Vibrational corrections in NMR spectra of oriented molecules

Sýkora, S.; Volt, J; Bösiger, H.; Diehl, P.

doi:10.1016/0022-2364(79)90214-2

Cited by 87 publications

(74 citation statements)

References 9 publications

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“…A specific interaction between Phase IV and acetone could explain t h s discrepancy. This is in line with other observations that Phase ZV distorts the geometry of host molecules [20] [21] and cannot therefore be regarded as an 'inert' solvent.…”

Section: ' )supporting

confidence: 89%

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by ¹⁷O‐ and ¹H‐NMR in Nematic Phases

Tricot¹,

Niederberger²

1984

Helvetica Chimica Acta

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SummaryLinear relationships between the inverse of the quadrupolar coupling constant, 1 /x and the asymmetry parameter r] are obtained for the '70-nucleus of acetone oriented in four different nematic phases, using the information contained in 'H-and I70-NMR spectra. The absence of a unique intersecting point of these relations shows that the quadrupolar constants differ slightly between polar and apolar nematic phases, while the orientation remains similar. By combination of the experimentally derived relations with predictions from the theory of Townes and Dailey, values for x = 11.15 MHz and r] = 0.47 in polar media and x = 11.35 MHz and = 0.51 in an apolar medium are obtained, which are similar to those found in the gas and solid phases.Introduction. -Direct determination of quadrupolar coupling constants for I7O is usually performed in the solid state by nuclear quadrupole resonance (NQR) [l-81 or in the gas phase by microwave spectroscopy [9] [lo]. In isotropic liquids, an indirect method based on quadrupolar relaxation yields the quadrupolar coupling constant from the linewidth of the I70-NMR signal, using the asymmetry parameter predicted by theory [ll]. In this work, a method based on the orientation of host molecules by nematic phases is used. This technique has been applied to the I4N-and *H-nuclei [12], but not yet to the '70-nucleus. Knowledge of the quadrupolar coupling constants and the asymmetry parameter gives an insight into the electronic repartition in a molecule and provides a test for the theoretical calculations of molecular orbitals and electric field gradients [13] [14].

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Section: ' )supporting

confidence: 89%

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by ¹⁷O‐ and ¹H‐NMR in Nematic Phases

Tricot¹,

Niederberger²

1984

Helvetica Chimica Acta

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“…[17] Harmonic vibrational corrections can be applied with the help of the VIBR program if the harmonic force fields of the considered molecules are known. [18] Unfortunately, only that of pentafluorobenzene is available. [19] As it was demonstrated in many works, [20] vibrational corrections are not very sensitive to the quality of the force field and it has been suggested that one can build acceptable valence force fields for molecules like C 6 F 5 Cl and C 6 F 5 I from those of C 6 Cl 5 H [21] and C 6 F 5 H. [19] These determinations were carried out according to the procedure described in literature.…”

Section: Corrections For Harmonic Vibrationsmentioning

confidence: 99%

r_αStructures of partially oriented pentafluorobenzenes C₆F₅X (X = H, Cl, I) as determined from¹⁹F NMR spectra with¹³C satellites

Haloui¹,

Haloui²

2011

Magnetic Reson in Chemistry

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The (19)F spectra with natural-abundance carbon-13 satellites of C(6)F(5)X (X = H, Cl or I) in ZLI 1695 liquid crystal were analysed. Excluding fluorine-fluorine dipolar coupling constants from the fitting, the vibrationally corrected structures of these molecules were derived and compared with those calculated at DFT/B3LYP level of theory with the aug-cc-pVTZ basis set. The results show that pentafluorobenzene did not exhibit noticeable distortion of the aromatic ring, while chloropentafluorobenzene and iodopentafluorobenzene molecules showed some deformations in their determined structures. Relative anisotropies of F-F couplings have been deduced with accuracy for C(6)F(5)H molecule. Due to uncertainties in structure determination of C(6)F(5)Cl and C(6)F(5)I molecules, it was not possible to obtain precise values for all the corresponding anisotropies. In addition, it was found that the orientation of these molecules in the solvent used can be qualitatively explained in terms of dispersion forces.

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“…For the derivation of the molecular geometries, an iterative program SHAPE 29 is used and the vibrational corrections for the molecular geometries are applied with the use of computer program VIBR. 30 The force fields required for such a correction are available in the literature. 5 The geometries, including r˛structures, of these molecules have been studied earlier by NMR 19,31 -34 and by other methods 35 -38 .…”

Section: Analysis Of the Spectra Of Pyrimidine And Pyridazinementioning

confidence: 99%

Determination of natural abundance ¹⁵N–¹H and ¹³C–¹H dipolar couplings of molecules in a strongly orienting media using two‐dimensional inverse experiments

Deepak

Joy

Suryaprakash

2006

Magnetic Reson in Chemistry

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NMR spectra of molecules oriented in liquid crystals provide homo- and heteronuclear dipolar couplings and thereby the geometry of the molecules. Several inequivalent dilute spins such as 13C and 15N coupled to protons form different coupled spin systems in their natural abundance and appear as satellites in the proton spectra. Identification of transitions belonging to each spin system is essential to determine heteronuclear dipolar couplings, which is a formidable task. In the present study, using 15N-1H and 13C-1H HSQC, and HMQC experiments we have selectively detected spectra of each rare spin coupled to protons. The 15N-1H and 13C-1H dipolar couplings have been determined in the natural abundance of 13C and 15N for the molecules pyrazine, pyrimidine and pyridazine oriented in a thermotropic liquid crystal.

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Vibrational corrections in NMR spectra of oriented molecules

Cited by 87 publications

References 9 publications

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by ¹⁷O‐ and ¹H‐NMR in Nematic Phases

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by ¹⁷O‐ and ¹H‐NMR in Nematic Phases

r_αStructures of partially oriented pentafluorobenzenes C₆F₅X (X = H, Cl, I) as determined from¹⁹F NMR spectra with¹³C satellites

Determination of natural abundance ¹⁵N–¹H and ¹³C–¹H dipolar couplings of molecules in a strongly orienting media using two‐dimensional inverse experiments

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Vibrational corrections in NMR spectra of oriented molecules

Cited by 87 publications

References 9 publications

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by 17O‐ and 1H‐NMR in Nematic Phases

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by 17O‐ and 1H‐NMR in Nematic Phases

rαStructures of partially oriented pentafluorobenzenes C6F5X (X = H, Cl, I) as determined from19F NMR spectra with13C satellites

Determination of natural abundance 15N–1H and 13C–1H dipolar couplings of molecules in a strongly orienting media using two‐dimensional inverse experiments

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Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by ¹⁷O‐ and ¹H‐NMR in Nematic Phases

Determination of the Quadrupolar Coupling Constant and the Asymmetry Parameter of Oxygen‐17 in Acetone by ¹⁷O‐ and ¹H‐NMR in Nematic Phases

r_αStructures of partially oriented pentafluorobenzenes C₆F₅X (X = H, Cl, I) as determined from¹⁹F NMR spectra with¹³C satellites

Determination of natural abundance ¹⁵N–¹H and ¹³C–¹H dipolar couplings of molecules in a strongly orienting media using two‐dimensional inverse experiments