The Weizmann Institute of Science, Rehovot 76100, Israel.
Phys Chem Chem Phys. 2009 Nov 7;11(41):9562-8. doi: 10.1039/b908029p. Epub 2009 Aug 20.
The crown form of nona-octanoyloxy tribenzocyclononatriene (C8) with C(3) symmetry was prepared and separated into its enantiomers (C8A and C8B) by HPLC. Like the racemate, the neat enantiomers are also mesogenic, exhibiting two mesophases, M and Col(h). Differential scanning calorimetry, X-ray diffraction, carbon-13 NMR and UV circular dichroism are used to study the structural and dynamic properties of these chiral mesophases. The high-temperature mesophase (Col(h)) was identified by X-ray diffraction as columnar hexagonal; this phase is thermally unstable, undergoing racemization on heating before its clearing point is reached. The low-temperature mesophase (M) is most likely also columnar, but its symmetry could not be determined. In comparison with the racemate, the chiral mesophases are less well ordered, more tightly packed and they have a lower tendency to crystallize. On the other hand they are considerably more mobile, as reflected in their NMR spectra. No helical structure has been identified in the X-ray diffraction of the mesophases.
具有 C(3) 对称性的非八-辛酰氧基三苯并环壬三烯（C8）冠醚被制备出来，并通过 HPLC 将其对映异构体（C8A 和 C8B）分离出来。与外消旋体一样，纯对映异构体也是介晶的，表现出两种介晶相，M 和 Col(h)。差示扫描量热法、X 射线衍射、碳-13 NMR 和紫外圆二色性用于研究这些手性介晶相的结构和动态性质。高温介晶相（Col(h)）通过 X 射线衍射被鉴定为柱状六方相；该相在达到清亮点之前因热异构化而热不稳定。低温介晶相（M）很可能也是柱状的，但无法确定其对称性。与外消旋体相比，手性介晶相的有序性较差，堆积更紧密，结晶倾向较低。另一方面，它们的流动性要强得多，这反映在它们的 NMR 谱中。在介晶相的 X 射线衍射中没有发现螺旋结构。
