13C shielding tensor

Complete assignment of 13C shielding tensors in the entire molecule from single crystal studies has been developed to the highest level by D. M. Grant and co-workers. Single crystal NMR measurements provide complete tensor information and... 

Fig. 7. The 13C powder lineshape calculated for the Cp ring hopping between chemically equivalent sites in [A1C14] [AlCp 2]+ using the 13C-shielding tensor determined from ab initio electronic structure calculations.12 The figure illustrates how the lineshape varies with the ring hopping rate k. The orientation of the principal axes of the 13C-shielding tensor determined from the ab initio calculations is shown in the inset.

Figure 7. 13CP alanine shielding tensor results. A, 11 Tesla 13C CP-MAS NMR spectrum of crystalline ala-[l3C]ala-ala,vr =1.2 kHz. B, graph showing experimental shift tensor elements versus computed shieldings slope = 1.07, R2 = 0.99. 

Ab initio calculations of 29Si and 13C NMR chemical shielding tensors have been used as an aid in the interpretation of experimental results aimed at elucidating the role of alkoxyalkylsilanes as external electron donors in Ziegler-Natta catalysis of propene. The results support a model in which dialkoxydialkylsilanes are loosely attached to two adjacent magnesium ions on the surface of magnesium chloride, but trialkoxyalkylsilanes are attached primarily by only one magnesium ion. 

Y. Ruiz-Morales, G. Schreckenbach, and T. Ziegler, J. Phys. Chem., 100, 3359 (1996). Theoretical Study of 13C and 170 NMR Shielding Tensors in Transition Metal Carbonyls Based on Density Functional Theory and Gauge-Including Atomic Orbitals. 

C Chemical Shielding Tensors Obtained from NMR, Molecular Structure and... 

Naito A, McDowell CH (1984) Determination of the UN quadrupole coupling tensors and the 13C chemical shielding tensors in a single crystal of L-aspaigine monohydrate. J Chem Phys 81 4795-4803... 

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