New Chemical Family of [<i>n</i>-C<i><sub>x</sub></i>H<sub>(2</sub><i><sub>x</sub></i><sub>+1)</sub>NEt<sub>3</sub>][BEt<sub>3</sub>Me] Showing Ionic Plastic-Crystal (<i>x</i> = 4, 5), Rotator-Crystal (<i>x</i> = 6, 7) and Liquid-Crystal Phases (<i>x</i> = 8–16)
作者:Yudai Yamada、Erina Kashimoto、Hisashi Honda
DOI:10.1246/bcsj.20190085
日期:2019.8.15
New ionic liquid crystals of [n-CxH(2x+1)NEt3][BEt3Me] (abbreviated to [CxNEt3][BEt3Me]) were detected for species with even numbers of 8 ≤ x ≤ 16. In contrast, plastic- and rotator-crystal phases were obtained for [CxNEt3][BEt3Me] species with lower x values of x = 4, 5, and 6, 7, respectively. Because we previously documented plastic phases for the [CxNEt3][BEt3Me] (x = 1–3) species, [CxNEt3][BEt3Me] can be classified as a novel chemical family adopting the entire range of states (mesophases) between solid and isotropic liquid phases (plastic, rotator, and liquid crystals) as a function of the alkyl chain length. Polarized optical microscope (POM) and X-ray diffraction (XRD) measurements revealed that these liquid crystals (x = 8–16 with even numbers of x) form smectic B (x = 8) and A (x = 10), and nematic phases (x ≥ 12) in the liquid-crystal phases. In the case of x = 4, 5, XRD analysis showed that the salts form cubic crystal structures. Furthermore, the NMR line shapes revealed that both the cation and anion underwent isotropic reorientation. In contrast, the NMR spectra showed that the cations rotated about their long axis in the [C6NEt3][BEt3Me] and [C7NEt3][BEt3Me] crystals.
新型的离子液晶 [n-CxH(2x+1)NEt3][BEt3Me](简称 [CxNEt3][BEt3Me])被发现存在于具有偶数碳原子数(8 ≤ x ≤ 16)的物种中。相比之下,对于碳原子数较少的 [CxNEt3][BEt3Me](x = 4, 5 和 6, 7),分别获得了塑性和旋转晶相。因为我们之前记录了 [CxNEt3][BEt3Me](x = 1–3)物种的塑性相,[CxNEt3][BEt3Me] 可以被归类为一个新型化学家族,该家族采用了一系列状态(介相),这些状态介于固态和各向同性液态之间(塑性相、旋转相和液晶相),并且这些状态随着烷基链长度的变化而变化。偏光显微镜(POM)和 X 射线衍射(XRD)测量揭示了这些液晶(x = 8–16 且 x 为偶数)在液晶相中形成了碟状 B(x = 8)、碟状 A(x = 10)和向列相(x ≥ 12)。对于 x = 4, 5,XRD 分析显示这些盐形成了立方晶体结构。此外,NMR 线形状揭示了阳离子和阴离子都经历了各向同性的重新定向。相比之下,NMR 光谱显示,阳离子在 [C6NEt3][BEt3Me] 和 [C7NEt3][BEt3Me] 晶体中围绕其长轴旋转。