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氟是否参与卤素键合?

Does fluorine participate in halogen bonding?

作者信息

Eskandari Kiamars, Lesani Mina

机构信息

Department of Chemistry, Isfahan University of Technology, Isfahan, 84156-83111 (Iran).

出版信息

Chemistry. 2015 Mar 16;21(12):4739-46. doi: 10.1002/chem.201405054. Epub 2015 Feb 4.

Abstract

When R is sufficiently electron withdrawing, the fluorine in the R-F molecules could interact with electron donors (e.g., ammonia) and form a noncovalent bond (F⋅⋅⋅N). Although these interactions are usually categorized as halogen bonding, our studies show that there are fundamental differences between these interactions and halogen bonds. Although the anisotropic distribution of electronic charge around a halogen is responsible for halogen bond formations, the electronic charge around the fluorine in these molecules is spherical. According to source function analysis, F is the sink of electron density at the F⋅⋅⋅N BCP, whereas other halogens are the source. In contrast to halogen bonds, the F⋅⋅⋅N interactions cannot be regarded as lump-hole interactions; there is no hole in the valence shell charge concentration (VSCC) of fluorine. Although the quadruple moment of Cl and Br is mainly responsible for the existence of σ-holes, it is negligibly small in the fluorine. Here, the atomic dipole moment of F plays a stabilizing role in the formation of F⋅⋅⋅N bonds. Interacting quantum atoms (IQA) analysis indicates that the interaction between halogen and nitrogen in the halogen bonds is attractive, whereas it is repulsive in the F⋅⋅⋅N interactions. Virial-based atomic energies show that the fluorine, in contrast to Cl and Br, stabilize upon complex formation. According to these differences, it seems that the F⋅⋅⋅N interactions should be referred to as "fluorine bond" instead of halogen bond.

摘要

当R具有足够强的吸电子能力时,R-F分子中的氟可与电子供体(如氨)相互作用并形成非共价键(F⋅⋅⋅N)。尽管这些相互作用通常被归类为卤键,但我们的研究表明,这些相互作用与卤键之间存在根本差异。虽然卤素周围电子电荷的各向异性分布是卤键形成的原因,但这些分子中氟周围的电子电荷是球形的。根据源函数分析,在F⋅⋅⋅N键临界点处,F是电子密度的汇聚点,而其他卤素是电子密度的源点。与卤键不同,F⋅⋅⋅N相互作用不能被视为“团-空穴”相互作用;氟的价层电荷浓度(VSCC)中不存在空穴。虽然Cl和Br的四极矩是σ-空穴存在的主要原因,但在氟中其可忽略不计。在此,F的原子偶极矩在F⋅⋅⋅N键的形成中起稳定作用。相互作用量子原子(IQA)分析表明,卤键中卤素与氮之间的相互作用是吸引性的,而在F⋅⋅⋅N相互作用中是排斥性的。基于维里定理的原子能量表明,与Cl和Br不同,氟在形成络合物时会稳定下来。根据这些差异,似乎F⋅⋅⋅N相互作用应被称为“氟键”而非卤键。

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