超级卤素作为离子液体的基础,The Journal of Physical Chemistry A

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超级卤素作为离子液体的基础
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2021-03-05 , DOI: 10.1021/acs.jpca.1c00599
Ambrish Kumar Srivastava ₁ , Abhishek Kumar ₂ , Neeraj Misra ₂

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离子液体（ILs）由大型不对称有机阳离子和多种阴离子组成。简单的阴离子（例如卤素）会导致不稳定的IL，因此，IL通常由复杂的阴离子（例如BF ₄和PF _6）组成。这些阴离子恰好属于一种称为超卤素的特殊类别。这促使我们询问是否可以利用超卤素的概念来设计新的离子液体。我们研究了1-丁基-3-甲基咪唑鎓（BMIM）阳离子和典型的超卤素（X）阴离子，例如LiF ₂，BeF ₃，BO ₂，NO ₃，BF ₄和PF _{6的配合物。}包括使用密度泛函理论和分子中原子的量子理论的Cl。我们的ωB97XD/ 6-311 ++ G（d，p）计算表明，BMIM–X络合物是稳定的，其中BMIM向X发生0.90–0.97 e的电荷转移。X的大小增加。这些配合物通过几种离子和/或共价分子内相互作用（H键）稳定。BMIM–X络合物更倾向于解离成离子碎片（BMIM ⁺ + X ^–），而不是中性片段（BMIM + X）。BMIM-X配合物的离解能和能隙与超卤素（X）的电子亲和力密切相关。这些发现不仅揭示了超级卤素作为IL的组成部分，而且还暗示了通过使用具有更高电子亲和力的超级卤素来设计高度稳定的IL的设计。

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Superhalogens as Building Blocks of Ionic Liquids

Ionic liquids (ILs) are composed of large asymmetric organic cations with a wide range of anions. The simple anions, e.g., halogen, result in less stable ILs, and therefore, ILs generally consist of complex anions such as BF₄ and PF₆. These anions coincidently belong to a special class known as superhalogen. This prompted us to enquire whether the concept of superhalogen can be exploited to design new ILs. We study the complexes of 1-butyl-3-methylimidazolium (BMIM) cation and typical superhalogen (X) anions such as LiF₂, BeF₃, BO₂, NO₃, BF₄, and PF₆ including Cl using density functional theory and the quantum theory of atoms in molecule. Our ωB97XD/6-311++G(d,p) calculations suggest that the BMIM–X complexes are stable in which the charge transfer of 0.90–0.97 e takes place from BMIM to X. The charge-transferred tends to delocalize as the size of X increases. These complexes are stabilized by several ionic and/or covalent intramolecular interactions (H-bonds). The BMIM–X complexes prefer to dissociate into ionic fragments (BMIM⁺ + X^–) than neutral fragments (BMIM + X). The dissociation energy and energy gap of BMIM–X complexes are closely related to the electron affinity of superhalogens (X). These findings not only reveal the superhalogens as building blocks of ILs but also suggest the design of highly stable ILs by employing the superhalogens with higher electron affinities.

更新日期：2021-03-18

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