A relativistic density functional theory (DFT) study is reported which aims to understand the complexation chemistry of An4+ ions (An = Th, U, Np, and Pu) with a potential decorporation agent, 5‐LIO(Me‐3,2‐HOPO). The calculations show that the periodic change of the metal binding free energy has an excellent correlation with the ionic radii and such change of ionic radii also leads to the structural modulation of actinide–ligand complexes. The calculated structural and binding parameters agree well with the available experimental data. Atomic charges derived from quantum theory of atoms in molecules (QTAIM) and natural bond order (NBO) analysis shows the major role of ligand‐to‐metal charge transfer in the stability of the complexes. Energy decomposition analysis, QTAIM, and electron localization function (ELF) predict that the actinide–ligand bond is dominantly ionic, but the contribution of orbital interaction is considerable and increases from Th4+ to Pu4+. A decomposition of orbital contributions applying the extended transition state‐natural orbital chemical valence method points out the significant π‐donation from the oxygen donor centers to the electron‐poor actinide ion. Molecular orbital analysis suggests an increasing trend of orbital mixing in the context of 5f orbital participation across the tetravalent An series (Th‐Pu). However, the corresponding overlap integral is found to be smaller than in the case of 6d orbital participation. An analysis of the results from the aforementioned electronic structure methods indicates that such orbital participation possibly arises due to the energy matching of ligand and metal orbitals and carries the signature of near‐degeneracy driven covalency.

中文翻译：

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四价锕系离子与潜在锕系脱模剂 5-LIO(Me-3,2-HOPO) 的周期趋势和络合化学：相对论密度泛函理论探索

报道了一项相对论密度泛函理论 (DFT) 研究，旨在了解 An4+ 离子（An = Th、U、Np 和 Pu）与潜在的脱色剂 5-LIO(Me-3,2-HOPO) 的络合化学）。计算表明，金属结合自由能的周期性变化与离子半径具有极好的相关性，离子半径的这种变化也导致锕系 - 配体配合物的结构调制。计算出的结构和结合参数与可用的实验数据非常吻合。源自分子中原子量子理论 (QTAIM) 和自然键序 (NBO) 分析的原子电荷表明配体到金属的电荷转移在配合物稳定性中的主要作用。能量分解分析，QTAIM，和电子定位函数 (ELF) 预测锕系 - 配体键主要是离子键，但轨道相互作用的贡献相当大，并且从 Th4+ 到 Pu4+ 增加。应用扩展过渡态-自然轨道化学价方法对轨道贡献的分解指出了从氧供体中心到缺电子的锕系离子的显着 π 供体。分子轨道分析表明，在四价 An 系列 (Th-Pu) 中 5f 轨道参与的背景下，轨道混合有增加的趋势。然而，发现相应的重叠积分小于 6d 轨道参与的情况。