Solvation of Carbohydrates in N,N′-Dialkylimidazolium Ionic Liquids: A Multinuclear NMR Spectroscopy Study

详细信息    查看全文

• 作者：Richard C. Remsing ; Gonzalo Hernandez ; Richard P. Swatloski ; Walter W. Massefski ; Robin D. Rogers ; Guillermo Moyna
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：September 4, 2008
• 年：2008
• 卷：112
• 期：35
• 页码：11071-11078
• 全文大小：463K
• 年卷期：v.112,no.35(September 4, 2008)
• ISSN：1520-5207

文摘

The solvation of carbohydrates in N,N′-dialkylimidazolium ionic liquids (ILs) was investigated by means of p>13p>C and p>35/37p>Cl NMR relaxation and p>1p>H pulsed field gradient stimulated echo (PFG-STE) diffusion measurements. Solutions of model sugars in 1-n-butyl-3-methylimidazolium chloride ([C₄mim]Cl), 1-allyl-3-methylimidazolium chloride ([CC₂mim]Cl), and 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) were studied to evaluate the effects of cation and anion structure on the solvation mechanism. In all cases, the changes in the relaxation times of carbon nuclei of the IL cations as a function of carbohydrate concentration are small and consistent with the variation in solution viscosities. Conversely, the p>35/37p>Cl and p>13p>C relaxation rates of chloride ions and acetate ion carbons, respectively, have a strong dependency on sugar content. For [C₂mim][OAc], the correlation times estimated from p>13p>C relaxation data for both ions reveal that, as the carbohydrate concentration increases, the reorientation rate of the anion decreases faster than that of the cation. Although not as marked as the variations observed in the relaxation data, similar trends were obtained from the analysis of cation and, in the case of [C₂mim][OAc], anion self-diffusion coefficients of the sugar/IL systems. Our results show that the interactions between the IL cation and the solutes are nonspecific, confirm that the process is governed by the interactions between the IL anion and the carbohydrate, and, more importantly, indicate no change in the solvation mechanism regardless of the structure of the anion.