Anusiewicz Iwona, Freza Sylwia, Bobrowski Maciej, Skurski Piotr
Laboratory of Quantum Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
Department of Technical Physics and Applied Mathematics, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland.
J Chem Phys. 2021 Mar 14;154(10):104302. doi: 10.1063/5.0043805.
Using ab initio electronic structure methods with flexible atomic orbital basis sets, we investigated the electronic structure and stability of reduction products of selected representative cations (C) constituting ionic liquids. We found that an electron attachment to such cations leads to the neutral radicals, whereas a subsequent attachment of another (i.e., excess) electron leads to adiabatically stable anions only in two cases {[P(CH)] and [MeMePyr]}. The possibility of the formation of various dimers (such as CC, CC, and CC) was also considered, and the resulting systems were characterized by predicting their lowest energy structures, ionization potentials, electron affinities, and susceptibilities to the fragmentation process. Among the cations studied, only the [MeMePyr] was found to form a typical Rydberg radical (MeMePyr) and double-Rydberg anion ([MeMePyr]), whereas the remaining cations were predicted to form neutral radicals of a primarily valence (MeMeIm and MePy) or mixed Rydberg-valence [P(CH)] character. Our calculations confirmed the stability of all CC and CC dimers against fragmentation yielding the corresponding monomers (the binding energies of 12.2-20.5 kcal/mol and 11.3-72.3 kcal/mol were estimated for CC and CC dimers, respectively). [(MeMePyr)] was identified as the only adiabatically stable CC dimeric anion having its vertical electron detachment energy of 0.417 eV. We also found that in the [(MeMePyr)] anionic state, three outermost electrons are described by Rydberg orbitals, which results in the (σ)(σ) configuration.
使用具有灵活原子轨道基组的从头算电子结构方法，我们研究了构成离子液体的选定代表性阳离子（C）还原产物的电子结构和稳定性。我们发现，此类阳离子附着一个电子会形成中性自由基，而随后再附着另一个（即多余的）电子仅在两种情况下会形成绝热稳定的阴离子{[P(CH)]和[MeMePyr]}。我们还考虑了形成各种二聚体（如CC、CC和CC）的可能性，并通过预测其最低能量结构、电离势、电子亲和势以及对碎片化过程的敏感性来表征所得体系。在所研究的阳离子中，仅发现[MeMePyr]会形成典型的里德堡自由基（MeMePyr）和双里德堡阴离子（[MeMePyr]），而其余阳离子预计会形成主要为价态（MeMeIm和MePy）或混合里德堡 - 价态[P(CH)]特征的中性自由基。我们的计算证实了所有CC和CC二聚体对碎片化生成相应单体的稳定性（CC和CC二聚体的结合能分别估计为12.2 - 20.5千卡/摩尔和11.3 - 72.3千卡/摩尔）。[(MeMePyr)]被确定为唯一绝热稳定的CC二聚体阴离子，其垂直电子脱离能为0.417电子伏特。我们还发现，在[(MeMePyr)]阴离子状态下，最外层的三个电子由里德堡轨道描述，这导致了(σ)(σ)构型。
