Although my research is centered around synthetic inorganic chemistry, the work draws heavily from organic chemistry and biochemistry. My research group is developing small molecule sensors for reactive oxygen species, homogeneous catalysts for the oxidation of hydrocarbons and the degradation of superoxide, and homogeneous electrocatalysts for the reduction of dioxygen to water.

Small Molecule Sensors for Reactive Oxygen Species:

Reactive oxygen species (ROS) have been implicated in a huge number of health conditions, including numerous inflammatory, cardiovascular, and neurological pathologies (e.g. Huntington’s and Alzheimer’s diseases). The ability to monitor aberrant oxidative activity within living subjects would be a tremendous boon for medicine, with the potential to improve both diagnostic and treatment options for the associated diseases. 

Recent work from my lab has produced a series of redox-active contrast agents for magnetic resonance imaging (MRI). Activation by hydrogen peroxide, the most prevalent ROS in biology, enhances the contrast. We are currently exploring mononuclear manganese(II) and iron(II) complexes with redox-active ligands as sensors. Upon oxidation, the relaxivity of the compound increases, providing a signal that can be detected and quantified by MRI.  

Catalysts for Reactive Oxygen Species Degradation

Superoxide dismutases (SODs) and catalases (CATs) are enzymes that catalyze the degradation of superoxide and hydrogen peroxide, respectively. Small molecule mimics of SOD and CAT can potentially be used to treat the many health conditions associated with oxidative stress.

The manganese(II) and iron(II) complexes that were developed for hydrogen peroxide sensing have been found to catalytically degrade superoxide and/or hydrogen peroxide. The redox-active ligands are responsible for much of this activity, and we have found that we can substitute other metals, such as zinc(II) and nickel(II), to prepare SOD and CAT mimics with similar, or even improved, activity.

Electrocatalysts for Dioxygen Reduction

Metal-air and hydrogen batteries have the potential to ease society's reliance on fossil fuels, but these devices need further refinement if they are to see widespread use. The catalysts used at the cathodes to reduce dioxygen to water are currently both expensive and inefficient.

We have recently reported electrocatalysts for dioxygen reduction that consist of first-row transition metals (iron, cobalt) complexed to redox-active ligands. The redox activity of the ligands improves the rate and product selectivity for dioxygen reduction while keeping the effective overpotential low.