ABSTRACT
One of the most fascinating and important transformations in nature is the biological generation of O2 by the oxygen-evolving complex (OEC) of photosystem II (PSII) in cyanobacteria and plants.1-8 This transformation was responsible for the formation of the oxygenic atmosphere that has shaped the evolution of life on Earth as we know it. In this process, solar energy is converted to the reducing equivalents and proton gradient necessary to power carbon dioxide xation and other processes of life, while forming dioxygen as a by-product. The biological catalyst PSII has been studied in detail for >50 years. Progress in understanding the site of catalysis, the OEC, has depended on advances in several elds, including biochemistry, biophysics, spectroscopy, inorganic chemistry, and computational chemistry. While many properties of the OEC are well documented and generally agreed on, many aspects of the catalytic site remain controversial, with computational and experimental chemists
5.1 Photosynthesis and Photosystem II .............................................................. 165 5.2 Oxygen-Evolving Complex: Composition and KOK Cycle .......................... 167 5.3 Structural Proposals for the OEC: A Historical Perspective ........................ 168 5.4 Computational Investigations of the OEC .................................................... 172 5.5 Mechanism of O-O Bond Formation ........................................................... 176 5.6 Synthetic OEC Model Coordination Complexes .......................................... 178 5.7 Site-Differentiated OEC Model Complexes ................................................. 181 5.8 Conclusions ................................................................................................... 188 References .............................................................................................................. 188
still pushing the boundaries of our understanding of the OEC. Herein, we provide an overview of the structural and mechanistic proposals of the OEC as they were reported chronologically, and the technologies and methods that supported them, with a focus on the insight gained from recent synthetic inorganic and computational work in the eld.
