二面角
乙醚
化学
氢键
分子内力
侧链
烷基
酰胺
离子液体
齿合度
密度泛函理论
拉曼光谱
傅里叶变换红外光谱
计算化学
结晶学
有机化学
分子
化学工程
晶体结构
聚合物
工程类
催化作用
物理
光学
作者
Beatriz Rocha de Moraes,Vitor H. Paschoal,Nicolas Keppeler,Omar A. El Seoud,Rômulo Augusto Ando
标识
DOI:10.1021/acs.jpcb.3c08162
摘要
The inherently high viscosity of ionic liquids (ILs) can limit their potential applications. One approach to address this drawback is to modify the cation side chain with ether groups. Herein, we assessed the structure–property relationship by focusing on acetate (OAc), a strongly coordinating anion, with 1,3-dialkylimidazolium cations with different side chains, including alkyl, ether, and hydroxyl functionalized, as well as their combinations. We evaluated their viscosity, thermal stabilities, and microstructure using Raman and infrared (IR) spectroscopies, allied to density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. The viscosity data showed that the ether insertion significantly enhances the fluidity of the ILs, consistent with the coiling effect of the cation chain. Through a combined experimental and theoretical approach, we analyzed how the OAc anion interacts with ether ILs, revealing a characteristic bidentate coordination, particularly in hydroxyl functionalized ILs due to specific hydrogen bonding with the OH group. IR spectroscopy showed subtle shifts in the acidic hydrogens of imidazolium ring C(2)–H and C(4,5)–H, suggesting weaker interactions between OAc and the imidazolium ring in ether-functionalized ILs. Additionally, spatial distribution functions (SDF) and dihedral angle distribution obtained via AIMD confirmed the intramolecular hydrogen bonding due to the coiling effect of the ether side chain.
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