Molecular organization in the thin films of gallium(III) phthalocyanine chloride and its μ-(oxo)dimer: Optical spectroscopy and XPS study

Molecular arrangement in the thin films of gallium(III) phthalocyanine chloride (PcGaCl) and its μ-(oxo)dimer (μ-(oxo)bis[phthalocyaninato] gallium(III), (PcGa)2O) has been studied using complementary spectroscopic techniques: viz., X-ray photoelectron and optical (polarized Raman and UV-vis) spectroscopies, as well as atomic force microscopy. The former films grown by physical vapor deposition on ITO substrates transformed into the films of the latter μ-(oxo)dimer upon thermal annealing at 300 °C under controlled environmental conditions. The polarized Raman spectroscopy revealed that both films are well organized, and the mean tilt angle between the molecular planes and the substrate surface increases from 53 ± 5° (PcGaCl) to 85 ± 5° ((PcGa)2O). All intense bands in the experimental Raman spectra of PcGaCl and (PcGa)2O were assigned using density functional theory calculations. The theoretically predicted wavenumbers are in a good agreement with the experimental values.