Tetrafluorosubstituted titanyl phthalocyanines: Structure of single crystals and phase transition in thin films.

In this work, tetrafluorinated titanyl phthalocyanines with F-substituents in both peripheral (TiOPcF 4 -p) and non-peripheral (TiOPcF 4 -np) positions were synthesized and characterized by the methods of elemental analysis, IR and electronic absorption spectroscopies. The influence of the position of F-substituents on the structure of TiOPcF 4 -p and TiOPcF 4 -np single crystals and thin films grown by vacuum sublimation was studied. TiOPcF 4 -p crystallizes in the I4/m space group and its molecules form uniform stacks along the tetragonal axis. Introduction of F-substituents to non-peripheral positions leads to the change of the crystal structure: TiOPcF 4 -np crystallizes in the P-1 space group and its molecules are packed into 2D layers. Both phthalocyanines form oriented polycrystalline films when deposited by thermal sublimation in vacuum, but their phase composition is different from that of single crystals. The effect of post-deposition annealing of TiOPcF 4 -p and TiOPcF 4 -np films on their phase composition, morphology, optical absorption and Raman spectra, as well as conductivity was revealed. It was shown that a phase transition, which led to the appearance of an additional band in the near-IR region in the optical absorption spectrum, was observed in TiOPcF 4 -p films when heated, whereas no phase transition was observed in TiOPcF 4 -np films. • Structure of single crystals and films of fluorinated titanyl phthalocyanines were determined. • The position of F-substituent affects the structure and phase composition of thin films. • Phase transition in thin films was studied by XRD and spectral methods. • Phase transition leads to the change in optical absorption spectra. [ABSTRACT FROM AUTHOR]