Structures, Stabilities, and Electronic Properties of Endo- and Exohedral Complexes of T10-Polyhedral Oligomeric Silsesquioxane Cages

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• 作者：Delwar Hossain ; Charles U. Pittman ; Jr. ; Svein Saebo ; Frank Hagelberg
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：May 3, 2007
• 年：2007
• 卷：111
• 期：17
• 页码：6199 - 6206
• 全文大小：454K
• 年卷期：v.111,no.17(May 3, 2007)
• ISSN：1932-7455

文摘

The geometries of endohedral and exohedral complexes of the polyhedral oligomeric silsesquioxane (POSS)cage molecule (HSiO_3/2)₁₀ with the atomic or ionic species Li⁰, Li⁺, Li^-, Na⁰, Na⁺, Na^-, K⁰, K⁺, K^-, F^-, Cl^-,Br^-, He, Ne, and Ar have been optimized at the B3LYP/6-311G(d,p) level of theory. Single point MP2calculations were carried out at the DFT-optimized geometries. The properties of these complexes depend onthe nature of the species encapsulated in, or attached to, the (HSiO_3/2)₁₀ cage. Encapsulation of noble gasatoms (He, Ne, and Ar) has almost no effect on the cage geometry. Encapsulation of alkali metal cations, incontrast, exhibits attractive interactions with cage oxygen atoms and leads to cage shrinkage. Encapsulationof halide ions results in cage expansion. Endohedral Li⁺, Li^-, Na⁺, F^-, Cl^-, and Br^- complexes are energeticallyfavored relative to the separated species. The fluoride ion is predicted to migrate into the (HSiO_3/2)₁₀ cagewith little or no energy barrier with the cage remaining intact. The very low ionization potentials of endohedralLi⁰, Na⁰, and K⁰ complexes suggest that enclosed alkali metals behave like "superalkalis". Overall, many ofthe endohedral complexes with small guest species appear to be viable synthetic targets.