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

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 {1-[4'-(4'-hexyloxyphenyloazo)phenyl]-3-alkylaminoprop-2-en-1-ones} and their complexes form enantiotropic nematic and smectic C phases with the nematic phase of. some of the complexes broader than 80 degrees 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.