Role of O Substitution in Expanded Porphyrins on Uranyl Complexation: Orbital- and Density-Based Analyses,Inorganic Chemistry

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Role of O Substitution in Expanded Porphyrins on Uranyl Complexation: Orbital- and Density-Based Analyses
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2021-09-29 , DOI: 10.1021/acs.inorgchem.1c01981
Saparya Chattaraj _{1,

2} , Arunasis Bhattacharyya _{2,

3} , Biswajit Sadhu ₁

Affiliation

Search for new U(VI) sequestering macrocyclic ligands is an important area of research due to manifold applications. Besides hard- or soft-donor-based ligands, mixed-donor ligands are also gaining popularity in achieving optimized performances. However, how the combination of hard–soft-donor centers alters the bonding interactions with U(VI) is still not well-understood. Moreover, a consensus is yet to be reached on the nature and role of underlying covalent interactions in mixed N,O-donor ligands. In this work, using the relativistic density functional theory (DFT), we attempted to address these intriguing issues by investigating the subtle change in bonding characteristics of the uranyl ion upon binding with an expanded porphyrin, viz. sapphyrin, with subsequent O substitutions at the cavity. The results obtained from a range of modern analysis tools suggest that in the O-substituted sapphyrin variants, UO₂²⁺ prefers to bind with N over O, and an increase in the number of O-donor sites at the cavity prompts UO₂²⁺ to have a better interaction with the rest of the N-donor-centers. Although O donors are involved in more numbers of mixed molecular orbitals, the variation in the amplitude of overlap and the better σ-donation ability favor N to have stronger bonding interactions with uranyl. Molecular orbital (MO) and density of states (DOS) analyses show favorable participation of U(d), and the involvement of U(f) orbitals in bonding is of a low extent but non-negligible. Although electrostatic interaction dominates at U–O/N bonds in the equatorial plane, the quantum theory of atoms in molecules descriptors, MO analysis, and overlap-integral calculations confirm the presence of underlying near-degeneracy-driven covalent interactions.

中文翻译：

O 取代在扩展卟啉中对铀酰络合的作用：基于轨道和密度的分析

由于多种应用，寻找新的 U(VI) 螯合大环配体是一个重要的研究领域。除了基于硬或软供体的配体，混合供体配体在实现优化性能方面也越来越受欢迎。然而，硬-软-供体中心的组合如何改变与 U(VI) 的键合相互作用仍不清楚。此外，尚未就混合 N，O 供体配体中潜在共价相互作用的性质和作用达成共识。在这项工作中，使用相对论密度泛函理论 (DFT)，我们试图通过研究铀酰离子与膨胀卟啉结合后的键合特性的细微变化来解决这些有趣的问题，即。蓝宝石，随后在空腔处发生 O 取代。₂²⁺更喜欢与 N 结合而不是 O，空腔中 O 供体位点数量的增加促使 UO ₂²⁺与其他 N 个供体中心进行更好的互动。尽管 O 供体涉及更多数量的混合分子轨道，但重叠幅度的变化和更好的 σ 供体能力有利于 N 与铀酰具有更强的键合相互作用。分子轨道 (MO) 和态密度 (DOS) 分析显示 U(d) 的有利参与，并且 U(f) 轨道在键合中的参与程度较低但不可忽略。尽管静电相互作用在赤道平面的 U-O/N 键中占主导地位，但分子描述符中原子的量子理论、MO 分析和重叠积分计算证实了潜在的近简并驱动的共价相互作用的存在。

更新日期：2021-10-18

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