11B Nuclear Spin–Electron Spin Interactions in 11B MAS NMR Spectra of Paramagnetic Metal Borohydrides,The Journal of Physical Chemistry C

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11B Nuclear Spin–Electron Spin Interactions in 11B MAS NMR Spectra of Paramagnetic Metal Borohydrides
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-12-22 , DOI: 10.1021/acs.jpcc.0c09829
Jørgen Skibsted ₁ , SeyedHosein Payandeh ₁ , Morten B. Ley ₁ , Torben R. Jensen ₁

Affiliation

Isotropic and anisotropic couplings between the ¹¹B nuclear spin and the electron spin of paramagnetic electrons are observed in ¹¹B MAS NMR spectra of α-Pr(BH₄)₃ and LiCe(BH₄)₃Cl. The ¹¹B NMR spectra of the central and satellite transitions are strongly influenced by the anisotropic nuclear spin–paramagnetic electron spin dipole–dipole interaction, which affects the spectra in a similar manner as the ¹¹B chemical shift anisotropy. The ¹¹B MAS NMR spectra are analyzed numerically, considering the quadrupole interaction and the anisotropic paramagnetic electron–nuclear spin dipole coupling along with the relative orientation of the two tensorial interactions. The observed isotropic shifts (δ_obs) show a linear dependency with the inverse temperature for both compounds, indicating that δ_obs is dominated by the contribution from the isotropic hyperfine shift. A similar temperature dependency is observed for the paramagnetic shift anisotropy for α-Pr(BH₄)₃. The isotropic and anisotropic paramagnetic interactions are approximately 5 and 4 times larger for α-Pr(BH₄)₃ as compared to LiCe(BH₄)₃Cl. This reflects mainly the difference in electron spin for the Pr³⁺ and Ce³⁺ ions and that the B site in α-Pr(BH₄)₃ has two Pr³⁺ ions within a 3 Å distance, whereas boron in LiCe(BH₄)₃Cl only has a single Ce³⁺ site within this distance.

中文翻译：

顺磁性金属硼氢化物的¹¹ B MAS NMR光谱中的¹¹ B核自旋-电子自旋相互作用

在α-Pr（BH ₄）₃和LiCe（BH ₄）₃ Cl的¹¹ B MAS NMR光谱中观察到¹¹ B核自旋与顺磁性电子的电子自旋之间的各向同性和各向异性耦合。中心和卫星跃迁的¹¹ B NMR光谱受到各向异性核自旋-顺磁电子自旋偶极-偶极相互作用的强烈影响，这以与¹¹ B化学位移各向异性相似的方式影响光谱。在¹¹考虑到四极相互作用和各向异性的顺磁电子-核自旋偶极偶合以及两个张量相互作用的相对取向，对B MAS NMR谱进行了数值分析。观察到的各向同性位移（_δobs）与两种化合物的逆温度呈线性关系，表明_δobs由各向同性超精细位移的贡献所决定。对于α-Pr（BH ₄）₃的顺磁位移各向异性观察到相似的温度依赖性。与LiCe（BH ₄）相比，α-Pr（BH ₄）₃的各向同性和各向异性顺磁相互作用分别大约大5到4倍₃ Cl。这主要反映了Pr ³⁺和Ce ³⁺离子的电子自旋差异，以及α-Pr（BH ₄）₃中的B位在3Å距离内有两个Pr ³⁺离子，而LiCe（BH）中的硼₄）₃ Cl在此距离内仅具有一个Ce ³⁺位点。

更新日期：2021-01-14

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