Mesogenic properties of novel enamino ketone ligands and their copper (II) complexes

Abstract

Several novel homologous series of ligands incorporating an enamino ketone quasi-ring and their copper complexes are synthesized and studied by thermal microscopy, DSC and EPR methods. The ligands {l-[4′-(4″hexyloxyphenyloazo)phenyl]-3-alkylaminoprop-2-en-l-ones} and their complexes form enantiotropic nematic and smectic C phases with the nematic phase of some of the complexes broader than 80 °C. The EPR spectra of the paramagnetic complexes show that the chelate centre is planar in dilute solution as well as in the magnetically concentrated smectic C phase. Exchanging the hexyloxy moiety for a hexylamino or N-hexyl-N-methylamino group gives a series of ligands and complexes with lower melting and clearing temperatures. Further molecular modifications including a reversal of the substitution pattern on the enamino ketone ring are also presented.