Porphine

Porphine or porphin is an organic chemical compound with formula C
20H
14N
4. The molecule consists of four pyrrole-like rings joined by four methine (=CH−) groups to form a larger macrocycle ring, which makes it the simplest of the tetrapyrroles. It is an aromatic and heterocyclic compound, solid at room temperature.[1]

Porphine
Names
Other names
Porphin
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.002.690
UNII
Properties
C20H14N4
Molar mass 310.35196 g/mol
Appearance Dark red, shiny leaflets
Melting point N/A
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Porphine does not occur in nature, and is almost only of theoretical interest; however, substituted derivatives include many biochemically significant compounds called porphyrins, with the dominant example being protoporphyrin IX.[2] Many synthetic analogues are also known, including octaethylporphyrin[3] and tetraphenylporphyrin.[4]

Structural characteristics of porphine and its derivatives
  • Common porphyrins
  • Derivatives of protoporphyrin IX are common in nature, the precursor to hemes.
  • Octaethylporphyrin (H2OEP) is a synthetic analogue of protoporphyrin IX. Unlike the natural porphyrin ligands, OEP2− is highly symmetrical.
  • Tetraphenylporphyrin (H2TPP)is another synthetic analogue of protoporphyrin IX. Unlike the natural porphyrin ligands, TPP2− is highly symmetrical. Another difference is that its methine centers are occupied by phenyl groups.

Porphine is planar. The two NH centers are trans.

Two resonance structures of porphine.

Complex with metal in the center

Concomitant with the displacement of two N-H protons, porphine binds metal ions at its center. The insertion of the metal center is slow in the absence of catalysts. In nature, these catalysts (enzymes) are called chelatases. When there is no metal ion (or atom) bound to the nitrogens in the center, then the compounds are called free porphine or free porphyrin. If they are bonded to a metal in the center, then they are bound. A porphyrin with an iron atom of the type found in myoglobin, hemoglobin, or certain cytochromes is called heme. See the Porphyrin article for further details.

Compounds similar to porphine are the parent compounds for similar ring systems with other central metal atoms in biochemistry. These include chlorin, which has a magnesium ion in several types of chlorophyll; bacteriochlorin, found in bacteriochlorophyll; and corrin, which has a cobalt center in cobalamin (vitamin B12).

See also
  • Tetrahydroporphine

Further reading
  • Budavari, Susan (1989). "7574. Porphine". The Merck Index (11th ed.). Merck & Co., Inc. p. 1210. ISBN 0-911910-28-X. LCCN 89-60001.

References
  1. "Porphyrin". Encyclopedia of Inorganic and Bioinorganic Chemistry. Wiley-VCH. 2011. doi:10.1002/9781119951438.eibd0638. ISBN 9781119951438.
  2. Paul R. Ortiz de Montellano (2008). "Hemes in Biology". Wiley Encyclopedia of Chemical Biology. John Wiley & Sons. doi:10.1002/9780470048672.wecb221. ISBN 978-0470048672.
  3. Jonathan L. Sessler; Azadeh Mozaffari; Martin R. Johnson (1992). "3,4-Diethylpyrrole and 2,3,7,8,12,13,17,18-Octaethylporphyrin". Org. Synth. 70: 68. doi:10.15227/orgsyn.070.0068.
  4. Lindsey, Jonathan S. (2000). "Synthesis of meso-substituted porphyrins". In Kadish, Karl M.; Smith, Kevin M.; Guilard, Roger (eds.). Porphyrin Handbook. 1. pp. 45–118. ISBN 0-12-393200-9.
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