SYNTHESIS AND LIQUID-CRYSTAL BEHAVIOR OF A NOVEL CLASS OF DISK-LIKE METALLOMESOGENS - HEXASUBSTITUTED TRIAZOLEHEMIPORPHYRAZINES

The synthesis, characterization and mesomorphic properties of two seri es of new discotic molecules based on the triazolehemiporphyrazine cor e is described. This central unit has been attached to six lipophilic chains, two dodecyl groups on the triazole ring and four dodecyloxy or dioctylaminocarbonilmethoxy on the isoindole moiety, and metallic com plexes (Cu, Ni) have been prepared. The mesogenic behavior has been st udied using optical microscopy, DSC, and X-ray diffraction. The alkoxy -substituted macrocycles melt from the solid to the liquid-crystalline phase at relatively low temperatures (ca. 30 degrees C), exhibiting h exagonal columnar mesophases (D-ho) (despite being elliptical molecule s) in a large temperature range, up to 300 degrees C in the case of me tallic complexes. The dialkylamide derivatives are not mesogenic despi te the extent of the paraffinic part. This fact is probably due to the steric hindrance between the branched chains, thus difficulting colum nar stacking of the cores.