Ion Pair Formation of Alkylimidazolium Ionic Liquids in Dichloromethane
Ion Pair Formation of Alkylimidazolium Ionic Liquids in Dichloromethane
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DOI：
10.1021/je800152d
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发表时间：
2008-06
影响因子：
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通讯作者：
S. Katsuta;Kazuo Imai;Y. Kudo;Y. Takeda;H. Seki;M. Nakakoshi
中科院分区：
文献类型：
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作者：
S. Katsuta;Kazuo Imai;Y. Kudo;Y. Takeda;H. Seki;M. Nakakoshi
1-烷基-3-甲基咪唑（[RMeIm]+; R =丁基、己基和辛基）和1-丁基-2,3-二甲基咪唑（[BuMe2Im]+）离子与四氟硼酸盐（[BF4]−）、六氟磷酸盐（[PF6]−）、二（三氟甲烷磺酰基）酰胺（[NTf2]−）和2,4,6-三硝基苯酚（pic酸盐，[Pic]−）离子的1:1离子对形成常数（KIP0）在25℃二氯甲烷中进行了电导法测定。对对称四烷基铵离子（[R4N]+; R =甲基、乙基、丙基和丁基）的KIP0测定也进行了比较。对于给定阴离子，[RMeIm]+盐的KIP0值几乎与烷基链长度(R)无关，而[R4N]+盐的KIP0值随着烷基链长度的增加而减小。这种对离子对形成能力的烷基链长依赖性的差异，可以用密度泛函理论计算的离子对结构来解释。[BuMeIm]+、[BuMe2Im]+和[Et4N]+的KIP0值在van der W中相似。
The 1:1 ion pair formation constants (KIP0) of 1-alkyl-3-methylimidazolium ([RMeIm]+; R = butyl, hexyl, and octyl) and 1-butyl-2,3-dimethylimidazolium ([BuMe2Im]+) ions with tetrafluoroborate ([BF4]−), hexafluorophosphate ([PF6]−), bis(trifluoromethanesulfonyl)amide ([NTf2]−), and 2,4,6-trinitrophenolate (picrate, [Pic]−) ions have been determined conductometrically in dichloromethane at 25 °C. The KIP0 determinations have also been made for symmetric tetraalkylammonium ions ([R4N]+; R = methyl, ethyl, propyl, and butyl) for comparison. For a given anion, the KIP0 value of the [RMeIm]+ salt is almost independent of the length of the alkyl chain (R), whereas that of the [R4N]+ salt decreases with increasing alkyl chain length. Such a difference in the alkyl chain length dependence of the ion pair formation ability can be explained on the basis of the structures of the ion pairs calculated by density functional theory. The KIP0 values of [BuMeIm]+, [BuMe2Im]+, and [Et4N]+, which are similar in the van der W...