The heterocycle chlorin is a macrocyclic tetrapyrrole derivative. It is found in the photosynthetic center either as the uncoordinated phaeophytin or as its magnesium complex, which acts as a primary acceptor in chlorophyll.


In chlorin (2,3-dihydroporphyrin), unlike in porphyrin, the ring system is partially hydrogenated. In phaeophytin an additional ring is condensed onto the macrocycle.

Schematic depiction of the phaeophytin ring system

3D-depiction of the uncoordinated phaeophytin

Chlorin ring system

coordinated Mg2+-ion in Chlorophyll

details of photosynthesis
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