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1H and 19F spin-lattice relaxation and CH3 or CF3 reorientation in molecular solids containing both H and F atoms
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2016-04-19 13:41:52 , DOI: 10.1063/1.4944981
Peter A. Beckmann 1 , Arnold L. Rheingold 2
Affiliation  

The dynamics of methyl (CH3) and fluoromethyl (CF3) groups in organic molecular (van der Waals) solids can be exploited to survey their local environments. We report solid state 1H and 19F spin-lattice relaxationexperiments in polycrystalline 3-trifluoromethoxycinnamic acid, along with an X-ray diffraction determination of the molecular and crystal structure, to investigate the intramolecular and intermolecular interactions that determine the properties that characterize the CF3 reorientation. The molecule is of no particular interest; it simply provides a motionless backbone (on the nuclear magnetic resonance(NMR) time scale) to investigate CF3 reorientation occurring on the NMR time scale. The effects of 19F–19F and 19F–1H spin-spin dipolar interactions on the complicated nonexponential NMRrelaxation provide independent inputs into determining a model for CF3 reorientation. As such, these experiments provide much more information than when only one spin species (usually 1H) is present. In Sec. IV, which can be read immediately after the Introduction without reading the rest of the paper, we compare the barrier to CH3 and CF3 reorientation in seven organic solids and separate this barrier into intramolecular and intermolecular components.

中文翻译:

包含H和F原子的分子固体中的1H和19F自旋晶格弛豫以及CH3或CF3重新取向

可以利用有机分子(范德华)固体中甲基(CH 3)和氟甲基(CF 3)的动力学来调查其局部环境。我们报告了多晶3-三氟甲氧基肉桂酸中的固态1 H和19 F自旋晶格弛豫实验,以及分子和晶体结构的X射线衍射测定,以研究分子内和分子间相互作用,从而确定表征CF的特性3重新定位。该分子没有特别的意义。它只是提供了一个静止的主干(在核磁共振(NMR)时间尺度上)来研究CF 3在NMR时间尺度上发生重新定向。的影响19 F- 19 F和19 F- 1上的复杂非指数NMRrelaxationħ自旋-自旋偶极相互作用提供独立的投入确定用于CF的模型3重新定位。因此,与仅存在一种自旋物种(通常为1 H)时相比,这些实验提供的信息更多。在秒 IV,可以在介绍后立即阅读而无需阅读本文的其余部分,我们比较了7种有机固体中CH 3和CF 3重取向的障碍,并将该障碍分为分子内和分子间组分。
更新日期:2016-04-20
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