Transition metals complexed to ordered mesophases XIII. Synthesis and mesomorphic properties of potentially ferroelectric Schiff's bases palladium(II) complexes

A series of N-[4'-(dodecyloxy)resorcylidene]-4-(RO*)-anilines (HL(n) n = 1, R*O = (-)-cis-myrtanyl; n = 2, R*O = (-)-menthyl; n = 3, R*O = S(-)-beta-citronellyl; n = 4, R*O = R-(-)-2-octyl) has been synthesized and the mesomorphic properties investigated. These ligands are able to chelate a metal atom; accordingly three different series of palladium complexes, [(Ln)Pd(Ln)], [(Ln)Pd(Azoxy-6)] and [(L3)Pd(Ph-Py(n))] (where Azoxy-6 and PhPy(n) are cyclopalladated 4,4'-dihexyloxyazoxybenzene and 5-substituted-244-substituted-phenyl)pyrimidine, respectively) have been prepared. The mesogenic HL3 and HL4 ligands exhibit a S(C)* phase, retained in [(L3)Pd(L3)], which changes to a cholesteric phase in [(L4)Pd(L4)] and becomes the more ordered S(H)* phase in the [(Ln)Pd(Azoxy-6)] (n = 3,4) derivatives. In contrast, in the [(L3)Pd(Ph-Py(n))] compounds the mesomorphic phase is a S(A) phase.