Synthesis and mesomorphic properties of bent-core mesogens with isomeric naphthylene central units

New bent-core mesogens that possess only ester linking groups between the aromatic rings and 1,6-, 1,7-, 2,3- or 2,7-naphthylene unit as a central aromatic ring were synthesized. A remarkable finding is that the bent-core ester mesogens with unsymmetrical or highly bent central unit can form banana-phase in a wide temperature range. The compounds with 1,6- and 2,3-naphthylene units showed an antiferroelectric switchable smectic phase, which has been designated a B₂ phase. While compounds with 2,7-naphthylene unit was known to form B₂ phase, the compound with 1,7-naphthylene unit failed to form the mesophase in the melt.