Investigations Involving Mononuclear and Dinuclear Transition Metal Catalysts for Photochemical Carbon Dioxide Reduction

There is currently a global energy crisis, which is in desperate need of solutions. New energy sources are required that will not pollute as much as our longstanding reliance on nonrenewable fossil fuels as an energy source. This pollution involves large amounts of greenhouse gas emissions, predominantly carbon dioxide (CO2), that contribute to environmental problems such as climate change. In this context, a fairly recent research direction to address this problem is the development of transition metal catalysts that can convert CO2 into reduced carbon products that can serve as chemical fuels. This work focuses on the synthesis and evaluation of mononuclear and dinuclear ruthenium-based molecular catalysts and the exploration of ligand substitution and the trans effect to increase the efficiency of self-sensitized photocatalytic CO2 reduction to carbon monoxide (CO). While we were not able to synthesize the target dinuclear ruthenium catalyst, we deduced that the mononuclear catalyst exhibited qualities consistent with a weak-to-moderate trans effect as we saw increased turnovers (TON) for photocatalytic CO2 reduction with some added ligands such as pyrazine. Additionally, we attempted to synthesize a new series of tetradentate ligands that would extend the conjugation of a previously reported bipyridine-based ligand containing N-heterocyclic carbene (NHC) donors as a strategy to increase the efficiency of CO2 reduction of catalysts prepared from these ligands. However, this synthesis project is still ongoing due to synthetic challenges that are being navigated