Role of coordinated metal ions on the orientation of phthalocyanine based coatings

In the present work, we have investigated the molecular orientation of phthalocyanine films deposited on polycrystalline gold. Three films built from the following molecules are investigated: phthalocyanine (H2Pc), cobalt phthalocyanine (CoPc) and copper phthalocyanine (CuPc). The films are prepared by spin coating and drop casting methods. Orientation analysis has been performed using polarization dependent Fourier transform infrared (FTIR) spectroscopy using transmission and grazing angle reflectance mode. The FTIR study suggests that each phthalocyanine film contains both α- and β-phases. H2Pc based films demonstrate deposition method dependence on the molecular orientation, while the CuPc and CoPc films preserve their molecular orientation independent of deposition method. Grazing angle analysis also suggests that CoPc films show negligible preferred orientation irrespective of film deposition methods. In literature, the band at 878 cm−1 in CuPc has been assigned to out-of-plane bending of C–H. Our grazing angle experiments suggest that this band cannot be assigned to out-of-plane bending vibrations of C–H. Accurate band assignments are also described here for the phthalocyanine system.