Orientation Selected Endor Studies of a Manganese Dimer
Bi- and polynuclear Mn-containing active sites of biological material are responsible for the reduction of ribonucleotides in bacteria, disproportio- nation of hydrogeneperoxide by cataiases and most important for the photosynthetic oxidation of water to oxygen in higher plants and cyano- bacteria. For the photosynthetic watersplitting four Mn-ions are necessary and during light driven turnovers of the Photosystem II (PSII) they adopt different, partially stable oxidation states (S0-S4) involving metal oxidation states in the range II-IV. In recent efforts to model the complex Mn-cluster synthetically prepared Mn-dimers were often used1. Their EPR characteristic is a well known 16 line hf pattern in the MnIII MnIV oxidation state comparable to the “multiline” signal around g=2 of the S2 state of PSII.