Ligand Modification Transforms a Catalase Mimic into a Water Oxidation Catalyst

Angewandte Chemie International Edition by Wei-Tsung Lee, Salvador B. Muñoz, Diane A. Dickie, Jeremy M. Smith  /  6h  //  keep unread  //  hide  //  preview Abstract The catalytic reactivity of the high-spin MnII pyridinophane complexes [(Py2NR2)Mn(H2O)2]2+ (R=H, Me, tBu) toward O2 formation is reported. With small macrocycle N-substituents (R=H, Me), the complexes catalytically disproportionate H2O2 in aqueous solution; with a bulky substituent (R=tBu), this catalytic reaction is shut down, but the complex becomes active for aqueous electrocatalytic H2O oxidation. Control experiments are in support of a homogeneous molecular catalyst and preliminary mechanistic studies suggest that the catalyst is mononuclear. This ligand-controlled switch in catalytic reactivity has implications for the design of new manganese-based water oxidation catalysts. Ligand-controlled switch: Simple modification of the substituent on a pyridinophane macrocycle ligand converts the corresponding MnII complex from a hydrogen peroxide disproportionation catalyst to a water oxidation catalyst. Preliminary results indicate that the catalyst is mononuclear. Visit Website