Recent advances in solid-state NMR spectroscopy of quadrupolar nuclei
Recent advances in solid-state NMR spectroscopy of quadrupolar nuclei
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DOI：
10.1039/b907183k
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
Ashbrook, Sharon E.
中科院分区：
文献类型：
--
作者：
Ashbrook, Sharon E.
四极核（即自旋量子数 I > 1/2）的核磁共振 (NMR) 光谱一直被视为“困难”，因为核电四极矩与电场梯度的相互作用会产生各向异性展宽。这种四极相互作用可能相当大，导致光谱共振展宽通常超过许多 MHz。此外，魔角旋转 (MAS) 是一种提高光谱分辨率的传统方法。固态核磁共振通常无法完全消除展宽，并且通常无法获得高分辨率光谱，但直到最近，分辨率和灵敏度的挑战在一定程度上限制了固态核磁共振在四极核中的应用。一般来说，通过重耦合技术或二维相关光谱获得的结构信息要容易、准确地提取要困难得多。脉冲序列的发展显着提高了研究四极自旋和获得高分辨率光谱的便利性，并且最近的应用开始利用丰富的可用信息。在本次讨论中，我们重点介绍了该领域的一些最新进展，包括新的最先进的相关实验、低旋磁比 g 的核的扩展研究、固态第一原理计算的不断增加的应用，以及利用四极展宽提供动力学信息的方法。虽然不是完整的综述，但希望对一些更令人兴奋的最新进展的简要概述能够深入了解四极核核磁共振研究中涉及的挑战和回报。
Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei (i. e., those with a spin quantum number I > 1/2) has always been viewed as "difficult'' owing to the presence of an anisotropic broadening arising from the interaction of the nuclear electric quadrupole moment with the electric field gradient. This quadrupolar interaction can be considerable, resulting in broadening of the spectral resonances often over many MHz. Furthermore, magic-angle spinning (MAS), a conventional approach for increasing the resolution in solid-state NMR, is often unable to remove the broadening completely and high-resolution spectra are generally not obtained. Despite the vast amount of information contained in the anisotropic linewidths and lineshapes, the resolution and sensitivity challenges have, until recently, somewhat limited the application of solid-state NMR for quadrupolar nuclei. In general, structural information, such as that obtained through recoupling techniques or from two-dimensional correlation spectroscopy, is much more difficult to extract easily and accurately. However, recent advances in magnet design, probe hardware and pulse sequence development have significantly improved the ease with which quadrupolar spins can be studied and high-resolution spectra can be obtained, and recent applications are beginning to exploit the wealth of information available. In this discussion, we highlight just a few of the recent developments in this area, including new state-of-the art correlation experiments, the expanding study of nuclei with low gyromagnetic ratio, g, the increasing application of first-principles calculations in the solid state, and methods which exploit the quadrupolar broadening to provide information on dynamics. Whilst not a complete review, it is hoped that this brief overview of some of the more exciting recent developments can provide insight into the challenges, and the rewards, involved in the NMR study of quadrupolar nuclei.