Flipping hosts in hyperfine fields of paramagnetic guests

Novotný, Jan; Chyba, Jan; Hruzíková, Anna; Pikulová, Petra; Kursit, Aliaksandra; Knor, Michal; Marková, Kateřina; Marek, Jaromı́r; Jurček, Pia; Jurček, Ondřej; Marek, Radek

doi:10.1016/j.xcrp.2023.101461

Cited by 2 publications

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“…Therefore, the averaged signals are affected by various factors, such as the HG affinity (binding constant and free–bound ratio), the geometry of the HG assembly, and the magnetic anisotropy of the paramagnetic center. pNMR spectroscopy has been used to characterize the relative position of the cyclodextrin (CD) host in the hyperfine field of the ruthenium guest . The NMR spectra for CD at various HG ratios with compound Ru3 and the calculated hyperfine shielding maps are shown in Figure .…”

Section: Applicationsmentioning

confidence: 99%

“…Theory Comput.201915201214 Signs of electronic g-tensor and paramagnetic spin–orbit contribution to hyperfine NMR shifts are interpreted by the molecular-orbital theory and linked to the electron configuration at the transition-metal atom. Flipping hosts in hyperfine fields of paramagnetic guestsNovotnýJ.ChybaJ.HruzíkováA.PikulováP.KursitA.KnorM.MarkováK.MarekJ.JurčekP.JurčekO.MarekR. Novotný, J. Chyba, J. Hruzíková, A. Pikulová, P. Kursit, A. Knor, M. Marková, K. Marek, J. Jurček, P. Jurček, O. Marek, R. Cell Rep. Phys. Sci.20234101461 Through-space hyperfine shifts in electronic doublet systems, given by the paramagnetic spin–orbit and spin–dipolar contributions, are used to determine relative orientation in supramolecular host–guest assemblies. …”

Section: Key Referencesmentioning

confidence: 99%

“…Sci. 2023 4 101461 ( 4 ) Through-space hyperfine shifts in electronic doublet systems, given by the paramagnetic spin–orbit and spin–dipolar contributions, are used to determine relative orientation in supramolecular host–guest assemblies.…”

Section: Key Referencesmentioning

confidence: 99%

“…pNMR spectroscopy has been used to characterize the relative position of the cyclodextrin (CD) host in the hyperfine field of the ruthenium guest. 4 The NMR spectra for CD at various HG ratios with compound Ru3 and the calculated hyperfine shielding maps are shown in Figure 15 . This approach allowed the determination of head versus tail HG binding.…”

Section: Applicationsmentioning

confidence: 99%

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Paramagnetic Effects in NMR Spectroscopy of Transition-Metal Complexes: Principles and Chemical Concepts

Novotny,

Komorovsky,

Marek

2024

Acc. Chem. Res.

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Metrics & More Article Recommendations CONSPECTUS: Magnetic resonance techniques represent a fundamental class of spectroscopic methods used in physics, chemistry, biology, and medicine. Electron paramagnetic resonance (EPR) is an extremely powerful technique for characterizing systems with an open-shell electronic nature, whereas nuclear magnetic resonance (NMR) has traditionally been used to investigate diamagnetic (closed-shell) systems. However, these two techniques are tightly connected by the electron−nucleus hyperfine interaction operating in paramagnetic (open-shell) systems. Hyperfine interaction of the nuclear spin with unpaired electron(s) induces large temperaturedependent shifts of nuclear resonance frequencies that are designated as hyperfine NMR shifts (δ HF ).Three fundamental physical mechanisms shape the total hyperfine interaction: Fermi-contact, paramagnetic spin−orbit, and spin− dipolar. The corresponding hyperfine NMR contributions can be interpreted in terms of through-bond and through-space effects. In this Account, we provide an elemental theory behind the hyperfine interaction and NMR shifts and describe recent progress in understanding the structural and electronic principles underlying individual hyperfine terms. The Fermi-contact (FC) mechanism reflects the propagation of electron-spin density throughout the molecule and is proportional to the spin density at the nuclear position. As the imbalance in spin density can be thought of as originating at the paramagnetic metal center and being propagated to the observed nucleus via chemical bonds, FC is an excellent indicator of the bond character. The paramagnetic spin−orbit (PSO) mechanism originates in the orbital current density generated by the spin−orbit coupling interaction at the metal center. The PSO mechanism of the ligand NMR shift then reflects the transmission of the spin polarization through bonds, similar to the FC mechanism, but it also makes a substantial through-space contribution in long-range situations. In contrast, the spin−dipolar (SD) mechanism is relatively unimportant at short-range with significant spin polarization on the spectator atom. The PSO and SD mechanisms combine at long-range to form the so-called pseudocontact shift, traditionally used as a structural and dynamics probe in paramagnetic NMR (pNMR). Note that the PSO and SD terms both contribute to the isotropic NMR shift only at the relativistic spin−orbit level of theory.We demonstrate the advantages of calculating and analyzing the NMR shifts at relativistic two-and four-component levels of theory and present analytical tools and approaches based on perturbation theory. We show that paramagnetic NMR effects can be interpreted by spin-delocalization and spin-polarization mechanisms related to chemical bond concepts of electron conjugation in πspace and hyperconjugation in σ-space in the framework of the molecular orbital (MO) theory. Further, we discuss the effects of environment (supramolecular interactions, solvent, and crystal packing) and demonstrat...

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Section: Applicationsmentioning

confidence: 99%

Section: Key Referencesmentioning

confidence: 99%

Section: Key Referencesmentioning

confidence: 99%

Section: Applicationsmentioning

confidence: 99%

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Paramagnetic Effects in NMR Spectroscopy of Transition-Metal Complexes: Principles and Chemical Concepts

Novotny,

Komorovsky,

Marek

2024

Acc. Chem. Res.

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“…In contrast, the spin-dipolar mechanism is based on the through-space interaction of the nuclear and electron spins and is proportional to the anisotropy of the spin density around the magnetic nucleus. , The picture changes at the spin–orbit relativistic level via an additional paramagnetic spin–orbit mechanism. This mechanism can dominate the hyperfine interaction of ligand atoms directly bonded to a paramagnetic metal center, − it can contribute significantly to the NMR shifts of some ligand atoms, and it is important at the NMR long-distance limit. ,, …”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Ligand Hyperfine Coupling in Transition-Metal Complexes: σ and π Transmission Pathways

Novotný,

Munzarová,

Marek

2024

Inorg. Chem.

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Theoretical interpretation of hyperfine interactions was pioneered in the 1950s−1960s by the seminal works of McConnell, Karplus, and others for organic radicals and by Watson and Freeman for transition-metal (TM) complexes. In this work, we investigate a series of octahedral Ru(III) complexes with aromatic ligands to understand the mechanism of transmission of the spin density from the d-orbital of the metal to the s-orbitals of the ligand atoms. Spin densities and spin populations underlying ligand hyperfine couplings are analyzed in terms of π-conjugative or σ-hyperconjugative delocalization vs spin polarization based on symmetry considerations and restricted open-shell vs unrestricted wave function analysis.The transmission of spin density is shown to be most efficient in the case of symmetry-allowed π-conjugative delocalization, but when the π-conjugation is partially or fully symmetry-forbidden, it can be surpassed by σ-hyperconjugative delocalization. Despite a lower spin population of the ligand in σhyperconjugative transmission, the hyperfine couplings can be larger because of the direct involvement of the ligand s-orbitals in this delocalization pathway. We demonstrate a quantitative correlation between the hyperfine couplings of aromatic ligand atoms and the characteristics of the metal−ligand bond modulated by the trans substituent, a hyperfine trans ef fect.

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Flipping hosts in hyperfine fields of paramagnetic guests

Cited by 2 publications

References 60 publications

Paramagnetic Effects in NMR Spectroscopy of Transition-Metal Complexes: Principles and Chemical Concepts

Paramagnetic Effects in NMR Spectroscopy of Transition-Metal Complexes: Principles and Chemical Concepts

Mechanisms of Ligand Hyperfine Coupling in Transition-Metal Complexes: σ and π Transmission Pathways

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