Ana Moore

Artificial photosynthetic constructs can in principle operate more efficiently than natural photosynthesis because they can be rationally designed to optimize solar energy conversion for meeting human demands rather than the multiple needs of an organism competing for growth and reproduction in a complex ecosystem. The artificial photosynthetic constructs that we study consist primarily of covalently linked synthetic chromophores, electron donors and acceptors, and proton donors and acceptors that carry out the light absorption, electron transfer, and proton coupled electron transfer (PCET) processes characteristic of photosynthetic cells. PCET and the transport of protons over tens of Å are important in all living cells because they are a fundamental link between redox processes and the establishment of transmembrane gradients of proton electrochemical potential, known as proton-motive force (PMF), which is the unifying concept in bioenergetics. Moreover, in nature the management of proton activity in space and time is key to the efficient, low overpotential catalysis characteristic of myriad biochemical processes including water oxidation, oxygen reduction and the synthesis of energy rich biomass. Artificial photosynthetic constructs, based on mimicry of PCET found in photosynthesis, provides a basis for discovering the principles upon which these catalysts operate. This is a step towards developing efficient water/oxygen redox catalysts for electrolysis and fuel cells, and catalysts for the efficient conversion of intermittent, renewable energy to chemical potential for storage.

We have chosen a benzimidazole phenol (BIP) system as a platform for the study of PCET because with appropriate substitutions it is possible to design assemblies where one or multiple proton transfers can accompany the oxidation of the phenol. We can envision systems based on BIPs where through a Grotthuss-type process redox-driven translocation of protons over long distances (>>10 Å) can be obtained.