Liquid Crystalline Samples: Deuterium NMR

Dong, Ronald Y.

doi:10.1002/9780470034590.emrstm0265

Cited by 3 publications

(3 citation statements)

References 40 publications

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“…Deuterium NMR spectroscopy on deuterated molecules or at natural abundance level (1.55 × 10 À2 % compared to 1 H) noted thereafter natural abundance deuterium (NAD) is a powerful tool for a broad range of applications in (bio)chemistry. This includes the following: (i) the elucidation of chemical reaction mechanisms, [1,2] (ii) the determination of metabolic pathways, [3][4][5][6] (iii) the identification of geographical or botanical origin and the fight against counterfeiting, [7,8] (iv) the study of orientational order in anisotropic media (liquid crystals, membranes, and confined or stretched polymer chains), [9][10][11][12][13][14][15][16] and (v) the analysis of atom-scale dynamics in various systems, including biomolecules and advanced materials. [17][18][19] Recently, 2 H NMR using chiral anisotropic solvents has been proposed as an efficient and versatile technique for stereochemical analysis.…”

Section: General Introductionmentioning

confidence: 99%

Correlation 2D‐NMR experiments involving both ¹³C and ²H isotopes in oriented media: methodological developments and analytical applications

Lesot

Lafon

Berdagué

2014

Magnetic Reson in Chemistry

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Correlation 2D-NMR experiments for (13)C and (2)H isotopes turn out to be powerful methods for the assignment of the quadrupolar doublets in the (2)H NMR spectra of isotopically modified (polydeuterated or perdeuterated) or unmodified solutes in homogeneously oriented solvents, such as thermotropic systems or lyotropic liquid crystals. We review here the different pulse sequences, which have been employed, their properties, and their most salient applications. These 2D-NMR sequences have been used for (i) (13)C-(2)H correlation with and without (1)H relay and (ii) (2)H-(2)H correlation with (13)C relay. The (13)C-(2) H correlation experiments without (1)H relay have been achieved for specifically deuterated or non-selectively deuterated analytes, but also more recently for isotopically unmodified ones thanks to the high sensitivity of very high-field NMR spectrometers (21.1 T) equipped with cryogenic probes. The (13)C-(2)H correlation 2D-NMR experiments are especially useful for the assignment of overcrowded deuterium spectra because the (2)H signals are correlated to (13)C signals, which benefit from a much larger dispersion of chemical shifts. In this contribution, particular attention will be paid to the use of correlation 2D-NMR experiments for (2)H and (13)C nuclei in weakly aligning, polypeptide oriented chiral solvents, because these methods are useful and original tools for enantiomeric and enantiotopic analyses.

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Section: General Introductionmentioning

confidence: 99%

Correlation 2D‐NMR experiments involving both ¹³C and ²H isotopes in oriented media: methodological developments and analytical applications

Lesot

Lafon

Berdagué

2014

Magnetic Reson in Chemistry

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“…The theory of NMR spectra of solutes dissolved in nematic liquid has been extensively reviewed . In this section, we briefly summarize the relevant equations, using the notations reported in references , and .…”

Section: Nmr Spectra Of Solutes In Nematic Liquid Crystalsmentioning

confidence: 99%

“…The theory of NMR spectra of solutes dissolved in nematic liquid has been extensively reviewed. [18,26] In this section, we briefly summarize the relevant equations, using the notations reported in references 20, 24 and 25. The spin Hamiltonian of a solute molecule dissolved in an aligned nematic liquid is similar to that of an isolated molecule in a single crystal and consists of a sum of single nuclei H k (including the Zeeman energy (k = Z), the electronic shielding effect (k = cs), the quadrupole interaction (for I ≥ 1, k = Q), the indirect (k = J) and the direct (k = D) spin-spin coupling.…”

Section: Nmr Spectra Of Solutes In Nematic Liquid Crystalsmentioning

confidence: 99%

NMR discrimination in nonrigid prochiral solutes dissolved in chiral liquid crystals: symmetry considerations

Lesot

Luz

Aroulanda

et al. 2014

Magnetic Reson in Chemistry

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Enantiodiscrimination in the NMR spectra of flexible prochiral solutes dissolved in chiral liquid crystals (CLCs) is reviewed and compared with the analog phenomenon in such rigid solutes. In rigid prochiral solutes, the discrimination is brought about by the cancellation of improper symmetry elements upon dissolving in CLC within the frame of solute-solvent ordering mechanisms. If this reduction in symmetry renders the ordering of enantiotopic sites dissimilar, spectral discrimination may be observed. Symmetry considerations indicate that this is only possible for improper nonaxial groups lacking inversion symmetry. Nonrigid prochiral solutes consist of rapidly (on the NMR timescale) interconverting enantiomers, in which the racemization is accompanied by exchange of nonequivalent sites. These sites become, on the average, enantiotopically related, and in CLC, they exhibit spectral discrimination. The mechanism of the effect and the symmetry selection rules are different for the two cases. Specifically, the discrimination in flexible prochiral compounds results from the different ordering of the interchanging enantiomers in CLC. Using Altman's definition of average symmetry (Proc. R. Soc. A, 1967, 298, 184), selection rules for the phenomenon are derived. It follows that chiral discrimination in nonrigid prochiral solutes is much more abundant and can occur in all symmetry types except those possessing inversion. In particular, contrary to earlier thoughts, the effect can occur in compounds with axial symmetry. Illustrative examples of such studies with particular emphasis on compounds with average axial symmetry of the type D(3h), C(3v) and C(3h) are reviewed in this contribution.

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¹³C NMR investigations and molecular order of nematogens with biphenyl and bithiophene at terminus

et al. 2021

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Liquid Crystalline Samples: Deuterium NMR

Cited by 3 publications

References 40 publications

Correlation 2D‐NMR experiments involving both ¹³C and ²H isotopes in oriented media: methodological developments and analytical applications

Correlation 2D‐NMR experiments involving both ¹³C and ²H isotopes in oriented media: methodological developments and analytical applications

NMR discrimination in nonrigid prochiral solutes dissolved in chiral liquid crystals: symmetry considerations

¹³C NMR investigations and molecular order of nematogens with biphenyl and bithiophene at terminus

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Liquid Crystalline Samples: Deuterium NMR

Cited by 3 publications

References 40 publications

Correlation 2D‐NMR experiments involving both 13C and 2H isotopes in oriented media: methodological developments and analytical applications

Correlation 2D‐NMR experiments involving both 13C and 2H isotopes in oriented media: methodological developments and analytical applications

NMR discrimination in nonrigid prochiral solutes dissolved in chiral liquid crystals: symmetry considerations

13C NMR investigations and molecular order of nematogens with biphenyl and bithiophene at terminus

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Correlation 2D‐NMR experiments involving both ¹³C and ²H isotopes in oriented media: methodological developments and analytical applications

Correlation 2D‐NMR experiments involving both ¹³C and ²H isotopes in oriented media: methodological developments and analytical applications

¹³C NMR investigations and molecular order of nematogens with biphenyl and bithiophene at terminus