Synthesis and characterization of fluorophthalocyanines bearing four 2-(2-thienyl) ethoxy moieties: from the optimization of the fluorine substitution to chemosensing

The energy levels of the HOMO/LUMO Frontier orbitals and the electronic properties of phthalocyanine macrocycles can be tuned by the introduction of substituents. Starting from tetrafluorophthalonitrile, we studied the substitution of fluorine atoms by (2-thienyl) ethoxy moieties. An optimization of the experimental conditions (nature and stoichiometry of the alcohol and base, temperature) allowed us to obtain the monoalkoxy derivative with a very good yield. It was fully characterized using F-19 and H-1 NMR spectroscopies, thermal analysis and X-ray diffraction on single crystals. Then, the corresponding zinc phthalocyanine was synthesized, characterized by means of 19F and 1H NMR spectroscopies, thermal analysis, and also by electronic spectroscopy and electrospray mass spectrometry. The unsymmetrical zinc phthalocyanine bearing also four (2-thienyl) ethoxy moieties was prepared by the mixed condensation of the tetraalkoxyphthalonitrile with the tetrafluorophthalonitrile. The phthalocyanines were used to build an electronic device, a p-type Molecular Semiconductor - Doped Insulator heterojunction (MSDI), in combination with the lutetium bisphthalocyanine as a molecular semiconductor, and their chemosensing behavior towards ammonia was studied.