Air- and water-stable 1-alkyl-3-methylimidazolium tetrafluoroborate salts with the general formula [C_n-mim][BF₄] (n = 0–18) have been prepared by metathesis from the corresponding chloride or bromide salts. The salts have been characterised by ¹H NMR and IR spectroscopy, microanalysis, polarising optical microscopy and differential scanning calorimetry. Those with short alkyl chains (n = 2–10) are isotropic ionic liquids at room temperature and exhibit a wide liquid range, whereas the longer chain analogues are low melting mesomorphic crystalline solids which display an enantiotropic smectic A mesophase. The thermal range of the mesophase increases with increasing chain length and in the case of the longest chain salt prepared, [C₁₈-mim][BF₄], the mesophase range is ca. 150 °C.

中文翻译：

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1-烷基-3-甲基咪唑鎓四氟硼酸酯的相行为; 离子液体和离子液晶

通式[C _n -mim] [BF ₄ ]（n  = 0-18）的空气和水稳定性1-烷基-3-甲基咪唑鎓四氟硼酸盐是通过相应的氯化物或溴化物盐的复分解反应制备的。这些盐已通过¹ H NMR和IR光谱，显微分析，偏振光学显微镜和差示扫描量热法进行了表征。烷基短链的那些（n = 2–10）是室温下的各向同性离子液体，并显示出较宽的液体范围，而长链类似物是低熔点的介晶结晶固体，表现出对映的近晶A中间相。中间相的热范围随链长的增加而增加，在制备最长链盐[C ₁₈ -mim] [BF ₄ ]的情况下，中间相的范围为。150℃。