Lewis Acids in the Secondary Coordination Sphere for Kinetic Enhancement Toward Reduction of Nitrite

Metal complexes utilizing the redox non-innocent pyridinediimine ligand scaffold have been shown to form ligand centered radicals. The reduction potential of the ligand-based redox sites is effectively uncoupled from the secondary coordination sphere, allowing for installation of bioinspired secondary sphere motifs to tune reactivity, without attenuating the reductive ability of the metal center. This thesis aims to explore the utility of this ligand design by installing various functionality, reminiscent of those found in Nature, into the secondary coordination sphere, such as Lewis acidic residues, polarized active sites, and allosteric docking sites. Installation of a pendant benzo-15-crown-5 ether moiety, capable of encapsulating redox-inactive Na+ ions, has been shown to entice corresponding counter ions in close-proximity to the metal center, with modest shifts in reduction potential (\u3c 30 mV). The rate of reactivity on anions of interest was investigated, and in the case of NO2- reduction to NO, initial rate analysis revealed an acceleration in anion reduction attributed to encapsulating the Na+ ion, which causes an increased effective concentration of NO2- near the metal center, primed for reactivity. Preliminary results of installing redox activity into a tripodal ligand scaffold have been presented. These novel ligand scaffolds have shown ligand centered redox activity when utilizing a redox-inactive Zn2+ metal. The synthesis of a family of “base-safe” pyridinediimine ligand scaffolds featuring the dibenzoylpyridine backbone have been presented. These ligands will be stable in the presence of organic superbases, which are necessary for the envisioned tandem catalytic cycle for the reduction of CO2 to CO