Seymour Jake M, Gousseva Ekaterina, Large Alexander I, Clarke Coby J, Licence Peter, Fogarty Richard M, Duncan David A, Ferrer Pilar, Venturini Federica, Bennett Roger A, Palgrave Robert G, Lovelock Kevin R J
Department of Chemistry, University of Reading, Reading, RG6 6AD, UK.
Diamond Light Source, Didcot, Oxfordshire, OX11 0DE, UK.
Phys Chem Chem Phys. 2021 Sep 29;23(37):20957-20973. doi: 10.1039/d1cp02441h.
Ionic liquid (IL) valence electronic structure provides key descriptors for understanding and predicting IL properties. The ionisation energies of 60 ILs are measured and the most readily ionised valence state of each IL (the highest occupied molecular orbital, HOMO) is identified using a combination of X-ray photoelectron spectroscopy (XPS) and synchrotron resonant XPS. A structurally diverse range of cations and anions were studied. The cation gave rise to the HOMO for nine of the 60 ILs presented here, meaning it is energetically more favourable to remove an electron from the cation than the anion. The influence of the cation on the anion electronic structure (and ) were established; the electrostatic effects are well understood and demonstrated to be consistently predictable. We used this knowledge to make predictions of both ionisation energy and HOMO identity for a further 516 ILs, providing a very valuable dataset for benchmarking electronic structure calculations and enabling the development of models linking experimental valence electronic structure descriptors to other IL properties, electrochemical stability. Furthermore, we provide design rules for the prediction of the electronic structure of ILs.
离子液体（IL）的价电子结构为理解和预测离子液体性质提供了关键描述符。测量了60种离子液体的电离能，并结合X射线光电子能谱（XPS）和同步加速器共振XPS确定了每种离子液体最容易电离的价态（最高占据分子轨道，HOMO）。研究了一系列结构多样的阳离子和阴离子。对于本文介绍的60种离子液体中的9种，阳离子产生了HOMO，这意味着从阳离子中移除一个电子在能量上比从阴离子中移除更有利。确定了阳离子对阴离子电子结构（以及）的影响；静电效应已得到充分理解，并证明具有一致的可预测性。我们利用这些知识对另外516种离子液体的电离能和HOMO身份进行了预测，为基准电子结构计算提供了非常有价值的数据集，并能够开发将实验价电子结构描述符与其他离子液体性质（如电化学稳定性）联系起来的模型。此外，我们提供了预测离子液体电子结构的设计规则。
