Bejaoui Younes K J, Philippi Frederik, Stammler Hans-Georg, Radacki Krzysztof, Zapf Ludwig, Schopper Nils, Goloviznina Kateryna, Maibom Kristina A M, Graf Roland, Sprenger Jan A P, Bertermann Rüdiger, Braunschweig Holger, Welton Tom, Ignat'ev Nikolai V, Finze Maik
Julius-Maximilians-Universität Würzburg, Institut für Anorganische Chemie, Institut für Nachhaltige Chemie & Katalyse mit Bor (ICB) Am Hubland 97074 Würzburg Germany
Imperial College London, Department of Chemistry, Molecular Sciences Research Hub White City Campus London W12 0BZ UK.
Chem Sci. 2023 Jan 30;14(8):2200-2214. doi: 10.1039/d2sc06758g. eCollection 2023 Feb 22.
Room temperature ionic liquids of cyclic sulfonimide anions cPFSI (ring size: = 4-6) with the cations [EMIm] (1-ethyl-3-methylimidazolium), [BMIm] (1-butyl-3-methylimidazolium) and [BMPL] (BMPL = 1-butyl-1-methylpyrrolidinium) have been synthesized. Their solid-state structures have been elucidated by single-crystal X-ray diffraction and their physicochemical properties (thermal behaviour and stability, dynamic viscosity and specific conductivity) have been assessed. In addition, the ion diffusion was studied by pulsed field gradient stimulated echo (PFGSTE) NMR spectroscopy. The decisive influence of the ring size of the cyclic sulfonimide anions on the physicochemical properties of the ILs has been revealed. All ILs show different properties compared to those of the non-cyclic TFSI anion. While these differences are especially distinct for ILs with the very rigid 6cPFSI anion, the 5-membered ring anion 5cPFSI was found to result in ILs with relatively similar properties. The difference between the properties of the TFSI anion and the cyclic sulfonimide anions has been rationalized by the rigidity (conformational lock) of the cyclic sulfonimide anions. The comparison of selected IL properties was augmented by MD simulations. These highlight the importance of π-π interactions between pairs of [EMIm] cations in the liquid phase. The π-π interactions are evident for the solid state from the molecular structures of the [EMIm]-ILs with the three cyclic imide anions determined by single-crystal X-ray diffraction.
已合成出具有环状磺酰亚胺阴离子cPFSI（环大小： = 4 - 6）且阳离子为[EMIm]（1 - 乙基 - 3 - 甲基咪唑鎓）、[BMIm]（1 - 丁基 - 3 - 甲基咪唑鎓）和[BMPL]（BMPL = 1 - 丁基 - 1 - 甲基吡咯烷鎓）的室温离子液体。通过单晶X射线衍射阐明了它们的固态结构，并评估了它们的物理化学性质（热行为和稳定性、动态粘度和电导率）。此外，通过脉冲场梯度刺激回波（PFGSTE）核磁共振光谱研究了离子扩散。揭示了环状磺酰亚胺阴离子的环大小对离子液体物理化学性质的决定性影响。与非环状TFSI阴离子相比，所有离子液体都表现出不同的性质。虽然这些差异对于具有非常刚性的6cPFSI阴离子的离子液体尤为明显，但发现五元环阴离子5cPFSI导致离子液体具有相对相似的性质。环状磺酰亚胺阴离子的刚性（构象锁定）使TFSI阴离子和环状磺酰亚胺阴离子的性质差异合理化。通过分子动力学模拟增强了对选定离子液体性质的比较。这些突出了液相中[EMIm]阳离子对之间π - π相互作用的重要性。从通过单晶X射线衍射确定的具有三种环状酰亚胺阴离子的[EMIm] - 离子液体的分子结构来看，π - π相互作用在固态中是明显的。
