Brouwer E B, Challoner R, Harris R K
Department of Chemistry, University of Durham, United Kingdom.
Solid State Nucl Magn Reson. 2000;18(1-4):37-52. doi: 10.1006/snmr.2000.0009.
The supramolecular 1:1 host-guest inclusion compound, p-tert-butylcalix[4]arene x alpha,alpha,alpha-trifluorotoluene, 1, is characterized by 19F and 13C solid-state NMR spectroscopy. Whereas the 13C NMR spectra are easily interpreted in the context of earlier work on similar host-guest compounds, the 15F NMR spectra of solid 1 are, initially, more difficult to understand. The 19F[1H] NMR spectrum obtained under cross-polarization and magic-angle spinning conditions shows a single isotropic resonance with a significant spinning sideband manifold. The static 19F[1H] CP NMR spectrum consists of a powder pattern dominated by the contributions of the anisotropic chemical shift and the homonuclear dipolar interactions. The 19F MREV-8 experiment, which minimizes the 19F-19F dipolar contribution, helps to identify the chemical shift contribution as an axial lineshape. The full static 19F[1H] CP NMR spectrum is analysed using subspectral analysis and subsequently simulated as a function of the 19F-19F internuclear distance (D(FF) = 2.25 +/- 0.01 A) of the rapidly rotating CF3 group without including contributions from additional libration motions and the anisotropy in the scalar tensor. The shielding span is found to be 56 ppm. The width of the centerband in the 19F[1H] sample-spinning CP NMR spectrum is very sensitive to the angle between the rotor and the magnetic field. Compound 1 is thus an attractive standard for setting the magic angle for NMR probes containing a fluorine channel with a proton-decoupling facility.
超分子1:1主客体包合物对叔丁基杯[4]芳烃xα,α,α-三氟甲苯（1）通过19F和13C固态核磁共振光谱进行表征。虽然13C核磁共振光谱在早期关于类似主客体化合物的研究背景下易于解释，但固体1的19F核磁共振光谱最初较难理解。在交叉极化和魔角旋转条件下获得的19F[1H]核磁共振光谱显示出一个单一的各向同性共振以及一个显著的旋转边带多重峰。静态19F[1H] CP核磁共振光谱由一个粉末图谱组成，该图谱主要由各向异性化学位移和同核偶极相互作用的贡献主导。使19F-19F偶极贡献最小化的19F MREV-8实验有助于将化学位移贡献识别为轴向线形。使用子光谱分析对完整的静态19F[1H] CP核磁共振光谱进行分析，随后将其模拟为快速旋转的CF3基团的19F-19F核间距离（D(FF) = 2.25 +/- 0.01 Å）的函数，而不包括额外的摆动运动和标量张量中的各向异性的贡献。发现屏蔽跨度为56 ppm。19F[1H]样品旋转CP核磁共振光谱中中心带的宽度对转子与磁场之间的角度非常敏感。因此，化合物1是为具有质子去耦功能的含氟通道核磁共振探头设置魔角的有吸引力的标准物。
