A novel series of heteropolynuclear metallomesogens: Organopalladium complexes with ferrocenophane-containing ligands

Ferrocenophane-containing (Fcph) Schiff's bases p-C₁₂H ₂₅O-(C₆H₄)CH=N(C₆H₄)Fcph (L^AH) and p-C₁₂H₂₅O(C₆H ₄)COO-(C₆H₄)CH=N(C₆H ₄)Fcph (L^BH) react with palladium(II) acetate to form μ-acetato- and chloro-bridged dimeric organo-palladium complexes. By exchanging acetato-groups with the chloride anions, μ-chloro-bridged heteropolynuclear dimers are obtained that show thermotropic smectic A phases over a temperature range of 198 to 260°C. The complexes [PdClL ^A]₂ and [PdClL^B]₂ can be transformed into a variety of mixed-ligand Pd^II complexes by treatment with salicyl-aldimine p-C₁₂H₂₅O(C₆H ₄)COO(C₆H₃)(OH)CH=N(C₆H ₄)-Fcph (L^CH) and β-aminovinyl ketone p-C ₁₂H₂₅O(C₆H₄)-COCH=CHNH(C ₆H₄)Fcph (LDH). The obtained mixed-ligand heterometallic complexes [PdL^AL^C], [PdL^BL^C], [PdL^AL^D] and [PdL^BL^D] exhibit enantiotropic, thermotropic nematic phases over a broad temperature range from 71 to 205°C. The structures of the synthesized compounds were characterized by means of ¹H NMR, IR and UV spectroscopy, as well as elemental analysis. The liquid crystalline properties were studied by polarising optical microscopy and DSC.