Elevated levels of reactive oxygen species and peroxidase expression are often associated with inflammation and inflammatory diseases. We developed two novel Co(II) complexes that can be used to detect oxidative activity associated with inflammation using F-19 magnetic resonance imaging (MRI). These agents display a large change in F-19 chemical shift upon oxidation from Co(II) to Co(III), facilitating selective visualization of both species using chemical shift selective pulse sequences. This large chemical shift change is attributed to a large magnetic anisotropy in the high spin Co(II) complexes. Importantly, the differing reactivity of the two agents allows for detection of either H2O2 production and/or the activity of peroxidase enzymes, providing two useful platforms for F-19 MR hot spot imaging of oxidative events associated with biological inflammation.