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首页> 外文期刊>Crystal growth & design >H-1, C-13, and N-15 Solid-State NMR Studies of Imidazole- and Morpholine-Based Model Compounds Possessing Halogen and Hydrogen Bonding Capabilities
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H-1, C-13, and N-15 Solid-State NMR Studies of Imidazole- and Morpholine-Based Model Compounds Possessing Halogen and Hydrogen Bonding Capabilities

机译：H-1，C-13和N-15含卤素和氢键能力的咪唑和吗啉基模型化合物的NMR研究

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摘要

The halogen and hydrogen bonding interactions present in solid 1-(2,3,3-triiodoallyl)imidazole (1), morpholinium iodide (2), the 1:1 cocrystal 1-(2,3,3-triiodoallyl)imidazole-morpholinium iodide (3), morpholine (4), imidazole (5), and 1-(3-iodopropargyl)imidazole (6) have been investigated by solid-state H-1, C-13, and N-15 NMR spectroscopies. Comparison of the N-15 CP MAS NMR spectrum of 3 with that of 2 indicates that protonated morpholine is present in solid 3, but this conclusion must be taken with caution as GIPAW calculations predict a N-15 chemical shift for morpholine similar to that of the morpholinium cation. Conclusive evidence for the presence of a morpholinium cation in crystalline 3 was obtained by recording the static N-15 NMR spectrum of this host-guest complex and comparing the morpholiniun/morpholine part of the spectrum with the static spectra of 3 and 4 as obtained from ab initio calculations of NMR parameters based on the X-ray structures of these compounds. Concerning the imidazolyl group, N-15 NMR spectroscopy has proven quite valuable to identify changes in the bonding situation of the C-N = C nitrogen on passing from 1 to 3. In addition, slight differences are observed between the N-15 chemical shifts of 1 and 6 that are ascribed to differences in halogen bond strengths between the two compounds. Attempts have also been made to study halogen bonding by C-13 NMR spectroscopy, but this method did not provide exploitable results as signals corresponding to the sp and sp(2) carbon atoms bonded to iodine could not be observed experimentally. H-1 NMR spectroscopy is a powerful tool to study hydrogen bonding interactions of moderate energies such as +NH2 center dot center dot center dot X (X = N, O, I). Indeed, we have found that the chemical shifts of the NH hydrogens were quite sensitive to the nature of X and to the N-H center dot center dot center dot X distance. This is demonstrated by the fact that the chemical shifts of the +NH2 protons of the morpholinium cation in 2 and 3 are noticeably different.
机译：固体1-（2,3,3-三碘代烯丙基）咪唑（1），碘吗啉（2），1：1共晶1-（2,3,3-三碘代烯丙基）咪唑-吗啉鎓中存在的卤素和氢键相互作用通过固态H-1，C-13和N-15 NMR光谱研究了碘化物（3），吗啉（4），咪唑（5）和1-（3-碘丙炔基）咪唑（6）。比较3的N-15 CP MAS NMR谱和2的N-15 CP MAS NMR谱表明，固体3中存在质子化的吗啉，但是必须谨慎对待这一结论，因为GIPAW计算预测吗啉的N-15化学位移与N相似。吗啉阳离子。通过记录该主体-客体复合物的静态N-15 NMR光谱，并将光谱中的吗啉基/吗啉部分与静态质谱图3和4进行比较，获得了晶体3中存在吗啉阳离子的确凿证据。从头开始计算这些化合物的X射线结构。关于咪唑基，N-15 NMR光谱已被证明对于鉴定CN = C氮从1传递到3时的键合状态变化非常有价值。此外，在N-15的化学位移1与化学位移之间观察到细微差异。和6归因于两种化合物之间的卤素键强度的差异。还尝试通过C-13 NMR光谱研究卤素键，但是该方法没有提供可利用的结果，因为无法通过实验观察到与sp和sp（2）碳原子键合到碘上的信号。 H-1 NMR光谱是研究中等能量（如+ NH2中心点，中心点，中心点X（X = N，O，I））的氢键相互作用的强大工具。确实，我们发现NH氢的化学位移对X的性质和N-H中心点中心点中心点中心点X的距离非常敏感。这通过以下事实证明：在2和3中，吗啉阳离子的+ NH2质子的化学位移明显不同。

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