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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Investigation of Magnetic Shielding in Xenon Difluoride Using Solid-State NMR Spectroscopy and Relativistic Density Functional Theory
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Investigation of Magnetic Shielding in Xenon Difluoride Using Solid-State NMR Spectroscopy and Relativistic Density Functional Theory

机译：固态NMR光谱和相对论密度泛函理论研究二氟化氙中的磁屏蔽

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摘要

The xenon and fluorine magnetic shielding tensors, σ, of XeF_2 are characterized using solid-state ~(129)Xe and ~(19)F NMR spectroscopy and nonrelativistic and spin-orbit relativistic zeroth-order regular approximation density functional theory (ZORA DFT). Analysis of ~(129)Xe and ~(19)F NMR spectra acquired with magic-angle spinning at several spinning rates indicates that the Xe and F magnetic shielding tensors are axially symmetric, as dictated by the crystal symmetry. The isotropic ~(129)Xe chemical shift is -1603 ± 5 ppm with respect to OXeF_4 (neat liquid, 24 ℃) and the Xe magnetic shielding anisotropy, Ω, is 4245 ± 20 ppm, the first anisotropy measured directly for a xenon compound. The parallel component of the experimentally determined xenon chemical shift tensor, δ_‖ = -4433 ppm differs from δ(Xe(free atom)) by ～1000 ppm, providing the first experimental demonstration that relativistic effects play an important role in the nuclear magnetic shielding for xenon. Both the sign and magnitude of the isotropic indirect ~(129)Xe,19F nuclear spin-spin coupling constant are determined, -5560 ± 50 Hz. Analysis of the ~(19)F NMR spectra yield (F) = 150 ± 20 ppm. The ZORA DFT method has been employed to calculate σ(Xe) and σ(F) for isolated XeF_2 and XeF_4 molecules, as well as σ(Kr) and σ(F) for an isolated KrF_2 molecule, at the relativistic and nonrelativistic levels of theory. Spin-orbit relativistic DFT results for Ω(Xe) are in very good agreement with those determined experimentally and highlight the importance of relativistic effects.
机译：XeF_2的氙气和氟磁屏蔽张量σ使用固态〜（129）Xe和〜（19）F NMR光谱以及非相对论和自旋轨道相对论零阶正则逼近密度泛函理论（ZORA DFT）进行表征。对在多个旋转速率下以魔角旋转获得的〜（129）Xe和〜（19）F NMR光谱进行分析，表明Xe和F磁屏蔽张量是轴向对称的，这取决于晶体的对称性。相对于OXeF_4（纯液体，24℃），各向同性的〜（129）Xe化学位移为-1603±5 ppm，Xe磁屏蔽各向异性Ω为4245±20 ppm，这是对氙化合物直接测量的第一个各向异性。实验确定的氙化学位移张量的平行分量δ_‖= -4433 ppm与δ（Xe（游离原子））相差约1000 ppm，这提供了第一个实验证明相对论效应在核磁屏蔽中起重要作用氙气各向同性间接〜（129）Xe，19F核自旋-自旋耦合常数的符号和幅度都确定为-5560±50 Hz。 〜（19）F NMR谱分析的收率（F）= 150±20 ppm。 ZORA DFT方法已被用于计算相对论和非相对论水平的分离的XeF_2和XeF_4分子的σ（Xe）和σ（F）以及分离的KrF_2分子的σ（Kr）和σ（F）。理论。 Ω（Xe）的自旋轨道相对论DFT结果与实验确定的结果非常吻合，突出了相对论效应的重要性。

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