Synthesis and liquid crystal behavior of tris[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth complexes

Abstract

A series of tris[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth(III) complexes M 2[ Pc ( OC 8 H 17)8]3 [ M = Eu , Gd , Y , Lu ] has been prepared by the reaction of corresponding bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth complexes with M ( acac )3·n H 2 O in refluxing 1,2,4-trichlorobenzene. These liquid crystalline sandwich, triple-decker complexes were characterized by elemental analysis and various spectroscopic methods including 1 H NMR, UV-vis, IR and mass spectroscopies. Their liquid crystal phase transition behavior was studied by Polarized Optical Microscope, Differential Scanning Calorimeter and X-ray diffraction. The complexes, with octyloxy attached as side chains, showed rectangular columnar liquid crystal phases in a liquid crystal temperature range between 83 and 305°C. In addition to the rare earth contraction, both the transition temperature and the wide temperature range of the mesophase show a slight but obvious trend to decrease, respectively, in the same order. In contrast, the molecular packing of these complexes as revealed by X-ray diffraction was found to be almost independent of the ionic size of the central rare earth.