Substituent effects in C6F6-C6H5X stacking interactions
Substituent effects in C6F6-C6H5X stacking interactions
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DOI：
10.1021/jo061235h
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发表时间：
2006-12-08
影响因子：
3.6
通讯作者：
Amicangelo, Jay C.
中科院分区：
文献类型：
--
作者：
Gung, Benjamin W.;Amicangelo, Jay C.
用从头算方法在MP2（full）/aug-cc-pVDZ水平上研究了六氟苯取代苯二聚体的平行位移构型和夹心构型，揭示了取代基对π-π相互作用的影响.发现了两种最小能量构型，一种是取代基远离六氟苯环的π面（2a-f），另一种是取代基在六氟苯的π面顶部（3a-f）。较高的结合能被预测为二聚体与π-面（3a-f）上的取代基。所有的夹心二聚体（4a-e）被发现是鞍点的势能面上。一个平行位移的最小能量配置也预测为母复合物，C6 F6-C6 H6，这是在对比的基础上苯和六氟苯的四极矩的预测。平行位移的偏好，而不是三明治配置，是合理的基础上较小的面间距离在前者。平行位移的二聚体中的紧密接触导致更大的结合能。单体的电子密度等值面的形状，建议提供一个指导的芳烃如何相互堆叠的预测。计算了苯胺（3e）和N，N-二甲基苯胺（3f）的C6 F6络合物之间的结合能差异，并提出电荷转移相互作用在后者中起作用。
Parallel displaced and sandwich configurations of hexafluorobenzene-substituted benzene dimers are studied by ab initio molecular orbital methods up to the MP2(full)/aug-cc-pVDZ level of theory to reveal how substituents influence pi-pi interactions. Two minimum energy configurations are found, one with the substituent group away from the pi-face of the hexafluorobenzene ring (2a-f) and the other with the substituent group on top of the pi-face of the hexafluorobenzene (3a-f). Higher binding energies are predicted for dimers with the substituent on the pi-face (3a-f). All sandwich dimers (4a-e) are found to be saddle points on the potential energy surfaces. A parallel-displaced minimum energy configuration is also predicted for the parent complex, C6F6-C6H6, which is in contrast to predictions based on quadrupole moments of benzene and hexafuorobenzene. The preference for the parallel displaced, rather than the sandwich configuration, is rationalized based on the smaller interplanar distance in the former. The closeness of contact in the parallel-displaced dimers leads to greater binding energies. The shape of the electron density isosurface of the monomers is suggested to provide a guide for the prediction of how arenes stack with one another. A large difference in binding energy between the C6F6 complex of aniline (3e) and N,N-dimethylaniline (3f) is calculated, and charge-transfer interactions are suggested to play a role in the latter.