论文标题
使用分裂脉冲PM-Respdor固态NMR实验，碳和溴之间的距离测量
Distance measurements between carbon and bromine using a split-pulse PM-RESPDOR solid-state NMR experiment
论文作者
论文摘要
固态NMR长期以来一直用于探测附近核自旋之间的原子距离，这是由于偶极相互作用。新的技术进步已使带有密切Larmor频率的射频共振电路同时调整射频共振电路，这也为这种核之间的距离测量带来了巨大的希望，尤其是对于一个大于一半的旋转的核。但是，由于不能同时辐射两个核，因此这种新的可能性也需要对这些实验进行修改。当测量自旋s = 1/2和四极旋转（S> 1/2）之间的距离时，可以通过将施加到四极核的连续波再耦脉冲分开来克服此缺点。我们在这里表明，与高效的相位调节（PM）重耦脉冲进行了类似的调整，可实现具有近距离频率的核之间的距离测量，其中耦合旋转经历非常大的耦合。在13C-81BR系统上证明了这样的实验，分裂相位调节的回位，其中Larmor频率的差异仅为14.1T磁铁的7％或11.2 MHz。使用未量化的分析公式提取核间距离。由于溴通常会经历特别高的四极耦合，因此，如当前情况一样，我们建议分裂的PM-Respdor实验对Bromo-Compound的研究可能非常有益，包括许多药物，其中许多药物键是普遍存在的碳 - 溴键，以及利用高疗法药物反应性的有机体诱导者。我们表明，对于丁基三苯基溴化物，距离与低溶剂化合物而不是半静态形式一致。拆分PM-Respdor实验适用于任何四极/自旋1/2对之间的距离测量，特别是当四极旋转经历明显大的耦合时。
Solid-state NMR have been long used to probe atomic distances between nearby nuclear spins by virtue of the dipolar interaction. New technological advances have enabled simultaneous tuning of the radio-frequency resonance circuits to nuclei with close Larmor frequencies, bringing a great promise also to distance measurements between such nuclei, in particular for nuclei with a spin larger than one-half. However, this new possibility has also required modifications of those experiments since the two nuclei cannot be irradiated simultaneously. When measuring distances between a spin S=1/2 and a quadrupolar spin (S > 1/2), this drawback can be overcome by splitting the continuous-wave recoupling pulse applied to the quadrupolar nucleus. We show here that a similar adjustment to a highly-efficient phase-modulated (PM) recoupling pulse enables distance measurements between nuclei with close Larmor frequencies, where the coupled spin experiences a very large coupling. Such an experiment, split phase-modulated RESPDOR, is demonstrated on a 13C-81Br system, where the difference in Larmor frequencies is only 7%, or 11.2 MHz on a 14.1T magnet. The inter-nuclear distances are extracted using an unscaled analytical formula. Since bromine usually experiences particularly high quadrupolar couplings, as in the current case, we suggest that the split-PM-RESPDOR experiment can be highly beneficial for the research of bromo-compounds, including many pharmaceuticals, where carbon-bromine bonds are prevalent, and organo-catalysts utilizing the high reactivity of bromides. We show that for butyl triphenylphosphonium bromide, distances are in agreement with a low-hydration compound rather than a semi-clathrate form. The split-PM-RESPDOR experiment is suitable for distance measurement between any quadrupolar/spin-1/2 pairs, in particular when the quadrupolar spin experiences a significantly large coupling.
