State of manganese in the photosynthetic apparatus. 1. Extended x-ray absorption fine structure studies on chloroplasts and di-.mu.-oxo-bridged dimanganese model compounds

In this paper, extended X-ray absorption fine structure studies on the manganese contained in spinach chloroplasts and on certain di-p-oxo-bridged manganese dimers of the form (X₂Mn)O₂(MnX₂) (X = 2,2'-bipyridine and 1 ,10-phenanthroline) are reported. From these studies, the manganese associated with photosynthetic oxygen evolution is suggested to occur as a bridged transition-metal dimer with most likely another manganese. Finally, extensive details on the analysis are included.