Stepwise versus pseudo-concerted two-electron-transfer in a triarylamine-iridium dipyrrin-naphthalene diimide triad

Phys Chem Chem Phys. 2013 Oct 14;15(38):16024-30. doi: 10.1039/c3cp51981c. Epub 2013 Aug 20.

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%.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines / chemistry*
  • Coordination Complexes / chemistry
  • Electron Transport
  • Electrons
  • Imides / chemistry*
  • Iridium / chemistry*
  • Naphthalenes / chemistry*
  • Oxidation-Reduction
  • Quantum Theory

Substances

  • Amines
  • Coordination Complexes
  • Imides
  • Naphthalenes
  • naphthalenediimide
  • Iridium