Synthesis and photophysical properties of novel unsymmetrical metal-free and metallophthalocyanines

The synthesis of novel, unsymmetrical, octasubstituted metal-free and metallo phthalocyanines (zinc, manganese) bearing two ethynylthiophene moieties and six hexylthio substituents was achieved by a statistical condensation reaction of 4,5-di(hexylthio) phthalonitrile with 4,5-bis(thiophen-3-ylethynyl) phthalonitrile in the presence of zinc and manganese salts (without metal salt for metal-free phthlocyanine). 4,5-Bis(thiophen-3-ylethynyl)phthalonitrile was obtained through Sonogashira coupling reaction. The new compounds have been characterized by using elemental analyses, mass, proton nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV-vis) techniques. The aggregation properties of the compounds were investigated in different concentrations in tetrahydrofuran before and after addition of surfactant Triton X-100. General trends for fluorescence quantum yields and lifetimes of unsymmetrical phthalocyanines (metal-free and zinc) are also described in tetrahydrofuran (THF). The fluorescence of these compounds is effectively quenched by 1,4-benzoquinone (BQ) in THF.