Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
J Chem Phys. 2013 Apr 28;138(16):164307. doi: 10.1063/1.4801787.
Cerium, praseodymium, and neodymium complexes of 1,3,5,7-cyclooctatetraene (COT) complexes were produced in a laser-vaporization metal cluster source and studied by pulsed-field ionization zero electron kinetic energy spectroscopy and quantum chemical calculations. The computations included the second-order Møller-Plesset perturbation theory, the coupled cluster method with single, double, and perturbative triple excitations, and the state-average complete active space self-consistent field method. The spectrum of each complex exhibits multiple band systems and is assigned to ionization of several low-energy electronic states of the neutral complex. This observation is different from previous studies of M(COT) (M = Sc, Y, La, and Gd), for which a single band system was observed. The presence of the multiple low-energy electronic states is caused by the splitting of the partially filled lanthanide 4f orbitals in the ligand field, and the number of the low-energy states increases rapidly with increasing number of the metal 4f electrons. On the other hand, the 4f electrons have a small effect on the geometries and vibrational frequencies of these lanthanide complexes.
铈、镨和钕的 1,3,5,7-环辛四烯（COT）配合物通过激光蒸发金属团簇源生成，并通过脉冲场电离零电子动能光谱和量子化学计算进行研究。计算包括二级 Møller-Plesset 微扰理论、单、双和微扰三重激发的耦合簇方法以及状态平均完整活性空间自洽场方法。每个配合物的光谱都表现出多个带系，并分配给中性配合物的几个低能电子态的电离。这种观察结果与以前对 M(COT)（M = Sc、Y、La 和 Gd）的研究不同，以前的研究只观察到单个带系。部分填充的镧系元素 4f 轨道在配体场中的分裂导致了多个低能电子态的存在，并且随着金属 4f 电子数的增加，低能态的数量迅速增加。另一方面，4f 电子对这些镧系元素配合物的几何形状和振动频率影响很小。
