Institute of Chemical Physics, Beijing Institute of Technology, Beijing, China.
J Mol Model. 2009 Nov;15(11):1329-36. doi: 10.1007/s00894-009-0496-z. Epub 2009 Apr 22.
The equilibrium geometries, total energies, and vibrational frequencies of anions X(2)Y(2)(-) (X = C, Si, Ge and Y = N, P, As) are theoretically investigated with density functional theory (DFT) method. Our calculation shows that for C(2)N(2)(-) species, the D(2h) isomer is the most stable four-membered structure, and for other species the C(2v) isomer in which two X atoms are contrapuntal is the most stable structure at the B3LYP/6-311 +G(*) level. Wiberg bond index (WBI) and negative nucleus-independent chemical shift (NICS) value indicate the existence of delocalization in stable X(2)Y(2)(-) structures. A detailed molecular orbital (MO) analysis further reveals that stable isomers of these species have strongly aromatic character, which strengthens the structural stability and makes them closely connected with the concept of aromaticity.
采用密度泛函理论（DFT）方法对阴离子 X(2)Y(2)(-)（X = C、Si、Ge 和 Y = N、P、As）的平衡几何形状、总能量和振动频率进行了理论研究。我们的计算表明，对于 C(2)N(2)(-) 物种，D(2h)异构体是最稳定的四元结构，而对于其他物种，在 B3LYP/6-311 + G(*) 水平下，两个 X 原子呈对位的 C(2v)异构体是最稳定的结构。Wiberg 键指数（WBI）和负核独立化学位移（NICS）值表明，在稳定的 X(2)Y(2)(-) 结构中存在离域。详细的分子轨道（MO）分析进一步表明，这些物种的稳定异构体具有强烈的芳香性，这增强了结构稳定性，并使它们与芳香性概念紧密相连。
