1,1 '-Disubstituted ferrocene containing hexacatenar thermotropic liquid crystals

The preparation and characterization of ferrocene containing hexacatenar me tallomesogens 4a-h based on alkoxy terminal groups with hexyloxy (4a), octy loxy (4b), decyloxy (4c), dodecyloxy (4d), tetradecyloxy (4e), hexadecyloxy (4f), octadecyloxy (4g) and eicosyloxy (4h) chains are described. The intr oduction of alkyl chains of different lengths induces a rich variety of sel f-assembled liquid crystalline structures. In the crystalline state, the fe rrocene containing hexacatenar metallomesogens 4a-h organize into a microph ase-separated monolayer lamellar structure. In contrast, a dramatic phase c hange after crystalline melting of the metallomesogens is observed with var iation of the chain length. The ferrocene containing hexacatenar metallomes ogens 4b and c display a bicontinuous cubic mesophase with Ia3d symmetry, w hile the ferrocene containing hexacatenar metallomesogens 4d-g exhibit a he xagonal columnar mesophase. Further increasing the length of the alkyl chai n as in the case of 4h suppresses liquid crystallinity and induces only a c rystalline phase. This unique behavior in the ferrocene containing metallom esogenic molecules can be understood to originate from the anisotropic aggr egation of ferrocene containing aromatic segments and consequent entropic p enalties associated with chain stretching.