Catalytic O−O Activation Chemistry Mediated by Iron Hangman Porphyrins with a Wide Range of Proton-Donating Abilities

[reaction: see text] A library of hanging porphyrin xanthene (HPX) compounds containing pendant groups with various proton-donating abilities (pK(a) ranging from approximately 2 to 25) has been synthesized. Their corresponding chloroiron(III) complexes promote the catalase-like disproportionation of hydrogen peroxide. The overall activity and turnover numbers (TONs) are maximal for iron HPX complexes bearing acidic hydrogen-bond pendants. These results establish that careful control of intramolecular proton inventory can dramatically influence the catalytic activation of O-O bonds.