Carbon-13 shielding tensors: experimental and theoretical determination

Facelli, Julio C.; Grant, David M.; Michl, Josef

doi:10.1021/ar00136a005

Cited by 43 publications

(19 citation statements)

References 47 publications

(4 reference statements)

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“…(RMSD = 3.4 ppm). (8) The RMSDs for these two models of 9.5 ppm (isolatedmolecule model) and 3.4 ppm (cluster model) indicate that the cluster model is superior to the isolated-molecule model. The deviation from the ideal slope may reflect the choice of exchange-correlation functional and basis set employed in the calculation.…”

Section: E Linear Regression To Define Reference Chemical Shieldingmentioning

confidence: 93%

“…7 Despite this strong dependence on structure, it remains difficult to interpret data in terms of local structure without quantum chemical models. [8][9][10] Experimental chemical shifts are often correlated with calculated magnetic shieldings to gain a deeper insight into a material's local structure. The ever-increasing number of published solid-state 13 C chemical-shift measurements has been met with a corresponding demand for highly accurate computational models for calculating magnetic shielding in solids.…”

Section: Introductionmentioning

confidence: 99%

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Density functional investigation of intermolecular effects on 13C NMR chemical-shielding tensors modeled with molecular clusters

Holmes

Iuliucci

Mueller

et al. 2014

The Journal of Chemical Physics

156

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A quantum-chemical method for modeling solid-state nuclear magnetic resonance chemical-shift tensors by calculations on large symmetry-adapted clusters of molecules is demonstrated. Four hundred sixty five principal components of the (13)C chemical-shielding tensors of 24 organic materials are analyzed. The comparison of calculations on isolated molecules with molecules in clusters demonstrates that intermolecular effects can be successfully modeled using a cluster that represents a local portion of the lattice structure, without the need to use periodic-boundary conditions (PBCs). The accuracy of calculations which model the solid state using a cluster rivals the accuracy of calculations which model the solid state using PBCs, provided the cluster preserves the symmetry properties of the crystalline space group. The size and symmetry conditions that the model cluster must satisfy to obtain significant agreement with experimental chemical-shift values are discussed. The symmetry constraints described in the paper provide a systematic approach for incorporating intermolecular effects into chemical-shielding calculations performed at a level of theory that is more advanced than the generalized gradient approximation. Specifically, NMR parameters are calculated using the hybrid exchange-correlation functional B3PW91, which is not available in periodic codes. Calculations on structures of four molecules refined with density plane waves yield chemical-shielding values that are essentially in agreement with calculations on clusters where only the hydrogen sites are optimized and are used to provide insight into the inherent sensitivity of chemical shielding to lattice structure, including the role of rovibrational effects.

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Section: E Linear Regression To Define Reference Chemical Shieldingmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Density functional investigation of intermolecular effects on 13C NMR chemical-shielding tensors modeled with molecular clusters

Holmes

Iuliucci

Mueller

et al. 2014

The Journal of Chemical Physics

156

View full text Add to dashboard Cite

show abstract

“…The B o field experienced by the nuclear spins is modulated by the electron distribution around the nucleus (Facelli et al 1987). The electron distribution depends on the chemical environment of the nucleus, and leads to small shifts of the Zeeman energy levels.…”

Section: Chemical Shift Interactionsmentioning

confidence: 99%

Magic angle spinning NMR spectroscopy of membrane proteins

Smith

Aschheim

Groesbeek

1996

Quart. Rev. Biophys.

109

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The passage of molecules and information across cell membranes is mediated largely by membrane-spanning proteins acting as channels, pumps, receptors and enzymes. These proteins perform many tasks: they control electrochemical gradients across the membrane, receive signals from the environment or from other cells, convert light energy into chemical signals, transport small molecules into and out of cells, and harness proton gradients to generate the energy consumed in metabolism. Indeed, of the estimated 50000–100000 genes in the human genome, fully 20–40 % are thought to encode integral membrane proteins. If one also includes membrane-associated proteins, which are attached to the membrane surface through fatty acyl chains or electrostatic interactions, this percentage is likely to be much higher.

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“…Considering that the chemical shift observed in liquids is merely the isotropic average of the three components of the chemical shift tensor, and each component can vary independently with changes in structure (25), it is perhaps surprising that observed chemical shifts agree as well as they do with values from purely empirical calculation schemes. We certainly cannot detect the hoped-for small chemical shift effects arising from nonbonded interactions (6, 7) because of much larger variations due to other factors.…”

Section: Discussionmentioning

confidence: 99%

Carbon-13 chemical shifts of alkene carbons in 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles and related benzothiazoles and -selenazoles, and their relationship to other push-pull alkenes

Mueller¹,

Gibson²,

Hartman³

1996

Can. J. Chem.

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Carbon-13 chemical shifts of alkene carbons are observed in the ranges 78-109 ppm (Cu) and 154-164 ppm (CP) for a series of 11 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles, 3 2-acylidene-3-alkyl-2,3-dihydrobenzothiazoles and 2 2-acylidene-3-alkyl-2,3-dihydrobenzoselenaz0les of known geometry, indicating appreciable charge polarization in these compounds as in other push-pull olefins. Substitution that promotes more extensive charge delocalization results in the C a signal shifting to the higher-frequency end of the chemical shift range. The observed shifts are compared with those calculated according to the Pretsch scheme.Key words: carbon-13 NMR, chemical shifts, push-pull olefins, 1.3.4-thiadiazoles, benzothiazoles, benzoselenazoles.RCsumC : On a observe les dtplacements chimiques du I3c des carbones des alcknes dans des rCgions allant de 78 B 109 ppm (Ca) et 156 i 164 (CP), d'une sCrie de 11 2-acylidkne-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles, de 3 2-acylidkne-3-alkyl-2, 3-dihydrobenzothiazoles, et de 2 2-acylid~ne-3-alkyl-2,3-dihydrobenzostlnazoles de gComCtries connues; ces rCsultats indiquent qu'il existe une polarisation importante de la charge dans ces composCs, comme dans les autres olefines (( push-pull D.La substitution qui provoque la plus grande dklocalisation conduit B un dkplacement du signal C a vers les plus grandes frCquences de la plage des dkplacements chimiques. On a compart les dkplacements chimiques observts avec ceux calculCs B l'aide du schCma de Pretsch.

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Carbon-13 shielding tensors: experimental and theoretical determination

Abstract: is now being supported by the Office of Naval Research. This support is gratefully acknowledged. Finally, the inspiration for these advances can be attributed to Dr.

Cited by 43 publications

References 47 publications

Density functional investigation of intermolecular effects on 13C NMR chemical-shielding tensors modeled with molecular clusters

Density functional investigation of intermolecular effects on 13C NMR chemical-shielding tensors modeled with molecular clusters

Magic angle spinning NMR spectroscopy of membrane proteins

Carbon-13 chemical shifts of alkene carbons in 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles and related benzothiazoles and -selenazoles, and their relationship to other push-pull alkenes

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