Quantum mechanical study of the oxidation pathway of the oxygen-evolving catalyst, [(bpy)(2)(H2O)Ru-III-O-Ru-III(H2O)(bpy)(2)](+4)

Quantum mechanical density functional calculations are performed for the va rious oxidized forms of the water-oxidation catalyst [(bpy)(2)(H2O)Ru-III - O-Ru-III (H2O)(bpy)(2)](+4) (where bpy is 2,2 ' -bipyridine). Two possible structural forms of [(bpy)(2) (H2O)Ru-O-Ru(H2O)(bpy)(2)](+4) are investigat ed. One has two Of the interior to two waters bpy Ligands and the other has the two water ligands exterior. Our calculations show the interior form to be around 4 kcal/mol lower in energy The calculated electronic structures for the interior form [(bpy)(2)(H2O)Ru-O-Ru(H2O)(bpy)(2)](+4) and the exter ior from [(bpy)(2)(H2O)Ru-O-Ru(OH)(bpy)(2)](+4) compare well with structure s determined from X-ray crystallography. (C) 2001 John Wiley & Sons, Inc.