Nakajo Erika, Masuda Tomohide, Yabushita Satoshi
Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
J Phys Chem A. 2016 Dec 8;120(48):9529-9544. doi: 10.1021/acs.jpca.6b10930. Epub 2016 Nov 22.
We have performed a theoretical analysis of the recently reported photoelectron (PE) spectra of the series of sandwich complex anions Ln(COT) (Ln = La-Lu, COT = 1,3,5,7-cyclooctatetraene), focusing on the Ln dependence of the vertical detachment energies. For most Ln, the π molecular orbitals, largely localized on the COT ligands, have the energy order of e < e < e < e as in the actinide analogues, reflecting the substantial orbital interaction with the Ln 5d and 5p orbitals. Thus, it would be expected that the lanthanide contraction would increase the orbital interaction so that the overlaps between the COT π and Ln atomic orbitals tend to increase across the series. However, the PE spectra and theoretical calculations were not consistent with this expectation, and the details have been clarified in this study. Furthermore, the energy level splitting patterns of the anion and neutral complexes have been studied by multireference ab initio methods, and the X peak splittings observed in the PE spectra only for the middle-range Ln complexes were found to be due to the specific interaction between the Ln 4f and ligand π orbitals of the neutral complexes in e symmetry. Because the magnitude of this 4f-ligand interaction depends critically on the final state 4f electron configuration and the spin state, a significant Ln dependence in the PE spectra is explained.
我们对最近报道的夹心配合物阴离子系列Ln(COT)（Ln = La-Lu，COT = 1,3,5,7-环辛四烯）的光电子（PE）能谱进行了理论分析，重点关注垂直脱附能的Ln依赖性。对于大多数Ln，主要定域在COT配体上的π分子轨道，其能量顺序为e < e < e < e，与锕系类似物中的情况相同，这反映了与Ln 5d和5p轨道的显著轨道相互作用。因此，可以预期镧系收缩会增强轨道相互作用，使得COT π轨道与Ln原子轨道之间的重叠在整个系列中趋于增加。然而，PE能谱和理论计算与这一预期并不一致，本研究已阐明了其中的细节。此外，通过多参考从头算方法研究了阴离子和中性配合物的能级分裂模式，发现仅在中等范围的Ln配合物的PE能谱中观察到的X峰分裂是由于中性配合物中Ln 4f与配体π轨道在e对称性下的特定相互作用。由于这种4f-配体相互作用的大小严重依赖于终态4f电子构型和自旋态，从而解释了PE能谱中显著的Ln依赖性。
