Multistep photoinduced electron transfer in self-organised nanoscale porphyrin triads

Well-defined structurally organised porphyrin triads of a controlled geometry and nanoscale size have been formed in liquid solutions using the combination of a covalent approach and non-covalent self-assembly. The triads contain zinc-octaethylporphyrin chemical dimer, (ZnOEP)2Ph, with covalently linked electron acceptors (p-benzoquinone, Q or pyromellitimide, Pim), and additional dipyridyl-substituted tetrapyrrole extra-ligands. Steady-state, picosecond fluorescence View the MathML source and femtosecond pump–probe View the MathML source data show that non-radiative deactivation of the dimer S1-states View the MathML source is due to both the S–S energy transfer (ZnOEP)2Ph→extra-ligand and the sequential photoinduced electron transfer (ZnOEP)2Ph→Q (or Pim) at View the MathML source. The additional decay shortening of the extra-ligand S1-states by 3–6 times (toluene, View the MathML source is attributed to the increased “superexchange” mediated long distant (rDA≈18–View the MathML source one-step electron transfer extra-ligand→Q (or Pim).