Effect of substituents on the orientation of octasubstituted copper(II) phthalocyanine thin films

Octasubstituted copper(II) phthalocyanines containing alkylthio-, alkyloxy-, (trioxyethylene)thio- and (trioxyethylene)oxy- substituents in peripheral positions have been synthesized and characterized using UV–vis, IR, and mass spectroscopies. The mesogenic properties of the copper(II) phthalocyanines have been studied by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The effect of the nature of substituents in the phthalocyanine ring on the liquid crystalline properties and the orientation of the molecules in thin films have also been investigated using a range of spectral methods as well as by X-ray diffraction analysis. Visible absorption spectroscopy yielded an evidence of a thermally induced molecular reorganization in the films. Polarized Raman spectroscopy was used to study the preferential orientation of molecules relative to the substrate surface. Influence of the nature of substituents in the phthalocyanine molecule in the thin films conductivity was also investigated.

► Octasubstituted copper(II) phthalocyanines form columnar-hexagonal mesophase over a wide temperature range.
► Phthalocyanines form oriented films on the substrate surface.
► Substituents in the phthalocyanine molecule have a significant effect on the orientation and electrical properties.