Structural aspects of Langmuir–Blodgett and cast films of zinc phthalocyanine and zinc hexadecafluorophthalocyanine

The processing of macrocyclic phthalocyanines (Pc) in the form of thin, nanostructured films has been usually carried out via evaporation techniques, owing to the low solubility exhibited by these compounds. The fabrication of Pc ultrathin films via the Langmuir–Blodgett technique may be advantageous from a technological point of view, since parameters such as film architecture and organization can be achieved without post-thermal treatments. In this study, a parent zinc phthalocyanine (ZnPc) and its fluorinated derivative (F16ZnPc) were synthesized and manipulated in the form of LB films. The morphological and structural features of ZnPc and F16ZnPc Langmuir–Blodgett films containing up to 31 layers were investigated using Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy and X-ray diffraction analyses and were compared to ZnPc and F16ZnPc cast films. The interplanar distance obtained by X-ray specular reflection decreases from 12.64 Å for ZnPc to 12.16 Å for F16ZnPc. FTIR spectra indicated absence of order in the LB films from ZnPc and F16ZnPc, at least in the direction perpendicular to the substrate surface. Therefore, the order observed in the X-ray diffractograms means that the molecules might be organized in crystallites that are randomly oriented in the film.