Jia Qingqing, Li Hai-Bei, Luo Mo, Wang Jingjing
School of Ocean, Shandong University, Weihai, 264209, People's Republic of China.
J Comput Chem. 2019 Oct 30;40(28):2473-2481. doi: 10.1002/jcc.26022. Epub 2019 Jul 7.
We investigate the effects of the electronic structure of carbon atom on the organofluorine hydrogen bonds, C─F⋯H─F. Our results show that we can modulate the strength of organofluorine hydrogen bonds by adjusting the volume of fluorine atom in C─F via changing the electronic structure of adjacent carbon atoms. Different with the conventional hydrogen bonds, we found that instead of carbon rehybridization and hyperconjugative effects, the magnitude of fluorine atomic volume plays important roles in determining the strength of the C─F⋯H─F organofluorine hydrogen bonds. The lone pair electrons at both the proximal and the vicinal carbon dramatically reinforce the strength of C─F⋯H─F organofluorine hydrogen bond with its interaction energy in the range of about 15-25 kcal/mol, that is, the carbanion-mediated organofluorine hydrogen bond could be very strong. Due to the high electronegativity of fluorine atom, it easily attracts the excess electron from the proximal and vicinal carbon, which results in the increase of its volume and negative charge. The enhanced volume of fluorine atom gives rise to the large polarization energy, and its enhanced negative charge favors the large electrostatic interaction, both of which substantially contribute to making the organofluorine hydrogen bonds strong. © 2019 Wiley Periodicals, Inc.
我们研究了碳原子的电子结构对有机氟氢键C─F⋯H─F的影响。我们的结果表明，通过改变相邻碳原子的电子结构来调整C─F中氟原子的体积，我们可以调节有机氟氢键的强度。与传统氢键不同，我们发现，决定C─F⋯H─F有机氟氢键强度的重要因素不是碳的重新杂化和超共轭效应，而是氟原子体积的大小。近端和邻位碳上的孤对电子通过其约15 - 25千卡/摩尔范围内的相互作用能显著增强了C─F⋯H─F有机氟氢键的强度，也就是说，碳负离子介导的有机氟氢键可能非常强。由于氟原子的高电负性，它很容易从近端和邻位碳吸引多余的电子，这导致其体积和负电荷增加。氟原子体积的增大产生了较大的极化能，其增强的负电荷有利于较大的静电相互作用，这两者都极大地有助于使有机氟氢键变强。© 2019威利期刊公司
