Synthesis and properties of terphenyl- and quaterphenyl-based chiral diesters

A new synthetic approach for the chiral terphenyl- and quaterphenyl-based diesters, bis[(1S)-1-methylheptyl] 1,1′:4′,1″-terphenyl-4,4″-dicarboxylates and bis[(1S)-1-methylheptyl] 1,1′:4′,1″:4″,1″′-quaterphenyl-4,4″′-dicarboxylates, has been developed and optimised. The approach presented allows the synthesis of a range of laterally substituted oligophenyl diesters in good yield. A number of pairs of S,S and R,R isomers have been synthesised and their thermodynamic properties measured. Most of the compounds have very good solubility in a variety of liquid crystalline host mixtures, and moderate helical twisting power, which has been determined for a number of nematic materials, either dielectrically positive or negative. The high birefringence of the oligophenyl core makes them suitable candidates as chiral dopants for medium to highly birefringent nematic materials for generating cholesteric and blue phase materials.