Jennifer G Abigail, Gao Yang, Schreckenbach Georg, Varathan Elumalai
Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Chennai 603203, Tamil Nadu, India.
Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada.
Dalton Trans. 2022 Jul 5;51(26):10006-10019. doi: 10.1039/d2dt01142e.
The separation of minor actinides in their dioxocation (, actinyl) form in high-valence oxidation states requires efficient ligands for their complexation. In this work, we evaluate the complexation properties of actinyls including americyl, curyl, berkelyl, and californyl in their pentavalent and hexavalent oxidation states with the dipyriamethyrin ligand (L) using density functional theory calculations. The calculated bond parameters show shorter AnO bonds with covalent character and longer An-N bonds with ionic character. The bonding between the actinyl cation and the ligand anion shows a flow of charges from the ligand to actinyl in all [AnO-L] complexes. However, across the series, backdonation of charges from the metal to the ligand becomes prominent and stabilizes the complexes. The thermodynamic parameters in the gas phase and solution suggest that the complex formation reaction is spontaneous for [CfO-L] complexes and spontaneous at elevated temperatures (>298.15 K) for all other complexes. Spin-orbit corrections have a quantitative impact while the overall trend remains the same. Energy decomposition analysis (EDA) reveals that the interaction between actinyl and the ligand is mainly due to electrostatic contributions that decrease from Am to Cf along with an increase in orbital contributions due to the backdonation of charges from the actinyl metal center to the ligand that greatly stabilizes the Cf complex. The repulsive Pauli energy contribution is observed to increase in the case of [AnO-L] complexes from Am to Cf while a decrease is observed among [AnO-L] complexes, showing minimum repulsion in [CfO-L] complex formation. Overall, the hexavalent actinyl complexes show greater stability (increasing from Am to Cf) than their pentavalent counterparts.
在高价氧化态下以二氧阳离子（酰基）形式分离次锕系元素需要高效的配体进行络合。在这项工作中，我们使用密度泛函理论计算评估了五价和六价氧化态下的酰基，包括镅酰、锔酰、锫酰和锎酰与二嘧啶甲噻啉配体（L）的络合性质。计算得到的键参数显示，具有共价性质的AnO键较短，具有离子性质的An-N键较长。在所有[AnO-L]络合物中，酰基阳离子与配体阴离子之间的键合显示出电荷从配体流向酰基。然而，在整个系列中，从金属到配体的电荷反馈变得显著，并使络合物稳定。气相和溶液中的热力学参数表明，[CfO-L]络合物的络合形成反应是自发的，而所有其他络合物在高温（>298.15 K）下是自发的。自旋轨道校正具有定量影响，而总体趋势保持不变。能量分解分析（EDA）表明，酰基与配体之间的相互作用主要归因于静电贡献，该贡献从Am到Cf逐渐减小，同时由于电荷从酰基金属中心反馈到配体而导致的轨道贡献增加，这极大地稳定了Cf络合物。在[AnO-L]络合物中，从Am到Cf观察到排斥性泡利能量贡献增加，而在[AnO-L]络合物中观察到减少，在[CfO-L]络合物形成中显示出最小排斥。总体而言，六价酰基络合物比其五价对应物表现出更高的稳定性（从Am到Cf增加）。
