A functional model for O-O bond formation by the O-2-evolving complex in photosystem II

The formation of molecular oxygen from water in photosynthesis is catalyzed by photosystem II at an active site containing four manganese ions that ar e arranged in di-mu-oxo dimanganese units (where mu is a bridging mode). Th e complex [H2O(terpy)Mn(O)(2)Mn(terpy)OH2](NO3)(3) (terpy is 2,2':6',2 "-te rpyridine), which was synthesized and structurally characterized, contains a di-mu-oxo manganese dimer and catalyzes the conversion of sodium hypochlo rite to molecular oxygen. Oxygen-18 isotope labeling showed that water is t he source of the oxygen atoms in the molecular oxygen evolved, and so this system is a functional model for photosynthetic water oxidation.