电子封装。聚腈法
Towards electron encapsulation. Polynitrile approach
摘要：
有没有可能设计一个超分子笼，它可以像几个溶剂分子在极性液体中合作那样，以同样的方式“溶剂化”多余的电子？概述了两种一般策略的“电子封装”，即电子本地化使用的极性基团安排在（i）内的笼或（ii）外的笼。第二种方法仅限于聚腈。我们证明，后者面临着一个艰巨的问题：电子连接到腈基团形成分子阴离子弯曲的C-C-N片段。由于这种弯曲的能量成本非常高，对于正己烷中的二腈阴离子，电子的结合能非常低，对于单腈，这些结合能更低，并且电子附着的熵非常小。密度泛函理论模拟正己烷中的单腈的电子捕获表明，单腈分子取代的溶剂分子在电子腔，“溶剂化”的电子由他们的甲基。这种“溶剂化电子”类似于多聚体自由基阴离子，其中电子密度（主要）在溶质/溶剂分子中的C 2 p轨道之间共享，而不是作为腔电子存在。这些分子共享过量电子密度的方式类似于这种共享在大的二腈和聚腈阴离子如1，2，4，5，7，8，10，11-八氰基-环十二烷阴离子中发生的方式。这一工作揭示了有机液体“溶剂化电子”概念的局限性。论证了“电子封装”的可行性。"
英文摘要：
Is it possible to design a supramolecular cage that would "solvate" the excess electron in the same fashion in which several solvent molecules do that co-operatively in polar liquids? Two general strategies are outlined for "electron encapsulation," viz. electron localization using polar groups arranged on the (i) inside of the cage or (ii) outside of the cage. The second approach is limited to polynitriles. We demonstrate that the latter faces a formidable problem: the electron attaches to the nitrile groups forming molecular anions with bent C-C-N fragments. Since the energy cost of this bending is very high, for dinitrile anions in n-hexane, the binding energies for the electron are very low and for mononitriles, these binding energies are lower still, and the entropy of electron attachment is anomalously small. Density functional theory modeling of electron trapping by mononitriles in n-hexane suggests that the mononitrile molecules substitute for the solvent molecules at the electron cavity, "solvating" the electron by their methyl groups. Such "solvated electrons" resemble multimer radical anions in which the electron density is shared (mainly) between C 2p orbitals in the solute/solvent molecules, instead of existing as cavity electrons. The way in which the excess electron density is shared by such molecules is similar to the way in which this sharing occurs in large di- and poly- nitrile anions, such as 1,2,4,5,7,8,10,11-octacyano-cyclododecane anion. The work thus reveals limitations of the concept of "solvated electron" for organic liquids. It also demostrates the feasibility of "electron encapsulation."
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