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Not to be confused with chlorine.
CAS number 2683-84-3 YesY
PubChem 65106
ChemSpider 58616 YesY
Jmol-3D images Image 1
Molecular formula C20H16N4
Molar mass 312.36784
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

In organic chemistry, a chlorin is a large heterocyclic aromatic ring consisting, at the core, of three pyrroles and one pyrroline coupled through four =CH- linkages. Unlike porphin, the central aromatic ring structure of porphyrins, a chlorin is therefore largely aromatic but not aromatic through the entire circumference of the ring.

Magnesium-containing chlorins are called chlorophylls, and are the central photosensitive pigment in chloroplasts.

Related compounds, with two pyrroles and two pyrrolines (which are like pyrroles with one double bond reduced to a single bond) in the macrocycle are called bacteriochlorins and isobacteriochlorins.[1]

Structures comparing porphin, chlorin, bacteriochlorin, and isobacteriochlorin. Note relocation of C=C double bond between the two bacteriochlorin isomers. There are two π electrons (symbolized by π e) for every double bond in the macrocycle.

Because of their photosensitivity, chlorins are in active use as photosensitizing agents in experimental photodynamic therapy.

See also[edit]


  1. ^ "ChEBI". June 16, 2009. pp. isobacteriochlorin (CHEBI:52583). Retrieved 1 February 2012.