Abstract: 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.

Key words: Nucleus independent chemical shifts, Aromaticity, Sandwich complex