摘要/Abstract

非水溶液体系的锕系元素化学是一个极具挑战性的前沿研究领域, 近年来在分子磁性、多重键以及小分子活化等方面获得了迅速发展. 化学键是化学科学中最重要的基本概念之一, 而金属-配体多重键是该领域重要的研究内容. 多重键的形成与锕系元素的电子结构密切相关, 相对论效应使得锕系元素的s轨道和p轨道收缩, 轨道能量降低, 收缩的s和p轨道增加了对核电荷的屏蔽效应, 从而使d和f轨道具有一定的延展性和不稳定性. 这种不稳定性降低了5f电子的结合能, 电子更容易离去, 可使锕系元素具有丰富的氧化态. 由于较高的主量子数和相对论效应, 锕系元素的5f轨道具有更大的径向延展, 在锕系元素中5f轨道的电子行为影响较大. 目前, 锕系金属-配体多重键因其独特的成键方式和电子结构特征而受到科学家的广泛关注, 在合成和分离方面存在极大的挑战, 研究锕系-配体多重键将有助于我们了解它们的电子结构和反应性. 基于口袋型拓扑结构的三脚架配体被广泛地应用于锕系-配体多重键的研究, 这为探索锕系元素的5f电子结构和锕系多重键丰富的化学行为提供了重要支撑. 本综述总结了近年来基于三脚架配体构筑的锕系-配体多重键的研究进展, 并对未来进行了展望.
关键词: 锕系元素, 三脚架配体, 配合物, 锕系-配体多重键, 小分子活化
Nonaqueous actinide chemistry is a challenging frontier field, which has made rapid progress in molecular magnetism, multiple bonds and small molecular activation in recent years. Chemical bond is an important basic concept in chemical science, and metal-ligand multiple bond becomes important research content in this field. The formation of multiple bonds is closely related to the electronic configuration of actinides. The s and p-orbitals of actinides contract toward the nucleus and thus produce lower energy level, which increase the shielding effect on nuclear charge. This leads to indirect relativistic effects where the d and f-orbitals experience expansion and destabilization. This destabilization decreases the binding energy of 5f electrons and make them more easily to leave, giving rise to a large range of available oxidation states. Due to higher principle quantum number and relativistic effects, the 5f orbitals of actinides have a much greater radial extension, and the electronic effect of 5f orbitals has a greater influence. At present, the research of actinide-ligand multiple bonds has become one of the most remarkable fields in actinide chemistry and received extensive attention. It is a great challenge to synthesize and separate compounds with actinide-ligand multiple bonds due to their strong radioactivity and toxicity and complex electronic structures. To study actinide-ligand multiple bonds, especially double- and triple-bonded complexes, will assist us to understand their electronic structure, reactivity and physical properties such as electrical conductivity, magnetism, and photochemistry. Tripodal ligands with pocket topology have been widely used in the research of actinide-ligand multiple bonds. This gives a window into exploring the diverse chemical behavior of actinide multiple bonds and observing how actinides can utilize its 5f electrons to exhibit interesting and novel chemistry. The research progress of actinide-ligand multiple bonds based on tripodal ligand is summarized in this review, and the prospect of this field is prognosticated.
Key words: actinide element, tripodal ligand, coordination complex, actinide-ligand multiple bond, small molecule activation


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