Phthalocyanine is a macrocyclic compound, consists of four isoindole-class [(C₆H₄)C₂N] units linked by four nitrogen atoms to form a conjugated chain, which take play in hosting various different metal ions in its center. This structure shows a striking feature as a colorant like porphyrins (biopigments) in nature. Phthalocyanine derivatives derived from the basic compound of (C₆H₄C₂N)₄N₄ are used as light-fast blue or green pigments.

The hosted metals and substituted groups result in the distinct colors; phthalocyanine (blue-green), copper phthalocyanine (blue), chlorinated copper phthalocyanine (green), and sulfonated copper phthalocyanine (green). Recently they are involved in the study of photosensitizer chemistry or metal complex chemistry such as transition-metal complex catalyst chemistry for uniform polymerization, luminescence chemistry and spectrophotometric analysis, organic synthesis and polymerization. Phthalocyanine pigments are used in enamels, linoleum, inks, plastics, and rubber goods. Photoisomerizable phthalocyanines are used in rewritable CD or DVD printing. Some phthalocyanines such as fluoraluminium phthalocyanine are used in cancer treatment.