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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]

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]

In this review, we focus on the preclinical development and study of coordination complexes that act as magnetic resonance imaging (MRI) contrast agent sensors for hydrogen peroxide. Redox-responsive probes have been developed that provide signals that can be detected through traditional T 1 -weighted 1H, 19F, and Chemical Exchange Saturation Transfer MRI. The sensors can also be classified with respect to whether the change in the signal corresponds to the oxidation of the metal ion or the organic ligand. The article reviews coordination complexes that detect reactive H 2 O 2 through changes to their magnetic resonance imaging (MRI) properties. Changes to the oxidation state of either the metal or the organic ligand in the contrast agent alter either the T 1w 1H, 19F, or Chemical Exchange Saturation Transfer MRI signal. [Display omitted] • Magnetic resonance imaging techniques that have been used to detect H 2 O 2 are described. • Magnetic resonance imaging contrast agent sensors for H 2 O 2 are summarized. • Sensor response can result from oxidation of either the inorganic or organic portion. [ABSTRACT FROM AUTHOR]