Abstract
The development of an efficient water oxidation catalyst is crucial in the framework of constructing an artificial photo(electro)synthetic apparatus for the production of solar fuels. Herein, new hydroxy-pyridine-carboxylate iridium complexes are reported exhibiting high activity in water oxidation with both cerium ammonium nitrate and NalO(4) as sacrificial oxidants. With the latter, the catalytic activity strongly depends on the pH and position of the OH-substituent in the pyridine ring, reaching a record turnover frequency of 458 min(-1) and turnover number (>14 500) limited only by the amount of NalO(4). Kinetic experiments measuring O-2 evolution paralleled by NMR studies on oxidative transformation with NalO(4) suggest that Cp* of the catalyst is readily degraded, whereas the hydroxypyridine-carboxylate ligands remain coordinated at iridium, tuning its activity.