Ferroelectric liquid crystals with fluoro‐ and aza‐fluorenone cores: the effect of stereo‐polar coupling

Abstract

The chiral fluorenone mesogens (R)‐1‐fluoro‐2‐(2‐octyloxy)‐7‐(4‐undecyloxybenzoyloxy)fluoren‐9‐one (2) and (R)‐2‐(2‐octyloxy)‐7‐(4‐undecyloxybenzoyloxy)‐3‐azafluoren‐9‐one (3) were synthesized using a combined ortho‐directed and remote metalation strategy, which also incorporates a Suzuki–Miyaura crosscoupling step. These compounds form chiral SmC* liquid crystal phases with reduced polarizations (P _o) of +475 and +332 nC cm⁻² at 10 K below the Curie point, respectively. These values are considerably larger than that previously reported for the unsubstituted fluorenone (R)‐2‐(2‐octyloxy)‐7‐(4‐undecyloxybenzoyloxy)fluoren‐9‐one (1), which is +111 nC cm⁻² at 10 K below the Curie point. Molecular modelling based on the Boulder model suggests that the larger polarizations result from a conformational bias of the fluorenone core dipole moment along the polar axis of the SmC* phase caused by stereo‐polar coupling with the chiral 2‐octyloxy side chain.

Acknowledgements

We are grateful to the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation and the Ontario Challenge Fund for support of this work.