Measurements of two‐dimensional NMR powder patterns in rotating solids
Measurements of two‐dimensional NMR powder patterns in rotating solids
复制标题
旋转固体中二维 NMR 粉末图案的测量
DOI：
10.1063/1.454497
复制
发表时间：
1988
影响因子：
4.4
通讯作者：
T. Terao
中科院分区：
文献类型：
--
作者：
T. Nakai;J. Ashida;T. Terao
描述了用于测量异质偶极/化学位移二维（2D）粉末图案的样品旋转NMR技术。对于具有多于一个化学上不同的核的化合物，可以通过3D开关角样品旋转NMR单独获得单个2D粉末图案。用甲酸钙中两个晶体学上不等价的甲酸根离子的~（13）C ~（23）D粉末图证明了3D NMR的实际应用。化学位移张量和质子的位置，得到了个别甲酸根离子，这与13 C NMR和中子衍射的单晶研究已经报道的结果一致。还获得了聚乙烯的2D粉末图案作为CH 2系统的实例。确定了化学位移主值、键长和键角。化学位移主轴仅沿着CH 2基团的对称方向，表明电子膜的强烈扰动。
Sample‐spinning NMR techniques for measuring the heteronuclear dipolar/chemical shift two‐dimensional (2D) powder patterns are described. For compounds with more than one chemically distinct nucleus, the individual 2D powder patterns can be separately obtained by 3D switching‐angle sample‐spinning NMR. A practical application of the 3D NMR is demonstrated with the 13C 2D powder patterns of the two crystallographically inequivalent formate ions in calcium formate. The chemical shift tensors and proton positions were obtained for the individual formate ions, which agree with the results already reported by single crystal studies of 13C NMR and neutron diffraction. The 2D powder pattern of polyethylene was also obtained as an example of the CH2 system. The chemical shift principal values, the bond length, and the bond angle were determined. The chemical shift principal axes were found to be only approximately along the symmetry directions of the CH2 group, indicating a strong perturbation of the electric env...