Thermal and photochemical assembly of light-harvesting complexes: an electrochemical, optical and computational investigation.

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Solar energy conversion of light into chemical energy offers humankind the possibility to forgo our current dependence on fossil fuels. This step forward towards alternative energy would curb global warming and guarantee a cleaner environment for future generations. In this Discovery Grant application, I propose to mimic natural photosynthesis using coordination and supramolecular chemistry to assemble light-harvesting complexes capable of capturing sunlight over most of the visible spectrum. We also propose to use a new synthetic methodology based on photochemical irradiation to produce our oligo- and poly-metallic light-harvesting complexes. This new approach is based on the fact that light excitation of metal-ligand bonds can in some instances break these bonds. By careful design and synthesis of ligands we can dictate which bonds will break and which bonds will not in any given metal complex. For example, bi- and tri-dentate ligands are more stable than mono-dentate ligands due to the chelate effect. By incorporating all three types of ligands into the same complex, we can push photoreactions towards the ejection of the mono-dentate ligand only. Indeed, careful design can even dictate the loss of one particular mono-dentate ligand over another. The self-assembly of squares, hexagons and octagons containing metal ions such as Ru, Pt, Re and Ir is envisaged. These multimetallic complexes will be photochemically assembled and examined by electrochemical and spectroscopic experiments to fully understand their fundamental properties. They will then be included into photocatalytic systems to examine the production of chemical energy. New Co-catalysts will allow us to produce dihydrogen from water. A new instrumental technique was developed in my group which will allow us to monitor the UV-visible absorption spectroscopy of the photoreaction while we monitor dihydrogen production. This powerful new technique will allow us to probe deeper into the catalytic cycle and develop the next generation of photocatalysts and light-harvesting complexes.