Computational Modeling and Simulation Section, National Institute for Interdisciplinary Science and Technology (CSIR), Trivandrum, India 695019.
J Phys Chem A. 2011 Aug 25;115(33):9300-7. doi: 10.1021/jp205064y. Epub 2011 Aug 3.
A molecular electrostatic potential (MESP) topography based approach has been proposed to quantify the substituent effects on cation-π interactions in complexes of mono-, di-, tri-, and hexasubstituted benzenes with Li(+), Na(+), K(+), and NH(4)(+). The MESP minimum (V(min)) on the π-region of C(6)H(5)X showed strong linear dependency to the cation-π interaction energy, E(M(+)). Further, cation-π distance correlated well with V(min)-π distance. The difference between V(min) of C(6)H(5)X and C(6)H(6) (ΔV(min)) is proposed as a good parameter to quantify the substituent effect on cation-π interaction. Compared to benzene, electron-donating groups stabilize the di-, tri-, and hexasubstituted cation-π complexes while electron-withdrawing groups destabilize them. In multiple substituted complexes, E(M(+)) is almost equal (∼95%) to the sum of the individual substituent contributions (E(M(+)) ≈ Σ(ΔE(M(+)))), suggesting that substituent effect on cation-π interactions is largely additive. The ΔV(min) of C(6)H(5)X systems and additivity feature have been used to make predictions on the interaction energies of 80 multiple substituted cation-π complexes with above 97% accuracy. The average mean absolute deviation of the V(min)-predicted interaction energy, E(M(+))(V) from the calculated E(M(+)) is -0.18 kcal/mol for Li(+), -0.09 kcal/mol for Na(+), -0.43 kcal/mol for K(+), and -0.67 kcal/mol for NH(4)(+), which emphasize the predictive power of V(min) as well as the additive feature of the substituent effect.
一种基于分子静电势（MESP）地形的方法已被提出，用于量化取代基对单、二、三、六取代苯与 Li(+)、Na(+)、K(+)和 NH(4)(+)形成的配合物中阳离子-π相互作用的影响。C(6)H(5)X 的 π 区域上的 MESP 最小值（V(min)）与阳离子-π相互作用能 E(M(+))呈强线性关系。此外，阳离子-π距离与 V(min)-π距离很好地相关。C(6)H(5)X 与 C(6)H(6)之间的 V(min)差值（ΔV(min)）被提议作为量化取代基对阳离子-π相互作用影响的良好参数。与苯相比，供电子基团稳定二、三、六取代阳离子-π配合物，而吸电子基团使它们不稳定。在多取代配合物中，E(M(+))几乎等于（∼95%）各个取代基贡献的总和（E(M(+))≈Σ(ΔE(M(+))))，这表明取代基对阳离子-π相互作用的影响在很大程度上是加和的。C(6)H(5)X 体系的 ΔV(min)和加和特征已被用于对 80 个以上多取代阳离子-π配合物的相互作用能进行预测，准确率超过 97%。V(min)预测的相互作用能 E(M(+))(V)与计算得到的 E(M(+))的平均绝对偏差为 Li(+)为-0.18 kcal/mol，Na(+)为-0.09 kcal/mol，K(+)为-0.43 kcal/mol，NH(4)(+)为-0.67 kcal/mol，这强调了 V(min)的预测能力以及取代基效应的加和特征。
