Ligand Modification Transforms a Catalase Mimic into a Water Oxidation Catalyst

摘要

The catalytic reactivity of the high-spin Mn~(II) 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 cata-lytically disproportionate H2O2 in aqueous solution; with a bulky substituent (R = tBu), this catalytic reaction is shut down, but the complex becomes active for aqueous electro-catalytic 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.