Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Porphyrin

  • Henderson James (Jim) CleavesII
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1258-3

Definition

Porphyrins are heterocyclic organic macrocycles composed of four modified pyrrole rings connected by their α-carbon atoms via methine [-CH=] linkages. Porphyrins are aromatic and thus obey Hückel’s 4n + 2 π electron rule. Porphyrins are highly conjugated and have very intense absorption in the visible region and may be deeply colored. The name porphyrin derives from the Greek word for purple. Porphyrins are the conjugate acids of ligands that form complexes by binding metal ions, which are usually in the +2 or +3 oxidation state. Some porphyrins, such as heme, coordinate iron; other porphyrins chelate cobalt, magnesium, manganese, or nickel. Porphyrin-like compounds have been reported in meteorites, and a prebiotic synthesis has been proposed starting from pyrroles and aldehydes. Acidic conditions are required for this synthesis.

History

F. M. Johnson proposed in the 1970s that the porphyrins were the carriers of the diffuse interstellar bands. This proposal has not been...

Keywords

Aromatic Hydrocarbon Bioorganic Chemistry Acidic Condition Absorption Feature Visible Region 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Earth-Life Science Institute (ELSI)Tokyo Institute of Technology, Meguro-kuTokyoJapan
  2. 2.Institute for Advanced StudyPrincetonUSA
  3. 3.Blue Marble Space Institute of ScienceWashingtonUSA
  4. 4.Center for Chemical EvolutionGeorgia Institute of TechnologyAtlantaUSA