My talk will cover work on two projects. One project focuses on the development of new Mn coordination complexes as a replacement for commercially available MRI contrast agents, which are all gadolinium-based. This work is driven by a high-state of anxiety surrounding well-established and newly emergent toxicity concerns related to Gd-based contrast agents. The other project is focused on developing redox active Mn coordination complexes as biochemically responsive MRI contrast agents that can be turned “off” and “on” by biochemical redox reactions. The different oxidation states of Mn have very different chelator preferences and a ligand that supports a stable complex of one oxidation state is very unlikely to support stable complexes of another. Development of redox active Mn complexes suitable for meaningful in vivo imaging applications is challenging and requires innovative ligand design.