Jia Qingqing, Li Qingzhong, Luo Mo, Li Hai-Bei
School of Ocean, Shandong University Weihai 264209 People's Republic of China
The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University Yantai 264005 People's Republic of China.
RSC Adv. 2018 Nov 20;8(68):38980-38986. doi: 10.1039/c8ra08122k. eCollection 2018 Nov 16.
An investigation of C-F⋯H-O hydrogen bonds in the complexes CH XCH F⋯HO ( = 0, 1, 2; X = H, F, Cl, Br) was performed at the MP2/aug-cc-pVTZ level. We found that the electron-withdrawing halogen substituents on the vicinal carbon cause the fluorine atom, participating in the hydrogen bond formation, to be less negatively charged. Thus, the halogen groups weaken the strength of organofluorine hydrogen bond by inductive effect. The position of the substituents on the vicinal carbon affects the strength of the C-F⋯H-O interaction. Compared with that in other isomers, the electron withdrawing substituent in 1-fluoro-ethane with conformation as well as in 1-fluoro-ethene with configuration much weakens the interaction of C-F⋯H-O due to the hyperconjugative interaction between σ and . By analogy, the electron-donating ones could largely strengthen it. We found that there is a good linear relationship between electron density at the BCP of F⋯H and Wiberg bond indexes (WBI) as well as between natural bond-bond polarizability (NBBP) and WBI, which indicates that the magnitude of NBBP and WBI could be a good indicator of the hydrogen bond strength.
在MP2/aug-cc-pVTZ水平上对配合物CHXCH2F⋯HO（X = 0, 1, 2；X = H, F, Cl, Br）中的C-F⋯H-O氢键进行了研究。我们发现，邻位碳上的吸电子卤素取代基会使参与氢键形成的氟原子带负电程度降低。因此，卤素基团通过诱导效应削弱了有机氟氢键的强度。邻位碳上取代基的位置会影响C-F⋯H-O相互作用的强度。与其他异构体相比，具有反式构象的1-氟乙烷以及具有反式构型的1-氟乙烯中的吸电子取代基由于σ和π之间的超共轭相互作用，大大削弱了C-F⋯H-O的相互作用。类似地，给电子取代基则会大大增强这种相互作用。我们发现，F⋯H的键临界点处的电子密度与维伯格键指数（WBI）之间以及自然键-键极化率（NBBP）与WBI之间存在良好的线性关系，这表明NBBP和WBI的大小可以很好地指示氢键强度。
