title: Structure-activity correlations among iridium(III) photosensitizers in a robust water-reducing system.
abstract: A photocatalytic water-reducing system utilizing a bis-cyclometalated bipyridyl iridium(III) photosensitizer (PS) and a platinum or palladium heterogeneous catalyst was used to identify systematic property-activity correlations among a library of structural derivatives of [Ir(ppy)(2)(bpy)](+). A heterogeneous Pd catalyst proved to be more durable than its previously reported Pt-based counterpart, allowing for more reliable photosensitizer study. The deliberate steric and electronic variations of the ppy and bpy moieties resulted in a dramatic decrease of the degradation rates observed with selected photosensitizers when compared to the more substitution-labile [Ir(ppy)(2)(bpy)](+) parent compound. An improved photosensitizer structure with a Pd catalyst in a nonligating solvent exhibited a 150-fold increase in catalyst turnover numbers compared to the system using [Ir(ppy)(2)(bpy)](+) and a Pt catalyst. Furthermore, photocatalytic and photophysical studies at varied temperatures provided information on the rate-limiting step of the photocatalytic process, which is shown to be dependent on both the PS and the Pt or Pd catalytic species.
authors.affiliation: Department of Chemistry, Princeton University, Princeton New Jersey 08544, USA.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Curtin
authors.forename: Leonard L
authors.initials: LL
authors.lastname: Tinker
authors.forename: Christine M
authors.initials: CM
authors.lastname: Burgess
authors.forename: Eric D
authors.initials: ED
authors.lastname: Cline
authors.forename: Stefan
authors.initials: S
authors.lastname: Bernhard