Synthesis, Stability and Electrochemical Characterization of New Ionic Liquids Based on Asymmetrical Borates

众所周知，缺乏对称性会导致近乎相等的物质的熔点下降。例如，碳酸亚乙酯的熔点约为+36°C，而碳酸亚丙酯的液体范围扩展到约-49°C，尽管其摩尔质量较高，并且很容易过冷到约-80°C。因此，与基于对称硼酸盐的已知离子液体(如EMIBF4)相比，基于不对称硼酸盐的离子液体(ILS)可以获得更大的液体范围。一些具有锂反离子的不对称硼酸盐是已知的。然而，它们显示出缺乏化学稳定性。交换反应需要对称和不对称硼酸盐的混合物。我们假设这种交换反应主要是由非常小的锂离子辅助的，并尝试合成了一些具有不对称硼酸盐和惰性阳离子的盐，如咪唑离子。我们有希望的初步工作表明，我们的假设是正确的。合成了第一个具有热稳定性的新型离子液体化合物--四乙基氨二氟1，2-草酸(2-)-O，O？]硼酸盐(1-)。因此，我们提出了一项基于不对称硼酸盐的新型离子液体的合成和电化学性质的研究，其中包括单齿和双齿配体以及咪唑、硫和铵类型的阳离子。此外，还计划在中温下进行长期稳定性研究，通过长时间的核磁共振测量来研究上述硼酸盐溶液的组成。

It is well known that lack of symmetry entails a drop in the fusion point of nearly equal substances. E.g., ethylene carbonate shows a fusion point of about +36°C whereas the liquid range of propylene carbonate extends to roughly -49°C despite its higher molar mass and may be easily supercooled to about -80°C. Thus larger liquid ranges may be obtained for ionic liquids (ILs) based on asymmetric borates when compared to known ILs which are based on symmetric borates such, e.g. EMIBF4. Some asymmetric borates with lithium counter ions are already known. However they show a lack of chemical stability. Exchange reactions entail mixtures of the symmetric and asymmetric borates. We have assumed that this exchange reaction is mainly assisted by the very small lithium ion and tried to synthesize some salts with asymmetric borates and inert cations such as imidazolium ions. Our promising preliminary work showed that our assumption is correct. The first thermally stable member of a new class of ILs was synthesised, tetraethylammoniumdifluoromono1, 2-oxalato(2-)-O,O¿]borate (1-). Therefore we propose a project including synthesis and electrochemical characterisation of new ILs based on asymmetric borates with one- and bidentate ligands and cations of imidazolium, sulfonium and ammonium types. In addition, a long time stability investigation is planned at moderate temperatures, where the composition of the solution of above mentioned borates is studied by NMR-measurements over a long period.