Sun Gang, Duan Xi-Xin, Liu Chun-Guang
Chemistry and Biology Academy, Beihua University, Jilin, 132013, People's Republic of China.
College of Chemical Engineering, Northeast Dianli University, Jilin, 132012, People's Republic of China.
J Mol Model. 2016 Jan;22(1):21. doi: 10.1007/s00894-015-2879-7. Epub 2016 Jan 5.
The similar molecules [2.2]paracyclophane (22PCP) and 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane (8F22PCP) have both generated considerable synthetic interest since they were first prepared. In this work, the nonlinear optical properties of 22PCP, 8F22PCP, and the related Li-doped systems 22PCP-Li and 8F22PCP-Li (which have a Li atom above 22PCP and 8F22PCP, respectively) were investigated. An analysis of natural bond orbital charges showed that there is greater charge transfer from the Li atom to the benzene rings in 8F22PCP-Li than in 22PCP-Li. The variation in the calculated nucleus independent chemical shift (NICS) value as a function of the distance from the lower benzene ring towards the upper benzene ring was found to be W-shaped for both 22PCP and 22PCP-Li. Moreover, whereas all of the NICS values of 22PCP and 22PCP-Li were markedly negative, all of the NICS values of 8F22PCP and 8F22PCP-Li were either positive or only moderately negative. Calculations of the electro-optical properties of these systems showed that the first hyperpolarizability of 22PCP-Li was noticeably larger than that of 8F22PCP-Li. According to the two-level model, the larger first hyperpolarizability of 22PCP-Li is due to its smaller transition energy.
自首次制备以来，类似的分子[2.2]对环芳烷（22PCP）和1,1,2,2,9,9,10,10-八氟[2.2]对环芳烷（8F22PCP）都引起了相当大的合成兴趣。在这项工作中，研究了22PCP、8F22PCP以及相关的锂掺杂体系22PCP-Li和8F22PCP-Li（分别在22PCP和8F22PCP上方有一个锂原子）的非线性光学性质。自然键轨道电荷分析表明，8F22PCP-Li中从锂原子到苯环的电荷转移比22PCP-Li中更大。对于22PCP和22PCP-Li，计算得到的核独立化学位移（NICS）值随从下苯环到上苯环距离的变化呈W形。此外，22PCP和22PCP-Li的所有NICS值均显著为负，而8F22PCP和8F22PCP-Li的所有NICS值要么为正，要么仅为中度负。这些体系的电光性质计算表明，22PCP-Li的第一超极化率明显大于8F22PCP-Li。根据双能级模型，22PCP-Li较大的第一超极化率是由于其较小的跃迁能。
