Discotic Liquid Crystals of Transition Metal Complexes, 3: the First-Established Discotic Lamellar Phase in Bis[1,3- di(p-n-alkoxyphenyl)propane-1,3-dionato]copper(II)

Abstract

A new series of disk-like complexes, bis[1,3-di(p-n-alkoxyphenyl)propane-1,3-dionato]copper(II) (abbreviated as C_nO-Cu, n = 1-12), has been synthesized. It was found that each of the complexes from C₃O-Cu to C₁₂O-Cu is a discogen, and that each of them has only one discotic mesophase. C₃O-Cu is the first compound substituted by the shortest side chains in the discogen, so far as we know. The mesomorphic textures could be observed as mosaic textures for C₃O-Cu ~ C₅O-Cu and as big broken fan-like textures for C₆O-Cu ~ C₁₂O-Cu. The cutectic point calculated from Le Chatelier-Schröder relations agrees well with the found eutectic point in the binary phase diagram between C₈O-Cu and C₈-Cu. This is the first example of such agreement in the discogens of the organic transition metal complexes. It has been established for the first time from X-ray diffraction measurements that each of the discotic mesophases in the complexes from C₆O-Cu to C₁₂O-Cu is a discotic lamellar phase. It becomes clear that this discotic mesophase is truly a new discotic lamellar phase (D_L) different from the mesophase in C₁₀-Cu, and that the D_L phase has a structure in which the molecules tilt to the layers.

Keywords:

• discotic liquid crystal
• transition metal complex
• bis(β-diketonato)copper(II)
• discotic lamellar phase