Department of Physics, Virginia Commonwealth University, Richmond, VA, 23284-2000, USA.
Nat Commun. 2018 Jun 15;9(1):2357. doi: 10.1038/s41467-018-04799-0.
Alkali atoms have unusually low ionization energies because their electronic structures have an excess electron beyond that of a filled electronic shell. Quantum states in metallic clusters are grouped into shells similar to those in atoms, and clusters with an excess electron beyond a closed electronic may also exhibit alkali character. This approach based on shell-filling is the way alkali species are formed as explained by the periodic table. We demonstrate that the ionization energy of metallic clusters with both filled and unfilled electronic shells can be substantially lowered by attaching ligands. The ligands form charge transfer complexes where the electronic spectrum is lifted via crystal field like effect. We demonstrate that the effect works for the weakly bound ligand, N-ethyl-2-pyrrolidone (EP = CHNO), and that the effect leads to a dramatic lowering of the ionization energy independent of the shell occupancy of the cluster.
碱金属原子的电离能非常低，因为它们的电子结构比填满电子壳层的原子多一个额外的电子。金属团簇中的量子态类似于原子中的壳层，并且具有超过封闭电子的额外电子的团簇也可能表现出碱金属的性质。这种基于壳层填充的方法是通过元素周期表解释碱金属形成的方式。我们证明，通过附着配体，可以大大降低具有填满和未填满电子壳层的金属团簇的电离能。配体形成电荷转移配合物，其中电子光谱通过类似晶体场的效应被提升。我们证明该效应适用于弱结合配体 N-乙基-2-吡咯烷酮 (EP=CHNO)，并且该效应导致电离能显著降低，而与团簇的壳层占据无关。
