Shirota Hideaki, Kakinuma Shohei, Itoyama Yu, Umecky Tatsuya, Takamuku Toshiyuki
Department of Nanomaterial Science and Department of Chemistry, Chiba University , 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan.
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University , Honjo-machi, Saga 840-8502, Japan.
J Phys Chem B. 2016 Jan 28;120(3):513-26. doi: 10.1021/acs.jpcb.5b10917. Epub 2016 Jan 13.
The microscopic aspects of the two series of mixtures of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4])-benzene and 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide ([MOIm][NTf2])-benzene were investigated by several spectroscopic techniques such as attenuated total reflectance IR (ATR-IR), NMR, and fs-Raman-induced Kerr effect spectroscopy (fs-RIKES). All three different spectroscopic results indicate that the anions more strongly interact with the cations in the [MOIm][BF4]-benzene mixtures than in the [MOIm][NTf2]-benzene mixtures. This also explains the different miscibility features between the two mixture systems well. The xC6H6 dependences of the chemical shifts and the C-H out-of-plane bending mode of benzene are similar: the changes are large in the high benzene concentration (xC6H6 > ∼ 0.6) compared to the low benzene concentration. In contrast, the linear xC6H6 dependences of the first moments of the low-frequency spectra less than 200 cm(-1) were observed in both the [MOIm][BF4]-benzene and [MOIm][NTf2]-benzene systems. The difference in the xC6H6 dependent features between the chemical shifts and intramolecular vibrational mode and the intermolecular/interionic vibrational bands might come from the different probing space scales. The traces of the parallel aromatic ring structure and the T-shape structure were found in the ATR-IR and NMR experiments, but fs-RIKES did not observe a clear trace of the local structure. This might imply that the interactions between the imidazolium and benzene rings are not strong enough to librate the imidazolium and benzene rings together. The bulk properties, such as miscibility, density, viscosity, and surface tension, of the two ionic liquid-benzene mixture series were also compared to the microscopic aspects.
通过衰减全反射红外光谱（ATR-IR）、核磁共振（NMR）和飞秒拉曼诱导克尔效应光谱（fs-RIKES）等多种光谱技术，对1-甲基-3-辛基咪唑四氟硼酸盐（[MOIm][BF4]）-苯和1-甲基-3-辛基咪唑双（三氟甲基磺酰）酰胺（[MOIm][NTf2]）-苯这两个系列混合物的微观特性进行了研究。所有这三种不同的光谱结果表明，与[MOIm][NTf2]-苯混合物相比，[MOIm][BF4]-苯混合物中的阴离子与阳离子之间的相互作用更强。这也很好地解释了两个混合体系之间不同的混溶性特征。苯的化学位移和C-H面外弯曲模式的xC6H6依赖性相似：与低苯浓度相比，在高苯浓度（xC6H6 > ∼ 0.6）下变化较大。相比之下，在[MOIm][BF4]-苯和[MOIm][NTf2]-苯体系中均观察到低于200 cm(-1)的低频光谱一阶矩的线性xC6H6依赖性。化学位移与分子内振动模式以及分子间/离子间振动带在xC6H6依赖性特征上的差异可能源于不同的探测空间尺度。在ATR-IR和NMR实验中发现了平行芳环结构和T形结构的痕迹，但fs-RIKES未观察到明显的局部结构痕迹。这可能意味着咪唑鎓环与苯环之间的相互作用不够强，无法使咪唑鎓环和苯环一起摆动。还将这两个离子液体-苯混合体系的体相性质，如混溶性、密度、粘度和表面张力，与微观特性进行了比较。
