Substituent effects in the benzene dimer are due to direct interactions of the substituents with the unsubstituted benzene.
Substituent effects in the benzene dimer are due to direct interactions of the substituents with the unsubstituted benzene.
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DOI：
10.1021/ja802849j
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发表时间：
2008-08-20
影响因子：
15
通讯作者：
Houk, K. N.
中科院分区：
文献类型：
--
作者：
Wheeler, Steven E.;Houk, K. N.
关于苯二聚体夹层结构中取代基效应的普遍观点是有缺陷的。例如，在Cozzi和他的同事(J. Am.；化学。在苯二聚体中，吸电子取代基通过吸离被取代环π云上的电子密度，降低与非被取代苯的斥力静电相互作用，从而增强了苯二聚体的结合。相反，给电子取代基将多余的电子提供给π-体系，并减弱π-堆积相互作用。我们计算了苯二聚体和24取代二聚体的夹心构型的相互作用能，以及取代苯与全氟苯的夹心配合物。虽然计算出的相互作用能与取代基的σm值有很好的相关性，但相关模型系统的相互作用能表明，这种趋势与取代环无关。相反，观察到的趋势与取代基与未取代环的直接静电和色散相互作用是一致的。
The prevailing views of substituent effects in the sandwich configuration of the benzene dimer are flawed. For example, in the polar/π model of Cozzi and co-workers (J. Am. Chem. Soc. 1992, 114, 5729), electron-withdrawing substituents enhance binding in the benzene dimer by withdrawing electron density from the π-cloud of the substituted ring, reducing the repulsive electrostatic interaction with the non-substituted benzene. Conversely, electron-donating substituents donate excess electrons into the π-system and diminish the π-stacking interaction. We present computed interaction energies for the sandwich configuration of the benzene dimer and 24 substituted dimers, as well as sandwich complexes of substituted benzenes with perfluorobenzene. While the computed interaction energies correlate well with σm values for the substituents, interaction energies for related model systems demonstrate that this trend is independent of the substituted ring. Instead, the observed trends are consistent with direct electrostatic and dispersive interactions of the substituents with the unsubstituted ring.
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影响因子：
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Grimme, Stefan
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