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Gonzálvez MA, Harmer JR, Bernhardt PV. Mapping the Pathway to Organocopper(II) Complexes Relevant to Atom Transfer Radical Polymerization. Inorg Chem 2021; 60:10648-10655. [PMID: 34185989 DOI: 10.1021/acs.inorgchem.1c01309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rare organocopper(II) complex [Cu(Me6tren)(CH2CN)]+ (Me6tren = tris(2-(dimethylamino)ethyl)amine) has emerged as an important model of potential byproducts in copper-catalyzed atom transfer radical polymerization. This complex has been generated by controlled potential electrolysis of [Cu(Me6tren)(NCMe)]2+ in the presence of BrCH2CN. Time-resolved UV-vis and continuous wave and pulse electron paramagnetic resonance (EPR) spectra identified [Cu(Me6tren)Br]+ as an intermediate. Hyperfine sublevel correlation and electron nuclear double resonance spectroscopy of samples at different timepoints reveal signals that are assigned to a C-bound cyanomethylate ligand, with distinct 14N and 1H hyperfine coupling constants in comparison with the corresponding N-bound acetonitrile and bromido complexes. The experimental EPR data are supported by density functional theory calculations to understand how the geometries of the species involved produce distinct spectroscopic signatures, and a clear picture of how this unusual organocopper(II) complex is formed has emerged.
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Affiliation(s)
- Miguel A Gonzálvez
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
| | - Jeffrey R Harmer
- Centre for Advanced Imaging, University of Queensland, Brisbane 4072, Australia
| | - Paul V Bernhardt
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
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2
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Zalibera M, Ziegs F, Schiemenz S, Dubrovin V, Lubitz W, Savitsky A, Deng SHM, Wang XB, Avdoshenko SM, Popov AA. Metallofullerene photoswitches driven by photoinduced fullerene-to-metal electron transfer. Chem Sci 2021; 12:7818-7838. [PMID: 34168836 PMCID: PMC8188499 DOI: 10.1039/d0sc07045a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report on the discovery and detailed exploration of the unconventional photo-switching mechanism in metallofullerenes, in which the energy of the photon absorbed by the carbon cage π-system is transformed to mechanical motion of the endohedral cluster accompanied by accumulation of spin density on the metal atoms. Comprehensive photophysical and electron paramagnetic resonance (EPR) studies augmented by theoretical modelling are performed to address the phenomenon of the light-induced photo-switching and triplet state spin dynamics in a series of Y x Sc3-x N@C80 (x = 0-3) nitride clusterfullerenes. Variable temperature and time-resolved photoluminescence studies revealed a strong dependence of their photophysical properties on the number of Sc atoms in the cluster. All molecules in the series exhibit temperature-dependent luminescence assigned to the near-infrared thermally-activated delayed fluorescence (TADF) and phosphorescence. The emission wavelengths and Stokes shift increase systematically with the number of Sc atoms in the endohedral cluster, whereas the triplet state lifetime and S1-T1 gap decrease in this row. For Sc3N@C80, we also applied photoelectron spectroscopy to obtain the triplet state energy as well as the electron affinity. Spin distribution and dynamics in the triplet states are then studied by light-induced pulsed EPR and ENDOR spectroscopies. The spin-lattice relaxation times and triplet state lifetimes are determined from the temporal evolution of the electron spin echo after the laser pulse. Well resolved ENDOR spectra of triplets with a rich structure caused by the hyperfine and quadrupolar interactions with 14N, 45Sc, and 89Y nuclear spins are obtained. The systematic increase of the metal contribution to the triplet spin density from Y3N to Sc3N found in the ENDOR study points to a substantial fullerene-to-metal charge transfer in the excited state. These experimental results are rationalized with the help of ground-state and time-dependent DFT calculations, which revealed a substantial variation of the endohedral cluster position in the photoexcited states driven by the predisposition of Sc atoms to maximize their spin population.
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Affiliation(s)
- Michal Zalibera
- Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology in Bratislava Radlinského 9 81237 Bratislava Slovakia .,Max Planck Institute for Chemical Energy Conversion Mülheim (Ruhr) Germany
| | - Frank Ziegs
- Leibniz Institute for Solid State and Materials Research Helmholtzstraße 20 01069 Dresden Germany
| | - Sandra Schiemenz
- Leibniz Institute for Solid State and Materials Research Helmholtzstraße 20 01069 Dresden Germany
| | - Vasilii Dubrovin
- Leibniz Institute for Solid State and Materials Research Helmholtzstraße 20 01069 Dresden Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion Mülheim (Ruhr) Germany
| | - Anton Savitsky
- Max Planck Institute for Chemical Energy Conversion Mülheim (Ruhr) Germany.,Faculty of Physics, Technical University Dortmund Otto-Hahn-Str. 4a 44227 Dortmund Germany
| | - Shihu H M Deng
- Physical Sciences Division, Pacific Northwest National Laboratory Richland Washington 99352 USA
| | - Xue-Bin Wang
- Physical Sciences Division, Pacific Northwest National Laboratory Richland Washington 99352 USA
| | - Stanislav M Avdoshenko
- Leibniz Institute for Solid State and Materials Research Helmholtzstraße 20 01069 Dresden Germany
| | - Alexey A Popov
- Leibniz Institute for Solid State and Materials Research Helmholtzstraße 20 01069 Dresden Germany
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Van Stappen C, Decamps L, Cutsail GE, Bjornsson R, Henthorn JT, Birrell JA, DeBeer S. The Spectroscopy of Nitrogenases. Chem Rev 2020; 120:5005-5081. [PMID: 32237739 PMCID: PMC7318057 DOI: 10.1021/acs.chemrev.9b00650] [Citation(s) in RCA: 111] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Indexed: 01/08/2023]
Abstract
Nitrogenases are responsible for biological nitrogen fixation, a crucial step in the biogeochemical nitrogen cycle. These enzymes utilize a two-component protein system and a series of iron-sulfur clusters to perform this reaction, culminating at the FeMco active site (M = Mo, V, Fe), which is capable of binding and reducing N2 to 2NH3. In this review, we summarize how different spectroscopic approaches have shed light on various aspects of these enzymes, including their structure, mechanism, alternative reactivity, and maturation. Synthetic model chemistry and theory have also played significant roles in developing our present understanding of these systems and are discussed in the context of their contributions to interpreting the nature of nitrogenases. Despite years of significant progress, there is still much to be learned from these enzymes through spectroscopic means, and we highlight where further spectroscopic investigations are needed.
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Affiliation(s)
- Casey Van Stappen
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Laure Decamps
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - George E. Cutsail
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Ragnar Bjornsson
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Justin T. Henthorn
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - James A. Birrell
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Serena DeBeer
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
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Masys Š, Rinkevicius Z, Tamulienė J. On the magnetic properties of nanodiamonds: Electronic g-tensor calculations. J Chem Phys 2019; 151:044305. [PMID: 31370534 DOI: 10.1063/1.5111024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The electronic g-tensor calculations are carried out for various paramagnetic defects introduced into hydrogenated diamond nanocrystal C35H36, showing that such a system can be successfully used to model magnetic properties of nanodiamonds (NDs) with paramagnetic centers containing no vacancies. In addition, it is revealed that, depending on the geometric positions in ND, paramagnetic centers of the same type produce noticeable variations of the g-tensor values. A side-by-side comparison of the performance of effective nuclear charge and spin-orbit mean field (SOMF) approaches indicates that the latter is more sensitive to the quality of basis sets, especially concerning diffuse functions, the inclusion of which is found to be nonbeneficial. What is more, the SOMF method also exhibits a much more pronounced gauge-origin dependence. Compared to electronic charge centroid, spin centers (SCs) demonstrate a superior suitability as gauge origins, providing a better agreement with diamagnetic and paramagnetic contributions of g-tensor obtained employing gauge-including atomic orbitals (GIAOs). Therefore, SCs can be recommended for the g-tensor calculations of NDs whenever GIAOs are not available.
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Affiliation(s)
- Š Masys
- Institute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, LT-10257 Vilnius, Lithuania
| | - Z Rinkevicius
- Department of Theoretical Chemistry & Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - J Tamulienė
- Institute of Theoretical Physics and Astronomy, Faculty of Physics, Vilnius University, LT-10257 Vilnius, Lithuania
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Rao G, Bansal S, Law WX, O’Dowd B, Dikanov SA, Oldfield E. Pulsed Electron Paramagnetic Resonance Insights into the Ligand Environment of Copper in Drosophila Lysyl Oxidase. Biochemistry 2017; 56:3770-3779. [DOI: 10.1021/acs.biochem.7b00308] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guodong Rao
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Sandhya Bansal
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Wen Xuan Law
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Bing O’Dowd
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Sergei A. Dikanov
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Eric Oldfield
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
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Characterization of Radical S-adenosylmethionine Enzymes and Intermediates in their Reactions by Continuous Wave and Pulse Electron Paramagnetic Resonance Spectroscopies. FUTURE DIRECTIONS IN METALLOPROTEIN AND METALLOENZYME RESEARCH 2017. [DOI: 10.1007/978-3-319-59100-1_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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Tait CE, Neuhaus P, Anderson HL, Timmel CR. Triplet state delocalization in a conjugated porphyrin dimer probed by transient electron paramagnetic resonance techniques. J Am Chem Soc 2015; 137:6670-9. [PMID: 25914154 PMCID: PMC4569061 DOI: 10.1021/jacs.5b03249] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The
delocalization of the photoexcited triplet state in a linear
butadiyne-linked porphyrin dimer is investigated by time-resolved
and pulse electron paramagnetic resonance (EPR) with laser excitation.
The transient EPR spectra of the photoexcited triplet states of the
porphyrin monomer and dimer are characterized by significantly different
spin polarizations and an increase of the zero-field splitting parameter D from monomer to dimer. The proton and nitrogen hyperfine
couplings, determined using electron nuclear double resonance (ENDOR)
and X- and Q-band HYSCORE, are reduced to about half in the porphyrin
dimer. These data unequivocally prove the delocalization of the triplet
state over both porphyrin units, in contrast to the conclusions from
previous studies on the triplet states of closely related porphyrin
dimers. The results presented here demonstrate that the most accurate
estimate of the extent of triplet state delocalization can be obtained
from the hyperfine couplings, while interpretation of the zero-field
splitting parameter D can lead to underestimation
of the delocalization length, unless combined with quantum chemical
calculations. Furthermore, orientation-selective ENDOR and HYSCORE
results, in combination with the results of density functional theory
(DFT) calculations, allowed determination of the orientations of the
zero-field splitting tensors with respect to the molecular frame in
both porphyrin monomer and dimer. The results provide evidence for
a reorientation of the zero-field splitting tensor and a change in
the sign of the zero-field splitting D value. The
direction of maximum dipolar coupling shifts from the out-of-plane
direction in the porphyrin monomer to the vector connecting the two
porphyrin units in the dimer. This reorientation, leading to an alignment
of the principal optical transition moment and the axis of maximum
dipolar coupling, is also confirmed by magnetophotoselection experiments.
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Affiliation(s)
- Claudia E Tait
- †Department of Chemistry, Centre for Advanced Electron Spin Resonance, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Patrik Neuhaus
- ‡Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Harry L Anderson
- ‡Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Christiane R Timmel
- †Department of Chemistry, Centre for Advanced Electron Spin Resonance, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
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de Oliveira M, Wiegand T, Elmer LM, Sajid M, Kehr G, Erker G, Magon CJ, Eckert H. Solid-state EPR strategies for the structural characterization of paramagnetic NO adducts of frustrated Lewis pairs (FLPs). J Chem Phys 2015; 142:124201. [PMID: 25833572 DOI: 10.1063/1.4916066] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Marcos de Oliveira
- Instituto de Física de São Carlos, Universidade de São Paulo, P.O. Box 369, 13560-970 São Carlos, São Paulo, Brazil
| | - Thomas Wiegand
- Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, 8049 Zürich, Switzerland
| | - Lisa-Maria Elmer
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, D 48149 Münster, Germany
| | - Muhammad Sajid
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, D 48149 Münster, Germany
| | - Gerald Kehr
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, D 48149 Münster, Germany
| | - Gerhard Erker
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, D 48149 Münster, Germany
| | - Claudio José Magon
- Instituto de Física de São Carlos, Universidade de São Paulo, P.O. Box 369, 13560-970 São Carlos, São Paulo, Brazil
| | - Hellmut Eckert
- Instituto de Física de São Carlos, Universidade de São Paulo, P.O. Box 369, 13560-970 São Carlos, São Paulo, Brazil
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Bourrez M, Orio M, Molton F, Vezin H, Duboc C, Deronzier A, Chardon-Noblat S. Pulsed-EPR evidence of a manganese(II) hydroxycarbonyl intermediate in the electrocatalytic reduction of carbon dioxide by a manganese bipyridyl derivative. Angew Chem Int Ed Engl 2013; 53:240-3. [PMID: 24259443 DOI: 10.1002/anie.201306750] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 10/11/2013] [Indexed: 11/07/2022]
Abstract
A key intermediate in the electroconversion of carbon dioxide to carbon monoxide, catalyzed by a manganese tris(carbonyl) complex, is characterized. Different catalytic pathways and their potential reaction mechanisms are investigated using a large range of experimental and computational techniques. Sophisticated spectroscopic methods including UV/Vis absorption and pulsed-EPR techniques (2P-ESEEM and HYSCORE) were combined together with DFT calculations to successfully identify a key intermediate in the catalytic cycle of CO2 reduction. The results directly show the formation of a metal-carboxylic acid-CO2 adduct after oxidative addition of CO2 and H(+) to a Mn(0) carbonyl dimer, an unexpected intermediate.
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Affiliation(s)
- Marc Bourrez
- Université Joseph Fourier-Grenoble1/CNRS, Département de Chimie Moléculaire UMR5250, Laboratoire de Chimie Inorganique Redox, Institut de Chimie Moléculaire de Grenoble FR-CNRS-2607, BP53, 38041 Grenoble cedex 09 (France)
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Bourrez M, Orio M, Molton F, Vezin H, Duboc C, Deronzier A, Chardon-Noblat S. Pulsed-EPR Evidence of a Manganese(II) Hydroxycarbonyl Intermediate in the Electrocatalytic Reduction of Carbon Dioxide by a Manganese Bipyridyl Derivative. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306750] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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