Bioinspired catalysts of the water oxidizing complex of photosystem II are one of the promising routes to efficient water splitting. We have conducted an investigation on a series of manganese-oxo complexes containing a cubical [Mn₄O₄]⁷⁺ core in solution and suspended in nafion. This study has yielded important insights into the redox properties of the strongly oxidizing cubane core. More relevant, we have discovered conditions that enable it to catalyze the sustained photo-assisted electrolysis and photo-driven oxidation of water.