EHPG iron(III) complexes as potential contrast agents for MRI

A series of EHPG ligands and complexes were obtained. The derivatives of choice were p-OMe, 3,4-dimethyl, p-NHA-c and p-Ph substituted ones. The complexes were characterized by NMR relaxation decay (T₁), EPR and cyclic voltammetry (CV). r₁ Relaxivity of the Fe-EHPG-OMe, Fe-EHPG-Ph derivatives was found higher than that of Fe-EHPG. EPR measurements at liquid nitrogen temperature indicate a typical rhombohedral structure for both rac- and meso-diastereoisomers of the EHPG complexes. CV revealed the redox inactivity of the Fe-EHPG complexes at physiological conditions. Interpretation and discussion of the results is presented.