porphyrin
Pronunciation:
/ˈpɔːfɪɹɪn//ˈpɔɹfəɹɪn/noun
Definitions
Any of a class of heterocyclic compounds containing pyrrole rings arranged in a square or other similar shape; they are important in biochemistry in a form with a metal atom in the central cavity (hemoglobin with iron, chlorophyll with magnesium, etc.).