Syntheses and Physical Properties of Ferrocene Derivatives (XII) Crystal Structure of a Liquid Crystalline Ferrocene Derivative, ω-[4-(4-methoxy-phenoxycarbonyl)phenoxycarbonyl] hexyl 4-ferrocenylbenzoate

The structure of a liquid crystalline monosubstituted ferrocene derivative was determined by the single crystal X-ray structure analysis. The title compound, ω-[4-(4-methoxyphenoxycarbony!) phenox-ycarbonyl]hexyl 4-ferrocenylbenzoate has a characteristic chemical structure in which a flexible spacer (hexyl chain) is located between the ferrocenyl and mesogenic groups. The flexible spacer is an all-trans conformation. In order to form a rod-like structure, the molecule is slightly bent around the ester group neighboring the ferrocenylbenzoate group. This rod-like molecular geometry may play an important role in the appearance of the liquid crystal phase and lead to efficient packing, because it is generally known that the derivatives having a bulky ferrocenyl group are not suitable for liquid crystalline compounds. By the way, two cyclopentadienyl rings exhibit an eclipsed conformation rather than a staggered one. The molecules are arranged in layers just like those in the smectic phase of the liquid crystals. The structure obtained is discussed with those of homologues having different flexible spacer lengths and related ferrocene derivatives containing a different mesogenic group, already reported previously.