NMR crystallography of campho[2,3-c]pyrazole (Z' = 6): combining high-resolution 1H-13C solid-state MAS NMR spectroscopy and GIPAW chemical-shift calculations.
NMR crystallography of campho[2,3-c]pyrazole (Z' = 6): combining high-resolution 1H-13C solid-state MAS NMR spectroscopy and GIPAW chemical-shift calculations.
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樟脑[2,3-c]吡唑 (Z = 6) 的 NMR 晶体学：结合高分辨率 1H-13C 固态 MAS NMR 光谱和 GIPAW 化学位移计算。
DOI：
10.1021/jp104901j
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
S. Brown
中科院分区：
文献类型：
--
作者：
Amy L. Webber;L. Emsley;R. Claramunt;S. Brown
（1）利用MAS-J-HMQC实验，获得了双（13）C魔角旋转（MAS）固体核磁共振相关谱。对于每个（13）C部分，存在与不对称晶胞（Z' = 6）中的六个不同分子相关的六个共振。在2D（1）H-（13）C MAS-J-HMQC光谱中观察到的单键C-H相关性允许实验测定与单独的CH、CH（2）和CH（3）基团相关的（1）H和（13）C化学位移。(1)H用GIPAW（Gauge Including Projector Augmented Waves）平面波赝势方法计算了（13）C化学位移。对整个晶胞（12 × 29 = 348个原子，所有原子的几何优化）的计算允许将实验的（1）H和（13）C化学位移分配给六个不同的分子。计算出的化学位移的完整的晶体结构进行了比较与孤立的分子提取的几何优化的晶体结构。通过这种方式，量化了分子间相互作用对所观察到的化学位移的影响。特别地，计算足够精确以区分与每个不同CH或CH（2）部分相关的六个共振的（1）H化学位移之间的小（<1 ppm）差异。
(1)H-(13)C two-dimensional magic-angle spinning (MAS) solid-state NMR correlation spectra, recorded with the MAS-J-HMQC experiment, are presented for campho[2,3-c]pyrazole. For each (13)C moiety, there are six resonances associated with the six distinct molecules in the asymmetric unit cell (Z' = 6). The one-bond C-H correlations observed in the 2D (1)H-(13)C MAS-J-HMQC spectra allow the experimental determination of the (1)H and (13)C chemical shifts associated with the separate CH, CH(2), and CH(3) groups. (1)H and (13)C chemical shifts calculated by using the GIPAW (Gauge Including Projector Augmented Waves) plane-wave pseudopotential approach are presented. Calculations for the whole unit cell (12 × 29 = 348 atoms, with geometry optimization of all atoms) allow the assignment of the experimental (1)H and (13)C chemical shifts to the six distinct molecules. The calculated chemical shifts for the full crystal structure are compared with those for isolated molecules as extracted from the geometry-optimized crystal structure. In this way, the effect of intermolecular interactions on the observed chemical shifts is quantified. In particular, the calculations are sufficiently precise to differentiate the small (<1 ppm) differences between the (1)H chemical shifts of the six resonances associated with each distinct CH or CH(2) moiety.