Busato Matteo, Lapi Andrea, D'Angelo Paola, Melchior Andrea
Dipartimento di Chimica, Università di Roma "La Sapienza", Piazzale Aldo Moro 5, 00185 Roma, Italy.
DPIA, Laboratorio di Scienze e Tecnologie Chimiche, Università di Udine, Via del Cotonificio 108, 33100 Udine, Italy.
J Phys Chem B. 2021 Jun 24;125(24):6639-6648. doi: 10.1021/acs.jpcb.1c03395. Epub 2021 Jun 10.
Molecular dynamics (MD) simulations and X-ray absorption spectroscopy (XAS) have been combined to study the coordination of the Co and Ni ions in ionic liquids (ILs) based on the bis(trifluoromethylsulfonyl)imide ([TfN]) anion and having different organic cations, namely, 1-butyl-3-methylimidazolium ([Cmim]), 1,8-bis(3-methylimidazolium-1-yl)octane ([C(mim)]), ,,-trimethyl--(2-hydroxyethyl)ammonium ([choline]), and butyltrimethylammonium ([BTMA]). Co and Ni K-edge XAS data have been collected on 0.1 mol L Co(TfN) and Ni(TfN) solutions and on the metallic salts. MD simulations have been carried out to obtain structural information on the metal ion coordination. The analysis of the extended X-ray absorption fine structure (EXAFS) spectra of the solutions has been carried out based on the atomistic description provided by MD, and the studied ILs have been found to be able to dissolve both the Co(TfN) and Ni(TfN) salts giving rise to a different structural arrangement around the metal ions as compared to the solid state. The combined EXAFS and MD results showed that the Co and Ni ions are surrounded by a first solvation shell formed by six [TfN] anions, each coordinating in a monodentate fashion by means of the oxygen atoms. The nature of the IL organic cation has little or no influence on the overall spatial arrangement of the [TfN] anions, so that stable octahedral complexes of the type [M(TfN)] (M = Co, Ni) have been observed in all the investigated ILs.
分子动力学（MD）模拟和X射线吸收光谱（XAS）已被结合起来，用于研究基于双（三氟甲基磺酰）亚胺（[TfN]）阴离子且具有不同有机阳离子的离子液体（ILs）中Co和Ni离子的配位情况，这些有机阳离子分别为1-丁基-3-甲基咪唑鎓（[Cmim]）、1,8-双（3-甲基咪唑鎓-1-基）辛烷（[C(mim)]）、三甲基-（2-羟乙基）铵（[胆碱]）和丁基三甲基铵（[BTMA]）。已收集了0.1 mol/L Co(TfN)和Ni(TfN)溶液以及金属盐的Co和Ni K边XAS数据。进行了MD模拟以获得关于金属离子配位的结构信息。基于MD提供的原子描述对溶液的扩展X射线吸收精细结构（EXAFS）光谱进行了分析，发现所研究的离子液体能够溶解Co(TfN)和Ni(TfN)盐，与固态相比，在金属离子周围产生了不同的结构排列。EXAFS和MD的联合结果表明，Co和Ni离子被由六个[TfN]阴离子形成的第一溶剂化壳包围，每个阴离子通过氧原子以单齿方式配位。离子液体有机阳离子的性质对[TfN]阴离子的整体空间排列几乎没有影响，因此在所有研究的离子液体中都观察到了[M(TfN)]（M = Co，Ni）类型的稳定八面体配合物。
