13C and 1H chemical-shift anisotropies in chloroform

Bhattacharyya, Pranab K.; Dailey, B. P.

doi:10.1016/0022-2364(73)90099-1

Cited by 7 publications

(6 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The differences between the Δσ values corresponding to the two values of the carbon–proton distance are not very large. The free chloroform anisotropies are in reasonable agreement with the values reported a long time ago for chloroform dissolved in ethylene glycol by Mäler and Kowalewski (Δσ(C) = −32 ± 8 ppm, Δσ(H) = 12 ± 2 ppm from CCR rates in isotropic solution) and by Bhattacharyya and Dailey(Δσ(C) = −39 ± 1 ppm, Δσ(H) = 9.8 ± 2.5 ppm, based on a liquid-crystalline (LC) solution). Higher absolute values of Δσ(C) values for chloroform were reported in more recent work on LC systems. − The latter two papers also presented somewhat scattered Δσ(H) values as well as results of quantum chemical calculations.…”

Section: Resultssupporting

confidence: 89%

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

2015

View full text Add to dashboard Cite

The case of (13)C-labeled chloroform exchanging between a free site in solution and the encaged site within the cryptophane-D cavity is investigated using the measurements of longitudinal cross-correlated relaxation rates, involving the interference of the dipole-dipole and chemical shielding anisotropy interactions. A compact theoretical expression is provided, along with an experimental protocol, based on INEPT (insensitive nuclei enhanced by polarization)-enhanced double-quantum-filtered inversion recovery measurements. The analysis of the build-up curves results in a set of cross-correlated relaxation rates for both the (13)C and (1)H spins at the two sites. It is demonstrated that the results can be given a consistent interpretation in terms of molecular-level properties, such as rotational correlation times, the Lipari-Szabo order parameter, and interaction strength constants. The analysis yields the bound-site carbon-13 chemical shielding anisotropy, ΔσC = -58 ± 8 ppm, in good agreement with most recent liquid-crystal measurements and the corresponding proton shielding anisotropy, ΔσH = 14 ± 2 ppm.

show abstract

Section: Resultssupporting

confidence: 89%

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

2015

View full text Add to dashboard Cite

show abstract

“…[68–69] The so-called residual CSA (RCSA) shift between an LC and an isotropic phase provides information on the magnitude and orientation of the chemical shielding tensor relative to the molecule’s alignment frame. For the interpretation of the RCSA, the orientation and the order parameter of the molecular alignment are determined based on the effects of dipolar interactions on the spectra.…”

Section: Introductionmentioning

confidence: 99%

“…[33, 70–72] Improved experimental methods have been developed over the years, mainly by Jokisaari and coworkers, greatly increasing the reliability by demonstrating good agreement with theoretical ab initio predictions. [73] The great majority of 1 H CSA determinations by LC NMR were performed before the turn of the century on small symmetric molecules, such as methyl halides, [68, 71, 73–75] CH 3 CCl 3 , CH 3 SiCl 3 , (CH 3 ) 4 Si, and (CH 3 ) 4 C, [69] CH 3 NC, [76] ethane, ethene, and ethyne, [77] benzene, [76] and 1,3,5-trichlorobenzene. [78] …”

Section: Introductionmentioning

confidence: 99%

A Magic‐Angle‐Spinning NMR Spectroscopy Method for the Site‐Specific Measurement of Proton Chemical‐Shift Anisotropy in Biological and Organic Solids

Hou

Gupta

Polenova

et al. 2014

Israel Journal of Chemistry

View full text Add to dashboard Cite

Proton chemical shifts are a rich probe of structure and hydrogen bonding environments in organic and biological molecules. Until recently, measurements of 1H chemical shift tensors have been restricted to either solid systems with sparse proton sites or were based on the indirect determination of anisotropic tensor components from cross-relaxation and liquid-crystal experiments. We have introduced an MAS approach that permits site-resolved determination of CSA tensors of protons forming chemical bonds with labeled spin-1/2 nuclei in fully protonated solids with multiple sites, including organic molecules and proteins. This approach, originally introduced for the measurements of chemical shift tensors of amide protons, is based on three RN-symmetry based experiments, from which the principal components of the 1H CS tensor can be reliably extracted by simultaneous triple fit of the data. In this article, we expand our approach to a much more challenging system involving aliphatic and aromatic protons. We start with a review of the prior work on experimental-NMR and computational-quantum-chemical approaches for the measurements of 1H chemical shift tensors and for relating these to the electronic structures. We then present our experimental results on U-13C,15N-labeled histdine demonstrating that 1H chemical shift tensors can be reliably determined for the 1H15N and 1H13C spin pairs in cationic and neutral forms of histidine. Finally, we demonstrate that the experimental 1H(C) and 1H(N) chemical shift tensors are in agreement with Density Functional Theory calculations, therefore establishing the usefulness of our method for characterization of structure and hydrogen bonding environment in organic and biological solids.

show abstract

“…[6] DNP is performed in an isotropic glass containing the substrate generally in molar concentrations as well the paramagnetic polarizing agent in a vitrifying matrix, usually water-glycerol. [7] This technology was successfully applied to polarize a wide range of nuclei including 1 H, 13 C, 15 N, 31 P, 129 Xe, 6 Li, 133 Cs, 89 Y and 107, 109 Ag. [8] It must be emphasized that the hyperpolarized magnetization is not persistent but decays by spin-lattice (T 1 ) relaxation.…”

mentioning

confidence: 99%

“…For example, CHCl 3 belongs to the C 3v point group with a unique axis in the z-direction and has non-zero CSA. [15] Besides rapid relaxation, solubility issues and chemical incompatibility with the free radical polarizing agents may also hamper dissolution DNP. For example, we reported that 107, 109 Ag could only be polarized with the free radical BDPA because the commonly used polarizing agents (trityl OX063 and 4-oxo-TEMPO) failed to produce signal enhancements due to chemical incompatibility with Ag + ions.…”

mentioning

confidence: 99%

Dissolution Dynamic Nuclear Polarization of the ⁷⁷Se Nucleus

2022

View full text Add to dashboard Cite

77Se is a spin 1/2 ${{ 1/2 }}$ , low sensitivity nucleus with a natural abundance of 7.6 %. Although 77Se NMR is very useful in the characterization of selenium containing molecules including seleno‐proteins, the detection of 77Se is challenging in biological samples without enrichment. Therefore, the goal of this work was to establish whether the 77Se signal could be enhanced in the liquid state by dissolution dynamic nuclear polarization (DNP) NMR without the need of enrichment. The dominant spin‐lattice relaxation mechanism for 77Se is via chemical shift anisotropy, which is highly dependent on the molecular symmetry. Here we tested three selenium compounds (sodium selenate, sodium selenite and selenocystine) with different molecular symmetries in dissolution DNP experiments and demonstrated that 77Se DNP using commercially available hardware is feasible but the achieved NMR signal enhancements (1368‐fold for selenate, 125‐fold for selenite and no enhancement for selenocystine at 9.4 T) were strongly dependent on molecular symmetry.

show abstract

13C and 1H chemical-shift anisotropies in chloroform

Cited by 7 publications

References 4 publications

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

A Magic‐Angle‐Spinning NMR Spectroscopy Method for the Site‐Specific Measurement of Proton Chemical‐Shift Anisotropy in Biological and Organic Solids

Dissolution Dynamic Nuclear Polarization of the ⁷⁷Se Nucleus

Contact Info

Product

Resources

About

13C and 1H chemical-shift anisotropies in chloroform

Cited by 7 publications

References 4 publications

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

A Magic‐Angle‐Spinning NMR Spectroscopy Method for the Site‐Specific Measurement of Proton Chemical‐Shift Anisotropy in Biological and Organic Solids

Dissolution Dynamic Nuclear Polarization of the 77Se Nucleus

Contact Info

Product

Resources

About

Dissolution Dynamic Nuclear Polarization of the ⁷⁷Se Nucleus