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Dipolar and Contact Paramagnetic NMR Chemical Shifts in AnIV Complexes with Dipicolinic Acid Derivatives
Inorganic Chemistry ( IF 4.6 ) Pub Date : 2022-06-24 , DOI: 10.1021/acs.inorgchem.2c00845
Md Ashraful Islam 1 , Matthieu Autillo 2 , Laetitia Guérin 2 , Christelle Tamain 2 , Philippe Moisy 2 , Hélène Bolvin 1 , Claude Berthon 2
Affiliation  

Actinide +IV complexes (AnIV = ThIV, UIV, NpIV, and PuIV) with two dipicolinic acid derivatives (DPA and Et-DPA) have been studied by 1H and 13C NMR spectroscopies and first-principles calculations. The Fermi contact and dipolar contributions to the actinide-induced shifts (AIS) are evaluated from a temperature dependence analysis, combined with ab initio results. It allows an experimental estimation of the axial anisotropy of the magnetic susceptibility Δχax and of the hyperfine coupling constants of the NMR-active nuclei. Due to the compactness of the coordination sphere, the magnetic anisotropy of the paramagnetic center is small, and this makes the contact contribution to be the dominant one, even on the remote atoms. The sign of the hyperfine coupling constants and related spin densities is alternating on the nuclei of the ligand cycle, denoting a preponderant spin polarization mechanism. This is well reproduced by unrestricted density functional theory (DFT) calculations. Those values are furthermore slightly decreasing in the actinide series, which indicates a small decrease of the covalency from UIV to PuIV.

中文翻译:

AnIV 配合物与二吡啶甲酸衍生物的偶极和接触顺磁 NMR 化学位移

锕系元素 +IV 配合物(An IV = Th IV、U IV、Np IV和 Pu IV)与两种吡啶二羧酸衍生物(DPA 和 Et-DPA)已通过1 H 和13 C NMR 光谱和第一性原理计算进行了研究。费米接触和偶极对锕系元素引起的位移 (AIS) 的贡献从温度依赖性分析中评估,并结合从头算结果。它允许对磁化率 Δχ ax的轴向各向异性进行实验估计和核磁共振活性核的超精细耦合常数。由于配位球的致密性,顺磁中心的磁各向异性很小,这使得接触贡献占主导地位,即使在远程原子上也是如此。超精细耦合常数和相关自旋密度的符号在配体循环的核上交替出现,表示优势自旋极化机制。不受限制的密度泛函理论 (DFT) 计算很好地再现了这一点。这些值在锕系元素中进一步略有下降,这表明从 U IV到 Pu IV的共价略有下降。
更新日期:2022-06-24
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