Decoupling the artificial special pair to slow down the rate of singlet energy transfer

Pierre D. Harvey, Adam Langlois, Mikhail Filatov, Daniel Fortin, Kei Ohkubo, Shunichi Fukuzumi, Roger Guilard

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Trimer 2, composed of a cofacial heterobismacrocycle, octamethyl-porphyrin zinc(II) and bisarylporphyrin zinc(II) held by an anthracenyl spacer, and a flanking acceptor, bisarylporphyrin free-base (Ar = -3,5-(tBu)2C 6H3), has been studied by means of absorption spectroscopy, "steady state and time-resolved fluorescence" and fs transient absorption spectroscopy, and density functional theory (DFT) in order to assess the effect of decoupling the chromophores' low energy MOs on the rate of the singlet, S1, energy transfer, kET, compared to a recently reported work on a heavily coupled trimeric system, Trimer 1, [biphenylenebis(n-nonyl)porphyrin zinc(II)]-bisarylporphyrin free-base (Ar = -3,5-(tBu)2C6H3). The position of the 00 peaks of the absorption and fluorescence spectra of Trimer 2 indicates that these porphyrin units are respectively energy donor 1, donor 2, and acceptor. The DFT computations confirm that the MOs of the cofacial donor 1-donor 2 dyad are decoupled, but significant MO coupling between donor 2 and acceptor 1 is still present despite the strong dihedral angle between their respective average planes (77.5°: geometry optimization by DFT). The fs transient absorption spectra exhibit a clear S1-Sn fingerprint of the bisarylporphyrin zinc(II) chromophore and the kinetic trace exhibits a slow rise time of 87 ps, due to a S1 donor 1 → donor 2 ET. The transient species donor 2 and acceptor decay respectively in the short (∼1.5) ns and 6 ns time scale.

Original languageEnglish
Pages (from-to)685-694
Number of pages10
JournalJournal of Porphyrins and Phthalocyanines
Issue number5-6
StatePublished - 2012

Bibliographical note

Funding Information:
PDH thanks the Natural Sciences and Engineering Research Council of Canada (NSERC), the Agence National de la Recherche (ANR) for the grant of a Research Chair of Excellence, the Fonds Québécois pour la Recherche en Sciences Naturelles et Technologie (FQRNT) for funding. The research by SF and KO was supported by Grant-in-Aid (Nos. 20108010 and 23750014) and KOSEF/MEST through WCU project (R31-2008-000-10010-0) of Korea.


  • DFT computations
  • fs transient absorption spectroscopy
  • molecular orbital coupling
  • singlet energy transfer


Dive into the research topics of 'Decoupling the artificial special pair to slow down the rate of singlet energy transfer'. Together they form a unique fingerprint.

Cite this