Zurich: high-yield generation of metal-free phthalocyanines

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Researchers at the Institute of Inorganic Chemistry at the University of Zurich, Switzerland, have developed a method that yields highly stable metal-free phthalocyanines with variable metal centres. The technology consists of strongly chelating metal zinc templates and uses ionic liquids in the demetallation reaction to yield phthalocyanines with the photophysical properties required for the production of inks, dyes and plastics

Phthalocyanines are chemically and thermally stable, light-fast, blue or green organic pigments with high photostability. They are derived from the basic compound (C6H4C2N)4N4 and are used in enamels, printing inks, linoleum and plastics, as well as in vivo, acting as sensitisers for photodynamic therapy. Their photophysical properties also make them useful components of synthetic catalysts, chemical sensors and photovoltaic and data storage devices.

The yield of metal-free phthalocyanines by heating dicyano or diiminoisoindoline precursors, or phthalic anhydride and phthalimide precursors is lower than the yield obtained using ionic liquids in the demetallation reaction. The present invention relies on strong chelation of metal ion templates, allowing cyclotetramerisation of zinc-templates from which zinc is subsequently removed, so yielding phthalocyanines with variable metal centres such as copper, nickel and iron.

http://www.uzh.ch/