Gunther S Olivia, Qiao Yusen, Smith Patrick W, Ciccone Sierra R, Ditter Alexander S, Huh Daniel N, Moreau Liane M, Shuh David K, Sun Taoxiang, Arnold Polly L, Booth Corwin H, de Jong Wibe A, Evans William J, Lukens Wayne W, Minasian Stefan G
Chemical Sciences Division, Lawrence, Berkeley National Laboratory Berkeley CA 94720 USA
Department of Chemistry, University of California Irvine CA 92697 USA.
Chem Sci. 2024 Jun 11;15(32):12667-12675. doi: 10.1039/d4sc01300j. eCollection 2024 Aug 14.
Traditional models of lanthanide electronic structure suggest that bonding is predominantly ionic, and that covalent orbital mixing is not an important factor in determining magnetic properties. Here, 4f orbital mixing and its impact on the magnetic susceptibility of Cp'Eu (Cp' = CHSiMe) was analyzed experimentally using magnetometry and X-ray absorption spectroscopy (XAS) methods at the C K-, Eu M-, and L-edges. Pre-edge features in the experimental and TDDFT-calculated C K-edge XAS spectra provided unequivocal evidence of C 2p and Eu 4f orbital mixing in the π-antibonding orbital of a' symmetry. The charge-transfer configurations resulting from 4f orbital mixing were identified spectroscopically by using Eu M-edge and L-edge XAS. Modeling of variable-temperature magnetic susceptibility data showed excellent agreement with the XAS results and indicated that increased magnetic susceptibility of Cp'Eu is due to removal of the degeneracy of the F excited state due to mixing between the ligand and Eu 4f orbitals.
传统的镧系元素电子结构模型表明，其键合主要是离子性的，并且共价轨道混合在决定磁性方面不是一个重要因素。在此，使用磁强计以及在碳K边、铕M边和L边的X射线吸收光谱（XAS）方法，对Cp'Eu（Cp' = CHSiMe）的4f轨道混合及其对磁化率的影响进行了实验分析。实验和含时密度泛函理论（TDDFT）计算的碳K边XAS光谱中的前缘特征提供了明确证据，证明在a'对称的π反键轨道中存在碳2p和铕4f轨道混合。通过使用铕M边和L边XAS，光谱鉴定了由4f轨道混合产生的电荷转移构型。变温磁化率数据的建模与XAS结果显示出极好的一致性，并表明Cp'Eu磁化率的增加是由于配体和铕4f轨道之间的混合消除了F激发态的简并性。
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