porphyrins

https://doi.org/10.1351/goldbook.P04765
Natural pigments containing a fundamental skeleton of four pyrrole nuclei united through the α-positions by four methine groups to form a macrocyclic structure (porphyrin is designated porphine in Chemical Abstracts indexes).
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See also:
corrinoids (cobalamines, corphyrins, corrins, vitamin B12 compounds)
Sources:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1360 [Terms] [Paper]
White Book, 2nd ed., p. 281 [Terms] [Book]