化学
卟啉
含时密度泛函理论
反键分子轨道
原子轨道
密度泛函理论
谱线
电子结构
结晶学
共振(粒子物理)
计算化学
分子物理学
原子物理学
光化学
电子
物理
量子力学
天文
作者
Giampaolo Ricciardi,Angela Rosa,Evert Jan Baerends,Stan A J Van Gisbergen
摘要
The electronic absorption spectra of the bis(porphyrin) sandwich complexes of the metals Zr, Ce, and Th are studied with time-dependent density functional theory (TDDFT). A ground-state electronic structure analysis reveals that the highest occupied one-electron levels are, as expected, composed of the porphyrin a1u and a2u highest occupied orbitals (the Gouterman orbitals), but the level pattern is not simply a pair of low-lying nearly degenerate in-phase combinations and a pair of high-lying approximately degenerate antibonding combinations. Instead, the a1u split strongly and the a2u do not. Since the calculated spectrum agrees very well with experiment, the assignment leaves little doubt that although the experimental spectrum has porphyrin-like features, such as the well-known Q and B bands, the actual composition of the states is rather different from that in porphyrin. In particular the strong mixing of a1u → eg* and a2u → eg* is absent, there is mixing with excitations of non-Gouterman type, and, in Ce, ring to metal charge-transfer transitions play an important role. The composition of the states as calculated in this work does not lead to a classification of the excitations as purely “excitonic” or “charge-resonance”.
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