Chiral linear isocyanide palladium(II) and gold(I) complexes as ferroelectric liquid crystals

Abstract

Creation of helical SmC* and Ch mesophases has been achieved by means of metal ion complexation by chiral isocyanide ligands, which have already proven their ability to induce high optical activity in helical synthetic polymers. Thus, from unstable isocyanide compounds with a mesogenic core derived from phenyl benzoate, five stable complexes have been prepared. Four palladium(II) complexes have been obtained with different chiral tails and, in one case, with a three-ring mesogenic core. Their corresponding SmC* phases have been studied in terms of their ferroelectric properties. High P _s values have been found for complexes derived from (S)-octan-2-ol: 93 nC cm ^–2 for I ₂ Pd(C ₈ *) ₂ and 59 nC cm ^–2 for I ₂ Pd(COOPhC ₈ *) ₂ . A gold(I) complex with (R)-2-octyl as the chiral tail is presented as the first SmC* gold(I) complex whose ferroelectric behaviour has been studied. Indeed, the complex has been used as a chiral dopant in a binary mixture, the P _s value of which has been estimated.