A<unk>  is a heterocyclic macrocycle derived from four pyrrole-like subunits interconnected via their α carbon atoms via methine bridges (=CH-). The macrocycle, therefore, is a highly conjugated system, and is consequently deeply coloured—the name<unk>  comes from a Greek word for purple.  The macrocycle has 22 pi electrons. The parent<unk>  is porphine, and substituted porphines are called<unk> s.  Many<unk> s occur in nature, such as in green leaves and red blood cells, and in bio-inspired synthetic catalysts and devices.
Porphyrin
Hydroquinone
Phanquinone
Glycobiarsol
Hemocyanin
Methaemoglobin
Toxidrome
Chlorophyll