Mohan Neetha, Suresh Cherumuttathu H
Inorganic and Theoretical Chemistry Section, CSTD, CSIR-National Institute for Interdisciplinary Science and Technology , Trivandrum 695 019, India.
J Phys Chem A. 2014 Jun 19;118(24):4315-24. doi: 10.1021/jp5019422. Epub 2014 Jun 5.
Mono-, di-, and tri-pentafluorobenzyl-substituted hexafluorobenzene (HFB) scaffolds, viz., R(I), R(II), and R(III) are proposed as promising receptors for molecules of chemical, biological, and environmental relevance, viz., N2, O3, H2O, H2O2, F(-), Cl(-), BF4(-), NO3(-), ClO(-), ClO2(-), ClO3(-), ClO4(-), and SO4(2-). The receptor-guest complexes modeled using M06L/6-311++G(d,p) DFT show a remarkable increase in the complexation energy (E(int)) with an increase in the number of fluorinated aromatic moieties in the receptor. Electron density analysis shows that fluorinated aromatic moieties facilitate the formation of large number of lone pair-π interactions around the guest molecule. The lone pair strength of the guest molecules quantified in terms of the absolute minimum (V(min)) of molecular electrostatic potential show that E(int) strongly depends on the electron deficient nature of the receptor as well as strength of lone pairs in the guest molecule. Compared to HFB, R(I) exhibits 1.1-2.5-fold, R(II) shows 1.6-3.6-fold, and the bowl-shaped R(III) gives 1.8-4.7-fold increase in the magnitude of E(int). For instance, in the cases of HFB···F(-), R(I)···F(-), R(II)···F(-), and R(III)···F(-) the E(int) values are -21.1, -33.7, -38.1, and -50.5 kcal/mol, respectively. The results strongly suggest that tuning lone pair-π interaction provides a powerful strategy to design receptors for small molecules and anions.
单、二和三-五氟苄基取代的六氟苯（HFB）支架，即R(I)、R(II)和R(III)，被提议作为对化学、生物和环境相关分子，即N₂、O₃、H₂O、H₂O₂、F⁻、Cl⁻、BF₄⁻、NO₃⁻、ClO⁻、ClO₂⁻、ClO₃⁻、ClO₄⁻和SO₄²⁻有前景的受体。使用M06L/6-311++G(d,p) DFT建模的受体-客体复合物显示，随着受体中氟化芳族部分数量的增加，络合能（E(int)）显著增加。电子密度分析表明，氟化芳族部分促进了客体分子周围大量孤对-π相互作用的形成。根据分子静电势的绝对最小值（V(min)）量化的客体分子的孤对强度表明，E(int)强烈取决于受体的缺电子性质以及客体分子中孤对的强度。与HFB相比，R(I)的E(int)值增加了1.1 - 2.5倍，R(II)显示增加了1.6 - 3.6倍，碗状的R(III)使E(int)值增加了1.8 - 4.7倍。例如，在HFB···F⁻、R(I)···F⁻、R(II)···F⁻和R(III)···F⁻的情况下，E(int)值分别为-21.1、-33.7、-38.1和-50.5 kcal/mol。结果有力地表明，调节孤对-π相互作用为设计小分子和阴离子受体提供了一种强大的策略。
