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Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes

[Image: see text] Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and...

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Autores principales: Novotný, Jan, Jeremias, Lukáš, Nimax, Patrick, Komorovsky, Stanislav, Heinmaa, Ivo, Marek, Radek
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2021
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9597657/
https://www.ncbi.nlm.nih.gov/pubmed/34133172
http://dx.doi.org/10.1021/acs.inorgchem.1c00204
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author Novotný, Jan
Jeremias, Lukáš
Nimax, Patrick
Komorovsky, Stanislav
Heinmaa, Ivo
Marek, Radek
author_facet Novotný, Jan
Jeremias, Lukáš
Nimax, Patrick
Komorovsky, Stanislav
Heinmaa, Ivo
Marek, Radek
author_sort Novotný, Jan
collection PubMed
description [Image: see text] Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and the unpaired electron density. The Fermi-contact contribution to ligand hyperfine NMR shifts is particularly informative about the nature of the metal–ligand bonding and the structural arrangements of the ligands coordinated to the metal center. In this account, we provide a detailed experimental and theoretical NMR study of compounds of Cr(III) and Cu(II) coordinated with substituted acetylacetonate (acac) ligands in the solid state. For the first time, we report the experimental observation of extremely paramagnetically deshielded (13)C NMR resonances for these compounds in the range of 900–1200 ppm. We demonstrate an excellent agreement between the experimental NMR shifts and those calculated using relativistic density-functional theory. Crystal packing is shown to significantly influence the NMR shifts in the solid state, as demonstrated by theoretical calculations of various supramolecular clusters. The resonances are assigned to individual atoms in octahedral Cr(acac)(3) and square-planar Cu(acac)(2) compounds and interpreted by different electron configurations and magnetizations at the central metal atoms resulting in different spin delocalizations and polarizations of the ligand atoms. Further, effects of substituents on the (13)C NMR resonance of the ipso carbon atom reaching almost 700 ppm for Cr(acac)(3) compounds are interpreted based on the analysis of Fermi-contact hyperfine contributions.
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spelling pubmed-95976572022-10-27 Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes Novotný, Jan Jeremias, Lukáš Nimax, Patrick Komorovsky, Stanislav Heinmaa, Ivo Marek, Radek Inorg Chem [Image: see text] Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and the unpaired electron density. The Fermi-contact contribution to ligand hyperfine NMR shifts is particularly informative about the nature of the metal–ligand bonding and the structural arrangements of the ligands coordinated to the metal center. In this account, we provide a detailed experimental and theoretical NMR study of compounds of Cr(III) and Cu(II) coordinated with substituted acetylacetonate (acac) ligands in the solid state. For the first time, we report the experimental observation of extremely paramagnetically deshielded (13)C NMR resonances for these compounds in the range of 900–1200 ppm. We demonstrate an excellent agreement between the experimental NMR shifts and those calculated using relativistic density-functional theory. Crystal packing is shown to significantly influence the NMR shifts in the solid state, as demonstrated by theoretical calculations of various supramolecular clusters. The resonances are assigned to individual atoms in octahedral Cr(acac)(3) and square-planar Cu(acac)(2) compounds and interpreted by different electron configurations and magnetizations at the central metal atoms resulting in different spin delocalizations and polarizations of the ligand atoms. Further, effects of substituents on the (13)C NMR resonance of the ipso carbon atom reaching almost 700 ppm for Cr(acac)(3) compounds are interpreted based on the analysis of Fermi-contact hyperfine contributions. American Chemical Society 2021-06-16 2021-07-05 /pmc/articles/PMC9597657/ /pubmed/34133172 http://dx.doi.org/10.1021/acs.inorgchem.1c00204 Text en © 2021 American Chemical Society https://creativecommons.org/licenses/by-nc-nd/4.0/Permits non-commercial access and re-use, provided that author attribution and integrity are maintained; but does not permit creation of adaptations or other derivative works (https://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Novotný, Jan
Jeremias, Lukáš
Nimax, Patrick
Komorovsky, Stanislav
Heinmaa, Ivo
Marek, Radek
Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
title Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
title_full Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
title_fullStr Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
title_full_unstemmed Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
title_short Crystal and Substituent Effects on Paramagnetic NMR Shifts in Transition-Metal Complexes
title_sort crystal and substituent effects on paramagnetic nmr shifts in transition-metal complexes
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9597657/
https://www.ncbi.nlm.nih.gov/pubmed/34133172
http://dx.doi.org/10.1021/acs.inorgchem.1c00204
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