Liquid crystals chiral core discotics

Discotic liquid crystals based on carbohydrates are intrinsically chiral due to the chiral nature of their core.49,50 Numerous discotic liquid crystals derived from these mesogens have been reported however, the expression of chirality in the subsequent mesophases has only rarely been seen. An example of the latter is the a-anomer of penta- O -decanoylglucopyranosc (47), which forms a discotic mesophase in which the molecules pack helically in the columns... 

Compound 18 exhibits solely a chiral nematic discotic phase (N ) phase because the steric effect of the branched chains at the chiral centre disrupts the ability of the molecules to pack in columns. The large size of the planar aromatic core ensures a high clearing point, but the liquid crystal tendency depends critically on the type of chiral peripheral chain. Hexa-substituted phenylacetylenes were discussed in chapter 3 and exhibited the Np phase. Perhaps not surprisingly, when one of the peripheral acetylene units is chiral, the N phase is exhibited (compound 19). 

Since their discovery as discotic liquid crystals, both triphenylenes and phthalocyanines have been studied as chiral columns [74]. There are no chirooptic signatures such as circular dichroism or optical rotation changes for the triphenylenes that are substituted with chiral side chains. For the phthalocyanines, Nolte and coworkers have shown that when their exterior is substituted with chiral side chains the phthalocyanine core shows an altered CD spectrum in aggregates, in thin films and in concentrated solutions [75]. These helical stacks, wrapped like ropes, can be seen with electron... 

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