Physicochemical properties and structures of room temperature ionic liquids. 1. Variation of anionic species
Physicochemical properties and structures of room temperature ionic liquids. 1. Variation of anionic species
复制标题
DOI：
10.1021/jp047480r
复制
发表时间：
2004-10-21
影响因子：
3.3
通讯作者：
Watanabe, M
中科院分区：
文献类型：
--
作者：
Tokuda, H;Hayamizu, K;Watanabe, M
制备了基于1-丁基-3-甲基咪唑鎓（[bmim]）和多种氟化阴离子的室温离子液体（RTIL），并在较宽的温度范围内测量了阳离子和阴离子的热行为、密度、粘度、自扩散系数以及离子电导率。自扩散系数、粘度、离子电导率和摩尔电导率的温度依赖性已拟合到 Vogel-Fulcher-Tamman 方程，并估计了自扩散系数、粘度、离子电导率和摩尔电导率的最佳拟合参数，以及密度的线性拟合参数。通过脉冲场梯度自旋回波核磁共振方法测定的各个离子的自扩散系数在较宽的温度范围内显示出阳离子比阴离子更高的值，即使其半径大于阴离子半径。 RTIL 的阳离子和阴离子扩散系数之和遵循 30°C 时的顺序 [bmim][(CF3SO2)(2)N] > [bmim][CF3CO2] > [bmim][CF3SO3] > [bmim][BF4] > [bmim][(C2F5SO2)(2)N] > [bmim][PF6]，以及扩散顺序系数与粘度数据形成鲜明对比。离子缔合是根据阻抗测量获得的摩尔电导率与使用能斯特-爱因斯坦方程通过离子扩散率计算出的摩尔电导率的比率结果提出的。离子液体的比例在 30 ℃ 时遵循 [bmim][PF6] > [bmim][BF4] > [bmim][(C2F5SO2)(2)N] > [bmim][(CF3SO2)(2)N] > [bmim][CF3SO3] > [bmim][CF3CO2] 的顺序，并提供有关扩散中离子传导的活性离子的定量信息组件。
Room-temperature ionic liquids (RTILs) based on 1-butyl-3-methylimidazolium ([bmim]) with a variety of fluorinated anions were prepared, and the thermal behavior, density, viscosity, self-diffusion coefficients of the cations and anions, and ionic conductivity were measured over a wide temperature range. The temperature dependencies of the self-diffusion coefficient, viscosity, ionic conductivity, and molar conductivity have been fitted to the Vogel-Fulcher-Tamman equation, and the best-fit parameters for the self-diffusion coefficient, viscosity, ionic conductivity, and molar conductivity have been estimated, together with the linear fitting parameters for the density. The self-diffusion coefficients determined for the individual ions by pulsed-field-gradient spin-echo NMR method exhibit higher values for the cation compared with the anion over a wide temperature range, even if its radius is larger than that of the anionic radii. The summation of the cationic and anionic diffusion coefficients for the RTILs follows the order [bmim][(CF3SO2)(2)N] > [bmim][CF3CO2] > [bmim][CF3SO3] > [bmim][BF4] > [bmim][(C2F5SO2)(2)N] > [bmim][PF6] at 30 degreesC, and the order of the diffusion coefficients greatly contrasts to the viscosity data. The ionic association is proposed from the results of the ratios of molar conductivity obtained from impedance measurements to that calculated by the ionic diffusivity using the Nernst-Einstein equation. The ratio for the ionic liquids follows the order [bmim][PF6] > [bmim][BF4] > [bmim][(C2F5SO2)(2)N] > [bmim][(CF3SO2)(2)N] > [bmim][CF3SO3] > [bmim][CF3CO2] at 30 degreesC and provides quantitative information on the active ions contributing to ionic conduction in the diffusion components.