Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States.
Bruker Biospin Corporation, 15 Fortune Drive, Billerica, MA 01821, United States.
J Magn Reson. 2022 Jul;340:107227. doi: 10.1016/j.jmr.2022.107227. Epub 2022 Apr 26.
Fluorination is a versatile and valuable modification for numerous systems, and F NMR spectroscopy is the premier method for their structural characterization. F chemical shift anisotropy is a sensitive probe of structure and dynamics, even though F chemical shift tensors have been reported for only a handful of systems to date. Here, we explore γ-encoded R-symmetry based recoupling sequences for the determination of F chemical shift tensors in fully protonated organic solids at high, 60-100 kHz MAS frequencies. We show that the performance of F-RNCSA experiments improves with increasing MAS frequencies, and that H decoupling is required to determine accurate chemical shift tensor parameters. In addition, these sequences are tolerant to B-field inhomogeneity making them suitable for a wide range of systems and experimental conditions.
氟化是对众多系统进行多功能和有价值的修饰，而 F NMR 光谱学是其结构特征的主要方法。F 化学位移各向异性是结构和动力学的敏感探针，尽管迄今为止仅报道了少数几个系统的 F 化学位移张量。在这里，我们探索了基于γ编码 R 对称性的重聚序列，以在高 MAS 频率（60-100 kHz）下确定完全质子化有机固体中的 F 化学位移张量。我们表明，F-RNCSA 实验的性能随着 MAS 频率的增加而提高，并且需要 H 去耦才能确定准确的化学位移张量参数。此外，这些序列对磁场不均匀性具有耐受性，因此适用于广泛的系统和实验条件。
