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Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts

Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts
Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts
We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [ t Bu (PNP)Fe-H], where PNP is a carbazole based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation ( T 1 ~ 10 -11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.
Paramagnetic NMR, hydrido complex, magnetic anisotropy, paramagnetic relaxation enhancement, terahertz electron paramagnetic resonance
1433-7851
22856-22864
Gade, Lutz
f72aa3f0-ae96-4c2f-a1e5-247609f5a935
Ott, Jonas C.
cbd2a368-32c8-45f3-ad55-d718c1f2c221
Suturina, Elizaveta
24dd007d-949a-4852-99d1-ea42b00103ef
Kuprov, Ilya
bb07f28a-5038-4524-8146-e3fc8344c065
Nehrkorn, Joscha
bfea42df-393d-4706-8be4-dd4b73c25941
Schnegg, Alexander
c3b60cc7-449a-4093-9dd5-bd12fab9f9c7
Enders, Markus
231c9d50-3503-406e-bb9e-4c209b63272f
Gade, Lutz
f72aa3f0-ae96-4c2f-a1e5-247609f5a935
Ott, Jonas C.
cbd2a368-32c8-45f3-ad55-d718c1f2c221
Suturina, Elizaveta
24dd007d-949a-4852-99d1-ea42b00103ef
Kuprov, Ilya
bb07f28a-5038-4524-8146-e3fc8344c065
Nehrkorn, Joscha
bfea42df-393d-4706-8be4-dd4b73c25941
Schnegg, Alexander
c3b60cc7-449a-4093-9dd5-bd12fab9f9c7
Enders, Markus
231c9d50-3503-406e-bb9e-4c209b63272f

Gade, Lutz, Ott, Jonas C., Suturina, Elizaveta, Kuprov, Ilya, Nehrkorn, Joscha, Schnegg, Alexander and Enders, Markus (2021) Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts. Angewandte Chemie International Edition, 60 (42), 22856-22864. (doi:10.1002/anie.202107944).

Record type: Article

Abstract

We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [ t Bu (PNP)Fe-H], where PNP is a carbazole based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation ( T 1 ~ 10 -11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.

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More information

e-pub ahead of print date: 5 August 2021
Published date: 11 October 2021
Additional Information: Funding Information: The authors thank Heidelberg University for funding this work and acknowledge support by the state of Baden-W?rttemberg through bwHPC and the German Research Foundation through Grant INST 40/575-1 FUGG (JUSTUS 2 cluster). We thank Dr. Bernd Simon (European Molecular Biology Laboratory, Heidelberg) for the provision of measuring time at the 800 MHz NMR spectrometer. We thank Dr. Thomas Lohmiller, Dr. Karsten Holldack and Dirk Ponnwitz (HZB) for help with the FD-FT THz-EPR measurements at BESSY II, Andreas G?bels (MPI CEC) for conducting the SQUID magnetometry measurements and Dr. Eckhard Bill (MPI CEC) for making available a program for the simulation of SQUID magnetometry data and help with the data interpretation. Allocation of FD-FT THz-EPR beam time by Helmholtz Zentrum Berlin f?r Materialien und Energie (HZB) is gratefully acknowledged. EAS thanks the University of Bath HPC facility for the computational resources. Open access funding enabled and organized by Projekt DEAL. Funding Information: The authors thank Heidelberg University for funding this work and acknowledge support by the state of Baden‐Württemberg through bwHPC and the German Research Foundation through Grant INST 40/575‐1 FUGG (JUSTUS 2 cluster). We thank Dr. Bernd Simon (European Molecular Biology Laboratory, Heidelberg) for the provision of measuring time at the 800 MHz NMR spectrometer. We thank Dr. Thomas Lohmiller, Dr. Karsten Holldack and Dirk Ponnwitz (HZB) for help with the FD‐FT THz‐EPR measurements at BESSY II, Andreas Göbels (MPI CEC) for conducting the SQUID magnetometry measurements and Dr. Eckhard Bill (MPI CEC) for making available a program for the simulation of SQUID magnetometry data and help with the data interpretation. Allocation of FD‐FT THz‐EPR beam time by Helmholtz Zentrum Berlin für Materialien und Energie (HZB) is gratefully acknowledged. EAS thanks the University of Bath HPC facility for the computational resources. Open access funding enabled and organized by Projekt DEAL. Publisher Copyright: © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Keywords: Paramagnetic NMR, hydrido complex, magnetic anisotropy, paramagnetic relaxation enhancement, terahertz electron paramagnetic resonance

Identifiers

Local EPrints ID: 451113
URI: http://eprints.soton.ac.uk/id/eprint/451113
ISSN: 1433-7851
PURE UUID: 0709fce9-e258-4fdd-b604-8986ad7acd0f
ORCID for Ilya Kuprov: ORCID iD orcid.org/0000-0003-0430-2682

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Date deposited: 08 Sep 2021 16:30
Last modified: 17 Mar 2024 03:28

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Contributors

Author: Lutz Gade
Author: Jonas C. Ott
Author: Elizaveta Suturina
Author: Ilya Kuprov ORCID iD
Author: Joscha Nehrkorn
Author: Alexander Schnegg
Author: Markus Enders

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