Off-Set Interactions of Ruthenium-bda Type Catalysts for Promoting Water-Splitting Performance.

O-O bond formation with Ru(bda)L2 -type catalysts is well-known to proceed through a bimolecular reaction pathway, limiting the potential application of these catalysts at low concentrations. Herein, we achieved high efficiencies with mononuclear catalysts, with TOFs of 460±32 s-1 at high catalyst loading and 31±3 s-1 at only 1 μM catalyst concentration, by simple structural considerations on the axial ligands. Kinetic and DFT studies show that introduction of an off-set in the interaction between the two catalytic units reduces the kinetic barrier of the second-order O-O bond formation, maintaining high catalytic activity even at low catalyst concentrations. The results herein furthermore suggest that π-π interactions may only play a minor role in the observed catalytic activity, and that asymmetry can also rationalize high activity observed for Ru(bda)(isoq)2 type catalysts and offer inspiration to overcome the limitations of 2nd order catalysis.