Remsing Richard C, Hernandez Gonzalo, Swatloski Richard P, Massefski Walter W, Rogers Robin D, Moyna Guillermo
Department of Chemistry & Biochemistry, University of the Sciences in Philadelphia, 600 South 43rd Street, Philadelphia, Pennsylvania 19104-4495, USA.
J Phys Chem B. 2008 Sep 4;112(35):11071-8. doi: 10.1021/jp8042895. Epub 2008 Aug 9.
The solvation of carbohydrates in N, N'-dialkylimidazolium ionic liquids (ILs) was investigated by means of 13C and 35/37Cl NMR relaxation and 1H 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 ([CC2mim]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 35/37Cl and 13C 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 13C 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.
通过¹³C和³⁵/³⁷Cl NMR弛豫以及¹H脉冲场梯度刺激回波（PFG - STE）扩散测量，研究了碳水化合物在N，N'-二烷基咪唑鎓离子液体（ILs）中的溶剂化作用。研究了模型糖在1 - 正丁基 - 3 - 甲基咪唑鎓氯化物（[C₄mim]Cl）、1 - 烯丙基 - 3 - 甲基咪唑鎓氯化物（[CC₂mim]Cl）和1 - 乙基 - 3 - 甲基咪唑鎓乙酸盐（[C₂mim][OAc]）中的溶液，以评估阳离子和阴离子结构对溶剂化机制的影响。在所有情况下，IL阳离子碳核弛豫时间随碳水化合物浓度的变化都很小，且与溶液粘度的变化一致。相反，氯离子和乙酸根离子碳的³⁵/³⁷Cl和¹³C弛豫率分别强烈依赖于糖含量。对于[C₂mim][OAc]，根据两种离子的¹³C弛豫数据估计的相关时间表明，随着碳水化合物浓度的增加，阴离子的重排速率比阳离子下降得更快。虽然不像弛豫数据中观察到的变化那么明显，但从糖/IL体系的阳离子以及（对于[C₂mim][OAc]）阴离子自扩散系数的分析中也获得了类似的趋势。我们的结果表明，IL阳离子与溶质之间的相互作用是非特异性的，证实了该过程受IL阴离子与碳水化合物之间的相互作用支配，更重要的是，表明无论阴离子结构如何，溶剂化机制都没有变化。
