离子液体酸性的红外光谱探针法研究

Investigation of the Acidity of Ionic Liquids by IR Spectroscopy

以吡啶和乙腈分子为探针,使用红外光谱法研究了常用室温离子液体的酸性.采用吡啶为探针分子时,出现的～1450cm-1、～1540cm-1吸收带可以分别指示离子液体的Lewis、Br覬nsted酸性;采用乙腈为探针分子时,～2253cm-1的C≡N伸缩振动向高波数移动并伴有新峰的出现,可以指示离子液体的Lewis酸性.可以通过比较吡啶探针～1450cm-1吸收带的峰位置对离子液体的Lewis酸强度进行排序,并且可以用乙腈探针更灵敏地区分出不同离子液体的Lewis酸的强度.使用该方法研究了离子液体的结构对其Br覬nsted/Lewis酸性的影响,

The determination of the acidity of ionic liquids is of crucial significance to the utilization of ionic liquids. By using pyridine and acetonitrile as IR spectroscopic probes, the acidity of common room temperature ionic liquids was determined. For the probe pyridine, the IR band near 1450, 1540 cm(-1) of pyridine is indicative the Lewis/Bronsted acidity of ionic liquids respectively. For another probe acetonitrile, the increase of the C = N stretching wave number near 2253 cm(-1) with a new band appear at the higher wave number is indicative of the Lewis acidity. The influence of the structure of ionic liquids on the Lewis/Bronsted acidity by the IR spectroscopy was investigeted. The Lewis acid strength of different ionic liquids has been compared through the shift of the 1450 cm(-1) of pyridine. A more obvious comparison of the Lewis acid intensity of different ionic liquids has been made by acetonitrile probe.