Ionic liquids and ionic liquid crystals of vinyl functionalized imidazolium salts
作者:Shih-Ci Luo、Shaowen Sun、Amol R. Deorukhkar、Jung-Tang Lu、Amitabha Bhattacharyya、Ivan J. B. Lin
DOI:10.1039/c0jm02875d
日期:——
1-Vinyl-3-alkylimidazolium salts ([CnVIm]X, (where, CnVIm = vinylimidazolium cation with alkyl chains of CnH2n+1; n = 4, 6, 8, 10, 12, 14, 16 and 18 for X = Br and I, and n = 12, 14, 16 and 18 for X = BF4 and PF6), were prepared and characterized. Ethyl substituted congeners [C16EIm]Br and [C16EIm]I were also prepared to understand the unique property of the vinyl substitution. Salts with shorter alkyl chain lengths (n ≤ 12) are either room temperature or close to room temperature ionic liquids, whereas those with longer alkyl chain lengths are ionic liquid crystals with SmA mesophase. Diffractograms from powder X-ray diffraction studies suggest that in the solid state the [CnVIm]Br series salts adopt a double bilayer structure, whereas the ethyl substituted analogues and salts in the I−, BF4− and PF6− series have a simple bilayer structure. The thermal behavior of [C16VIm]Br and [C16VIm]I was compared with their saturated congeners. The vinyl functionalized salts, have slightly higher melting points and much higher clearing points than those of the saturated congeners, and therefore wider mesophases are found for the formers. Nuclear magnetic resonance spectroscopic studies suggest that vinyl functionalization provides additional hydrogen bonding interactions between the cations and anions.
1-乙烯基-3-烷基咪唑盐([CnVIm]X,其中,CnVIm = 具有CnH2n+1烷基链的乙烯基咪唑阳离子;n = 4, 6, 8, 10, 12, 14, 16和18(X = Br和I),以及n = 12, 14, 16和18(X = BF4和PF6))被制备和表征。为理解乙烯基取代的独特特性,还制备了乙基取代的同系物[C16EIm]Br和[C16EIm]I。短烷基链长度(n ≤ 12)的盐是室温或接近室温的离子液体,而长烷基链长度的盐则是具有 SmA 中相的离子液晶。从粉末X射线衍射研究的衍射图谱中可以看出,在固态下,[CnVIm]Br 系列盐呈现双层结构,而乙基取代的类似物及 I−、BF4− 和 PF6− 系列的盐则呈现简单的双层结构。[C16VIm]Br 和 [C16VIm]I 的热行为与其饱和同系物进行了比较。乙烯基功能化的盐,其熔点略高于饱和同系物,清除点又远高于饱和同系物,因此前者具有更宽的中相。核磁共振光谱研究表明,乙烯基功能化提供了阳离子与阴离子之间额外的氢键相互作用。