Supramolecular water oxidation with Ru-bda-based catalysts.

Extremely slow and extremely fast new water oxidation catalysts based on the Ru-bda (bda = 2,2'-bipyri- dine-6,6'-dicarboxylate) systems are reported with turnon- ver frequencies in the range of 1 and 900 cycles s 1 , re- spectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electro- chemical experiments, and DFT calculations. These analy- ses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of cat- alysts with very low energy barriers in all the steps in- volved in the water oxidation catalytic cycle. We show that for this type of system p-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. Today a transition from fossil to solar fuels is needed to pro- vide us with a clean and sustainable energy model. A viable option to achieve this challenge is to split water with sunlight; however, before this can be realized, one of the key issues that needs to be understood and mastered is water oxidation catal- ysis. In this respect significant progress has been accomplished over the last five years, mainly based on molecular transition- metal complexes. (1) Among the best water oxidation catalysts