Chemistry Department, University of Rome "La Sapienza", Piazzale Aldo Moro 5, 00185 Rome Italy.
J Phys Chem B. 2020 Mar 12;124(10):1955-1964. doi: 10.1021/acs.jpcb.9b09703. Epub 2020 Mar 2.
We present a computational analysis of the complex proton-transfer processes in two protic ionic liquids based on phosphorylated amino acid anions. The structure and the short time dynamics have been analyzed via ab initio and semi-empirical molecular dynamics. Given the presence of mobile protons on the side chain, such ionic liquids may represent a viable prototype of highly conductive ionic mediums. The results of our simulations are not entirely satisfactory in this respect. Our results indicate that conduction in these liquids may be limited due to a quick quenching of the proton-transfer processes. In particular, we have found that, while proton migration does occur on very short timescales, the amino groups act as proton scavengers preventing an efficient proton migration. Despite their limits as conductive mediums, we show that these ionic liquids possess an unconventional microscopic structure, where the anionic component is made by amino acid anions that the aforementioned proton transfer has transformed into zwitterionic isomers. This unusual chemical structure is relevant because of the recent use of amino acid-based ionic liquids, such as CO absorbent.
我们提出了基于磷酸化氨基酸阴离子的两种质子离子液体中复杂质子转移过程的计算分析。通过从头算和半经验分子动力学对结构和短时间动力学进行了分析。由于侧链上存在可移动的质子，因此这些离子液体可能代表了高导电性离子介质的可行原型。在这方面，我们模拟的结果并不完全令人满意。我们的结果表明，由于质子转移过程迅速猝灭，这些液体中的传导可能受到限制。具体来说，我们发现，虽然质子迁移确实在非常短的时间尺度上发生，但氨基充当质子清除剂，阻止有效质子迁移。尽管它们作为导电介质存在局限性，但我们表明这些离子液体具有非常规的微观结构，其中阴离子部分由上述质子转移转化为两性离子异构体的氨基酸阴离子组成。由于最近使用了基于氨基酸的离子液体，例如 CO 吸收剂，因此这种不寻常的化学结构很重要。
