| Summary: | Iron(III) complexes with N,O-ligands are compounds of high interest because they can be applied in catalysis and play an important role in living organisms, e.g., as models of catechol dioxygenase. Several N,O-ligands were studied: their synthesis, iron(III) complexation and the potential of the latter as T1-MRI contrast agents. A route to the tetrapodal N3O2-naphthyl ligand was investigated. The resulting iron complex was obtained in 26% total yield and its relaxivity value was moderate (r1 = 1.03 in water and 2.54 s−1 mM−1 in serum). Thus, phenyl isomeric salan complexes were obtained. These complexes differed in charge (positive and neutral) and in the presence of polar hydrogen-bonding substituents. The highest relaxivities (r1 = 2.39 in water and 5.37 s−1 mM−1 in serum) were obtained for the Fe(III) cationic complex with MeO groups in the ligand. EPR studies confirmed a high spin configuration of rhombically distorted Fe(III) complexes. Keywords: Fe(III) complexes, Phenolates, Salan ligand, MRI contrast agents, Relaxivity, T1 relaxation time
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