A
macrocyclic ring formed from the cyclisation of polypyrrole. Here's
how to draw one:
- Draw four Ns at the corners of a square.
- Eight lines radiate out from these Ns. 2 up, 2 down, 2 left, 2 right.
- The two lines connected to each N are joined into 4 separate pentagons.
- Join the pentagons with methylene (1 carbon) bridges.
The structure can now be embellished with double bonds and other modifications. Two of the pentagons (diagonally opposite) are the same (N1=CC=CC1) while the other two are (N1C=CC=C1) and (N1CC=CC1). The double bonds in the bridges are such that the whole system has
conjugated pi orbitals.
Porphrins(Pph) are found in many biological cofactors, with different metals in the center. Iron-Pph is haem, while magnesium-Pph is chlorophyll. More unusual metals (in biology) like nickel occur in some archaea (Ni-Pph is F450) while cobalt is found in vitamin B12.
Supramolecular chemists are also fond of making unlikely porphyrin structures, such as 'calix[4]arenoporphyrin'. This is the calixarene described in the node, but with porphyrin groups in place of the t-butyl groups. Weird.