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Updated: May 8, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Stepwise versus pseudo-concerted two-electron-transfer in a triarylamine-iridium dipyrrin-naphthalene diimide triad
Johannes H Klein1, Travis L Sunderland, Christina Kaufmann
1Institut 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.
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%.
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