Merging Photoredox and Ruthenium Catalysis for new C-H Activation Chemistry

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The proposed research looks to create new ways of manipulating C-H bonds using metal catalysts. Catalysis is central to modern chemistry, with the synthesis of 90% of industrially-produced molecules making use of catalytic chemistry (e.g. biological lipases in washing powder, transition metals used in the Haber process to produce ammonia). We propose to manipulate C-H bonds commonly found in organic molecules, as their selective activation offers a direct way of making new bonds in the creation of valuable chemicals. Selectivity is critical to success - how do we activate the one desired C-H 'tree' in the forest of C-H bonds that typically decorate organic molecules? Ruthenium catalysis offers an exciting solution to this difficult problem, with early work showing that precise C-H activations are possible on benzene rings for a small selection of transformations. In order to grow these exciting preliminary results into a general tool for making molecules, we need to substantially improve our control of the catalyst reactivity. We propose a light-driven solution to this challenge - using photochemistry to effectively tune the catalyst to react in the right way. Organic molecules are typically colourless, meaning they do not absorb visible light. As a result, the discipline of photochemistry is founded upon the use of UV light, which is absorbed by organic molecules and can initiate chemical reactions. Recent developments, however, have enabled visible light from simple domestic lightbulbs to be harnessed in chemical reactions. The process depends on a second catalyst to absorb the light, which can then interact with the organic substrates to enable new types of chemical reaction. By merging these two catalytic cycles together, C-H activation and photochemistry, we propose a new system that will dramatically accelerate the synthesis of new molecules for diverse applications in medicine, engineering and agriculture.