title: Synthesis, characterisation and application of iridium(III) photosensitisers for catalytic water reduction.
abstract: The synthesis of novel, monocationic iridium(III) photosensitisers (Ir-PSs) with the general formula [Ir(III)(C^N)(2)(N^N)](+) (C^N: cyclometallating phenylpyridine ligand, N^N: neutral bidentate ligand) is described. The structures obtained were examined by cyclic voltammetry, UV/Vis and photoluminescence spectroscopy and X-ray analysis. All iridium complexes were tested for their ability as photosensitisers to promote homogeneously catalysed hydrogen generation from water. In the presence of [HNEt(3)][HFe(3)(CO)(11)] as a water-reduction catalyst (WRC) and triethylamine as a sacrificial reductant (SR), seven of the new iridium complexes showed activity. [Ir(6-iPr-bpy)(ppy)(2)]PF(6) (bpy: 2,2'-bipyridine, ppy: 2-phenylpyridine) turned out to be the most efficient photosensitiser. This complex was also tested in combination with other WRCs based on rhodium, platinum, cobalt and manganese. In all cases, significant hydrogen evolution took place. Maximum turnover numbers of 4550 for this Ir-PS and 2770 for the Fe WRC generated in situ from [HNEt(3)][HFe(3)(CO)(11)] and tris[3,5-bis(trifluoromethyl)phenyl]phosphine was obtained. These are the highest overall efficiencies for any Ir/Fe water-reduction system reported to date. The incident photon to hydrogen yield reaches 16.4% with the best system.
authors.affiliation: Leibniz-Institut für Katalyse e.V., Albert-Einstein-Straße 29a, 18059 Rostock, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Gärtner
authors.forename: Daniela
authors.initials: D
authors.lastname: Cozzula
authors.forename: Sebastian
authors.initials: S
authors.lastname: Losse
authors.forename: Albert
authors.initials: A
authors.lastname: Boddien
authors.forename: Gopinatan
authors.initials: G
authors.lastname: Anilkumar
authors.forename: Henrik
authors.initials: H
authors.lastname: Junge
authors.forename: Thomas
authors.initials: T
authors.lastname: Schulz
authors.forename: Nicolas
authors.initials: N
authors.lastname: Marquet
authors.forename: Anke
authors.initials: A
authors.lastname: Spannenberg
authors.forename: Serafino
authors.initials: S
authors.lastname: Gladiali
authors.forename: Matthias
authors.initials: M
authors.lastname: Beller