Belhocine Tayeb, Forsyth Stewart A, Gunaratne H Q Nimal, Nieuwenhuyzen Mark, Nockemann Peter, Puga Alberto V, Seddon Kenneth R, Srinivasan Geetha, Whiston Keith
The QUILL Research Centre, School of Chemistry and Chemical Engineering, The Queen's University of Belfast, Stranmillis Road, Belfast BT9 5AG, UK.
Phys Chem Chem Phys. 2015 Apr 28;17(16):10398-416. doi: 10.1039/c4cp05936k.
A wide range of room temperature ionic liquids based on the 3-methylpiperdinium cation core were produced from 3-methylpiperidine, which is a derivative of DYTEK® A amine. First, reaction with 1-bromoalkanes or 1-bromoalkoxyalkanes generated the corresponding tertiary amines (Rmβpip, R = alkyl or alkoxyalkyl); further quaternisation reactions with the appropriate methylating agents yielded the quaternary [Rmmβpip]X salts (X(-) = I(-), CF3CO2 or OTf; Tf = -SO2CF3), and [Rmmβpip][NTf2] were prepared by anion metathesis from the corresponding iodides. All NTf2 salts are liquids at room temperature. [Rmmβpip]X (X(-) = I(-), CF3CO2 or OTf) are low-melting solids when R = alkyl, but room temperature liquids upon introduction of ether functionalities on R. Neither of the 3-methylpiperdinium ionic liquids showed any signs of crystallisation, even well below 0 °C. Some related non-C-substituted piperidinium and pyrrolidinium analogues were prepared and studied for comparison. Crystal structures of 1-hexyl-1,3-dimethylpiperidinium tetraphenylborate, 1-butyl-3-methylpiperidinium bromide, 1-(2-methoxyethyl)-1-methylpiperidinium chloride and 1-(2-methoxyethyl)-1-methylpyrrolidinium bromide are reported. Extensive structural and physical data are collected and compared to literature data, with special emphasis on the systematic study of the cation ring size and/or asymmetry effects on density, viscosity and ionic conductivity, allowing general trends to be outlined. Cyclic voltammetry shows that 3-methylpiperidinium ionic liquids, similarly to azepanium, piperidinium or pyrrolidinium counterparts, are extremely electrochemically stable; the portfolio of useful alternatives for safe and high-performing electrolytes is thus greatly extended.
基于3-甲基哌啶鎓阳离子核心的多种室温离子液体由3-甲基哌啶制备而成，3-甲基哌啶是DYTEK® A胺的衍生物。首先，与1-溴代烷烃或1-溴代烷氧基烷烃反应生成相应的叔胺（Rmβpip，R = 烷基或烷氧基烷基）；进一步与合适的甲基化剂进行季铵化反应得到季铵盐[Rmmβpip]X（X(-) = I(-)、CF3CO2或OTf；Tf = -SO2CF3），[Rmmβpip][NTf2]则通过相应碘化物的阴离子交换反应制备。所有NTf2盐在室温下均为液体。当R = 烷基时，[Rmmβpip]X（X(-) = I(-)、CF3CO2或OTf）为低熔点固体，但当R引入醚官能团时则为室温液体。这两种3-甲基哌啶鎓离子液体均未表现出任何结晶迹象，即使在远低于0°C的温度下也是如此。制备并研究了一些相关的非C-取代哌啶鎓和吡咯烷鎓类似物用于比较。报道了1-己基-1,3-二甲基哌啶四苯基硼酸盐、1-丁基-3-甲基哌啶溴化物、1-(2-甲氧基乙基)-1-甲基哌啶氯化物和1-(2-甲氧基乙基)-1-甲基吡咯烷溴化物的晶体结构。收集了大量的结构和物理数据并与文献数据进行比较，特别着重于对阳离子环大小和/或不对称性对密度、粘度和离子电导率影响的系统研究，从而勾勒出一般趋势。循环伏安法表明，3-甲基哌啶鎓离子液体与氮杂环庚烷鎓、哌啶鎓或吡咯烷鎓类似物一样，具有极高的电化学稳定性；因此，安全且高性能电解质的有用替代品组合得到了极大扩展。
