Liquid structure of N

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• 作者：Shuhei Fukuda ; Munetaka Takeuchi ; Kenta Fujii ; Ryo Kanzaki ; Toshiyuki Takamuku ; Kazumi Chiba ; Hideo Yamamoto ; Yasuhiro Umebayashi ; Shin-ichi Ishiguro
• 关键词：Room temperature ionic liquids ; Liquid structure ; Large angle X-ray scattering ; Molecular dynamics simulations
• 刊名：Journal of Molecular Liquids
• 出版年：2008
• 出版时间：15 September 2008
• 年：2008
• 卷：143
• 期：1
• 页码：2-7
• 全文大小：560 K

文摘

Large angle X-ray scattering of the N-butyl-N-methylpyrrolidinium bis-(trifluoromethanesulfony) amide (P₁₄⁺TFSA⁻) ionic liquid was measured at 298 K. The total interference function i^LAXS(s) and the total pair correlation function G^LAXS(r) were successfully obtained. The i^LAXS(s) was analyzed in terms of the intra-molecular geometries of the conformational isomers of the P₁₄⁺ and TFSA⁻ ions based on the crystal structures, the inter-molecular correlation function G_inter^LAXS(r) and the inter-molecular radial distribution function as the form D_inter^LAXS(r) − 4πr²ρ₀ were evaluated. With D_inter^LAXS(r) − 4πr²ρ₀, the inter-molecular correlation peaks at 3.5, 4.5 and 5–6 Å evidently appeared as the short range interaction, while considerable long range interactions were found as the broad peaks at 10 and 15 Å. Molecular dynamics simulations of the ionic liquid based on the effective pairwise potentials were carried out. The X-ray total interference function derived from the MD simulations i^MD(s) was in agreement with the experimental one. According to the inter-molecular partial atom–atom correlation functions from MD simulations, the observed peaks at 3.5, 4.5 and 5–6 Å can be predominantly ascribed to the closest atom–atom correlations between the P₁₄⁺ and TFSA^– ions such as C···O and C···F. In the inter-molecular partial atom–atom correlation function between terminal methyl carbons of the butyl chain in the P₁₄⁺ ion, a peak at 4.0 Å was found as the inter-molecular correlation, suggesting that the ionic liquid shows an alkyl chain aggregation, which is similar to that observed for 1-alkyl-3-methylmidazolium ionic liquids.