title: Water Oxidation by Ruthenium Complexes Incorporating Multifunctional Bipyridyl Diphosphonate Ligands.
abstract: We describe herein the synthesis and characterization of ruthenium complexes with multifunctional bipyridyl diphosphonate ligands as well as initial water oxidation studies. In these complexes, the phosphonate groups provide redox-potential leveling through charge compensation and σ donation to allow facile access to high oxidation states. These complexes display unique pH-dependent electrochemistry associated with deprotonation of the phosphonic acid groups. The position of these groups allows them to shuttle protons in and out of the catalytic site and reduce activation barriers. A mechanism for water oxidation by these catalysts is proposed on the basis of experimental results and DFT calculations. The unprecedented attack of water at a neutral six-coordinate [Ru(IV) ] center to yield an anionic seven-coordinate [Ru(IV) -OH](-) intermediate is one of the key steps of a single-site mechanism in which all species are anionic or neutral. These complexes are among the fastest single-site catalysts reported to date.
authors.affiliation: Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Shaffer
authors.affiliation: Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.|Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614, Poznan, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Lewandowska-Andralojc
authors.affiliation: Department of Natural Sciences, Baruch College, CUNY, New York, NY, 10010, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Szalda
authors.affiliation: Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA. jconcepc@bnl.gov.
authors.forename: Javier J
authors.initials: JJ
authors.lastname: Concepcion
keywords: catalysis; electrochemistry; phosphonates; ruthenium; water splitting