Porphyrin

A porphyrin is a heterocyclic macrocycle made from 3 pyrrole subunits and one pyrroline subunit, and linked on opposite sides through 4 methine bridges. The macrocycle, therefore, is more aromatic, than the related corrins or chlorins. The extensive conjugated system makes the compound chromatic, hence the name "porphyrin" from a Greek word for purple.

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Porphyrins combine readily with metals, coordinating with them in the central cavity. Iron-, zinc-, copper-, nickel-, and cobalt-containing porphyrins are known, and many other metals can be inserted. A porphyrin in which no metal is inserted in its cavity is called a "free base".

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Some iron containing porphyrins are called hemes, and heme-containing proteins, or hemoproteins, are found extensively in biochemistry such as hemoglobin. Porphyrin-based compounds are also used in molecular memories

Macrocycle: A macrocycle is, as defined by IUPAC, "a cyclic macromolecule or a macromolecular cyclic portion of a molecule." In the chemical literature, organic chemists may consider any molecule containing a ring of seven, fifteen, or any arbitrarily large number of atoms to be macrocyclic. Generally however, ...

Pyrroline: Pyrrolines, also known under the name dihydropyrroles, are three different heterocyclic organic chemical compounds which differ in the position of the double bond. Pyrrolines are formally derived from the aromate pyrrole by hydrogenation. 1-Pyrroline is a cyclic imine while 2-pyrroline and 3-pyrroli...

Methine: In chemistry, methine is tri-valent functional group CH, derived formally from methane. The name "methine" is used for...