Unlocking Photoswitchable Main-group Catalysis Using Azophosphines

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Catalysts are substances that make chemical reactions more efficient and are crucial to the chemical industry; in fact, 90% of commercial chemicals involve at least one catalytic step in their production. A high proportion of these catalysts rely on precious metals (e.g., palladium, platinum, gold and rhodium); it is forecast that the global precious metal catalysts market will reach $26.73 billion by 2026. And yet precious metals have several disadvantages, predominantly arising from the fact that they are precious, i.e., they are scarce and very expensive. There is a huge economic cost associated with mining these low-abundance metals, and an increasing environmental cost with extracting and processing the ore that is leading to an increase in fossil fuel usage and carbon dioxide emissions. With a pressing need to better manage the planet's resources, we urgently need to find more sustainable alternatives to support the chemical industry of the future.The proposed research will drive forward the use of catalysts made from cheap and abundant elements, such as nitrogen, phosphorus, and boron, in systems known as Frustrated Lewis Pairs (FLPs). Most of the previous FLP catalysts that have been explored are air-sensitive, and require specialist techniques when using them, which has limited their uptake by organic chemists and more widely in industry. The research in this proposal will focus on the design of a new family of molecules that can change shape when light is shone on them, and can therefore act as switches with "on" or "off" states for catalysis. These new molecules, containing phosphorus and nitrogen as the key elements, will be used within an FLP that is stable and inactive under normal conditions ("off" state), but can be activated with light to become a functional metal-free catalyst ("on" state). The bench-stable precursors (pre-catalysts) will make FLP catalysis accessible to a broader academic and industrial audience.The project represents a priority area for the UK, and aligns strongly with the EPSRC's themes of Physical Sciences and Manufacturing the Future. It also tallies with the United Nations (UN) Sustainable Development Goals, specifically Goal 9: 'Industry, Innovation and Infrastructure.'