The name/synonym for ligand HEM (curated from ChEBI, PubChem, and PDB databases):

1HEME B
2PROTOPORPHYRIN IX CONTAINING FE
3PROTOHEME IX
4(PROTOPORPHYRINATO)IRON
5HEME
6HAEM B
7(7,12-DIETHENYL-3,8,13,17-TETRAMETHYLPORPHYRIN-2,18-DIPROPANOATO)IRON
8PROTOHEME
9[3,7,12,17-TETRAMETHYL-8,13-DIVINYLPORPHYRIN-2,18-DIPROPANOATO(2-)]IRON
10[DIHYDROGEN 3,7,12,17-TETRAMETHYL-8,13-DIVINYL-2,18-PORPHINEDIPROPIONATO(2-)]IRON