一氟化石墨（CF）n的固态核磁共振（19F和13C）研究：19F自旋晶格磁弛豫以及通过哈特曼-哈恩交叉极化测定19F/13C距离

Solid-state NMR (19F and 13C) study of graphite monofluoride (CF)n: 19F spin-lattice magnetic relaxation and 19F/13C distance determination by Hartmann-Hahn cross polarization.

作者信息

Giraudet Jérôme, Dubois Marc, Hamwi André, Stone William E E, Pirotte Pascal, Masin Francis

机构信息

Matière Condensée et Résonance Magnétique, Université Libre de Bruxelles, CP 232, Boulevard du Triomphe, B-1050 Bruxelles, Belgium.

出版信息

J Phys Chem B. 2005 Jan 13;109(1):175-81. doi: 10.1021/jp046833j.

DOI:10.1021/jp046833j

PMID:16851001

Abstract

Graphite monofluoride (CF)(n) was studied by solid-state NMR. (19)F spin-lattice relaxation time T(1) and second moment measurements of the (19)F line are presented. A "chair" conformation structure is found to be compatible with the experimental data. Relaxation is shown to be mainly due to paramagnetic oxygen. The presence of a molecular motion with an activation energy of 1.685 kJ.mol(-1) (202.7 K) is also evidenced. (19)F magic angle spinning (MAS) NMR and (13)C MAS NMR with (19)F to (13)C cross-polarization allows the determination of CF and CF(2) groups. Reintroduction of dipolar coupling by cross-polarization is used for C-F bond length determination (0.138 +/- 0.001 nm).

摘要

通过固态核磁共振研究了一氟化石墨（CF）ₙ。给出了¹⁹F自旋晶格弛豫时间T₁以及¹⁹F谱线的二级矩测量结果。发现“椅式”构象结构与实验数据相符。结果表明弛豫主要归因于顺磁性氧。还证实存在活化能为1.685 kJ·mol⁻¹（202.7 K）的分子运动。¹⁹F魔角旋转（MAS）核磁共振以及带有¹⁹F至¹³C交叉极化的¹³C MAS核磁共振可用于确定CF和CF₂基团。通过交叉极化重新引入偶极耦合用于确定C - F键长（0.138 ± 0.001 nm）。