A Highly Water‐ and Air‐Stable Iron‐Containing MRI Contrast Agent Sensor for H₂O₂

Abstract

Abstract A highly water‐ and air‐stable Fe(II) complex with the quinol‐containing macrocyclic ligand H 4 qp4 reacts with H 2 O 2 to yield Fe(III) complexes with less highly chelating forms of the ligand that have either one or two para ‐quinones. The reaction increases the T 1 ‐weighted relaxivity over four‐fold, enabling the complex to detect H 2 O 2 using clinical MRI technology. The iron‐containing sensor differs from its recently characterized manganese analog, which also detects H 2 O 2 , in that it is the oxidation of the metal center, rather than the ligand, that primarily enhances the relaxivity.