Theoretical Investigations of Geometry, Electronic Structure and Stability of UO6: Octahedral Uranium Hexoxide and Its Isomers
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- 作者：Hai Xiao ; Han-Shi Hu ; W. H. Eugen Schwarz ; Jun Li
- 刊名：Journal of Physical Chemistry A
- 出版年：2010
- 出版时间：August 26, 2010
- 年：2010
- 卷：114
- 期：33
- 页码：8837-8844
- 全文大小：292K
- 年卷期：v.114,no.33(August 26, 2010)
- ISSN：1520-5215
文摘
The existence of a novel octahedral UO6 complex had been suggested by Pyykk et al. [Pyykk, P.; Runeberg, N.; Straka, M.; Dyall, K. G. Chem. Phys. Lett. 2000, 328, 415]. We have now investigated the stability, the geometric and electronic structures, and the vibrations of various UO6 molecules, using spin−orbit density functional and scalar-relativistic coupled-cluster approaches. We find four different (meta-)stable species, namely 3D2h-UO2(η2-O2•)2 at lowest energy, 3C2v-UO4•(η2-O2•) and 1D3-U(η2-O2)3 at medium energies, and 1Oh-UO6 at highest energy. The decay of Oh-UO6 occurs via an activated spin-flip mechanism. The UO6 species correspond to local minima on singlet and triplet energy surfaces and might be trapped in noble gas matrices. Experimentally, the four species might be identified through their vibrational spectra. Uranium is best described as coordinated by oxygen atoms in various oxidation states as oxo O2−, oxido(1) O•−, peroxido O22−, and superoxido O2•− ligands. The occurrence of monovalent oxygen is remarkable. The resulting characterization of the central ion as UVI in all four cases does not fully reflect the electronic differences, nor the “valence-activity” of the U-6p6 semicore shell.