic state models for the electron transfer due to a high similarity between the corresponding Cu(i) and Cu(ii) complexes. The introduction of substituents leads to a further enhancement.![]()
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Affiliation(s)
- Joshua Heck
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Fabian Metz
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Sören Buchenau
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Melissa Teubner
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Benjamin Grimm-Lebsanft
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Thomas P. Spaniol
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Alexander Hoffmann
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Michael A. Rübhausen
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Sonja Herres-Pawlis
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
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Bleher K, Comba P, Gross JH, Josephy T. ESI and tandem MS for mechanistic studies with high-valent transition metal species. Dalton Trans 2022; 51:8625-8639. [DOI: 10.1039/d2dt00809b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The analysis of high-valent metal species has been in the focus of research for over 20 years. Mass spectrometry (MS) represents a technique routinely used for their characterization, in particular...
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Bleher K, Comba P, Faltermeier D, Gupta A, Kerscher M, Krieg S, Martin B, Velmurugan G, Yang S. Non-Heme-Iron-Mediated Selective Halogenation of Unactivated Carbon-Hydrogen Bonds. Chemistry 2021; 28:e202103452. [PMID: 34792224 PMCID: PMC9300152 DOI: 10.1002/chem.202103452] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Indexed: 12/23/2022]
Abstract
Oxidation of the iron(II) precursor [(L1)FeIICl2], where L1 is a tetradentate bispidine, with soluble iodosylbenzene (sPhIO) leads to the extremely reactive ferryl oxidant [(L1)(Cl)FeIV=O]+ with a cis disposition of the chlorido and oxido coligands, as observed in non‐heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C−H abstraction and the result of a rebound of the ensuing radical to an iron‐bound Cl−. The time‐resolved formation of the halogenation product indicates that this primarily results from sPhIO oxidation of an initially formed oxido‐bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe2+ and Fe3+ in comparison with [(L1)FeIICl2] indicate a high complex stability of the bispidine‐iron complexes. DFT analysis shows that, due to a large driving force and small triplet‐quintet gap, [(L1)(Cl)FeIV=O]+ is the most reactive small‐molecule halogenase model, that the FeIII/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects.
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Affiliation(s)
- Katharina Bleher
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Peter Comba
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Dieter Faltermeier
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Ashutosh Gupta
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Marion Kerscher
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Saskia Krieg
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Bodo Martin
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Gunasekaran Velmurugan
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Shuyi Yang
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
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Abu‐Odeh M, Bleher K, Johnee Britto N, Comba P, Gast M, Jaccob M, Kerscher M, Krieg S, Kurth M. Pathways of the Extremely Reactive Iron(IV)-oxido complexes with Tetradentate Bispidine Ligands. Chemistry 2021; 27:11377-11390. [PMID: 34121233 PMCID: PMC8456976 DOI: 10.1002/chem.202101045] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Indexed: 11/07/2022]
Abstract
The nonheme iron(IV)-oxido complex trans-N3-[(L1 )FeIV =O(Cl)]+ , where L1 is a derivative of the tetradentate bispidine 2,4-di(pyridine-2-yl)-3,7-diazabicyclo[3.3.1]nonane-1-one, is known to have an S=1 electronic ground state and to be an extremely reactive oxidant for oxygen atom transfer (OAT) and hydrogen atom abstraction (HAA) processes. Here we show that, in spite of this ferryl oxidant having the "wrong" spin ground state, it is the most reactive nonheme iron model system known so far and of a similar order of reactivity as nonheme iron enzymes (C-H abstraction of cyclohexane, -90 °C (propionitrile), t1/2 =3.5 sec). Discussed are spectroscopic and kinetic data, supported by a DFT-based theoretical analysis, which indicate that substrate oxidation is significantly faster than self-decay processes due to an intramolecular demethylation pathway and formation of an oxido-bridged diiron(III) intermediate. It is also shown that the iron(III)-chlorido-hydroxido/cyclohexyl radical intermediate, resulting from C-H abstraction, selectively produces chlorocyclohexane in a rebound process. However, the life-time of the intermediate is so long that other reaction channels (known as cage escape) become important, and much of the C-H abstraction therefore is unproductive. In bulk reactions at ambient temperature and at longer time scales, there is formation of significant amounts of oxidation product - selectively of chlorocyclohexane - and it is shown that this originates from oxidation of the oxido-bridged diiron(III) resting state.
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Affiliation(s)
- Mahmud Abu‐Odeh
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
| | - Katharina Bleher
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
| | | | - Peter Comba
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR) MathematikonIm Neuenheimer Feld 20569120HeidelbergGermany
| | - Michael Gast
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
| | | | - Marion Kerscher
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
| | - Saskia Krieg
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
| | - Marius Kurth
- Anorganisch-Chemisches InstitutUniversität HeidelbergINF 27069120HeidelbergGermany
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13
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Hong YH, Jang Y, Ezhov R, Seo MS, Lee YM, Pandey B, Hong S, Pushkar Y, Fukuzumi S, Nam W. A Highly Reactive Chromium(V)–Oxo TAML Cation Radical Complex in Electron Transfer and Oxygen Atom Transfer Reactions. ACS Catal 2021. [DOI: 10.1021/acscatal.1c00079] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Young Hyun Hong
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yuri Jang
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Roman Ezhov
- Department of Physics and Astronomy, Purdue University 525 Northwestern Avenue, West Lafayette, Indiana 47907, United States
| | - Mi Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Bhawana Pandey
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Seungwoo Hong
- Department of Chemistry, Sookmyung Women’s University, Seoul 04310, Korea
| | - Yulia Pushkar
- Department of Physics and Astronomy, Purdue University 525 Northwestern Avenue, West Lafayette, Indiana 47907, United States
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, People’s Republic of China
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14
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Kojima T. Study on Proton-Coupled Electron Transfer in Transition Metal Complexes. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20200213] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Takahiko Kojima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
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15
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Comba P, Faltermeier D, Martin B. Computational Approaches for Redox Potentials of Iron(IV)‐oxido Complexes. Z Anorg Allg Chem 2020. [DOI: 10.1002/zaac.202000355] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Peter Comba
- Anorganisch‐Chemisches Institut, INF 270und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR) Universität Heidelberg 69120 Heidelberg Germany
| | - Dieter Faltermeier
- Anorganisch‐Chemisches Institut, INF 270und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR) Universität Heidelberg 69120 Heidelberg Germany
| | - Bodo Martin
- Anorganisch‐Chemisches Institut, INF 270und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR) Universität Heidelberg 69120 Heidelberg Germany
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16
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Das A, Hessin C, Ren Y, Desage-El Murr M. Biological concepts for catalysis and reactivity: empowering bioinspiration. Chem Soc Rev 2020; 49:8840-8867. [PMID: 33107878 DOI: 10.1039/d0cs00914h] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Biological systems provide attractive reactivity blueprints for the design of challenging chemical transformations. Emulating the operating mode of natural systems may however not be so easy and direct translation of structural observations does not always afford the anticipated efficiency. Metalloenzymes rely on earth-abundant metals to perform an incredibly wide range of chemical transformations. To do so, enzymes in general have evolved tools and tricks to enable control of such reactivity. The underlying concepts related to these tools are usually well-known to enzymologists and bio(inorganic) chemists but may be a little less familiar to organometallic chemists. So far, the field of bioinspired catalysis has greatly focused on the coordination sphere and electronic effects for the design of functional enzyme models but might benefit from a paradigm shift related to recent findings in biological systems. The goal of this review is to bring these fields closer together as this could likely result in the development of a new generation of highly efficient bioinspired systems. This contribution covers the fields of redox-active ligands, entatic state reactivity, energy conservation through electron bifurcation, and quantum tunneling for C-H activation.
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Affiliation(s)
- Agnideep Das
- Université de Strasbourg, Institut de Chimie, UMR CNRS 7177, 67000 Strasbourg, France.
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17
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Ansari M, Senthilnathan D, Rajaraman G. Deciphering the origin of million-fold reactivity observed for the open core diiron [HO-Fe III-O-Fe IV[double bond, length as m-dash]O] 2+ species towards C-H bond activation: role of spin-states, spin-coupling, and spin-cooperation. Chem Sci 2020; 11:10669-10687. [PMID: 33209248 PMCID: PMC7654192 DOI: 10.1039/d0sc02624g] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/16/2020] [Indexed: 01/26/2023] Open
Abstract
High-valent metal-oxo species have been characterised as key intermediates in both heme and non-heme enzymes that are found to perform efficient aliphatic hydroxylation, epoxidation, halogenation, and dehydrogenation reactions. Several biomimetic model complexes have been synthesised over the years to mimic both the structure and function of metalloenzymes. The diamond-core [Fe2(μ-O)2] is one of the celebrated models in this context as this has been proposed as the catalytically active species in soluble methane monooxygenase enzymes (sMMO), which perform the challenging chemical conversion of methane to methanol at ease. In this context, a report of open core [HO(L)FeIII-O-FeIV(O)(L)]2+ (1) gains attention as this activates C-H bonds a million-fold faster compared to the diamond-core structure and has the dual catalytic ability to perform hydroxylation as well as desaturation with organic substrates. In this study, we have employed density functional methods to probe the origin of the very high reactivity observed for this complex and also to shed light on how this complex performs efficient hydroxylation and desaturation of alkanes. By modelling fifteen possible spin-states for 1 that could potentially participate in the reaction mechanism, our calculations reveal a doublet ground state for 1 arising from antiferromagnetic coupling between the quartet FeIV centre and the sextet FeIII centre, which regulates the reactivity of this species. The unusual stabilisation of the high-spin ground state for FeIV[double bond, length as m-dash]O is due to the strong overlap of with the orbital, reducing the antibonding interactions via spin-cooperation. The electronic structure features computed for 1 are consistent with experiments offering confidence in the methodology chosen. Further, we have probed various mechanistic pathways for the C-H bond activation as well as -OH rebound/desaturation of alkanes. An extremely small barrier height computed for the first hydrogen atom abstraction by the terminal FeIV[double bond, length as m-dash]O unit was found to be responsible for the million-fold activation observed in the experiments. The barrier height computed for -OH rebound by the FeIII-OH unit is also smaller suggesting a facile hydroxylation of organic substrates by 1. A strong spin-cooperation between the two iron centres also reduces the barrier for second hydrogen atom abstraction, thus making the desaturation pathway competitive. Both the spin-state as well as spin-coupling between the two metal centres play a crucial role in dictating the reactivity for species 1. By exploring various mechanistic pathways, our study unveils the fact that the bridged μ-oxo group is a poor electrophile for both C-H activation as well for -OH rebound. As more and more evidence is gathered in recent years for the open core geometry of sMMO enzymes, the idea of enhancing the reactivity via an open-core motif has far-reaching consequences.
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Affiliation(s)
- Mursaleem Ansari
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
| | - Dhurairajan Senthilnathan
- Center for Computational Chemistry , CRD , PRIST University , Vallam , Thanjavur , Tamilnadu 613403 , India
| | - Gopalan Rajaraman
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
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18
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Kotani H, Shimomura H, Ikeda K, Ishizuka T, Shiota Y, Yoshizawa K, Kojima T. Mechanistic Insight into Concerted Proton-Electron Transfer of a Ru(IV)-Oxo Complex: A Possible Oxidative Asynchronicity. J Am Chem Soc 2020; 142:16982-16989. [PMID: 32924508 DOI: 10.1021/jacs.0c05738] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have thoroughly investigated the oxidation of benzyl alcohol (BA) derivatives by a RuIV(O) complex (RuIV(O)) in the absence or presence of Brønsted acids in order to elucidate the proton-coupled electron-transfer (PCET) mechanisms in C-H oxidation on the basis of a kinetic analysis. Oxidation of BA derivatives by RuIV(O) without acids proceeded through concerted proton-electron transfer (CPET) with a large kinetic isotope effect (KIE). In contrast, the oxidation of 3,4,5-trimethoxy-BA ((MeO)3-BA) by RuIV(O) was accelerated by the addition of acids, in which the KIE value reached 1.1 with TFA (550 mM), indicating an alteration of the PCET mechanism from CPET to stepwise electron transfer (ET) followed by proton transfer (PT). Although the oxidized products of BA derivatives were confirmed to be the corresponding benzaldehydes in the range of acid concentrations (0-550 mM), a one-electron-reduction potential of RuIV(O) was positively shifted with increases in the concentrations of acids. The elevated reduction potential of RuIV(O) strongly influenced the PCET mechanisms in the oxidation of (MeO)3-BA, changing the mechanism from CPET to ET/PT, as evidenced by the driving-force dependence of logarithms of reaction rate constants in light of the Marcus theory of ET. In addition, dependence of activation parameters on acid concentrations suggested that an oxidative asynchronous CPET, which is not an admixture of the CPET and ET/PT mechanisms, is probably operative in the boundary region (0 mM < [TFA] < 50 mM) involving a one-proton-interacted RuIV(O)···H+ as a dominant reactive species.
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Affiliation(s)
- Hiroaki Kotani
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Hinatsu Shimomura
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Kei Ikeda
- Institute for Materials Chemistry and Engineering, Kyushu University and CREST (JST), Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Tomoya Ishizuka
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering, Kyushu University and CREST (JST), Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering, Kyushu University and CREST (JST), Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Takahiko Kojima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
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19
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Mukherjee G, Sastri CV. Eccentricities in Spectroscopy and Reactivity of Non‐Heme Metal Intermediates Contained in Bispidine Scaffolds. Isr J Chem 2020. [DOI: 10.1002/ijch.202000045] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Gourab Mukherjee
- Department of Chemistry Indian Institute of Technology Guwahati Guwahati, Assam 781039 India
| | - Chivukula V. Sastri
- Department of Chemistry Indian Institute of Technology Guwahati Guwahati, Assam 781039 India
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20
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Comba P, Löhr A, Pfaff F, Ray K. Redox Potentials of High‐Valent Iron‐, Cobalt‐, and Nickel‐Oxido Complexes: Evidence for Exchange Enhanced Reactivity. Isr J Chem 2020. [DOI: 10.1002/ijch.202000038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Peter Comba
- Universität Heidelberg Anorganisch-Chemisches Institut, INF 270 D-69120 Heidelberg Germany
- Universität Heidelberg Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR) D-69120 Heidelberg Germany
| | - Anna‐Maria Löhr
- Universität Heidelberg Anorganisch-Chemisches Institut, INF 270 D-69120 Heidelberg Germany
| | - Florian Pfaff
- Department of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 Berlin Germany 12489
| | - Kallol Ray
- Department of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 Berlin Germany 12489
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21
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Ren Y, Forté J, Cheaib K, Vanthuyne N, Fensterbank L, Vezin H, Orio M, Blanchard S, Desage-El Murr M. Optimizing Group Transfer Catalysis by Copper Complex with Redox-Active Ligand in an Entatic State. iScience 2020; 23:100955. [PMID: 32199288 PMCID: PMC7083792 DOI: 10.1016/j.isci.2020.100955] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 01/14/2020] [Accepted: 02/25/2020] [Indexed: 01/07/2023] Open
Abstract
Metalloenzymes use earth-abundant non-noble metals to perform high-fidelity transformations in the biological world. To ensure chemical efficiency, metalloenzymes have acquired evolutionary reactivity-enhancing tools. Among these, the entatic state model states that a strongly distorted geometry induced by ligands around a metal center gives rise to an energized structure called entatic state, strongly improving the reactivity. However, the original definition refers both to the transfer of electrons or chemical groups, whereas the chemical application of this concept in synthetic systems has mostly focused on electron transfer, therefore eluding chemical transformations. Here we report that a highly strained redox-active ligand enables a copper complex to perform catalytic nitrogen- and carbon-group transfer in as fast as 2 min, thus exhibiting a strong increase in reactivity compared with its unstrained analogue. This report combines two reactivity-enhancing features from metalloenzymes, entasis and redox cofactors, applied to group-transfer catalysis. We design a catalyst interfacing two reactivity-enhancing tools from metalloenzymes This work merges redox-active cofactors and entatic state reactivity The modifications in the coordination sphere lead to enhanced catalytic behavior These results open perspectives in bioinspired catalysis and group-transfer reactions
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Affiliation(s)
- Yufeng Ren
- Sorbonne Université, Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, 75005 Paris, France
| | - Jeremy Forté
- Sorbonne Université, Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, 75005 Paris, France
| | - Khaled Cheaib
- Sorbonne Université, Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, 75005 Paris, France
| | - Nicolas Vanthuyne
- Aix Marseille Université, CNRS, Centrale Marseille, iSm2, UMR CNRS 7313, 13397 Marseille, France
| | - Louis Fensterbank
- Sorbonne Université, Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, 75005 Paris, France
| | - Hervé Vezin
- Université des Sciences et Technologies de Lille, LASIR, UMR CNRS 8516, 59655 Villeneuve d'Ascq Cedex, France
| | - Maylis Orio
- Aix Marseille Université, CNRS, Centrale Marseille, iSm2, UMR CNRS 7313, 13397 Marseille, France
| | - Sébastien Blanchard
- Sorbonne Université, Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, 75005 Paris, France
| | - Marine Desage-El Murr
- Université de Strasbourg, Institut de Chimie, UMR CNRS 7177, 67000 Strasbourg, France.
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22
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Comba P, Faltermeier D, Krieg S, Martin B, Rajaraman G. Spin state and reactivity of iron(iv)oxido complexes with tetradentate bispidine ligands. Dalton Trans 2020; 49:2888-2894. [DOI: 10.1039/c9dt04578c] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The iron(iv)oxido complex [(bispidine)FeIVO(Cl)]+is shown by experiment and high-level DLPNO-CCSD(T) quantum-chemical calculations to be an extremely short-lived and very reactive intermediate-spin (S= 1) species.
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Affiliation(s)
- Peter Comba
- Universität Heidelberg
- Anorganisch-Chemisches Institut
- D-69120 Heidelberg
- Germany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR)
| | - Dieter Faltermeier
- Universität Heidelberg
- Anorganisch-Chemisches Institut
- D-69120 Heidelberg
- Germany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR)
| | - Saskia Krieg
- Universität Heidelberg
- Anorganisch-Chemisches Institut
- D-69120 Heidelberg
- Germany
| | - Bodo Martin
- Universität Heidelberg
- Anorganisch-Chemisches Institut
- D-69120 Heidelberg
- Germany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR)
| | - Gopalan Rajaraman
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai-400076
- India
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23
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Mirzoyan R, Hadt RG. The dynamic ligand field of a molecular qubit: decoherence through spin–phonon coupling. Phys Chem Chem Phys 2020; 22:11249-11265. [DOI: 10.1039/d0cp00852d] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A ligand field model highlights chemical design principles for the development of room temperature coherent materials for quantum information processing.
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Affiliation(s)
- Ruben Mirzoyan
- Division of Chemistry and Chemical Engineering
- Arthur Amos Noyes Laboratory of Chemical Physics
- California Institute of Technology
- Pasadena
- USA
| | - Ryan G. Hadt
- Division of Chemistry and Chemical Engineering
- Arthur Amos Noyes Laboratory of Chemical Physics
- California Institute of Technology
- Pasadena
- USA
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24
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Stroscio GD, Ribson RD, Hadt RG. Quantifying Entatic States in Photophysical Processes: Applications to Copper Photosensitizers. Inorg Chem 2019; 58:16800-16817. [DOI: 10.1021/acs.inorgchem.9b02976] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gautam D. Stroscio
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Ryan D. Ribson
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Ryan G. Hadt
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
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25
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Jonasson NSW, Daumann LJ. 5‐Methylcytosine is Oxidized to the Natural Metabolites of TET Enzymes by a Biomimetic Iron(IV)‐Oxo Complex. Chemistry 2019; 25:12091-12097. [PMID: 31211459 DOI: 10.1002/chem.201902340] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 06/15/2019] [Indexed: 12/28/2022]
Affiliation(s)
- Niko S. W. Jonasson
- Department ChemieLudwig-Maximilians-University München Butenandtstr. 5-13, Haus D Germany
| | - Lena J. Daumann
- Department ChemieLudwig-Maximilians-University München Butenandtstr. 5-13, Haus D Germany
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26
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Choudhary N, Dimmling A, Wang X, Southcott L, Radchenko V, Patrick BO, Comba P, Orvig C. Octadentate Oxine-Armed Bispidine Ligand for Radiopharmaceutical Chemistry. Inorg Chem 2019; 58:8685-8693. [DOI: 10.1021/acs.inorgchem.9b01016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Neha Choudhary
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
- Life Sciences Division, TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
| | - Alexander Dimmling
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing, Universität Heidelberg, INF 270, D-69120 Heidelberg, Germany
| | - Xiaozhu Wang
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Lily Southcott
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
- Life Sciences Division, TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
| | - Valery Radchenko
- Life Sciences Division, TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Brian O. Patrick
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | - Peter Comba
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing, Universität Heidelberg, INF 270, D-69120 Heidelberg, Germany
| | - Chris Orvig
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
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27
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Lee YM, Kim S, Ohkubo K, Kim KH, Nam W, Fukuzumi S. Unified Mechanism of Oxygen Atom Transfer and Hydrogen Atom Transfer Reactions with a Triflic Acid-Bound Nonheme Manganese(IV)-Oxo Complex via Outer-Sphere Electron Transfer. J Am Chem Soc 2019; 141:2614-2622. [PMID: 30646680 DOI: 10.1021/jacs.8b12935] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Outer-sphere electron transfer from styrene, thioanisole, and toluene derivatives to a triflic acid (HOTf)-bound nonheme Mn(IV)-oxo complex, [(N4Py)MnIV(O)]2+-(HOTf)2 (N4Py = N, N-bis(2-pyridylmethyl)- N-bis(2-pyridyl)methylamine), has been shown to be the rate-determining step of different types of redox reactions such as epoxidation, sulfoxidation, and hydroxylation of styrene, thioanisole, and toluene derivatives, respectively, by [(N4Py)MnIV(O)]2+-(HOTf)2. The rate constants of HOTf-promoted epoxidation of all styrene derivatives with [(N4Py)MnIV(O)]2+ and electron transfer from electron donors to [(N4Py)MnV(O)]2+ exhibit a remarkably unified correlation with the driving force of outer-sphere electron transfer in light of the Marcus theory of electron transfer. The same electron-transfer driving force dependence is observed in the oxygen atom transfer from [(N4Py)MnIV(O)]2+-(HOTf)2 to thioanisole derivatives as well as in the hydrogen atom transfer from toluene derivatives to [(N4Py)MnIV(O)]2+-(HOTf)2. Thus, mechanisms of oxygen atom transfer (epoxidation and sulfoxidation) reactions of styrene and thioanisole derivatives and hydrogen atom transfer (hydroxylation) reactions of toluene derivatives by [(N4Py)MnIV(O)]2+-(HOTf)2 have been unified for the first time as the same reaction pathway via outer-sphere electron transfer, followed by the fast bond-forming step, which exhibits the singly unified electron-transfer driving force dependence of the rate constants as outer-sphere electron-transfer reactions. In the case of the epoxidation of cis-stilbene by [(N4Py)MnIV(O)]2+-(HOTf)2, the isomerization of cis-stilbene radical cation to trans-stilbene radical cation occurs after outer-sphere electron transfer from cis-stilbene to [(N4Py)MnIV(O)]2+-(HOTf)2 to yield trans-stilbene oxide selectively, which is also taken as evidence for the occurrence of electron transfer in the acid-catalyzed epoxidation.
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Affiliation(s)
- Yong-Min Lee
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Surin Kim
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Kei Ohkubo
- Institute for Advanced Co-Creation Studies, Open and Transdisciplinary Research Initiatives , Osaka University , Suita , Osaka 565-0871 , Japan
| | - Kyung-Ha Kim
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea.,State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences , Lanzhou 730000 , China
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea.,Faculty of Science and Engineering , Meijo University , SENTAN, Japan Science and Technology Agency (JST), Nagoya , Aichi 468-0073 , Japan
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Kotani H, Shimomura H, Horimoto M, Ishizuka T, Shiota Y, Yoshizawa K, Yanagisawa S, Kawahara-Nakagawa Y, Kubo M, Kojima T. Fundamental electron-transfer and proton-coupled electron-transfer properties of Ru(iv)-oxo complexes. Dalton Trans 2019; 48:13154-13161. [DOI: 10.1039/c9dt02734c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reorganization energies (λ) of electron transfer (ET) and proton-coupled ET (PCET) from electron donors to isolated RuIV(O) complexes were determined to be in the range of 1.70–1.88 eV (ET) and 1.20–1.26 eV (PCET).
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Affiliation(s)
- Hiroaki Kotani
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Hinatsu Shimomura
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Momoka Horimoto
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Tomoya Ishizuka
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Fukuoka 819-0395
- Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Fukuoka 819-0395
- Japan
| | | | | | - Minoru Kubo
- Graduate School of Life Science
- University of Hyogo
- Hyogo 678-1297
- Japan
| | - Takahiko Kojima
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
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Stanek J, Konrad M, Mannsperger J, Hoffmann A, Herres-Pawlis S. Influence of Functionalized Substituents on the Electron-Transfer Abilities of Copper Guanidinoquinoline Complexes. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201801078] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Julia Stanek
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Marc Konrad
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Johannes Mannsperger
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Alexander Hoffmann
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Sonja Herres-Pawlis
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
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Comba P, Faltermeier D, Gieger S, Keppler F, Schöler HF, Schroll M. Iron catalyzed demethylation of acetic acid*. J COORD CHEM 2018. [DOI: 10.1080/00958972.2018.1490414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Peter Comba
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Heidelberg, Germany
| | - Dieter Faltermeier
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Heidelberg, Germany
| | - Sascha Gieger
- Institute of Earth Sciences and Heidelberg Center for the Environment (HCE), Heidelberg University, Heidelberg, Germany
| | - Frank Keppler
- Institute of Earth Sciences and Heidelberg Center for the Environment (HCE), Heidelberg University, Heidelberg, Germany
| | - Heinz Friedrich Schöler
- Institute of Earth Sciences and Heidelberg Center for the Environment (HCE), Heidelberg University, Heidelberg, Germany
| | - Moritz Schroll
- Institute of Earth Sciences and Heidelberg Center for the Environment (HCE), Heidelberg University, Heidelberg, Germany
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31
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Comba P, Jakob M, Rück K, Wadepohl H. Tuning of the properties of a picolinic acid-based bispidine ligand for stable copper(II) complexation. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.08.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Pandey B, Jaccob M, Rajaraman G. Mechanistic insights into intramolecular ortho-amination/hydroxylation by nonheme Fe IV[double bond, length as m-dash]NTs/Fe IV[double bond, length as m-dash]O species: the σ vs. the π channels. Chem Commun (Camb) 2018; 53:3193-3196. [PMID: 28220156 DOI: 10.1039/c6cc08761b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Comparative oxidative abilities of nonheme FeIV[double bond, length as m-dash]NTs and FeIV[double bond, length as m-dash]O species using DFT has been explored. Our calculations reveal that the FeIV[double bond, length as m-dash]NTs is found to be a stronger oxidant in two electron transfer reactions and react exclusively via π channels while the FeIV[double bond, length as m-dash]O species is found to be a stronger oxidant when the σ-pathway is activated such as in HAT reactions.
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Affiliation(s)
- Bhawana Pandey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India.
| | - Madhavan Jaccob
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India. and Department of Chemistry, Loyola College, Chennai 600 034, Tamil Nadu, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India.
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Abstract
The isolation of terminal oxo complexes of the late transition metals promises new avenues in oxidation catalysis like the selective and catalytic hydroxylation of unreactive CH bonds, the activation of water, or the upgrading of olefins. While terminal oxo ligands are ubiquitous for early transition metals, well-characterized examples with group 10 metals remain hitherto elusive. In search for palladium terminal oxo complexes, the relative stability/reactivity of such compounds are evaluated computationally (CASSCF/NEVPT2; DFT). The calculations investigate only well-known ligand systems with established synthetic procedures and relevance for coordination chemistry and homogeneous catalysis. They delineate and quantify, which electronic properties of ancillary ligands are crucial for taming otherwise highly reactive terminal oxo intermediates. Notably, carbene ligands with both strong σ-donor and strong π-acceptor properties are best suited for the stabilization of palladium(ii) terminal oxo complexes, whereas ligands with a weaker ligand field lead to highly reactive complexes. Strongly donating ligands are an excellent choice for high-valent palladium(iv) terminal oxo compounds. Low coordinate palladium(ii) as well as high-valent palladium(iv) complexes are best suited for the activation of strong bonds.
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Affiliation(s)
- Dominik Munz
- Friedrich-Alexander Universität Erlangen-Nürnberg , Egerlandstr. 1 , 91058 Erlangen , Germany .
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Dicke B, Hoffmann A, Stanek J, Rampp MS, Grimm-Lebsanft B, Biebl F, Rukser D, Maerz B, Göries D, Naumova M, Biednov M, Neuber G, Wetzel A, Hofmann SM, Roedig P, Meents A, Bielecki J, Andreasson J, Beyerlein KR, Chapman HN, Bressler C, Zinth W, Rübhausen M, Herres-Pawlis S. Transferring the entatic-state principle to copper photochemistry. Nat Chem 2018; 10:355-362. [DOI: 10.1038/nchem.2916] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Accepted: 11/17/2017] [Indexed: 01/10/2023]
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Abstract
Radiometal based radiopharmaceuticals for imaging and therapy require selective ligands (bifunctional chelators, BFCs) that form metal complexes, which are inert against trans-chelation under physiological conditions, linked to a biological vector, directing them to the targeted tissue. Bispidine ligands with a very rigid backbone and widely variable donor sets are reviewed as an ideal class of BFCs, and recent applications are discussed.
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Affiliation(s)
- Peter Comba
- Ruprecht-Karls Universität Heidelberg
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing (IWR)
- 69120 Heidelberg
- Germany
| | - Marion Kerscher
- Ruprecht-Karls Universität Heidelberg
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing (IWR)
- 69120 Heidelberg
- Germany
| | - Katharina Rück
- Ruprecht-Karls Universität Heidelberg
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing (IWR)
- 69120 Heidelberg
- Germany
| | - Miriam Starke
- Ruprecht-Karls Universität Heidelberg
- Anorganisch-Chemisches Institut and Interdisciplinary Center for Scientific Computing (IWR)
- 69120 Heidelberg
- Germany
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Stanek J, Sackers N, Fink F, Paul M, Peters L, Grunzke R, Hoffmann A, Herres-Pawlis S. Copper Guanidinoquinoline Complexes as Entatic State Models of Electron-Transfer Proteins. Chemistry 2017; 23:15738-15745. [DOI: 10.1002/chem.201703261] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Indexed: 12/17/2022]
Affiliation(s)
- Julia Stanek
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Nina Sackers
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Fabian Fink
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Melanie Paul
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Laurens Peters
- Department Chemie; Ludwig-Maximilians Universität München; Butenandtstraße 5-13 81377 München Germany
| | - Richard Grunzke
- Zentrum für Informationsdienste und Hochleistungsrechnen; Technische Universität Dresden; Zellescher Weg 12-14 01062 Dresden Germany
| | - Alexander Hoffmann
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Sonja Herres-Pawlis
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
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Benzing K, Comba P, Martin B, Pokrandt B, Keppler F. Nonheme Iron‐Oxo‐Catalyzed Methane Formation from Methyl Thioethers: Scope, Mechanism, and Relevance for Natural Systems. Chemistry 2017; 23:10465-10472. [DOI: 10.1002/chem.201701986] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Kathrin Benzing
- Institute of Inorganic ChemistryHeidelberg University Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Peter Comba
- Institute of Inorganic Chemistry and Interdisciplinary Center for Scientific Computing (IWR)Heidelberg University Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Bodo Martin
- Institute of Inorganic ChemistryHeidelberg University Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Bianca Pokrandt
- Institute of Inorganic ChemistryHeidelberg University Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Frank Keppler
- Institute of Earth Sciences and Heidelberg Center for the Environment (HCE)Heidelberg University Im Neuenheimer Feld 236 69120 Heidelberg Germany
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Park SV, Berry JF. Synthesis, characterization and solution behavior of a systematic series of pentapyridyl-supported Ru II complexes: comparison to bimetallic analogs. Dalton Trans 2017; 46:9118-9125. [PMID: 28664959 PMCID: PMC6774635 DOI: 10.1039/c7dt01847a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of RuII complexes stabilized with the pentapyridyl ligand Py5Me2 (Py5Me2 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine) and with an axial X ligand (X = Cl-, H2O, N3-, MeCN) were prepared and characterized in the solid state and in non-aqueous solution. The cyclic voltammograms of these complexes in MeCN reflect a reversible substitution of the axial X ligand with MeCN. Irreversible ligand substitution of [(Py5Me2)RuN3]+ is also observed in propylene carbonate, but only at oxidizing potentials that decompose the azide ligand. The monometallic chloride and azide species are compared with analogous Ru2 metal-metal bonded complexes, which have been reported to undergo irreversible chloride dissociation upon reduction.
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Affiliation(s)
- Sungho V Park
- Department of Chemistry, University of Wisconsin - Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
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40
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Comba P, Pokrandt B, Wadepohl H. Oxidation of Cobalt(II) Bispidine Complexes with Dioxygen. Aust J Chem 2017. [DOI: 10.1071/ch16674] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Bispidine (3,7-diazabicyclo[3.3.1]nonane) ligands, derivatives of diazaadamantane, possess a very rigid backbone and have a high degree of pre-organization for cis-octahedral coordination geometries. Despite their rigidity, they exert a flexible coordination sphere, resulting in stable complexes with a variety of metal ions in various oxidation states. Due to the known high III/II redox potentials of their cobalt complexes, the CoII bispidine complexes are generally resistant to oxidation by dioxygen. Discussed in the present study are various CoII bispidine complexes with tetra- and pentadentate bispidines, with one of these complexes shown to be unstable under aerobic conditions. The decay process has been identified as an oxidative elimination of the 2-methylene pyridine substituent at one of the tertiary amine donors, resulting in picolinate, which is found coordinated to a CoIII product, where the dealkylated N-donor remains unprotonated. The mechanism of this interesting reaction has been studied, and details of the resulting structure of the product complex are discussed.
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