杂硼原子簇B_6X^-(X=N,P,As,Sb,Bi)稳定性和芳香性研究

Stability and Aromaticity of B_6X^-(X=N, P, As, Sb, Bi) Clusters

利用Gaussian98程序,采用从头算和密度泛函理论方法,对B6X-(X=N,P,As,Sb,Bi)杂硼原子簇进行了理论研究,优化得到了其稳定平衡构型,讨论了其振动光谱和稳定性等,通过自然键轨道(NBO)、分子轨道(MO)和核独立化学位移(NICS)分析,确定这些杂硼原子簇都有离域的π电子和σ电子成键轨道,满足4n+2电子规则,具有芳香性,与纯B6-或B26-原子簇呈反芳香性不同.

The geometries and chemical bonding of B6Xˉ （ X = N, P, As, Sb, Bi） clusters have been investigated using ab initio and density functional theory computations with MP2, B3LYP and B3PW91 methods. Analytical gradients with the polarized split-valence basis sets （6-311 ＋ G^＊ ） were used for B, N, P, and As. The relativistic effective core potential with the LANL2DZ basis set was chosen for Sb and Bi. It is seems that the very reasonable looking pyramidal minimum structure （C2v symmetry） is the most stable. The analyses of molecular orbital, natural bond orbital, and nucleus-independent chemical shift for these quasi-pyramidal B6 X- systems revealed a double-aromatic character（ π and or）, which had been reported to play an important role in the chemical bonding, structure, and stability of the pure boron clusters.