Collaborative Innovation Center of Advanced Nuclear Energy Technology, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China.
Dalton Trans. 2018 Oct 30;47(42):15246-15253. doi: 10.1039/c8dt03303j.
The complexation of hexavalent plutonyl Pu(vi) with N,N,N',N'-tetramethyl-3-oxa-glutar-amide (TMOGA) and its carboxylate analogs, N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) and oxydiacetic acid (ODA), has been studied in 1.0 M NaClO4 by absorption spectrophotometry and density functional theory (DFT). Both 1 : 1 and 1 : 2 complexes of Pu(vi) with TMOGA, DMOGA and ODA have been identified and their stability constants were obtained and compared with those of hexavalent U(vi) and pentavalent Np(v). The resultant stability constants indicate that the ability of the three ligands to complex with Pu(vi) decreases in the order of ODA > DMOGA > TMOGA. While for one given ligand, the stability constants of both the 1 : 1 and 1 : 2 complexes decrease generally in the order U(vi) > Pu(vi) > Np(v). The trends of the complexation strength have been elucidated by the calculated Mulliken atomic charges of the central metal cations. Furthermore, the coordination modes of the Pu(vi) complexes with TMOGA, DMOGA and ODA have been illustrated by analyses of the optical features of the complexes as well as by DFT calculations. The results demonstrate that the 1 : 2 Pu(vi)/TMOGA complex is centrosymmetric, while the 1 : 2 complexes of Pu(vi) with DMOGA and ODA are non-centrosymmetric. Moreover, different coordination modes have been observed in actinyl complexes with the same ligand, suggesting the structurally similar actinyl ions (U(vi), Pu(vi) and Np(v)) could exhibit quite different coordination behavior due to the variation of cation size and electronic structure.
六价钚(vi)与 N,N,N',N'-四甲基-3-氧代戊酰胺(TMOGA)及其羧酸类似物 N,N-二甲基-3-氧代戊二酸(DMOGA)和氧代二乙酸(ODA)的络合作用已通过吸收分光光度法和密度泛函理论(DFT)在 1.0 M NaClO4 中进行了研究。已鉴定出 Pu(vi)与 TMOGA、DMOGA 和 ODA 的 1:1 和 1:2 配合物，并获得了它们的稳定常数，并与六价 U(vi)和五价 Np(v)的稳定常数进行了比较。所得稳定常数表明，三种配体与 Pu(vi)络合的能力按 ODA>DMOGA>TMOGA 的顺序降低。对于给定的配体，1:1 和 1:2 配合物的稳定常数通常按 U(vi)>Pu(vi)>Np(v)的顺序降低。通过计算中心金属阳离子的 Mulliken 原子电荷，阐明了络合强度的趋势。此外，通过分析配合物的光学特征以及通过 DFT 计算，说明了 Pu(vi)与 TMOGA、DMOGA 和 ODA 的配合物的配位方式。结果表明，1:2 Pu(vi)/TMOGA 配合物是中心对称的，而 Pu(vi)与 DMOGA 和 ODA 的 1:2 配合物是非中心对称的。此外，在具有相同配体的锕系元素配合物中观察到不同的配位方式，表明结构相似的锕系元素离子（U(vi)、Pu(vi)和 Np(v)）由于阳离子尺寸和电子结构的变化，可能表现出截然不同的配位行为。
