Phthalocyanine pigments: General principles

This chapter describes some of the fundamental chemical and structural principles underlying the phthalocyanine system. Historically, phthalocyanines had been isolated as insoluble blue products in the early twentieth century, although the structures were not established at the time. After the serendipitous re-discovery of metal complex phthalocyanines by industry, and the elucidation of their structures, copper phthalocyanine (CuPc) pigments were introduced industrially in the 1930s to become, and remain, by far the most important blue and green organic pigments, finding almost universal use as colorants for paints, printing inks, plastics, and a wide range of other applications. The phthalocyanines have become one of the most extensively studied classes of organic compounds, because of their unique molecular structures, light absorption properties that produce strong, bright colors, and their exceptionally high stability. While their dominant use is as colorants, they are also of interest for a range of other applications, for example in electronic devices, biological applications, and as catalysts.