Two origins for twisting power of a binaphthyl derivative in a host nematic liquid crystal

We prepare a series of homologues of novel binaphthyl derivatives, (R)-2, 2'-bis{-[4-(4-(octyloxycarbonyl)phenyl)phenyloxycabonyl]alkyloxy}-1, 1'-binaphthyl [(R)-Bi-n], and investigate their induced helical senses and pitches in different host nematic liquid-crystalline compounds. Pronounced odd-even effects were observed for the induced helical structure in each mixture with 5-heptyl-2-(4-hexyloxyphenyl)pyrimidine. Temperature-dependent helical twist inversion was observed for the mixture doped with the odd members, whereas a right-handed helix was observed for the mixture doped with the even members. On the other hand, a left-handed helix was induced in each mixture with 4-methyloxyphenyl 4-pentylcyclohexane. We discuss the change in sign of the induced pitch in terms of chirality transfer from the binaphthyl derivative to a host nematic liquid crystal.