Ferroelectric Behavior of Chiral Bis(salicylideneaniline) Copper(II), Vanadium(IV), and Palladium(II) Liquid Crystals

Abstract

Three series of chiral bis(salicylideneaniline)copper(II), -oxovanadium(IV), and -palladium(II) complexes, namely, series X = −CHCH−COO−, series X = −COO−, and series X = −O−, have been synthesized, and their mesogenic and ferroelectric properties evaluated. The potentially ferroelectric SC* phase has been found for all four compounds of the series X = −CHCH−COO− and the three complexes of the series X = −COO−. The values of the spontaneous polarization (Ps) of these compounds have been measured ranging from ca. 20 to 90 nC/cm2. A packing arrangement in which the molecules are tilted to one edge within the SC* phase is proposed. In this situation the net molecular dipole must principally lie with the polar axis of the ferroelectric phase, thus explaining the Ps values measured. In addition, all the compounds have been studied as chiral dopants for ferroelectric liquid-crystalline mixtures.