Synthesis and liquid crystal behavior of bis[3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyaninato] rare earth complexes

Abstract

A series of novel bis[3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyaninato] rare earth(III) complexes M [ Nc ( SC 12 H 25)8]2( M = Nd , Eu , Gd , Tb , Y , Ho , Er ) have been prepared by tetramerization of 2,3-bis(dodecylthio)-6,7-dicyanonaphthalene with M ( acac )3·n H 2 O in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing n-octanol. These sandwich double-decker complexes were characterized by elemental analysis and various spectroscopic methods including UV-vis, near IR, IR, and mass spectroscopies. Their liquid crystal behavior was studied by polarized optical microscope (POM), differential scanning calorimeter (DSC), and X-ray diffraction. These alkylthio-substituted bis(2,3-naphthalocyaninato) rare earth complexes yield a hexagonal columnar liquid crystal whose stable temperature range is between 42 and 243°C. The stable temperature domain of the mesophase shows a trend to be dependent on the central rare earth ionic size. 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.