Electric field effects on the carbon-13 nuclear magnetic shielding in several organic molecules

Grayson, Martin; Raynes, W.T.

doi:10.1080/00268979400100351

Cited by 33 publications

(14 citation statements)

References 43 publications

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“…Calculated values of e ͑C͒ and e ͑H͒ obtained by a variety of authors [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] are listed in Table II. Noncorrelated results ͑Refs.…”

Section: Calculations At Equilibrium Geometrymentioning

confidence: 99%

Nuclear magnetic shielding in the acetylene isotopomers calculated from correlated shielding surfaces

Wigglesworth

Raynes

Kirpekar

et al. 2000

The Journal of Chemical Physics

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Articles you may be interested inCurrent density maps, magnetizability, and nuclear magnetic shielding tensors of bis-heteropentalenes. I. Dihydro-pyrrolo-pyrrole isomers Natural chemical shielding analysis of nuclear magnetic resonance shielding tensors from gauge-including atomic orbital calculations Ab initio, symmetry-coordinate and internal valence coordinate carbon and hydrogen nuclear shielding surfaces for the acetylene molecule are presented. Calculations were performed at the correlated level of theory using gauge-including atomic orbitals and a large basis set. The shielding was calculated at equilibrium and at 34 distinct geometries corresponding to 53 distinct sites for each nucleus. The results were fitted to fourth order in Taylor series expansions and are presented to second order in the coordinates. The carbon-13 shielding is sensitive to all geometrical parameters and displays some unexpected features; most significantly, the shielding at a carbon nucleus ͑C 1 , say͒ is six times more sensitive to change of the C 1 C 2 H 2 angle than it is to change of the H 1 C 1 C 2 angle. In addition, for small changes, ͑C 1 ͒ is more sensitive to the C 2 H 2 bond length than it is to the C 1 H 1 bond length. These, and other, examples of ''unexpected differential sensitivity'' are discussed. The proton shielding surface is much more as expected with ͑H 1 ͒ being most sensitive to the C 1 H 1 bond length, less so to the CC bond length and hardly at all to the C 2 H 2 bond length. The surfaces have been averaged over a very accurate force field to give values of ͑C͒, ͑H͒, and ͑D͒ for the ten isotopomers containing all possible combinations of 12 C, 13 C, 1 H, and 2 H nuclei at 0 K and at a number of selected temperatures in the range accessible to experiment. For the carbon shielding the dominant nuclear motion contribution comes from the bending at ''the other'' carbon atom with the combined stretching contributions being only 20% of those from bending. For the proton shielding it is the stretching of the CH bond containing the proton of interest which provides the major nuclear motion contribution. For ͑C͒ in H 13 C 13 CH at 300 K our best result is 117.59 ppm which is very close to the experimental value of 116.9 ͑Ϯ0.9͒ ppm. For ͑H͒ in H 13 C 13 CH at 300 K we obtain 29.511 ppm which is also in very close agreement with the experimental value of 29.277 ͑Ϯ0.001͒ ppm. Calculated values are also very close to recent, highly accurate carbon and proton isotope shifts in the ten isotopomers; carbon isotope shifts differ by no more than 10% from the measured values and proton isotope shifts are generally in even better agreement than this. The observed anomaly whereby the 13 C isotope shift in H 13 C 12 CD is greater than that in D 13 C 12 CH both with respect to H 13 C 12 CH is explained in terms of the bending contribution at ''the other'' carbon. The observed nonadditivity of deuterium isotope effects on the carbon shielding can be traced to a cross term involving second order bending.

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Section: Calculations At Equilibrium Geometrymentioning

confidence: 99%

Nuclear magnetic shielding in the acetylene isotopomers calculated from correlated shielding surfaces

Wigglesworth

Raynes

Kirpekar

et al. 2000

The Journal of Chemical Physics

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“…The Einstein summation convention is used. The shielding (hyper)polarizabilities (σ‘ αβ , γ and σ‘‘ αβ , γ , δ ) have been calculated for the water molecule − and the transferability of these types of parameters from one molecule to another has been studied recently. , The electric field (and its gradient) at the atoms of interest may be obtained from molecular dynamics simulations of liquid water . Note that the effect due to distortions of the geometry is not included here.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Chemical Shifts in Liquid Water Calculated by Molecular Dynamics Simulations and Shielding Polarizabilities

1997

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The gas-to-liquid chemical shifts of water have been calculated by combining molecular dynamics simulations and quantum chemically derived shielding polarizabilities. The use of a force field based on intermolecular perturbation theory ensures that the electric fields are adequately modeled. The experimental proton shift and its temperature dependence are reproduced, but the oxygen shift lacks higher order terms such as the linear field-gradient contribution. Shifts arising from the difference in the gas phase and liquid geometries of the water molecule have been estimated and discussed.

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“…Semiempirical results are available for all the anisotropies. − It appears worthwhile to reinvestigate particularly the full J CC tensors for these molecules by using modern ab initio methods and good basis sets. Theoretical 1 H and 13 C shielding tensors have recently been reported. − Accurate σ constants by the CCSD method were calculated by Gauss and Stanton …”

Section: Introductionmentioning

confidence: 99%

Experimental and Theoretical ab Initio Study of the ¹³C−¹³C Spin−Spin Coupling and ¹H and ¹³C Shielding Tensors in Ethane, Ethene, and Ethyne

et al. 1998

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Experimentally and theoretically (ab initio) determined CC spin−spin coupling tensors and 1H and 13C nuclear shielding tensors are reported for ethane (13C2H6), ethene (13C2H4), and ethyne (13C2H2). The experimental anisotropies of the CC coupling tensors, ΔJ CC, for all these molecules, and also the combination J CC, xx − J CC, yy for ethene, were derived from sets of anisotropic couplings (D exp) analyzed from the 1H and 13C NMR spectra of molecules partially oriented in liquid−crystalline environments. Both harmonic vibrations and structural deformations arising from the correlation of vibrational and reorientational motions were taken into account in the D couplings. The ab initio calculations of all the J tensors were performed using MCSCF linear response theory. The best calculated and experimental ΔJ CC values (along with J CC, xx − J CC, yy for ethene) are found to be in good mutual agreement. Together with earlier work on the n J CC tensors in benzene, this study shows that the indirect contribution, 1/2 J CC aniso, to experimental couplings between differently hybridized carbons is small and can generally be omitted. This means that the use of experimental D CC couplings in the determination of molecular order tensors and/or conformation does not introduce serious errors. The experimental determination of the 1H and 13C shielding tensors was based on the liquid crystal director rotation by 90° in mixtures of thermotropic nematogens with opposite anisotropy of diamagnetic susceptibility. Ab initio SCF and MCSCF calculations utilizing gauge-including atomic orbitals produce results in good agreement with experiments.

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Electric field effects on the carbon-13 nuclear magnetic shielding in several organic molecules

Cited by 33 publications

References 43 publications

Nuclear magnetic shielding in the acetylene isotopomers calculated from correlated shielding surfaces

Nuclear magnetic shielding in the acetylene isotopomers calculated from correlated shielding surfaces

Chemical Shifts in Liquid Water Calculated by Molecular Dynamics Simulations and Shielding Polarizabilities

Experimental and Theoretical ab Initio Study of the ¹³C−¹³C Spin−Spin Coupling and ¹H and ¹³C Shielding Tensors in Ethane, Ethene, and Ethyne

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Electric field effects on the carbon-13 nuclear magnetic shielding in several organic molecules

Cited by 33 publications

References 43 publications

Nuclear magnetic shielding in the acetylene isotopomers calculated from correlated shielding surfaces

Nuclear magnetic shielding in the acetylene isotopomers calculated from correlated shielding surfaces

Chemical Shifts in Liquid Water Calculated by Molecular Dynamics Simulations and Shielding Polarizabilities

Experimental and Theoretical ab Initio Study of the 13C−13C Spin−Spin Coupling and 1H and 13C Shielding Tensors in Ethane, Ethene, and Ethyne

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Experimental and Theoretical ab Initio Study of the ¹³C−¹³C Spin−Spin Coupling and ¹H and ¹³C Shielding Tensors in Ethane, Ethene, and Ethyne