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

•Unsymmetrical phthalocyanines bearing ethynylthiophene moieties were synthesized.•These phthalocyanines show the enhanced solubility in organic solvents.•Aggregation properties of these compounds were investigated.•Photophysical properties of these phthalocyanines have been investigated.•The fluorescence quenching behaviour of these phthalocyanines were also reported.

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.

Graphical abstractNovel, unsymmetrical, octasubstituted phthalocyanines bearing two ethynylthiophene moieties and six hexylthio substituents have been prepared and characterized. The aggregation properties of these compounds were investigated. General trends for fluorescence quantum yields and lifetimes of these phthalocyanines are also described. The fluorescence of these compounds is effectively quenched by 1,4-benzoquinone.Figure optionsDownload full-size imageDownload as PowerPoint slide