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

Abstract

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 ¹⁹F and ¹H 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.