Electron transfer in mixed-valent transition-metal complexes, clusters and materials is ubiquitous in both natural and synthetic systems. The degree to which intervalence charge transfer (IVCT) occurs, dependent on the degree of delocalization, places these within class II or III of the Robin–Day system. In contrast to the d-block, compounds of f-block elements typically exhibit class I behaviour (no IVCT) because of localization of the valence electrons and poor spatial overlap between metal and ligand orbitals. Here, we report experimental and computational evidence for delocalization of 5f electrons in the mixed-valent Pu^III/Pu^IV solid-state compound, Pu₃(DPA)₅(H₂O)₂ (DPA = 2,6-pyridinedicarboxylate). The properties of this compound are benchmarked by the pure Pu^III and Pu^IV dipicolinate complexes, [Pu^III(DPA)(H₂O)₄]Br and Pu^IV(DPA)₂(H₂O)₃·3H₂O, as well as by a second mixed-valent compound, Pu^III[Pu^IV(DPA)₃H_0.5]₂, that falls into class I instead. Metal-to-ligand charge transfer is involved in both the formation of Pu₃(DPA)₅(H₂O)₂ and in the IVCT.

中文翻译：

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a固态化合物中的初始II类混合化合价

混合价过渡金属络合物，簇和材料中的电子转移在天然和合成系统中无处不在。取决于离域化程度，间隔电荷转移（IVCT）发生的程度将其置于Robin-Day系统的II类或III类中。与d-嵌段相反，由于价电子的定位以及金属和配体轨道之间的不良空间重叠，f-嵌段元素的化合物通常表现出I类行为（无IVCT）。在这里，我们报告了5 f电子在混合价Pu ^III / Pu ^IV固态化合物Pu ₃（DPA）_5中离域的实验和计算证据。（H ₂ O）₂（DPA ＝ 2，6-吡啶二甲酸）。该化合物的性质由纯的Pu ^III和Pu ^IV吡啶二羧酸盐络合物[Pu ^III（DPA）（H ₂ O）₄ ] Br和Pu ^IV（DPA）₂（H ₂ O）₃ ·3H ₂ O表征，以及第二种混合价化合物Pu ^III [Pu ^IV（DPA）₃ H _0.5 ] ₂，它属于I类。金属到配体的电荷转移参与Pu ₃（DPA）的形成₅（H ₂ O）₂和在IVCT中。