Calculation of Hypershielding Contribution to Isotropic Nitrogen Shielding in Strong Magnetic Fields

Boyd, Jonathan; Pagola, Gabriel Ignacio; Caputo, M. C.; Ferraro, Marta B.; Lazzeretti, Paolo

doi:10.1021/ct900034d

Cited by 8 publications

(9 citation statements)

References 55 publications

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“…3 Boyd et al, in turn, computed field dependence of the order of 10 -5 ppmT -2 for nitrogen shielding in some nitroso and isodiazene compounds. 4 Similarly to nuclear shielding, the spin-spin coupling can be expected to be field-dependent as well. The semi-empirical study by Raynes and Stevens suggested that the coupling varies as 0.5´10 -5 HzT -2 for "strongly magnetic nuclei in large molecules".…”

Section: Introductionmentioning

confidence: 99%

Magnetic field-induced effects on NMR properties

Jokisaari

Kantola

Vaara

2017

Journal of Magnetic Resonance

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In principle, all the NMR observables, spin-spin coupling J, nuclear shielding σ and quadrupole coupling q, are magnetic field-dependent. The field dependence may be classified into two categories: direct and indirect (apparent) dependence. The former arises from the magnetic field-induced deformation of the molecular electronic cloud, while the latter stems from a slightly anisotropic orientation distribution of molecules, due to the interaction between the anisotropy of the molecular susceptibility tensor and the external magnetic field. Here we use 1,3,5-D-benzene as a model system to investigate the indirect effect on the one-bond H-C and H-C spin-spin couplings (J couplings) and the H quadrupole coupling. Experiments carried out at four magnetic fields (4.7, 9.4, 14.1, and 18.8 T) show that the indirect effect is significant already at the magnetic fields commonly used in NMR spectrometers. A joint fit of the data extracted at the different field strengths provides experimental results for the susceptibility anisotropy,H quadrupole coupling constant and the related asymmetry parameter, as well as the one-bond CH and CD coupling constants extrapolated to vanishing field strength. The field-induced contributions are found to exceed the commonly assumed error margins of the latter. The data also indicate a primary isotope effect on the one-bond CH coupling constant. There is a tendency to further increase the magnetic field of NMR spectrometers, which leads to more pronounced indirect contributions and eventually significant direct effects as well.

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Section: Introductionmentioning

confidence: 99%

Magnetic field-induced effects on NMR properties

Jokisaari

Kantola

Vaara

2017

Journal of Magnetic Resonance

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“…62,63 We report in Tables V-VII the 17 O nuclear magnetic shielding and pseudoscalar shielding polarisabilities for basis sets I and V, taking the gauge origin in the nucleus whose shielding is reported. Table V reports the results for HOOH (molecule 1 and its corresponding experimental geometry 60 ) and its lithium cation complexes.…”

Section: Resultsmentioning

confidence: 99%

Electric field effects on nuclear magnetic shielding of the 1:1 and 2:1 (homo and heterochiral) complexes of XOOX′ (X, X′ = H, CH3) with lithium cation and their chiral discrimination

Alkorta

Elguero

Provasi

et al. 2011

The Journal of Chemical Physics

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The set of 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with lithium cation has been studied to determine if they are suitable candidates for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. Conventional nuclear magnetic resonance is unable to distinguish between enantiomers in the absence of a chiral solvent. The criterion for experimental detection is valuated by the isotropic part of nuclear shielding polarisability tensors, related to a pseudoscalar of opposite sign for two enantiomers. The study includes calculations at coupled Hartree-Fock and density functional theory schemes for (17)O nucleus in each compound. Additional calculations for (1)H are also included for some compounds. A huge static homogeneous electric field, perpendicular to the magnetic field of the spectromer, as big as ≈1.7 × 10(8) V m(-1) should be applied to observe a shift of ≈1 ppm for (17)O magnetic shielding in the proposed set of complexes.

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“…The electronic structure of cis-, trans-and iso-diazenes has already been the subject of a number of theoretical investigations. [6,[75][76][77][78][79][80] All indicate that the iso form of the parent species H 2 NN has a triplet ground state and is the least-stable isomer (the trans isomer is the global minimum species). To get further insight into the structure and bonding of the experimentally isolated diazenes and their adducts described here, especial-ly of the unprecedented formation of the iso-diazene stabilized as the B(C 6 F 5 ) 3 adduct (7), DFT calculations were carried out at the B3LYP/6-31G(d,p) level of theory.…”

Section: Computationsmentioning

confidence: 99%

Synthesis, Structure, and Reactivity of Diazene Adducts: Isolation of iso‐Diazene Stabilized as a Borane Adduct

Reiß

Schulz

Villinger

2014

Chemistry A European J

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This work describes the synthesis and full characterization of a series of GaCl3 and B(C6 F5 )3 adducts of diazenes R(1) NNR(2) (R(1) =R(2) =Me3 Si, Ph; R(1) =Me3 Si, R(2) =Ph). Trans-PhNNPh forms a stable adduct with GaCl3 , whereas no adduct, but instead a frustrated Lewis acid-base pair is formed with B(C6 F5 )3 . The cis-PhNNPh⋅B(C6 F5 )3 adduct could only be isolated when UV light was used, which triggers the isomerization from trans- to cis-PhNNPh, which provides more space for the bulky borane. Treatment of trans-PhNNSiMe3 with GaCl3 led to the expected trans-PhNNSiMe3 ⋅GaCl3 adduct but the reaction with B(C6 F5 )3 triggered a 1,2-Me3 Si shift, which resulted in the formation of a highly labile iso-diazene, Me3 Si(Ph)NN; stabilized as a B(C6 F5 )3 adduct. Trans-Me3 SiNNSiMe3 forms a labile cis-Me3 SiNNSiMe3 ⋅B(C6 F5 )3 adduct, which isomerizes to give the transient iso-diazene species (Me3 Si)2 NN⋅B(C6 F5 )3 upon heating. Both iso-diazene species insert easily into one BC bond of B(C6 F5 )3 to afford hydrazinoboranes. All new compounds were fully characterized by means of X-ray crystallography, vibrational spectroscopy, CHN analysis, and NMR spectroscopy. All compounds were further investigated by DFT and the bonding situation was assessed by natural bond orbital (NBO) analysis.

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Calculation of Hypershielding Contribution to Isotropic Nitrogen Shielding in Strong Magnetic Fields

Cited by 8 publications

References 55 publications

Magnetic field-induced effects on NMR properties

Magnetic field-induced effects on NMR properties

Electric field effects on nuclear magnetic shielding of the 1:1 and 2:1 (homo and heterochiral) complexes of XOOX′ (X, X′ = H, CH3) with lithium cation and their chiral discrimination

Synthesis, Structure, and Reactivity of Diazene Adducts: Isolation of iso‐Diazene Stabilized as a Borane Adduct

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