氟代苯阳离子的理论研究

用B3LYP方法及6-311G(d，p)和6-311 G(d，p)基组，对十二种氟代苯阳离子做了理论研究，优化了它们的电子基态的结构，计算了对应分子的垂直电离势(VIP)和绝热电离势(AIP)．依据Jahn．Teller理论，计算确定了1，3，5-C6H3F^ 3和C6F^ 6离子分别具有C2v(2↑B)和D2h(2↑B2g)结构(对应分子分别为D3h和D6h结构)．其余十个离子的构型的对称点群与对应分子相同，但构型参数值有明显差别．自然布居分析计算表明这些离子的正电荷主要分布在与F原子相连的C原子和各H原子上．B3LYP／6-311 G(d，p)级别上计算的各氟代苯分子的VIP和AIP值和实验值符合得很好．

Theoretical Study of Fluorinated Benzene Cations

The C 6H 5F +, o C 6H 4F + 2, m C 6H 4F + 2, p C 6H 4F + 2, 1,2,3 C 6H 3F + 3, 1,2,4 C 6H 3F + 3, 1,3,5 C 6H 3F + 3, 1,2,3,4 C 6H 2F + 4, 1,2,3,5 C 6H 2F + 4, 1,2,4,5 C 6H 2F + 4, C 6HF + 5 and C 6F + 6 cations were studied by using the DFT B3LYP method in conjunction with the 6 311G (d,p) and 6 311+G (d,p) basis sets. The ground state geometries of these cations were predicted. The 1,3,5 C 6H 3F + 3 and C 6F + 6 ions are the Jahn Teller active species, and they are predicted to have C 2v and D 2h structures, in contrast with the D 3h and D 6h structures of their parent molecules, respectively. Differences in geometry between the cations and their parent molecules were examined. Natural population analysis calculations for these cations indicate that the positive charge resides mainly at the C atom(s) connecting with the F atom(s) and at the H atoms. The B3LYP calculations with the 6 311+G (d,p) basis predict vertical and adiabatic ionization potential values of the fluorinated benzene molecules in good agreement with the experimental values.