Synthetic biomimetic complexes of the oxygen evlolving complex of photosystem ii as water oxidation catalysts for energy applications

Abstract

Fossil fuels are the major source of greenhouse gasses. There is a global effort to find a replacement fuel. Renewable energy is a primary focus and already provides a substantial portion of energy demand. Among them is molecular hydrogen (H2). This is due to its combustion and fuel cell product being water as well as its use as energy storage. Further, H2 can be obtained in a green and renewable way through electrolysis of water. However, Clean H2 production is currently expensive, and catalysts are one solution to help bring the costs down. Development of catalysts for this purpose have the added benefit of elucidating complex redox reactions involved in photosynthesis and the formation of the O-O bond. Direct inspiration from nature has led to the development of proposed water oxidation catalysts. These are synthetic metal-ligand (organometallic) complexes attempting to mimic the structure and functionality of the oxygen evolving complex (OEC) found in photosystem II. The goal is to mimic this unique portion of photosynthesis. This is done by producing ligands capable of binding three to four metal atoms and testing each complexes’ ability to perform the redox reactions associated with splitting water into hydrogen and oxygen. Ligands are designed and produced that utilized terminal pyridine groups to chelate three or four metal atoms. These ligands are complexed with the manganese atom inspired by nature as well as the less expensive and more abundant iron atom. The iron complex is spectroscopically compared to that of the manganese. In the future these organometallic complexes will be reacted with calcium and oxidizing agents and undergo further spectroscopic, redox and electrochemical tests.