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

Abstract

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-(−)-β-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-2-(4-substituted-phenyl)pyrimidine, respectively) have been prepared. The mesogenic HL ₃ and HL ₄ 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.