The molecule is a dimer of hematin in which an iron-oxygen bond links the central iron of one hematin to the oxygen of one of the carboxylates of the adjacent hematin.
3-[18-(2-carboxyethyl)-7,12-bis(ethenyl)-3,8,13,17-tetramethylporphyrin-21,23-diid-2-yl]propanoate;3-[18-(2-carboxyethyl)-8,13-bis(ethenyl)-3,7,12,17-tetramethylporphyrin-22,24-diid-2-yl]propanoate;iron