Formation of a tris(catecholato) iron() complex with a nature-inspired cyclic peptoid ligand

Siderophore-mimicking macrocyclic peptoids were synthesized. Peptoid 3 with intramolecular hydrogen bonds showed an optimally arranged primary coordination sphere leading to a stable catecholate-iron complex. The tris(catecholato) structure of 3-Fe( iii ) was determined with UV-vis, fluorescence, and EPR spectroscopies and DFT calculations. The iron binding affinity was comparable to that of deferoxamine, with enhanced stability upon air exposure. Siderophore-mimicking catechol-containing macrocyclic peptoids were synthesized, and their Fe( iii ) complexes were characterized. The 3 -Fe( iii ) complex exhibited stable tris-complex with a 1 : 1 stoichiometry.