Bräuniger Thomas
Department of Chemistry, University of Munich (LMU), Butenandtstr. 5-13, 81377 Munich, Germany.
Molecules. 2024 Aug 31;29(17):4148. doi: 10.3390/molecules29174148.
In this review, the process of extracting precise values for NMR interaction tensors from single crystal samples is systematically explored. Starting with a description of the orientation dependence of the considered interactions, i.e., chemical shift, dipolar, and quadrupole interaction, the techniques for acquiring and analysing single-crystal spectra are outlined. This includes the 'classical' approach, which requires the acquisition of three rotation patterns around three rotation axes that are orthogonal to each other, as well as more recent strategies aimed at reducing the number of required NMR spectra. One such strategy is the 'single-rotation method', which exploits the symmetry relations between tensors in the crystal structure to reduce the necessary amount of orientation-dependent data. This concept may be extended to additionally include the orientation of the goniometer axis itself in the data fit, which may be termed the 'minimal-rotation method'. Other, more exotic schemes, such as the use of specialised probe designs or the investigation of single crystals under magic-angle-spinning, are also briefly discussed. Actual values of NMR interaction tensors as determined from the various single-crystal methods have been collected and are provided in tables for spin I=1/2, I=1, and half-integer spins with I>1/2.
在本综述中，系统地探讨了从单晶样品中提取核磁共振（NMR）相互作用张量精确值的过程。首先描述了所考虑的相互作用（即化学位移、偶极和四极相互作用）的取向依赖性，然后概述了获取和分析单晶光谱的技术。这包括“经典”方法，该方法需要获取围绕彼此正交的三个旋转轴的三个旋转模式，以及旨在减少所需NMR光谱数量的最新策略。其中一种策略是“单旋转法”，它利用晶体结构中张量之间的对称关系来减少所需的取向相关数据量。这个概念可以扩展到在数据拟合中额外包括测角仪轴本身的取向，这可以称为“最小旋转法”。还简要讨论了其他更奇特的方案，例如使用专门的探头设计或在魔角旋转下研究单晶。已收集通过各种单晶方法确定的NMR相互作用张量的实际值，并以表格形式给出了自旋I = 1/2、I = 1以及I>1/2的半整数自旋的相关数据。
