title: Ligand modification transforms a catalase mimic into a water oxidation catalyst.
abstract: 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 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.
authors.affiliation: Department of Chemistry, Indiana University, 800 East Kirkwood Ave., Bloomington, IN 47405 (USA).
authors.forename: Wei-Tsung
authors.initials: WT
authors.lastname: Lee
authors.forename: Salvador B
authors.initials: SB
authors.lastname: Muñoz
authors.forename: Diane A
authors.initials: DA
authors.lastname: Dickie
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Smith
mesh_terms: D002384:Catalysis; D004563:Electrochemistry; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D014867:Water / Q000737:chemistry*
chemical_list: D008024:Ligands; D014867:Water; D008345:Manganese
keywords: catalysis; macrocycles; manganese; molecular electrochemistry; water splitting