In photosynthesis, photoexcitation of chlorophyll causes a charge separation across a membrane. Transmembrane electron transfer is mediated stepwise by a chain of electron acceptors and leads to the conservation of solar energy.  During this process, water is oxidized to form molecular oxygen and protons. This water-oxidizing reaction is catalyzed in the photosynthetic reaction center protein, called photosystem II, by a manganese-calcium cluster and a redox-active tyrosine residue, YZ.  A critical feature of natural photosynthesis is the use of sunlight to oxidize water. Artificial systems, which use water as an electron source, would provide affordable and sustainable fuel production. One challenge in water oxidation chemistry is the precise coordination of proton and electron transfer to avoid the production of potentially damaging or off pathway intermediates.  Four light-driven charge separations are required to produce oxygen from water, generating the sequentially oxidized Sn states.  Spectroscopic progress in describing these states and de novo designed, biomimetics will be described.  Supported by NSF MCB 08-0842246 and CHE 12-133350.

Proton coupled electron transfer reactions in photosynthesis and biomimetics

248th National Meeting (2014)

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