Determination of NMR interaction parameters from double rotation NMR

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• 作者：I. Hung ; A. Wong ; A.P. Howes ; T. Anupõ ; ld ; J. Past ; A. Samoson ; X. Mo ; G. Wu ; M.E. Smith ; S.P. Brown ; R. Dupree
• 关键词：Solid-state NMR ; Double rotation ; Quadrupolar interaction ; Chemical shift anisotropy ; J-coupling ; Dipolar coupling ; Oxygen-17
• 刊名：Journal of Magnetic Resonance
• 出版年：2007
• 出版时间：October 2007
• 年：2007
• 卷：188
• 期：2
• 页码：246-259
• 全文大小：464 K

文摘

It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The ¹⁷O nuclei in isotopically enriched l-alanine and OPPh₃ are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 ± 20 ppm and 350 ± 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of ±5–10°. For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V₃₃ and δ₃₃) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh₃ the principal axis of the ¹⁷O EFG is found to be close to the O–P bond, and the ¹⁷O–³¹P one-bond J coupling (¹J_OP = 161 ± 2 Hz) is determined to a much higher accuracy than previously.