title: Stepwise versus pseudo-concerted two-electron-transfer in a triarylamine-iridium dipyrrin-naphthalene diimide triad.
abstract: A triad based on triarylamine donors, an iridium dipyrrin sensitiser and a naphthalene diimide acceptor is investigated using fs-pump-probe spectroscopy at two different pump wavelengths. Excitation of the naphthalene diimide induces a stepwise electron transfer process that yields within ca. 100 ps a charge separated state with 50-60% quantum yield in which one triarylamine is oxidised and the imide is reduced. Although being in the Marcus normal region, this state has a lifetime of 580 ns in MeCN. Excitation at the dipyrrin ligand centred absorption directly produces the charge separated state within ca. 1 ns however without formation of an intermediate. This pseudo-concerted two-electron transfer step was analysed with the help of a model dyad and a modified triad and is interpreted to be caused by inverted electron transfer rates. Although being much slower the latter process has a quantum yield of practically 100%.
authors: Institut für Organische Chemie, Universität Würzburg, Wilhelm Conrad Röntgen Research Center for Complex Material Systems, Würzburg, Center for Nanosystems Chemistry, Am Hubland, 97074 Würzburg, Germany. christoph.lambert@uni-wuerzburg.de.
authors: Johannes H
authors: JH
authors: Klein
authors: Travis L
authors: TL
authors: Sunderland
authors: Christina
authors: C
authors: Kaufmann
authors: Marco
authors: M
authors: Holzapfel
authors: Alexander
authors: A
authors: Schmiedel
authors: Christoph
authors: C
authors: Lambert
mesh_terms: D000588:Amines / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry; D004579:Electron Transport; D004583:Electrons; D007094:Imides / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D009281:Naphthalenes / Q000737:chemistry*; D010084:Oxidation-Reduction; D011789:Quantum Theory
chemical_list: D000588:Amines; D056831:Coordination Complexes; D007094:Imides; D009281:Naphthalenes; C542131:naphthalenediimide; D007495:Iridium