Zheng Xiu-Jun, Pan Qing-Jiang, Dong Yan-Ping
Institute of Food Engineering, Harbin University, Harbin, 150086, China.
Key Laboratory of Functional Inorganic Material Chemistry (Ministry of Education), School of Chemistry and Materials Science, Heilongjiang University, Harbin, 150080, China.
J Mol Model. 2025 May 14;31(6):159. doi: 10.1007/s00894-025-06382-z.
The safe immobilization of radionuclides and the removal of nuclear waste contamination from environment require a thorough understanding of the structures, reaction behaviour and bonding properties of uranium complexes. The cation-cation interaction (CCI), which is also known as the direct actinyl-actinyl bonding interaction, is common only for An(V). A series of binuclear uranyl compounds of Schiff-base polypyrrolic macrocycle (HL), [{(MeR)OUO}(L)] (R = C (1), Si (2), Ge (3), Sn (4) and Pb (5)), featuring CCIs, were systematically investigated by relativistic density functional theory (DFT). Three electronic states of singlet (f), symmetry-broken (ff), and triplet (ff) were calculated, which are labeled as s, s' and t, respectively. Calculations show that the latter two electronic states are energy-degenerate, and much lower in energy than the singlet state. Along compounds 1 t to 5 t, R - O bonds gradually decrease in strength, while U - O bond gradually increases. The quantum theory of atoms in molecule (QTAIM) analyses show that the R - O bond is a covalent one for 1 t, and it turns a covalent/ionic mixed bond in 2 t and 3 t, and is attributed to a dative bond for 4 t and 5 t. From 1 t to 4 t, the HOMO and H-1 orbitals, as well as the π(R - O) and π(U - O) orbitals ascend to the higher energy level. In addition, the shortest bond distance, the maximum vibration wavenumber and the most negative interaction energy E of R - O bond result in the strongest CCI in 1 t among 1 t - 5 t, along with the corresponding lowest reaction free energy. Our calculations reveal that the CCIs are instrumental in enhancing the stability of 1 t - 5 t.
Structural optimizations of all compounds were performed in the gas phase using the Priroda code. A generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhoff (PBE) functional was used. All-electron correlation-consistent double-ς polarized quality basis sets were used in all calculations. Single point calculations have been performed by using the ADF 2012 code on the basis of optimized geometries from Priroda code. The scalar relativistic zero-order regular approximation (ZORA) method and Slater-type triple-zeta polarization (TZP) basis sets were employed. Solvation effects were considered with the Conductor-Like Screening Model (COSMO) and spin-orbit coupling (SOC) effects were explicitly included in the calculations. Single-point calculations were carried out using the Gaussian09 program. Stuttgart relativistic large-core effective core potentials (RLC-ECPs) and corresponding basis sets were applied for U, def2SVP for Sn and Pb, and 6-31G* for other atoms. Then, the quantum theory of atoms in molecules (QTAIM) data were computed with the Multiwfn 3.3.3 package.
放射性核素的安全固定以及从环境中去除核废料污染需要深入了解铀配合物的结构、反应行为和键合性质。阳离子-阳离子相互作用（CCI），也称为直接锕酰-锕酰键合相互作用，仅在An(V)中常见。通过相对论密度泛函理论（DFT）系统研究了一系列具有CCI的席夫碱聚吡咯大环（HL）双核铀酰化合物[{(MeR)OUO}(L)]（R = C (1)、Si (2)、Ge (3)、Sn (4) 和Pb (5)）。计算了单重态（f）、对称破缺态（ff）和三重态（ff）三种电子态，分别标记为s、s'和t。计算表明，后两种电子态能量简并，且能量比单重态低得多。沿着化合物1 t到5 t，R - O键强度逐渐降低，而U - O键逐渐增强。分子中的原子量子理论（QTAIM）分析表明，R - O键在1 t中是共价键，在2 t和3 t中变为共价/离子混合键，在4 t和5 t中归因于配位键。从1 t到4 t，最高占据分子轨道（HOMO）和H - 1轨道以及π(R - O)和π(U - O)轨道上升到更高能级。此外，R - O键的最短键距、最大振动波数和最负相互作用能E导致1 t在1 t - 5 t中具有最强的CCI，同时具有相应的最低反应自由能。我们的计算表明，CCI有助于提高1 t - 5 t的稳定性。
使用Priroda代码在气相中对所有化合物进行结构优化。采用了Perdew - Burke - Ernzerhoff（PBE）泛函的广义梯度近似（GGA）。所有计算均使用全电子相关一致双ς极化质量基组。基于Priroda代码优化后的几何结构，使用ADF 2012代码进行单点计算。采用标量相对论零阶正则近似（ZORA）方法和斯莱特型三重ζ极化（TZP）基组。使用导体类屏蔽模型（COSMO）考虑溶剂化效应，并在计算中明确包含自旋轨道耦合（SOC）效应。使用Gaussian09程序进行单点计算。对U应用斯图加特相对论大核有效核势（RLC - ECPs）和相应的基组，对Sn和Pb应用def2SVP，对其他原子应用6 - 31G*。然后，使用Multiwfn 3.3.3软件包计算分子中的原子量子理论（QTAIM）数据。
