CNR-IMIP, Montelibretti, Rome I-00016, Italy.
Dalton Trans. 2014 Apr 7;43(13):5134-41. doi: 10.1039/c3dt53512f.
The gas phase photoelectron (PE) spectra of LnCp3 (Cp = η-C5H5; Ln = Pr, Nd, Sm), measured with a wide range of photon energy, are reported. Resonances observed in the photon energy regions of 4d to 4f excitation enable identification of ion states resulting from 4f ionization. For all three compounds molecular ion states characteristic of both 4f(n) and 4f(n-1) configurations are observed (Pr, n = 2; Nd, n = 3; Sm, n = 6). The molecular ion ground states have a hole in the uppermost ligand orbital of a' symmetry and are reached by either ligand or f electron ionization. The results are discussed in the context of the previously reported spectra of the Ce, Yb and Lu analogues. For YbCp3 f orbital/ligand interaction is proposed in the molecular ground state and for CeCp3(+) in the molecular ion ground state. For PrCp3 and NdCp3 final state effects are proposed as the origin of the dual configuration structure in their PE spectra. When the contributing orbitals are close in energy the 4f/a' interaction can give rise to significant covalent bonding even in the absence of effective overlap.
LnCp3（Cp = η-C5H5；Ln = Pr、Nd、Sm）的气相光电子（PE）光谱，在宽光子能量范围内进行了测量。在 4d 到 4f 激发的光子能量区域中观察到的共振，能够识别出源自 4f 电离的离子态。对于所有三种化合物，都观察到了特征为 4f(n)和 4f(n-1)构型的分子离子态（Pr，n=2；Nd，n=3；Sm，n=6）。分子离子基态在 a'对称性的最高配体轨道上有一个空穴，通过配体或 f 电子电离达到。结果在先前报道的 Ce、Yb 和 Lu 类似物的光谱背景下进行了讨论。对于 YbCp3，提出了在分子基态中 f 轨道/配体相互作用，对于 CeCp3(+)，则提出了在分子离子基态中 f 轨道/配体相互作用。对于 PrCp3 和 NdCp3，则提出了终态效应是其 PE 光谱中双重构型结构的起源。当贡献轨道能量相近时，即使没有有效的重叠，4f/a'相互作用也可能导致显著的共价键合。
