Unsymmetrical crown ether derivatives 7 and 12 with one lateral o-terphenyl unit bearing different ester substituents were synthesized starting from methoxymethyl (MOM) protected bromobenzenes 3 and 8 by conversion into the respective borolanes 4 and 9, twofold Suzuki coupling with dibromobenzo[15]crown-5, acidic deprotection and finally esterification either with various alkanoic chlorides or gallic acids. Reaction with NaI provided the complexes [NaI·(7a–g)] and [NaI·(12a–d)], respectively. Uncomplexed crown ethers as well as their complexes [NaI·7a–c] and [NaI·12a–d] are non-mesogenic. In the case of [NaI·(7d–g)], however, the complexation induced a mesophase formation. As exemplarily shown for [NaI·7d], different textures were observed upon cooling, a fan-shaped texture, which is typical for a columnar hexagonal mesophase, and a striped fan-shaped texture, indicating a second mesophase Colx at low-temperature. From the SAXS diffraction pattern this mesophase was assigned to be columnar rectangular. For [NaI·7g] a different diffraction pattern was found, from which the low-temperature mesophase might be attributed to a soft crystal or a highly ordered columnar mesophase with orthorhombic symmetry.
合成了不对称的
冠醚衍
生物7和12,这些衍
生物具有一个侧链o-三苯基单元,并带有不同的酯取代基。合成起始于甲氧甲基(MOM)保护的
溴苯3和8,通过转换成相应的
硼烯烃4和9,进行双重铃木偶联反应,与二
溴苯并[15]冠-5反应,随后进行酸性去保护,最后用各种烷基
氯化物或
鞣酸酯化。与NaI反应分别生成复合物[NaI·(7a–g)]和[NaI·(12a–d)]。未配位的
冠醚以及它们的复合物[NaI·7a–c]和[NaI·12a–d]均不具备介晶性。然而,对于[NaI·(7d–g)],复合作用引发了介相的形成。如[NaI·7d]所示,冷却时观察到不同的纹理,包括典型于柱状六角介相的扇形纹理,以及指示低温下第二种介相Colx的条纹扇形纹理。从小角X射线散射(
SAXS)衍射图谱来看,该介相被归类为柱状矩形。对于[NaI·7g],发现了不同的衍射图案,从中可以推测低温下的介相归因于软晶体或具有正交对称性的高度有序柱状介相。