title: Striking Differences in Properties of Geometric Isomers of [Ir(tpy)(ppy)H](+): Experimental and Computational Studies of their Hydricities, Interaction with CO2, and Photochemistry.
abstract: We prepared two geometric isomers of [Ir(tpy)(ppy)H](+), previously proposed as a key intermediate in the photochemical reduction of CO2 to CO, and characterized their notably different ground- and excited-state interactions with CO2 and their hydricities using experimental and computational methods. Only one isomer, C-trans-[Ir(tpy)(ppy)H](+), reacts with CO2 to generate the formato complex in the ground state, consistent with its calculated hydricity. Under photocatalytic conditions in CH3CN/TEOA, a common reactive C-trans-[Ir(tpy)(ppy)](0) species, irrespective of the starting isomer or monodentate ligand (such as hydride or Cl), reacts with CO2 and produces CO with the same catalytic efficiency.
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (USA).
authors.forename: Komal
authors.initials: K
authors.lastname: Garg
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (USA).|PRESTO, JST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan).|Present address: Kanagawa University, Rokkakubashi 3-27-1, Kanagawa-ku, Yokohama 221-8686 (Japan).
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Matsubara
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (USA). mzertem@bnl.gov.
authors.forename: Mehmed Z
authors.initials: MZ
authors.lastname: Ertem
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (USA).|Present address: Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614 Poznan (Poland).
authors.forename: Anna
authors.initials: A
authors.lastname: Lewandowska-Andralojc
authors.affiliation: PRESTO, JST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan).|Toyota Central R & D Labs, Inc., Nagakute, Aichi, 480-1192 (Japan).
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Sato
authors.affiliation: Department of Natural Science, Baruch College, CUNY, New York, NY 10010 (USA).
authors.forename: David J
authors.initials: DJ
authors.lastname: Szalda
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (USA).
authors.forename: James T
authors.initials: JT
authors.lastname: Muckerman
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (USA). fujita@bnl.gov.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Fujita
keywords: CO2 reduction; homogeneous catalysis; hydricity; iridium hydrides; photochemistry