Liquid-crystalline heterodimesogens and ABA-heterotrimesogens comprising a bent 3,5-diphenyl-1,2,4-oxadiazole central unit

• Govindaswamy Shanker,
• Marko Prehm and
• Carsten Tschierske

Beilstein J. Org. Chem. 2012, 8, 472–485, doi:10.3762/bjoc.8.54

• bent-core mesogens are of special interest for achieving biaxial nematic phases of the orthorhombic type. The orthogonal (NcybA) and skewed (NcybC) cybotactic nematic phases were distinguished by XRD and optical observations. Keywords: bent-core mesogens; cybotactic nematic phases; dimesogen; liquid

• ][82]. Finally, the spacer units of these thiadiazoles are also significantly longer (n = 5, 10) than those used for the related cyanobiphenyl-containing dimesogens (n = 3, 4). As a result, LC phases with a tilted organization of the molecules become dominant. The dimesogen Thia-Ox/5, with the shorter

• spacer, displays a SmC–NcybC dimorphism and, remarkably, the SmC phase is removed for the longer homologue Thia-Ox/10. A N-to-SmC transition is observed at T = 172–173 °C for the dimesogen Thia-Ox/5 on reduction of the temperature (Figure 5) [68]. In contrast to the NcybA–CybA-transition, for which no