As-5、[As5M]-、[As5MAs5]2- (M=Ti,Zr, Hf)的结构和芳香性

用密度泛函理论(DFT)研究了As-5、As5M]-和As5MAs5]2- (M=Ti, Zr, Hf)的结构、频率、能量以及芳香性, 详细讨论了体系中不同类型的键和电子如化学键、孤对电子、核电子等对总的核独立化学位移(NICS)的影响. 结果表明, As-5、As5M]-和As5MAs5]2-的基态结构分别具有D5h、C5v和D5h对称性, 而且都具有芳香性. As-5 (D5h)的芳香性主要来源于As—As π键和As—As σ键的作用. As5M]-(C5v)中各种As—M键的NICS分割值占主要优势, 其次是As—As之间形成的σ键. As5TiAs5]2-(D5h)中, As—As π键的作用占主要优势. As5ZrAs5]2-(D5h)中, As—As π键对体系总的NICS贡献相对减小, 而As—Zr键的作用增强. As5HfAs5]2-(D5h)的芳香性主要来自As—Hf键的作用.

Structures and Aromaticities of As-5, [As5M]-, and [As5Mas5]2-(M=Ti, Zr, Hf)

The structures, energies, harmonic vibrational frequencies, and nucleus independent chemical shifts (NICS) of As-5 , As5M]- and As5MAs5]2-(M=Ti, Zr, Hf) were calculated by the density functional theory (DFT) . The dissected NICS of these species were computed to discuss the NICS contributions of the σ bonds, π bonds, lone pairs, and core electrons of As and M atoms. The calculations showed that the ground states of As-5, As5M]-, and As5MAs5]2- were in D5h, C5v, and D5h symmetries, respectively, and they were aromatic with negative NICS values. The dissected NICS indicated that the aromaticity of As-5 (D5h) mainly arised fromthe contributions of As—As π and As—As σ bonds, and the total NICS of As5M]-(C5v) were dominated by the contributions of As—M bonds with the As—As σ bond followed. The total NICS of As5TiAs5]2-(D5h) arised mainly from the As—As π bonds, and in the As5ZrAs5]2-(D5h), the contribution of the As—As π bonds reduced while the contribution of the As—Zr bond increased relatively. In the As5HfAs5]2- (D5h), the aromaticity mainly owed to the effects of the As—Hf bonds.