Salt and Marine Chemicals Division, Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research (CSIR), G. B. Marg, Bhavnagar 364002, India.
Chemphyschem. 2011 Mar 14;12(4):836-45. doi: 10.1002/cphc.201000826. Epub 2011 Feb 21.
The molecular interactions of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate [C(4)mim][BF(4) ], 3-methyl-1-octylimidazolium tetrafluoroborate [C(8)mim][BF(4)] and 1-butyl-3-methylimidazolium octylsulfate [C(4)mim][C(8)OSO(3)] are investigated in ethylene glycol (EG) over the whole mole fraction range using fluorescence (steady-state and time-resolved), Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. The cybotactic region surrounding the pyrene fluorescent probe exhibits peculiar characteristics for different ILs in the EG-rich region. The extent of solute-solvent interactions is assessed by determining the deviations of experimentally observed vibronic band intensity ratios of peak 1 to peak 3 of pyrene fluorescence (I(1)/I(3)) from a composite I(1)/I(3) value obtained using a preferential solvation model. A distinct vibrational frequency shift for various stretching modes of EG (O−H) or ILs (C−H of ring protons, B−F and S=O of anions) indicates specific interactional preferences of EG toward the IL protons/anion. Splitting of the O−H vibration band of EG at 3000-3700 cm(-1) into three separate bands, and analysis of the changes in location and area of these bands as a function of concentration enable precise determination of the effect of ILs on hydrogen bridges of EG. NMR chemical shifts and their deviations from ideality show multiple hydrogen-bonding interactions of varying strengths between unlike molecules in the mixtures. A comparison of spectroscopic results with thermodynamic properties shows that the mixing microscopic behaviour of the investigated systems is completely different from the macroscopic behaviour, which is primarily governed by the difference in shape, size and nature of the molecules.
采用荧光（稳态和时间分辨）、傅里叶变换红外和核磁共振（NMR）光谱法研究了离子液体 1-丁基-3-甲基咪唑四氟硼酸盐 [C(4)mim][BF(4)]、3-甲基-1-辛基咪唑四氟硼酸盐 [C(8)mim][BF(4)]和 1-丁基-3-甲基咪唑辛基硫酸盐 [C(4)mim][C(8)OSO(3)]在整个摩尔分数范围内与乙二醇（EG）的分子相互作用。在富 EG 区域，芘荧光探针周围的胶束区域表现出不同 IL 的独特特性。通过确定实验观察到的芘荧光（I(1)/I(3)）的振动带强度比峰 1 到峰 3 的实验观察值与使用优先溶剂化模型获得的复合 I(1)/I(3)值的偏差来评估溶质-溶剂相互作用的程度。各种 EG（O−H）或 ILs（环质子的 C−H、阴离子的 B−F 和 S=O）的伸缩模式的明显振动频率位移表明 EG 对 IL 质子/阴离子具有特定的相互作用偏好。EG 的 O−H 振动带在 3000-3700 cm(-1)处分裂成三个单独的带，以及这些带的位置和面积随浓度变化的分析，使我们能够精确确定 ILs 对 EG 氢键的影响。NMR 化学位移及其与理想值的偏差表明混合物中不同分子之间存在多种不同强度的氢键相互作用。光谱学结果与热力学性质的比较表明，所研究体系的混合微观行为与宏观行为完全不同，宏观行为主要由分子的形状、大小和性质的差异决定。
