The search for renewable, clean sources of energy is critical for the future of the planet. The use of abundant sunlight to generate electricity or to efficiently and catalytically transform inexpensive simple molecules into clean fuels, such as hydrogen from water and formic acid from and carbon dioxide, remains a challenge. Systems for efficient conversion of sunlight into chemical fuels requires strong light absorption that is well-matched to the solar spectrum, catalysts that effect the desired transformation, followed by combining the light absorber (LA) with the catalyst (CAT) into functional LA-CAT architectures. Current LAs used in these applications typically do not absorb the entire solar spectrum efficiently from the ultraviolet, UV, to the near-IR (infrared) range, such that some fraction of photons that make up the solar spectrum are not utilized. We have developed new Rh<sub>2</sub>(II,II) complexes that serve as dyes that absorb light strongly throughout the visible region and into the near-IR. These compounds are capable of undergoing excited state redox processes, such as the photoinduced reduction of methyl viologen and known cobalt electrocatalysts that produce H<sub>2</sub> from protons, as measured using steady-state photolysis in the presence of a sacrificial donor and using transient absorption. In addition, new dirhodium complexes that act as catalysts for the reduction of water to hydrogen and carbon dioxide to formic acid will be presented.  The variation of the bridging ligand from formamidinate to acetamide and acetate in these dirhodium catalysts results in increased selectivity toward carbon dioxide reduction instead of hydrogen formation. Both proton and carbon dioxide reduction are believed to proceed via the formation of an axial hydride intermediate, the characterization and reactivity of which will be presented.

Multimetallic systems for the photocatalytic production of fuels from abundant sources

254th National Meeting (2017)

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