Oxygen evolution reaction manganese

Electrochemical and Spectroscopic Studies of Manganese(II, III, IV) Complexes as Models for the Photosynthetic Oxygen-Evolution Reaction... 

An increasing amount of attention is being given to oxides as possible anodes for oxygen evolution because of the importance of this reaction in water electrolysis. In this connection, numerous studies have been carried out on noble metal oxides, spinel and perovskite type oxides, and other oxides such as lead and manganese dioxide. Kinetic parameters for the oxygen evolution reaction at a variety of single oxides and mixed oxides are shown in Table 3. 

Ponce, J., Rehspringer, J.-L., Poillerat, G. and Gautier, J.L. Electrochemical study of nickel-aluminium-manganese spinel NijAli xMn204. Electrocatalytic properties for the oxygen evolution reaction and oxygen reduction reaction in alkaline media , Electrochim. Acta, 46 (2001) 3373-3380. 

Manganese plays a critical role in oxygen evolution catalyzed by the proteins of the photosynthetic reaction center. The superoxide dismutase of bacteria and mitochondria, as well as pyruvate carboxylase in mammals, are also manganese proteins. How the multiple manganese atoms of the photosynthetic reaction center participate in the removal of four electrons and protons from water is the subject of intense investigation by spectroscopists, synthetic inorganic chemists, and molecular biologists. ... 

Manganese-binding centers were first revealed in thylakoid membranes by EPR methods, and it is now understood that four manganese ions are necessary for oxygen evolution during water photo-oxidation. Plastoquinone (PQ) acts as a transmembrane carrier of electrons and protons between reaction centers of two photosystems in the case of noncyclic electron transfer and may also serve as a molecular tumbler that switches between one-electron reactions and two-electron reactions. Pheophytin is an intermediate acceptor in PS II. Direct formation of P680 pheophytin ion radical pairs was revealed by experiments on magnetic interactions between pheophytin and PQ reflected in the EPR spectra. 

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