Is [Co-4(H2O)(2)(alpha-PW9O34)(2)](10-) a genuine molecular catalyst in photochemical water oxidation? Answers from time-resolved hole scavenging experiments

Water oxidation catalysts: evolution of [Co-4(H2O)(2)(alpha-PW9O34)(2)](10-) to catalytically active species is assessed by laser flash photolysis in sacrificial photocatalytic cycles with Ru(bpy)(3)(2+) as a photosensitizer.