Communication: Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

Soncini, Alessandro; Heuvel, Willem Van den

doi:10.1063/1.4775809

Cited by 59 publications

(100 citation statements)

References 8 publications

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“…[8] Within this approach, the magnetic moments of the unpaired electrons are approximated by ap oint dipole at the metal position, the magnetic anisotropy axis aligns along the main molecular C n axis, the ligand field splitting is much less than kT (200 cm À1 at room temperature), and the contribution of higher-order terms of the ligand field are ignored.F rom these two last assumptions, the total angular momentum J of the cation is implicitly supposed to be ag ood quantum number so that Bleaney's constant C D a only depends on the cation a and not on the ligand.S ince its applicationo ver more than 40 years ago, it is still difficult to find out why NMR studies on some lanthanides complexes are consistent with these simplifications [9] and others are not. [10,11] Although the effectiveness of Bleaney's theoryc ould appear lower than recent quantum mechanical treatments, [12] we have undertaken to evaluate to what extent the ligand field could skew Bleaney'st heory by using An III instead of Ln III with 2,6-dipicolinic acid (dpa) as the ligand.D ue to the largerr adial extent of 5f orbitalsc ompared with 4f orbitals, larger covalence and ligand field effects are expected so that the applicability or validity of Bleaney's equation may be questioned. It also could be an opportunity to gain ab etter insight into the covalentb ehavior of An III and Ln III cations through Bleaney's parameters.…”

Section: Introductionmentioning

confidence: 99%

Insight of the Metal–Ligand Interaction in f‐Element Complexes by Paramagnetic NMR Spectroscopy

Autillo

Guérin

Dumas

et al. 2019

Chemistry A European J

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The magnetic properties of LnIII and AnIII complexes formed with dipicolinate ligands have been studied by NMR spectroscopy. To know precisely the geometries of these complexes, a crystallographic study by single‐crystal X‐ray diffraction (XRD) and extended X‐ray absorption fine structure (EXAFS) in solution was performed. Several methods to separate the paramagnetic shifts observed in the NMR spectra were applied to these complexes. Methods using a number of nuclei of the dipicolinate ligands revealed an abrupt change in the geometries of the complexes and a metal–ligand interaction in the middle of the lanthanide series. A study of the variation of the paramagnetic shifts with temperature demonstrated that higher‐order terms of the dipolar and contact contributions are required, especially for the lightest LnIII and almost all the studied AnIII. Bleaney's parameters a and CaD relating to the contact and dipolar terms, respectively, were deduced from experimental data and compared with the results of ab initio calculations. Quite a good agreement was found for the temperature dependencies of a and CaD . However, the CaD values obtained from cation magnetic anisotropy calculations showed some discrepancies with the values derived from Bleaney's equation defined for LnIII. Other parameters, such as the crystal field parameter and the hyperfine constants Fi obtained from the experimental data of the [An(ethyl‐dpa)3]3− complexes (ethyl‐dpa=4‐ethyl‐2,6‐dipicolinic acid), are at odds with the assumptions underlying Bleaney's theory.

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Section: Introductionmentioning

confidence: 99%

Insight of the Metal–Ligand Interaction in f‐Element Complexes by Paramagnetic NMR Spectroscopy

Autillo

Guérin

Dumas

et al. 2019

Chemistry A European J

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“…[28,[85][86][87][88]. Depending on the nature of the compound of interest, the theory to properly calculate the pNMR shielding tensor may take different forms.…”

Section: Ab-initio Paramagnetic Nmr Calculationsmentioning

confidence: 99%

Probing the Local Magnetic Structure of the [Fe^III(Tp)(CN)₃]⁻ Building Block Via Solid‐State NMR Spectroscopy, Polarized Neutron Diffraction, and First‐Principle Calculations

Flambard

Garnier

et al. 2019

Chemistry A European J

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The local magnetic structure in the [Fe III (Tp)(CN) 3 ] À building block was investigated by combining paramagnetic Nuclear Magnetic Resonance (pNMR) spectroscopy and polarized neutrond iffraction (PND) with first-principle calculations. The use of the pNMR and PND experimental techniques revealed the extension of spin-density from the metal to the ligands, as well as the different spin mechanisms that take place in the cyanidol igands: Spin-polarization on the carbon atomsa nd spin-delocalization on the nitrogen atoms.T he resultso fo ur combined density functional theory (DFT) and multireference calculations were found in good agreementw ith the PND results and the experimen-tal NMR chemical shifts. Moreover,t he ab-initio calculations allowedu st oc onnectt he experimental spin-density map characterized by PNDa nd the suggested distribution of the spin-density on the ligandso bserved by NMR spectroscopy. Interestingly,s ignificant differences were observed between the pseudo-contact contributions of the chemical shifts obtained by theoretical calculations and the values derived from NMR spectroscopy using as imple point-dipole model. These discrepancies underline the limitation of the pointdipole model and the need for more elaborate approaches to break down the experimental pNMR chemical shifts into contacta nd pseudo-contact contributions.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.org/10.1002/chem.201902239.A dditional data regarding the experimental and computational details,experimental NMR data for the diamagnetic reference and the paramagnetic complex, crystal structure data for the diamagnetic reference and the magnetization characterization:DFT spin-densities, NLMOs, g-factors, and HyFCCs for [Fe III (Tp)(CN) 3 ] À .Additional calculated NMR shielding constants and chemical shifts.

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“…Indeed, it is known that the experimental NMR shift (δ exp ) is the sum of an orbital component (δ dia ), a pseudocontact (PC) shift (δ PC ) and a Fermi contact (FC) shift (δ FC ) [24,25]. The determination of these paramagnetic shifts (δ p ) is currently based on a combination of empirical calculations using the Bleaney's theory for δ PC [26,27] and the McConnell and Robertson approach and its recent improvements for δ FC [28][29][30][31][32][33][34]. The theoretical prediction of paramagnetic shifts in the rare-earth series is intensively studied [24,35,36] especially for MRI contrast agents [37][38][39][40][41][42][43][44] and in metalloproteins [45][46][47][48].…”

Section: Introductionmentioning

confidence: 99%

Local structure and magnetism of LaxEu1−xPO4
Martel¹,
Rakhmatullin²,
Baldoví³
et al. 2019
Phys. Rev. B
6
0
3
0
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By combining high spinning speed (60 kHz) and low-field (4.7 T) 31 P solid-state NMR with magnetic susceptibility measurements, we experimentally characterized a series of solid solutions belonging to the La x Eu 1−x PO 4 (0 x 1) series. Analyses of the magnetic susceptibility data were carried out using the free ion model and crystal field theory calculations allowing to extract the electronic structure. The paramagnetic shifts of the P sites having one Eu 3+ cation in their surrounding were predicted by combining the determined crystal field and energy level values with density functional theory (DFT) calculations. For the La 0.9 Eu 0.1 PO 4 sample, these theoretical shifts gave a very good overall trend allowing the unambiguous attribution of each P site. This study paves the way for the future analysis of both magnetic susceptibility and NMR data for a broad range of materials containing paramagnetic rare-earth cations.

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Communication: Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

Abstract: Erratum: "Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules" [J.

Cited by 59 publications

References 8 publications

Insight of the Metal–Ligand Interaction in f‐Element Complexes by Paramagnetic NMR Spectroscopy

Insight of the Metal–Ligand Interaction in f‐Element Complexes by Paramagnetic NMR Spectroscopy

Probing the Local Magnetic Structure of the [Fe^III(Tp)(CN)₃]⁻ Building Block Via Solid‐State NMR Spectroscopy, Polarized Neutron Diffraction, and First‐Principle Calculations

Local structure and magnetism of LaxEu1−xPO4
Martel¹,
Rakhmatullin²,
Baldoví³
et al. 2019
Phys. Rev. B
6
0
3
0
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Communication: Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

Abstract: Erratum: "Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules" [J.

Cited by 59 publications

References 8 publications

Insight of the Metal–Ligand Interaction in f‐Element Complexes by Paramagnetic NMR Spectroscopy

Insight of the Metal–Ligand Interaction in f‐Element Complexes by Paramagnetic NMR Spectroscopy

Probing the Local Magnetic Structure of the [FeIII(Tp)(CN)3]− Building Block Via Solid‐State NMR Spectroscopy, Polarized Neutron Diffraction, and First‐Principle Calculations

Local structure and magnetism of LaxEu1−xPO4Martel1, Rakhmatullin2, Baldoví3 et al. 2019Phys. Rev. B6030View full textAdd to dashboardCite

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Probing the Local Magnetic Structure of the [Fe^III(Tp)(CN)₃]⁻ Building Block Via Solid‐State NMR Spectroscopy, Polarized Neutron Diffraction, and First‐Principle Calculations

Local structure and magnetism of LaxEu1−xPO4
Martel¹,
Rakhmatullin²,
Baldoví³
et al. 2019
Phys. Rev. B
6
0
3
0
View full text Add to dashboard Cite