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

A highly water‐ and air‐stable Fe(II) complex with the quinol‐containing macrocyclic ligand H4qp4 reacts with H2O2 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 T1‐weighted relaxivity over four‐fold, enabling the complex to detect H2O2 using clinical MRI technology. The iron‐containing sensor differs from its recently characterized manganese analog, which also detects H2O2, in that it is the oxidation of the metal center, rather than the ligand, that primarily enhances the relaxivity. [ABSTRACT FROM AUTHOR]