含酯基吡啶类离子液体异构体的设计合成及其二元体系导电行为

Synthesis and Binary-system Conductivities of Pyridinium Ionic Liquid Isomers Containing One Ester Group

离子液体型电解质在储能材料、电化学沉积等方面具有重要的研究意义。从酯基异构化的角度出发,设计合成了互为异构体的含酯基吡啶类离子液体,丁酸甲酯基吡啶六氟磷酸盐[n-C_4MePy][PF_6](记IL1)和异丙酸乙酯基吡啶六氟磷酸盐[i-C_3EAPy][PF_6](记IL2)。对离子液体(记IL)-有机溶剂体系的电导性能进行研究,在0.0005~0.01 mol·L^(-1)浓度范围内,酯基异构化对二元体系的电导率影响相对较大。与IL2-有机溶剂体系相比,IL1-CH_3OH的电导率约为IL2-CH_3OH的2倍,而IL1-CH_3CN和IL1-(CH_3)_2NOH的电导率相对较小。同时在相同条件下,其不同溶剂体系的电导率为κ_(甲醇)>κ_(乙腈)>κ_(N,N二甲基甲酰胺),这可能与溶剂的介电常数大小有关。进一步研究表明,离子液体异构体(IL)-有机溶剂体系的导电行为均符合阿伦尼乌斯行为,在N,N-二甲基甲酰胺溶剂体系中,离子液体的酯基异构使得体系的电导活化能变化较为显著。与IL1-(CH_3)_2NOH相比,IL2-(CH_3)_2NOH的电导活化能减小了8.454 k J·mol^(-1),这可能是由于IL2与溶剂分子上的基团相互吸引力增强,导致了其体系活化能减小。最后对离子液体异构体的热稳定性分析表明,与IL1的分解温度487.48℃相比,酯基异构化使IL2的热分解温度降低了301.77℃。

Ionic liquid electrolytes have important significance on energy storage materials, electrochemical deposition and so on. Pyridinium ionic liquid isomers [n-C4MePy] [PF6] （IL1） and [ i- C3EAPy][PF6] （IL 2 ） , were synthesized by the two-step process involving introduction of ester base group and anion metathesis. The results showed that ester base isomerization influenced obviously on the binary-system conductivities in the range of 0.0005 -0.01 mol · L^-1 . Compared with the IL2-solvent system, the IL1-CH3OH conductivity was double that of the IL2-CH3OH system, however the IL1- CH3CN and IL1-（ CH3 ）2NOH systems had relatively low conductivities. Additionly, the conductivities of these systems followed the order of k CH3OH 〉 k CH3CN 〉 k （CH3）2NOH,which was probably related to the dielectric constants of the solvents. Furthermore, it is proved that the relationship of absolute temperature and conductivity is accord with Arrhenius＂ equation. The activation energy in the IL1-（ CH3 ）2NOH system decreases 8. 454 kJ · mol^-1 than that in the IL2-（ CH3 ）2NOH system, this is relative to the attraction interaction among the groups. Finally, thermal analysis show that the decomposition temperature of IL2 reduces 301.77 ℃ than that of IL1.