1
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Ramek M, Sabolović J. Structure prediction of physiological bis(amino acidato)copper(II) species in aqueous solution: The copper(II) compounds with l-glutamine and l-histidine. J Inorg Biochem 2024; 251:112430. [PMID: 38006660 DOI: 10.1016/j.jinorgbio.2023.112430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 10/27/2023] [Accepted: 11/13/2023] [Indexed: 11/27/2023]
Abstract
Neutral (l-histidinato)(l-glutaminato)copper(II) [Cu(His)(Gln)] has been established as the most abundant ternary copper(II) amino acid compound of the exchangeable copper(II) pool in blood plasma. The experimental studies of Cu(His)(Gln) and bis(glutaminato)copper(II) [Cu(Gln)2] in solutions did not specify their complete geometries. To determine the geometries, this paper investigates the conformers, energy landscapes, and a structure-magnetic parameters relation of Cu(Gln)2 and Cu(His)(Gln) by the density functional theory (DFT) calculations. We assume a glycine-like coordination of Gln (other coordination patterns are dismissed because of steric reasons), and three His in-plane copper(II) binding modes. The conformational analyses are performed in the gas phase and implicitly modeled aqueous solution. The reliability of the DFT relative electronic and Gibbs free energies of the Cu(His)(Gln) conformers is confirmed by benchmarking against the corresponding energies obtained by the domain-based local pair natural orbital coupled-cluster method with singles, doubles, and perturbative triples [DLPNO-CCSD(T)]. Several cis- and trans-Cu(His)(Gln) conformers with His in the histaminate-like and glycine-like modes have low Gibbs free energies, and the greatest estimated metal-binding affinities. The DFT-calculated magnetic parameters of the low-energy conformers reproduce best the experimental electron paramagnetic resonance parameters measured in aqueous solutions for trans- and cis-Cu(Gln)2 conformers having two oxygen atoms (either from Gln or water molecules) at the apical positions, and Cu(His)(Gln) conformers having His in the histaminate-like mode with an apically placed carboxylato oxygen atom. The predicted conformational flexibility of His‑copper(II)-amino acid compounds may be connected with their physiological abundance, and the role in copper(II) exchange reactions in blood plasma.
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Affiliation(s)
- Michael Ramek
- Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010 Graz, Austria
| | - Jasmina Sabolović
- Institute for Medical Research and Occupational Health, Ksaverska cesta 2, HR-10000 Zagreb, Croatia.
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2
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Jodts RJ, Wittkop M, Ho MB, Broderick WE, Broderick JB, Hoffman BM, Mosquera MA. Computational Description of Alkylated Iron-Sulfur Organometallic Clusters. J Am Chem Soc 2023; 145:13879-13887. [PMID: 37307050 PMCID: PMC10573082 DOI: 10.1021/jacs.3c03062] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The radical S-adenosyl methionine (SAM) enzyme superfamily has widespread roles in hydrogen atom abstraction reactions of crucial biological importance. In these enzymes, reductive cleavage of SAM bound to a [4Fe-4S]1+ cluster generates the 5'-deoxyadenosyl radical (5'-dAdo•) which ultimately abstracts an H atom from the substrate. However, overwhelming experimental evidence has surprisingly revealed an obligatory organometallic intermediate Ω exhibiting an Fe-C5'-adenosyl bond, whose properties are the target of this theoretical investigation. We report a readily applied, two-configuration version of broken symmetry DFT, denoted 2C-DFT, designed to allow the accurate description of the hyperfine coupling constants and g-tensors of an alkyl group bound to a multimetallic iron-sulfur cluster. This approach has been validated by the excellent agreement of its results both with those of multiconfigurational complete active space self-consistent field computations for a series of model complexes and with the results from electron nuclear double-resonance/electron paramagnetic resonance spectroscopic studies for the crystallographically characterized complex, M-CH3, a [4Fe-4S] cluster with a Fe-CH3 bond. The likewise excellent agreement between spectroscopic results and 2C-DFT computations for Ω confirm its identity as an organometallic complex with a bond between an Fe of the [4Fe-4S] cluster and C5' of the deoxyadenosyl moiety, as first proposed.
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Affiliation(s)
- Richard J. Jodts
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208
| | - M Wittkop
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
| | - Madeline B. Ho
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208
| | - William E. Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
| | - Joan B. Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
| | - Brian M. Hoffman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208
| | - Martín A. Mosquera
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
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3
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Gleeson R, Andersen CL, Rapta P, Machata P, Christensen JB, Hammerich O, Sauer SPA. A Combined Experimental and Theoretical Study of ESR Hyperfine Coupling Constants for N,N,N',N'-Tetrasubstituted p-Phenylenediamine Radical Cations. Int J Mol Sci 2023; 24:3447. [PMID: 36834859 PMCID: PMC9967363 DOI: 10.3390/ijms24043447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 01/26/2023] [Accepted: 02/03/2023] [Indexed: 02/11/2023] Open
Abstract
A test set of N,N,N',N'-tetrasubstituted p-phenylenediamines are experimentally explored using ESR (electron spin resonance) spectroscopy and analysed from a computational standpoint thereafter. This computational study aims to further aid structural characterisation by comparing experimental ESR hyperfine coupling constants (hfccs) with computed values calculated using ESR-optimised "J-style" basis sets (6-31G(d,p)-J, 6-31G(d,p)-J, 6-311++G(d,p)-J, pcJ-1, pcJ-2 and cc-pVTZ-J) and hybrid-DFT functionals (B3LYP, PBE0, TPSSh, ωB97XD) as well as MP2. PBE0/6-31g(d,p)-J with a polarised continuum solvation model (PCM) correlated best with the experiment, giving an R2 value of 0.8926. A total of 98% of couplings were deemed satisfactory, with five couplings observed as outlier results, thus degrading correlation values significantly. A higher-level electronic structure method, namely MP2, was sought to improve outlier couplings, but only a minority of couples showed improvement, whilst the remaining majority of couplings were negatively degraded.
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Affiliation(s)
- Ronan Gleeson
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Cecilie L. Andersen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Peter Rapta
- Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia
| | - Peter Machata
- Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia
| | - Jørn B. Christensen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Ole Hammerich
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Stephan P. A. Sauer
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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4
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Gómez-Piñeiro R, Drosou M, Bertaina S, Decroos C, Simaan AJ, Pantazis DA, Orio M. Decoding the Ambiguous Electron Paramagnetic Resonance Signals in the Lytic Polysaccharide Monooxygenase from Photorhabdus luminescens. Inorg Chem 2022; 61:8022-8035. [PMID: 35549254 PMCID: PMC9131454 DOI: 10.1021/acs.inorgchem.2c00766] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Indexed: 11/29/2022]
Abstract
Understanding the structure and function of lytic polysaccharide monooxygenases (LPMOs), copper enzymes that degrade recalcitrant polysaccharides, requires the reliable atomistic interpretation of electron paramagnetic resonance (EPR) data on the Cu(II) active site. Among various LPMO families, the chitin-active PlAA10 shows an intriguing phenomenology with distinct EPR signals, a major rhombic and a minor axial signal. Here, we combine experimental and computational investigations to uncover the structural identity of these signals. X-band EPR spectra recorded at different pH values demonstrate pH-dependent population inversion: the major rhombic signal at pH 6.5 becomes minor at pH 8.5, where the axial signal dominates. This suggests that a protonation change is involved in the interconversion. Precise structural interpretations are pursued with quantum chemical calculations. Given that accurate calculations of Cu g-tensors remain challenging for quantum chemistry, we first address this problem via a thorough calibration study. This enables us to define a density functional that achieves accurate and reliable prediction of g-tensors, giving confidence in our evaluation of PlAA10 LPMO models. Large models were considered that include all parts of the protein matrix surrounding the Cu site, along with the characteristic second-sphere features of PlAA10. The results uniquely identify the rhombic signal with a five-coordinate Cu ion bearing two water molecules in addition to three N-donor ligands. The axial signal is attributed to a four-coordinate Cu ion where only one of the waters remains bound, as hydroxy. Alternatives that involve decoordination of the histidine brace amino group are unlikely based on energetics and spectroscopy. These results provide a reliable spectroscopy-consistent view on the plasticity of the resting state in PlAA10 LPMO as a foundation for further elucidating structure-property relationships and the formation of catalytically competent species. Our strategy is generally applicable to the study of EPR parameters of mononuclear copper-containing metalloenzymes.
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Affiliation(s)
| | - Maria Drosou
- Inorganic
Chemistry Laboratory, National and Kapodistrian
University of Athens, Panepistimiopolis, Zografou 15771, Greece
| | - Sylvain Bertaina
- Aix-Marseille
Université, CNRS, IM2NP UMR 7334, Marseille 13397, France
| | - Christophe Decroos
- Aix
Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille 13397, France
| | - A. Jalila Simaan
- Aix
Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille 13397, France
| | - Dimitrios A. Pantazis
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an
der Ruhr 45470, Germany
| | - Maylis Orio
- Aix
Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille 13397, France
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5
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Investigating an efficient and accurate protocol for sampling structures from molecular dynamics simulations: a close look by different wavelet families. Theor Chem Acc 2021. [DOI: 10.1007/s00214-021-02816-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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6
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Gromov OI. Performance of the DLPNO-CCSD and recent DFT methods in the calculation of isotropic and dipolar contributions to 14N hyperfine coupling constants of nitroxide radicals. J Mol Model 2021; 27:194. [PMID: 34075533 DOI: 10.1007/s00894-021-04807-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 05/26/2021] [Indexed: 10/21/2022]
Abstract
In the present study, the performance of a set of density functionals: BP86, PBE, OLYP, BEEF, PBEpow, TPSS, SCAN, PBEGXPBE, M06L, MN15L, B3LYP, PBE0, mPW1PW, B97, BHandHLYP, mPW1PW, B98, TPSS0, PBE1KCIS, SCAN0, M06, M06-2X, MN15, CAM-B3LYP, ωB97x, B2PLYP, and the B3LYP/N07D and PBE/N07D schemes in the calculation of the 14N anisotropic hyperfine coupling (HFC) constants of a set of 23 nitroxide radicals is evaluated. The results are compared with those obtained with the DLPNO-CCSD method and experimental HFC values. Harmonic contribution to the 14N HFC vibrational correction was calculated at the revPBE0/def2-TZVPP level and included in the evaluation. With the vibrational correction, the DLPNO-CCSD method yielded HFC values in good agreement with the experiment (mean absolute deviation (MAD) = 0.3 G for the dipole-dipole contribution and MAD = 0.8 G for the contact coupling contribution). The best DFT results are obtained using the M06 functional with MAD = 0.2 G for the dipole-dipole contribution and MAD = 0.7 G for the contact coupling contribution. In general, vibrational correction significantly improved most DFT functionals' performance but did not change its overall ranking.
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Affiliation(s)
- Oleg I Gromov
- Chemistry Department, Lomonosov Moscow State University, Leninskiye Gory 1-3, Moscow, 119991, Russia.
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7
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Theibich YA, Sauer SP, Leggio LL, Hedegård ED. Estimating the accuracy of calculated electron paramagnetic resonance hyperfine couplings for a lytic polysaccharide monooxygenase. Comput Struct Biotechnol J 2020; 19:555-567. [PMID: 33510861 PMCID: PMC7807142 DOI: 10.1016/j.csbj.2020.12.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/11/2020] [Accepted: 12/13/2020] [Indexed: 11/07/2022] Open
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are enzymes that bind polysaccharides followed by an (oxidative) disruption of the polysaccharide surface, thereby boosting depolymerization. The binding process between the LPMO catalytic domain and polysaccharide is key to the mechanism and establishing structure-function relationships for this binding is therefore crucial. The hyperfine coupling constants (HFCs) from EPR spectroscopy have proven useful for this purpose. Unfortunately, EPR does not provide direct structural data and therefore the experimental EPR parameters have to be supported with parameters calculated with density functional theory. Yet, calculated HFCs are extremely sensitive to the employed computational setup. Using the LPMO Ls(AA9)A catalytic domain, we here quantify the importance of several choices in the computational setup, ranging from the use of specialized basis, the underlying structures, and the employed exchange-correlation functional. We show that specialized basis sets are an absolute necessity, and also that care has to be taken in the optimization of the underlying structure: only by allowing large parts of the protein around the active site to structurally relax could we obtain results that uniformly reproduced experimental trends. We compare our results to previously published X-ray structures and experimental HFCs for Ls(AA9)A as well as to recent experimental/theoretical results for another (AA10) family of LPMOs.
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Affiliation(s)
- Yusuf A. Theibich
- Department of Chemistry, University of University, Copenhagen, Denmark
| | | | - Leila Lo Leggio
- Department of Chemistry, University of University, Copenhagen, Denmark
| | - Erik D. Hedegård
- Division of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE-221 00 Lund, Sweden
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8
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Gómez-Piñeiro RJ, Pantazis DA, Orio M. Comparison of Density Functional and Correlated Wave Function Methods for the Prediction of Cu(II) Hyperfine Coupling Constants. Chemphyschem 2020; 21:2667-2679. [PMID: 33201578 PMCID: PMC7756273 DOI: 10.1002/cphc.202000649] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/13/2020] [Indexed: 12/19/2022]
Abstract
The reliable prediction of Cu(II) hyperfine coupling constants remains a challenge for quantum chemistry. Until recently only density functional theory (DFT) could target this property for systems of realistic size. However, wave function based methods become increasingly applicable. In the present work, we define a large set of Cu(II) complexes with experimentally known hyperfine coupling constants and use it to investigate the performance of modern quantum chemical methods for the prediction of this challenging spectroscopic parameter. DFT methods are evaluated against orbital‐optimized second‐order Møller‐Plesset (OO‐MP2) theory and coupled cluster calculations including singles and doubles excitations, driven by the domain‐based local pair natural orbital approach (DLPNO‐CCSD). Special attention is paid to the definition of a basis set that converges adequately toward the basis set limit for the given property for all methods considered in this study, and a specifically optimized basis set is proposed for this purpose. The results suggest that wave function based methods can supplant but do not outcompete DFT for the calculation of Cu(II) hyperfine coupling constants. Mainstream hybrid functionals such as B3PW91 remain on average the best choice.
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Affiliation(s)
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Maylis Orio
- Aix-Marseille Université, CNRS, iSm2, Marseille, France
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9
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Roy M, Pal AK, Adhikary A, Datta A, Mondal R. Paradoxical design of a serendipitous pyrazolate bridging mode: a pragmatic strategy for inducing ineluctable ferromagnetic coupling. Dalton Trans 2020; 49:13704-13716. [PMID: 32996512 DOI: 10.1039/d0dt02468f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In this contribution we have carried out a systematic magnetostructural investigation to establish a robust one-to-one correlation between the quasi-orthogonal bridging mode of a pyrazolate ring and ferromagnetic coupling. Generating a complex with an elusive quasi-orthogonal pyrazolate bridging is a challenging task but would ineluctably result in a ferromagnetic exchange pathway. Notwithstanding the rarity, we report herein a series of bis-pyrazolato copper complexes. We have successfully exploited a so-called hypothetical-deductive model on a particular set of ligand systems that forced the pyrazolate moiety to adopt an unusual bridging mode with the M-Npz-Npz-M torsion angles in the range from 49.7° to 72.8°. The corroborating variable temperature direct current (DC) magnetic susceptibility data unequivocally confirm the ferromagnetic coupling for the complexes with the torsion angles greater than 71.37°. Furthermore, the experimental results are in excellent agreement with theoretical calculations. Based on density functional theory (DFT) calculations, again a one-to-one correspondence is made between the ligand structure and magnetic behaviour. The diradical character (y0) of the complexes is correlated with the extent of bonding interactions between the Cu centers and hence, their ferromagnetic or antiferromagnetic nature. The broken symmetry (BS) calculations on the magnetically active molecular orbitals indicate the essential magnetic behaviour of the complexes, while the EPR g-tensor calculations confirm that dx2-y2 is the magnetic orbital.
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Affiliation(s)
- Manasi Roy
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata 700032, India.
| | - Arun K Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata 700032, India.
| | - Amit Adhikary
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata 700032, India.
| | - Ayan Datta
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata 700032, India.
| | - Raju Mondal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata 700032, India.
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10
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Haase PAB, Eliav E, Iliaš M, Borschevsky A. Hyperfine Structure Constants on the Relativistic Coupled Cluster Level with Associated Uncertainties. J Phys Chem A 2020; 124:3157-3169. [PMID: 32202783 PMCID: PMC7184561 DOI: 10.1021/acs.jpca.0c00877] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/20/2020] [Indexed: 11/29/2022]
Abstract
Accurate predictions of hyperfine structure (HFS) constants are important in many areas of chemistry and physics, from the determination of nuclear electric and magnetic moments to benchmarking of new theoretical methods. We present a detailed investigation of the performance of the relativistic coupled cluster method for calculating HFS constants within the finite-field scheme. The two selected test systems are 133Cs and 137BaF. Special attention has been paid to construct a theoretical uncertainty estimate based on investigations on basis set, electron correlation and relativistic effects. The largest contribution to the uncertainty estimate comes from higher order correlation contributions. Our conservative uncertainty estimate for the calculated HFS constants is ∼5.5%, while the actual deviation of our results from experimental values is <1% in all cases.
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Affiliation(s)
- Pi A. B. Haase
- Van
Swinderen Institute, University of Groningen, 9747 Groningen, The Netherlands
| | - Ephraim Eliav
- School
of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Miroslav Iliaš
- Department
of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovskèho 40, SK-97400 Banska Bystrica, Slovakia
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11
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First-Principles Calculation of Transition Metal Hyperfine Coupling Constants with the Strongly Constrained and Appropriately Normed (SCAN) Density Functional and its Hybrid Variants. MAGNETOCHEMISTRY 2019. [DOI: 10.3390/magnetochemistry5040069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Density functional theory (DFT) is used extensively for the first-principles calculation of hyperfine coupling constants in both main-group and transition metal systems. As with many other properties, the performance of DFT for hyperfine coupling constants is of variable quality, particularly for transition metal complexes, because it strongly depends on the nature of the chemical system and the type of approximation to the exchange-correlation functional. Recently, a meta-generalized-gradient approximation (mGGA) functional was proposed that obeys all known exact constraints for such a method, known as the Strongly Constrained and Appropriately Normed (SCAN) functional. In view of its theoretically superior formulation a benchmark set of complexes is used to assess the performance of SCAN for the challenging case of transition metal hyperfine coupling constants. In addition, two global hybrid versions of the functional, SCANh and SCAN0, are described and tested. The values computed with the new functionals are compared with experiment and with those of other DFT approximations. Although the original SCAN and the SCAN-based hybrids may offer improved hyperfine coupling constants for specific systems, no uniform improvement is observed. On the contrary, there are specific cases where the new functionals fail badly due to a flawed description of the underlying electronic structure. Therefore, despite these methodological advances, systematically accurate and system-independent prediction of transition metal hyperfine coupling constants with DFT remains an unmet challenge.
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12
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Gordon JB, Vilbert AC, DiMucci IM, MacMillan SN, Lancaster KM, Moënne-Loccoz P, Goldberg DP. Activation of Dioxygen by a Mononuclear Nonheme Iron Complex: Sequential Peroxo, Oxo, and Hydroxo Intermediates. J Am Chem Soc 2019; 141:17533-17547. [PMID: 31647656 DOI: 10.1021/jacs.9b05274] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The activation of dioxygen by FeII(Me3TACN)(S2SiMe2) (1) is reported. Reaction of 1 with O2 at -135 °C in 2-MeTHF generates a thiolate-ligated (peroxo)diiron complex FeIII2(O2)(Me3TACN)2(S2SiMe2)2 (2) that was characterized by UV-vis (λmax = 300, 390, 530, 723 nm), Mössbauer (δ = 0.53, |ΔEQ| = 0.76 mm s-1), resonance Raman (RR) (ν(O-O) = 849 cm-1), and X-ray absorption (XAS) spectroscopies. Complex 2 is distinct from the outer-sphere oxidation product 1ox (UV-vis (λmax = 435, 520, 600 nm), Mössbauer (δ = 0.45, |ΔEQ| = 3.6 mm s-1), and EPR (S = 5/2, g = [6.38, 5.53, 1.99])), obtained by one-electron oxidation of 1. Cleavage of the peroxo O-O bond can be initiated either photochemically or thermally to produce a new species assigned as an FeIV(O) complex, FeIV(O)(Me3TACN)(S2SiMe2) (3), which was identified by UV-vis (λmax = 385, 460, 890 nm), Mössbauer (δ = 0.21, |ΔEQ| = 1.57 mm s-1), RR (ν(FeIV═O) = 735 cm-1), and X-ray absorption spectroscopies, as well as reactivity patterns. Reaction of 3 at low temperature with H atom donors gives a new species, FeIII(OH)(Me3TACN)(S2SiMe2) (4). Complex 4 was independently synthesized from 1 by the stoichiometric addition of a one-electron oxidant and a hydroxide source. This work provides a rare example of dioxygen activation at a mononuclear nonheme iron(II) complex that produces both FeIII-O-O-FeIII and FeIV(O) species in the same reaction with O2. It also demonstrates the feasibility of forming Fe/O2 intermediates with strongly donating sulfur ligands while avoiding immediate sulfur oxidation.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Avery C Vilbert
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Ida M DiMucci
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry , Oregon Health & Science University , Portland , Oregon 97239 , United States
| | - David P Goldberg
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
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13
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Moore JT, Chatterjee S, Tarrago M, Clouston LJ, Sproules S, Bill E, Bernales V, Gagliardi L, Ye S, Lancaster KM, Lu CC. Enhanced Fe-Centered Redox Flexibility in Fe-Ti Heterobimetallic Complexes. Inorg Chem 2019; 58:6199-6214. [PMID: 30957996 PMCID: PMC6727590 DOI: 10.1021/acs.inorgchem.9b00442] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
![]()
Previously, we reported the synthesis
of Ti[N(o-(NCH2P(iPr)2)C6H4)3] and
the Fe–Ti complex, FeTi[N(o-(NCH2P(iPr)2)C6H4)3], abbreviated as TiL (1), and FeTiL
(2), respectively. Herein, we describe the synthesis
and characterization of the complete redox families of the monometallic
Ti and Fe–Ti compounds. Cyclic voltammetry studies on FeTiL
reveal both reduction and oxidation processes at −2.16 and
−1.36 V (versus Fc/Fc+), respectively. Two isostructural
redox members, [FeTiL]+ and [FeTiL]− (2ox and 2red, respectively)
were synthesized and characterized, along with BrFeTiL (2-Br) and the monometallic [TiL]+ complex (1ox). The solid-state structures of the [FeTiL]+/0/– series feature short metal–metal bonds, ranging from 1.94–2.38
Å, which are all shorter than the sum of the Ti and Fe single-bond
metallic radii (cf. 2.49 Å). To elucidate the bonding and electronic
structures, the complexes were characterized with a host of spectroscopic
methods, including NMR, EPR, and 57Fe Mössbauer,
as well as Ti and Fe K-edge X-ray absorption spectroscopy (XAS). These
studies, along with hybrid density functional theory (DFT) and time-dependent
DFT calculations, suggest that the redox processes in the isostructural
[FeTiL]+,0,– series are primarily Fe-based and that
the polarized Fe–Ti π-bonds play a role in delocalizing
some of the additional electron density from Fe to Ti (net 13%). An isostructural redox series of Fe≡Ti complexes was investigated
using a combination of spectroscopic methods and density functional
theory to elucidate their electronic structures and to understand
their polarized metal−metal bonding. Overall, the results support
that the redox changes occur primarily at the Fe site though some
electron density is delocalized to Ti. Hence, the Ti plays an important
role in enhancing the redox flexibility of the single Fe site.
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Affiliation(s)
- James T Moore
- Department of Chemistry , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455-0431 , United States
| | - Sudipta Chatterjee
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca New York 14853 , United States
| | - Maxime Tarrago
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
| | - Laura J Clouston
- Department of Chemistry , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455-0431 , United States
| | - Stephen Sproules
- WestCHEM, School of Chemistry , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany
| | - Varinia Bernales
- Department of Chemistry , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455-0431 , United States
| | - Laura Gagliardi
- Department of Chemistry , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455-0431 , United States
| | - Shengfa Ye
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca New York 14853 , United States
| | - Connie C Lu
- Department of Chemistry , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455-0431 , United States
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14
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Gromov OI, Kuzin SV, Golubeva EN. Performance of DFT methods in the calculation of isotropic and dipolar contributions to 14N hyperfine coupling constants of nitroxide radicals. J Mol Model 2019; 25:93. [PMID: 30859325 DOI: 10.1007/s00894-019-3966-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 02/07/2019] [Indexed: 10/27/2022]
Abstract
In the present study, we tested the widely used density functionals BP86, PBE, OLYP, TPSS, M06-L, B3LYP, PBE0, mPW1PW, B97, BHandHLYP, TPSS0, M06, M06-2X, CAM-B3LYP, ωB97x, and B2PLYP with the cc-pCVQZ basis set in calculations on a set of 23 nitroxide radicals with well-resolved 14N anisotropic hyperfine coupling (HFC) constants. The results were compared with those obtained using the B3LYP/N07D and PBE/N07D methods. The convergence of the HFC values to the complete basis set limit is briefly discussed. The best results were obtained using the M06/COSMO method, with a mean absolute deviation (MAD) of 0.4 G for the dipole-dipole contribution and MAD = 0.6 G for the contact coupling contribution (as compared to 1.1 G and 1.0 G, respectively, for the B3LYP/N07D/COSMO method and 1.7 G and 0.5 G, respectively, for the B3LYP/N07D method). The majority of the functionals yielded satisfactory results for the dipole-dipole contribution, but only the M06 functional yielded similar errors for both the dipole-dipole and isotropic contributions. The RIJCOSX and RI approximations introduced errors equal to or smaller than 0.01 G.
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Affiliation(s)
- Oleg I Gromov
- Chemistry Department, Lomonosov Moscow State University, Leninskiye Gory 1-3, Moscow, Russia, 119991.
| | - Sergei V Kuzin
- Chemistry Department, Lomonosov Moscow State University, Leninskiye Gory 1-3, Moscow, Russia, 119991
| | - Elena N Golubeva
- Chemistry Department, Lomonosov Moscow State University, Leninskiye Gory 1-3, Moscow, Russia, 119991
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15
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Gordon JB, Vilbert AC, Siegler MA, Lancaster KM, Moënne-Loccoz P, Goldberg DP. A Nonheme Thiolate-Ligated Cobalt Superoxo Complex: Synthesis and Spectroscopic Characterization, Computational Studies, and Hydrogen Atom Abstraction Reactivity. J Am Chem Soc 2019; 141:3641-3653. [PMID: 30776222 DOI: 10.1021/jacs.8b13134] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The synthesis and characterization of a Co(II) dithiolato complex Co(Me3TACN)(S2SiMe2) (1) are reported. Reaction of 1 with O2 generates a rare thiolate-ligated cobalt-superoxo species Co(O2)(Me3TACN)(S2SiMe2) (2) that was characterized spectroscopically and structurally by resonance Raman, EPR, and X-ray absorption spectroscopies as well as density functional theory. Metal-superoxo species are proposed to S-oxygenate metal-bound thiolate donors in nonheme thiol dioxygenases, but 2 does not lead to S-oxygenation of the intramolecular thiolate donors and does not react with exogenous sulfur donors. However, complex 2 is capable of oxidizing the O-H bonds of 2,2,6,6-tetramethylpiperidin-1-ol derivatives via H atom abstraction. Complementary proton-coupled electron-transfer reactivity is seen for 2 with separated proton/reductant pairs. The reactivity studies indicate that 2 can abstract H atoms from weak X-H bonds with bond dissociation free energy (BDFE) ≤ 70 kcal mol-1. DFT calculations predict that the putative Co(OOH) product has an O-H BDFE = 67 kcal mol-1, which matches the observed pattern of reactivity seen for 2. These data provide new information regarding the selectivity of S-oxygenation versus H atom abstraction in thiolate-ligated nonheme metalloenzymes that react with O2.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Avery C Vilbert
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Maxime A Siegler
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853 , United States
| | - Pierre Moënne-Loccoz
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239-3098 , United States
| | - David P Goldberg
- Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
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16
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Spencer J, Stevens J, Perry C, Murphy DM. An EPR Investigation of Binding Environments by N-Donor Chelating Exchange Resins for Cu Extraction from Aqueous Media. Inorg Chem 2018; 57:10857-10866. [DOI: 10.1021/acs.inorgchem.8b01519] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jacob Spencer
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, United Kingdom
| | - James Stevens
- Johnson Matthey Technology Center, Blounts Court Road, Sonning Common, Reading RG4 9NH, United Kingdom
| | - Christopher Perry
- Johnson Matthey, Building 22, CSIR, Meiring Naudé Road, Brummeria 0184, Pretoria, South Africa
| | - Damien M. Murphy
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, United Kingdom
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17
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Haase PAB, Repisky M, Komorovsky S, Bendix J, Sauer SPA. Relativistic DFT Calculations of Hyperfine Coupling Constants in 5d Hexafluorido Complexes: [ReF 6 ] 2- and [IrF 6 ] 2. Chemistry 2018; 24:5124-5133. [PMID: 29027277 PMCID: PMC5969236 DOI: 10.1002/chem.201704653] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Indexed: 11/08/2022]
Abstract
The performance of relativistic density functional theory (DFT) methods has been investigated for the calculation of the recently measured hyperfine coupling constants of hexafluorido complexes [ReF6 ]2- and [IrF6 ]2- . Three relativistic methods were employed at the DFT level of theory: the 2-component zeroth-order regular approximation (ZORA) method, in which the spin-orbit coupling was treated either variationally (EV ZORA) or as a perturbation (LR ZORA), and the 4-component Dirac-Kohn-Sham (DKS) method. The dependence of the results on the basis set and the choice of exchange-correlation functional was studied. Furthermore, the effect of varying the amount of Hartree-Fock exchange in the hybrid functionals was investigated. The LR ZORA and DKS methods combined with DFT led to very similar deviations (about 20 %) from the experimental values for the coupling constant of complex [ReF6 ]2- by using hybrid functionals. However, none of the methods were able to reproduce the large anisotropy of the hyperfine coupling tensor of complex [ReF6 ]2- . For [IrF6 ]2- , the EV ZORA and DKS methods reproduced the experimental tensor components with deviations of ≈10 and ≈5 % for the hybrid functionals, whereas the LR ZORA method predicted the coupling constant to be around one order of magnitude too large owing to the combination of large spin-orbit coupling and very low excitation energies.
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Affiliation(s)
- Pi A B Haase
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen Ø, Denmark
- Van Swinderen Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Michal Repisky
- CTCC, Department of Chemistry, University of Tromsø, N-9037, Tromsø, Norway
| | - Stanislav Komorovsky
- Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dubravska Cesta 9, SK-84536, Bratislava, Slovakia
| | - Jesper Bendix
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen Ø, Denmark
| | - Stephan P A Sauer
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen Ø, Denmark
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18
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Mendt M, Barth B, Hartmann M, Pöppl A. Low-temperature binding of NO adsorbed on MIL-100(Al)—A case study for the application of high resolution pulsed EPR methods and DFT calculations. J Chem Phys 2017; 147:224701. [DOI: 10.1063/1.4995551] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Matthias Mendt
- Felix-Bloch-Institut für Festkörperphysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
| | - Benjamin Barth
- Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
| | - Martin Hartmann
- Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
| | - Andreas Pöppl
- Felix-Bloch-Institut für Festkörperphysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
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19
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Exploring EPR Parameters of 99Tc Complexes for Designing New MRI Probes: Coordination Environment, Solvent, and Thermal Effects on the Spectroscopic Properties. J CHEM-NY 2017. [DOI: 10.1155/2017/8102812] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We have evaluated the solvent and thermal effects on spectroscopic parameters of 99Tc complexes coordinated to explicit water molecules. Molecular dynamics simulations were performed followed by hyperfine coupling constant calculations (Aiso). Our results show a significant increase of Aiso, which demonstrates that the studied compounds can be promising contrast agents in MRI.
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20
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Gonçalves MA, Santos LS, Prata DM, Peixoto FC, da Cunha EFF, Ramalho TC. Optimal wavelet signal compression as an efficient alternative to investigate molecular dynamics simulations: application to thermal and solvent effects of MRI probes. Theor Chem Acc 2016. [DOI: 10.1007/s00214-016-2037-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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21
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Adam AY, Yachmenev A, Yurchenko SN, Jensen P. Ro-vibrational averaging of the isotropic hyperfine coupling constant for the methyl radical. J Chem Phys 2015; 143:244306. [PMID: 26723670 DOI: 10.1063/1.4938253] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We present the first variational calculation of the isotropic hyperfine coupling constant of the carbon-13 atom in the CH3 radical for temperatures T = 0, 96, and 300 K. It is based on a newly calculated high level ab initio potential energy surface and hyperfine coupling constant surface of CH3 in the ground electronic state. The ro-vibrational energy levels, expectation values for the coupling constant, and its temperature dependence were calculated variationally by using the methods implemented in the computer program TROVE. Vibrational energies and vibrational and temperature effects for coupling constant are found to be in very good agreement with the available experimental data. We found, in agreement with previous studies, that the vibrational effects constitute about 44% of the constant's equilibrium value, originating mainly from the large amplitude out-of-plane bending motion and that the temperature effects play a minor role.
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Affiliation(s)
- Ahmad Y Adam
- Fakultät Mathematik und Naturwissenschaften, Physikalische und Theoretische Chemie, Bergische Universität Wuppertal, D-42097 Wuppertal, Germany
| | - Andrey Yachmenev
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Sergei N Yurchenko
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Per Jensen
- Fakultät Mathematik und Naturwissenschaften, Physikalische und Theoretische Chemie, Bergische Universität Wuppertal, D-42097 Wuppertal, Germany
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22
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Probing thermal and solvent effects on hyperfine interactions and spin relaxation rate of δ-FeOOH(100) and [MnH3buea(OH)]2−: Toward new MRI probes. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2015.07.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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23
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Pedersen MN, Hedegård ED, Kongsted J. Basis set error estimation for DFT calculations of electronic g-tensors for transition metal complexes. J Comput Chem 2014; 35:1809-14. [PMID: 25060998 DOI: 10.1002/jcc.23688] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 06/30/2014] [Accepted: 07/02/2014] [Indexed: 11/10/2022]
Abstract
We present a detailed study of the basis set dependence of electronic g-tensors for transition metal complexes calculated using Kohn-Sham density functional theory. Focus is on the use of locally dense basis set schemes where the metal is treated using either the same or a more flexible basis set than used for the ligand sphere. The performance of all basis set schemes is compared to the extrapolated complete basis set limit results. Furthermore, we test the performance of the aug-cc-pVTZ-J basis set developed for calculations of NMR spin-spin and electron paramagnetic resonance hyperfine coupling constants. Our results show that reasonable results can be obtain when using small basis sets for the ligand sphere, and very accurate results are obtained when an aug-cc-pVTZ basis set or similar is used for all atoms in the complex.
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Affiliation(s)
- Morten N Pedersen
- Department of Physics Chemistry Pharmacy, University of Southern Denmark, DK-5230, Odense M, Denmark
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24
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Sandhoefer B, Kossmann S, Neese F. Derivation and assessment of relativistic hyperfine-coupling tensors on the basis of orbital-optimized second-order Møller-Plesset perturbation theory and the second-order Douglas-Kroll-Hess transformation. J Chem Phys 2013; 138:104102. [PMID: 23514460 DOI: 10.1063/1.4792362] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The accurate calculation of hyperfine-coupling tensors requires a good description of the electronic spin density, especially close to and at the nucleus. Thus, dynamic correlation as well as relativistic effects have to be included in the quantum-chemical calculation of this quantity. In this paper, orbital-optimized second-order Møller-Plesset perturbation theory (MP2) is combined with the second-order Douglas-Kroll-Hess (DKH) transformation to yield an efficient and accurate ab initio method for the calculation of hyperfine couplings for larger molecules including heavy elements. Particular attention is paid to the derivation of the hyperfine-coupling tensor in the DKH framework. In the presence of a magnetic field, the DKH-transformation is not unique. Two different versions can be found in the literature. In this paper, a detailed derivation of one-electron contributions to the hyperfine-coupling tensor as they arise in linear-response theory is given for both DKH-transformations. It turns out that one of the two variants produces divergent hyperfine-coupling constants. The possibility to remove this divergence through a physically motivated finite-nucleus model taking into account the different extent of charge and magnetization distribution is discussed. Hyperfine-coupling values obtained at the orbital-optimized MP2 level with second-order DKH corrections for the non-divergent variant are presented. The influence of a Gaussian nucleus model is studied. The method is compared to four-component, high-accuracy calculations for a number of cations and atoms. Comparison to B3LYP and B2PLYP is made for a set of transition-metal complexes of moderate size.
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Affiliation(s)
- Barbara Sandhoefer
- Max-Planck-Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
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25
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Hedegård ED, Kongsted J, Sauer SPA. Validating and Analyzing EPR Hyperfine Coupling Constants with Density Functional Theory. J Chem Theory Comput 2013; 9:2380-8. [PMID: 26583728 DOI: 10.1021/ct400171c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Erik D Hedegård
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark
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26
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Un S. Structure and nature of manganese(II) imidazole complexes in frozen aqueous solutions. Inorg Chem 2013; 52:3803-13. [PMID: 23510244 DOI: 10.1021/ic302415s] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A common feature of a large majority of the manganese metalloenzymes, as well as many synthetic biomimetic complexes, is the bonding between the manganese ion and imidazoles. This interaction was studied by examining the nature and structure of manganese(II) imidazole complexes in frozen aqueous solutions using 285 GHz high magnet-field continuous-wave electron paramagnetic resonance (cw-HFEPR) and 95 GHz pulsed electron-nuclear double resonance (ENDOR) and pulsed electron-double resonance detected nuclear magnetic resonance (PELDOR-NMR). The (55)Mn hyperfine coupling and isotropic g values of Mn(II) in frozen imidazole solutions continuously decreased with increasing imidazole concentration. ENDOR and PELDOR-NMR measurements demonstrated that the structural basis for this behavior arose from the imidazole concentration-dependent distribution of three six-coordinate and two four-coordinate species: [Mn(H2O)6](2+), [Mn(imidazole)(H2O)5](2+), [Mn(imidazole)2(H2O)4](2+), [Mn(imidazole)3(H2O)](2+), and [Mn(imidazole)4](2+). The hyperfine and g values of manganese proteins were also fully consistent with this imidazole effect. Density functional theory methods were used to calculate the structures, spin and charge densities, and hyperfine couplings of a number of different manganese imidazole complexes. The use of density functional theory with large exact-exchange admixture calculations gave isotropic (55)Mn hyperfine couplings that were semiquantitative and of predictive value. The results show that the covalency of the Mn-N bonds play an important role in determining not only magnetic spin parameters but also the structure of the metal binding site. The relationship between the isotropic (55)Mn hyperfine value and the number of imidazole ligands provides a quick and easy test for determining whether a protein binds an Mn(II) ion using histidine residues and, if so, how many are involved. Application of this method shows that as much as 40% of the Mn(II) ions in Deinococcus radiodurans are ligated to two histidines (Tabares, L. C.; Un, S. J. Biol. Chem 2013, in press).
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Affiliation(s)
- Sun Un
- Service de Bioénergétique, Biologie Structurale et Mécanismes (CNRS/UMR-8221), Institut de Biologie et de Technologies de Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France.
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27
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Electric field gradients of transition metal complexes: Basis set uncontraction and scalar relativistic effects. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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28
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Sancho-García JC, Adamo C. Double-hybrid density functionals: merging wavefunction and density approaches to get the best of both worlds. Phys Chem Chem Phys 2013; 15:14581-94. [DOI: 10.1039/c3cp50907a] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Popov AA, Chen N, Pinzón JR, Stevenson S, Echegoyen LA, Dunsch L. Redox-active scandium oxide cluster inside a fullerene cage: spectroscopic, voltammetric, electron spin resonance spectroelectrochemical, and extended density functional theory study of Sc4O2@C80 and its ion radicals. J Am Chem Soc 2012; 134:19607-18. [PMID: 22924339 DOI: 10.1021/ja306728p] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The clusterfullerene Sc(4)O(2)@C(80) with a mixed redox state of scandium was found to be an exciting molecule for endohedral electrochemistry as demonstrated by means of an in situ electron spin resonance (ESR) spectroelectrochemical study of the spin density distribution in its electrochemically generated cation and anion radicals. The compound exhibits two reversible reduction and oxidation steps with a relatively small electrochemical gap of 1.10 V. The ESR spectra of the ion radicals have a rich hyperfine structure caused by two pairs of equivalent Sc atoms. The Sc-based hyperfine structure with large hyperfine coupling constants shows that both oxidation and reduction of Sc(4)O(2)@C(80) are in cavea redox processes, which is the subject of endohedral electrochemistry. The assignment of the experimentally determined a((45)Sc) values to the two types of Sc atoms in the Sc(4)O(2) cluster was accomplished by extended density functional theory and molecular dynamics simulations. Sc atoms adopting a divalent state in the neutral Sc(4)O(2)@C(80) exhibited an especially large coupling constant of 150.4 G in the cation radical, which is the record high a((45)Sc) value for Sc-based endohedral metallofullerenes. Such a high value is explained by the nature of the highest occupied molecular orbital (HOMO) localized on the six-atom Sc(4)O(2) cluster. This HOMO is a Sc-Sc bonding MO and hence has large contributions from the 4s atomic orbitals of Sc(II). We claim that ESR spectroelectrochemistry is an invaluable experimental tool in the studies of metal-metal bonding in endohedral metallofullerenes and in endohedral electrochemistry.
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Affiliation(s)
- Alexey A Popov
- Leibniz-Institute for Solid State and Materials Research, Department of Electrochemistry and Conducting Polymers, 01069 Dresden, Germany.
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