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采用PM3半经验分子轨道法, 在几何构型全优化的基础上考察了C_(120)XY (X, Y = O, S)分子和部分离子的稳定性、电子结构和红外光谱. 计算结果表明, 除了C_(120)O_2-和三重态C_(120)O_2-2-离子 外, 在五元环中平均引入一个双键, 体系能量增加约30～42 kJ/mol. 计算还发现, 中性分子和其相应离子几何构型相差不大, 如键长变化小于0.001 nm. 还有, 从氧化物到硫化物前线轨道能级变化很小. C_(120)O_2-2-和C_(120)OS-2的两种异构体的三重态离子均比其单重态离子更为稳定, 这意味着两种离子遵从Hund规则. 振动分析的结果表明C_(120)O_2和C_(120)OS分子的红外图谱与实验结果相符, 三重态C_(120)O_2-2离子的谱图与中性分子的相比较, 吸收峰位置变化很小, 但是振动强度明显增加.
The stability, electronic structure and infrared spectra of C_ (120) XY (X, Y = O, S) and some ions were investigated by using PM3 semi-empirical molecular orbital method. In addition to the C_ (120) O_2- and triplet C_ (120) O_2-2- ions, an average double bond introduced into the five-membered ring increased the energy of the system by about 30-42 kJ / mol. It was also found that the neutral Molecules and their corresponding ion geometries have little difference, for example, bond length variation is less than 0.001 nm. Moreover, the energy levels change from oxide to sulfide frontier orbitals are very small.C_ (120) O_2-2- and C_ (120) The triplet ions of both isomers of OS-2 are more stable than their singlet ions, which implies that the two ions follow the Hund rule. The results of the vibrational analysis show that both C 120 O 2 and C 120 The infrared spectrum of the molecule is consistent with the experimental results. The spectrum of the triplet C_ (120) O_2_2 ion shows little change in the position of absorption peak compared with the neutral molecule, but the vibration intensity increases obviously.