Porphyrins

A porphyrin is a heterocyclic macrocycle made from 4 pyrrole subunits linked on opposite sides (α position) through 4 methine bridges (=CH-). The macrocycle, therefore, is more aromatic than the related corrins, chlorins (2,3-dihydroporphyrin) and bacteriochlorins (2,3,12,13-tetrahydroporphyrin). The extensive conjugated system makes the compound chromatic, hence the name porphyrin, from a Greek word for purple. The macrocycle has 22 pi electrons, 18 of which are active in the conjugated s ...