"Porphyrins are a group of highly conjugated, macrocyclic organic compounds. Metal complexes of porphyrins occur naturally in hemoglobin, myoglobin and cytochromes and synthetic porphyrin complexes are used widely as catalysts, in new materials, and as potential therapeutic agents. These applications are possible because the porphyrin ligand imparts interesting and unusual properties to the chemistry of the central atom. The chemistry of porphyrins and their related macrocycles (e.g. phthalocyanines, corroles, porphyrazines) is a vast and rapidly expanding field with applications which span biochemistry, catalysis, supramolecular chemistry, molecular electronics, materials, energy and human health"-- Provided by publisher.