Yoshida Yukihiro, Baba Osamu, Larriba Carlos, Saito Gunzi
Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. yoshiday@ kuchem.kyoto-u.ac.jp
J Phys Chem B. 2007 Oct 25;111(42):12204-10. doi: 10.1021/jp0745236. Epub 2007 Oct 3.
Ionic liquids composed of dicyanamide anion and various imidazolium-based cations were prepared, and the influence of structural variations such as substituting a hydrogen at 2-position and changing the sort of alkyl group at 1-position of imidazolium cations on their thermal behavior, density, solvatochromic effects, viscosity, ionic conductivity, and surface tension was characterized. The substitution of the 2-hydrogen for methyl group or N-methylimidazole decreases the fluidity and ionic conductivity, mainly caused by the increased cohesive energy associated with the increasing cation size. Chain branching at 1-position also gives rise to the pronounced depression of the fluidity and ionic conductivity, presumably as a consequence of the increased pi-pi interactions between imidazolium rings. We found that the surface tension of the present ionic liquids is in inverse proportion to the molar concentration, which can be originally rationalized on the basis of the hole theory.
制备了由双氰胺阴离子和各种咪唑基阳离子组成的离子液体，并表征了咪唑阳离子2位上的氢取代和1位上烷基种类变化等结构变化对其热行为、密度、溶剂化显色效应、粘度、离子电导率和表面张力的影响。2位氢被甲基或N-甲基咪唑取代会降低流动性和离子电导率，这主要是由于阳离子尺寸增加导致内聚能增加所致。1位的链支化也会导致流动性和离子电导率显著降低，这可能是咪唑环之间π-π相互作用增加的结果。我们发现，本研究中的离子液体的表面张力与摩尔浓度成反比，这最初可以根据空穴理论得到合理解释。
