Complexes consisting of an iron ion coordinated to a porphyrin acting as a tetradentate ligand, and to one or two axial ligands.
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Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1339 (https://doi.org/10.1351/pac199567081307)
See also:
White Book, 2nd ed., p. 311 (https://iupac.qmul.ac.uk/bibliog/white.html)