Flying-seed-like liquid crystals 7(+): Synthesis and mesomorphism of novel octakis(m-chloropyridyloxy) phthalocyanato copper(II) complexes

We have synthesized three novel octakis(m-chloropyridyloxy) phthalocyaninato copper(II) complexes, [x-PyO(m-Cl)](8)PcCu(x = 2, 3, 4: 2a-2c), keeping a chlorine atom at the meta position on the 2-, 3- and 4-pyridyloxy group, in which the nitrogen atom is located at the 2-, 3-and 4-positions, respectively. Their phase transition behavior and the mesophase structure have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Very interestingly, the mesomorphism appears with strong dependence of the position of nitrogen in m-chloropyridyloxy group. The derivative [3-PyO(m-Cl)](8)PcCu (2b) introduced a nitrogen atom at the 3-position is not mesogenic but crystalline. On the other hand, the derivative [2-PyO(m-Cl)](8)PcCu (2a) introduced a nitrogen atom at the 2-position shows columnar mesomorphism only at very high temperatures over 325 degrees C. The derivative [4-PyO(m-Cl)](8)PcCu (2c) introduced a nitrogen atom at the 4-position shows columnar mesomorphism in a very wide temperature region from rt to the decomposition temperature at 306 degrees C. From the viewpoint of N center dot center dot center dot Cl halogen bond, we have discussed about relationship between their mesomorphism and the position of nitrogen atom in m-chloropyridyloxy group