Abstract: Redox-active ligands have given multi-electron reactivity to transition metal ions that are normally incapable of catalyzing those transformations. Redox-active ligands that are also capable of storing and delivering protons further expand their usefulness. In this dissertation, the structural and electronic properties that govern proton-coupled electron transfer (PCET) of a tridentate redox- and proton-active ligand in coordination complexes are explored.