Structures of ionic liquids with different anions studied by infrared vibration Spectroscopy
Structures of ionic liquids with different anions studied by infrared vibration Spectroscopy
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DOI：
10.1021/jp7120752
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发表时间：
2008-04-17
影响因子：
3.3
通讯作者：
Kim, Doseok
中科院分区：
文献类型：
--
作者：
Jeon, Yoonnam;Sung, Jaeho;Kim, Doseok
采用衰减全反射（ATR）红外吸收光谱和拉曼光谱研究了离子液体（1-丁基-3-甲基咪唑碘[BMIM][I]和1-丁基-3-甲基咪唑四氟硼酸盐[BMIM][BF 4]）及其水溶液的结构。[BMIM][BF_4]和[BMIM][I]在2800 ~ 3200 cm（-1）的CHx（x = 1，2，3）振动区的ATR光谱有很大的不同，尽管在此区域的所有光谱特征都来自同一阳离子的丁基链和咪唑环。无论[BMIM][BF 4]的水浓度如何，光谱都没有明显变化，而[BMIM][I]的光谱随着水浓度的增加而显示出显著变化，尤其是在咪唑环的CH-振动模式中。对于非常稀释的溶液，[BMIM][I]和[BMIM][BF 4]的水性混合物显示非常相似的光谱。[BMIM] [I]与重水（D2 O）的混合促进了连接到咪唑环的最酸性碳的质子从D2 O到氘的同位素交换，而即使长时间暴露于D2 O也不会诱导[BMIM][BF 4]的任何同位素交换。在[BMIM] [I]和[BMIM] [BF 4]之间，随着水浓度的增加，指示丁基链构象的600 cm（-1）附近的拉曼光谱也发生不同的变化。这些差异被认为是来自阴离子位置的变化，其中I-预计更接近咪唑鎓阳离子的C（2）氢，并且与BF 4-相比更具体地相互作用。
We investigated the structures of ionic liquids (1-butyl-3-methylimidazolium iodide [BMIM][I] and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]) and their aqueous mixtures using attenuated total reflection (ATR) infrared absorption and Raman spectroscopy. The ATR spectrum in the CHx (x = 1, 2, 3) vibration region from 2800 to 3200 cm(-1) was very different between [BMIM][BF4] and [BMIM][I] even though all the spectral features in this region were from the butyl chain and the imidazolium ring of the same cation. The spectrum did not change appreciably irrespective of the water concentration for [BMIM][BF4], whereas the spectrum from [BMIM][I] showed significant changes as the water concentration was increased, especially in CH-vibration modes from the imidazolium ring. For very diluted solutions both aqueous mixtures of [BMIM][I] and [BMIM][BF4] showed very similar spectra. Mixing of [BMIM] [I] with heavy water (D2O) facilitated the isotopic exchange of the proton attached to the most.acidic carbon of the imidazolium ring into deuterium from D2O, whereas even prolonged exposure to D2O did not induce any isotopic exchange for [BMIM][BF4]. Raman spectra around 600 cm(-1) indicative of the butyl chain conformation also changed differently as the water concentration was increased between [BMIM] [I] and [BMIM] [BF4]. These differences are considered to come from the variation in the position of the anion, where I- is expected to be closer to the C(2) hydrogen of the imidazolium cation and interacting more specifically as compared to BF4-.