Carbon shielding tensor

Carbon-shielding tensors, alkene and alkyne transition metal complexes, 1, 472 Carbon—silicon bond formation... 

E. Tarroni and C. Zannoni, Order parameters and carbon shielding tensors of some anthracene derivatives from C-13 NMR experiments, J. Phys. Chem., 100 (1996) 17157-17165. 

Nishiyama et al have illustrated a way of measuring the principal components of carbon shielding tensors in uniaxially drawn polypropylene. 

Carbon-shielding Tensors in Tj -Coordinated Transition Metal Complexes of Alkenes and Alkynes... 

The problem was revisited once more following the publication of the powder data of Yannoni et al., which yielded values for the principal values of the carbon shielding tensor. Again the nuclear origin (at carbon) was chosen and the same extrapolation procedure yielded results in moderately good agreement with experiment as shown in Table 4. Fowler and co-workers note that the discrepancy between the isotropic shielding observed in solution and that obtained from the powder data (6 ppm) may result from errors inherent in the line shape analysis required in the evaluation of powder data. 

This is precisely the case for the spectrum of the polycarbonate given in Figure 3b. To obtain a more highly resolved spectrum requires the averaging of the various carbon shielding tensors in the solid state. 

Facelli, J. C., Molecular Structure and Carbon-13 Chemical Shielding Tensors Obtained from Nuclear Magnetic Resonance, 19, 1. 

Optimized Geometries. As the elements of the NMR shielding tensor for a nucleus represent local properties, the most important geometrical parameter influencing the value of the 19F shielding constant can be expected to be the length of the bond which attaches the fluorine to the benzene ring. The optimized values of the carbon-fluorine... 

The m.p. line-narrowing technique has added an impressively long list of proton shielding tensors a to our knowledge of material properties. Complementary access to such tensors is to calculate them by quantum chemical methods. An important advantage of this approach is that, in addition to the symmetric constituent of a, it also yields the components of the antisymmetric constituent o " that are virtually inaccessible to measurements by spectroscopic means. So far only relaxation studies have provided experimental information about (Kuhn, 1983 Anet and O Leary, 1992). Note that these experiments were done on carbons. 

Fig. 7a, b The relationship between the distance d between the sulfur and the carbon in the P=S H-C and the P-S- H-C units and the values of the principal elements of the P nuclear magnetic shielding tensors calculated by the DPT GIAO method... 

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