Stilbenoid stars

The most comprehensive studies on shape-persistent Hekates have been performed on stilbenoid star-shaped molecules. Structures and mesomorphic properties are collected in Table 1. Core building blocks with only one repeating unit per arm and one flexible chain 26a,b, 28a-d, 30a did not show any liquid crystal properties [56-58]. In the series of two chain derivatives 28e, 30b,c the formation of meso-phases depend on the core [57-59]. The electron deficient triazine and the dicyanopyridine building block induced obviously columnar mesophases. The pyridine derivative 30b showed only a crystalline phase [58]. In the series of nine chain stars 26c-g [60-62] and 28f-n [57], the compounds formed columnar phases depending on the chain length of the peripheral chains. Propyloxy chains are too short but hexyloxy and dodecyloxy chains are sufficient for the formation of liquid crystal phases by nanosegregation [60-62]. This can be rationalised by a dense... 

Star-shaped compounds having a 1,3,5-triazine core and stilbenoid arms have been prepared. These compounds form nematic discotic systems <04T6881>. Discotic liquid crystalline... 

Finally, several, novel, star-shaped octakis(stilbenoid phthalocyaninato) zinc complexes ((7) R = or R, = 3, 6) were synthesized. The thermal behavior of the twenty-four-chained complex was not studied (R ), but that with hexyloxy side chains (R, n = 6) was found to self-organize into a Coin phase at room temperature up to 220 °C. 

Figure 5.11 Structure of a conjugated dendrimers, star-shaped stilbenoid phthalocyanines [54]. (Reproduced with permission.)...

Apart from the linear arrangement of repeat units, cyclic, star-shaped and dendritic arrangements can be realized. Scheme 11.4 shows some examples based on stilbenoid building blocks. 

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