Abstract: Metal complexes are important tools for chemical biology and have proven applications as diagnostics and therapeutics. Research in the Kodanko laboratory focuses on the development of novel metal complexes for biological applications. Our research lies at the interface of organic, inorganic and medicinal chemistry. Catalytic methods were developed for the oxidation of peptides and proteins by non-heme iron complexes, which utilize biologically available oxidants. Caged versions of these molecules were developed that release carbon monoxide upon photoexcitation, and elicit potent photoinduced toxicity in human prostate cancer cells. Recently a method for caging cysteine protease inhibitors with ruthenium complexes was described. Inhibitors are released by light, leading to high levels of selectivity for enzyme inhibition under light vs. dark conditions. This method provides a novel way to achieve great spatial and kinetic control over protease activity that may be useful for chemical biology and anticancer applications.