Abstract

The preparation and characterization of ferrocene containing hexacatenar metallomesogens 4a–h based on alkoxy terminal groups with hexyloxy (4a), octyloxy (4b), decyloxy (4c), dodecyloxy (4d), tetradecyloxy (4e), hexadecyloxy (4f), octadecyloxy (4g) and eicosyloxy (4h) chains are described. The introduction of alkyl chains of different lengths induces a rich variety of self-assembled liquid crystalline structures. In the crystalline state, the ferrocene containing hexacatenar metallomesogens 4a–h organize into a microphase-separated monolayer lamellar structure. In contrast, a dramatic phase change after crystalline melting of the metallomesogens is observed with variation of the chain length. The ferrocene containing hexacatenar metallomesogens 4b and c display a bicontinuous cubic mesophase with Ia3d symmetry, while the ferrocene containing hexacatenar metallomesogens 4d–g exhibit a hexagonal columnar mesophase. Further increasing the length of the alkyl chain as in the case of 4h suppresses liquid crystallinity and induces only a crystalline phase. This unique behavior in the ferrocene containing metallomesogenic molecules can be understood to originate from the anisotropic aggregation of ferrocene containing aromatic segments and consequent entropic penalties associated with chain stretching.