Structure and aromaticity of and Sb5M (M=Li, Na, and K) clusters

Abstract: The equilibrium geometries, electronic structures, harmonic vibrational frequencies, and nucleus independent chemical shifts (NICS) of and Sb5M (M=Li, Na, and K) clusters are calculated by the density functional theory (DFT) method. Our calculation show that the species has the aromatic planar cyclic D 5h structure and the Sb5M species have the pyramidal C 5v structures as the ground states, and the unit preserves its structural and electronic integrity in forming the Sb5M complexes. Molecular orbital analysis and NICS show that the planar anion satisfies the Hükcel rule of 4n +2π electrons and magnetic criteria for aromaticity with six delocalized π electrons and negative NICS values. The dissected NICS suggests that the aromaticity of and Sb5M (C 5v ) arise primarily from the contributions of Sb–Sb π bonds, Sb–Sb σ bonds, and the NICS distributions and contributions, and their changing tendencies of the Sb5M (C 5v ) species are similar to the isolated anion. [Copyright &y& Elsevier]