of urea yields . Using such methods, approximately 57,000 tonnes (63,000 Imperial tons) of various phthalocyanines were produced in 1985. More often, MPc is synthesized rather than due to the greater research interest in the former. To prepare these complexes, the phthalocyanine synthesis is conducted in the presence of metal salts. Two copper phthalocyanines are shown in the figure below. {|align="center" class="wikitable" ||| |} Halogenated and sulfonated derivatives of copper phthalocyanines are commercially important as dyes. Such compounds are prepared by treating CuPc with chlorine, bromine or oleum. Applications At the initial discovery of Pc, its uses were primarily limited to dyes and pigments. Modification of the substituents attached to the peripheral rings allows for the tuning of the absorption and emission properties of Pc to yield differently colored dyes and pigments. There has since been significant research on H2Pc and MPc resulting in a wide range of applications in areas including photovoltaics, photodynamic therapy, nanoparticle construction, and catalysis. The electrochemical properties of MPc make them effective electron-donors and -acceptors. As a result, MPc-based organic solar cells with power conversion efficiencies at or below 5% have been developed. Furthermore, MPcs have been used as catalysts for the oxidation of methane, phenols, alcohols, polysaccharides, and olefins; MPcs can also be used to catalyze C–C bond formation and various reduction reactions. Silicon and zinc phthalocyanines have been developed as photosensitizers for non-invasive cancer treatment. Various MPcs have also shown the ability to form nanostructures which have potential applications in electronics and biosensing. Phthalocyanine is also used on some recordable DVDs. Toxicity and hazards No evidence has been reported for acute toxicity or carcinogenicity of phthalocyanine compounds. The (rats, oral) is 10 g/kg. Related compounds Phthalocyanines are structurally related to other tetrapyrrole macrocyles including porphyrins and porphyrazines. They feature four pyrrole-like subunits linked to form a 16 membered inner ring composed of alternating carbon and nitrogen atoms. Structurally larger analogues include naphthalocyanines. The pyrrole-like rings within are closely related to isoindole. Both porphyrins and phthalocyanines function as planar tetradentate dianionic ligands that bind metals through four inwardly projecting nitrogen centers. Such complexes are formally derivatives of , the conjugate base of . Footnotes References External links Macrocycles Chelating agents