Energy transfer, excited-state deactivation, and exciplex formation in artificial caroteno-phthalocyanine light-harvesting antennas

Rudi Berera, Ivo H M Van Stokkum, Gerdenis Kodis, Amy E. Keirstead, Smitha Pillai, Christian Herrero, Rodrigo E. Palacios, Mikas Vengris, Rienk Van Grondelle, Devens Gust, Thomas Moore, Ana Moore, John T M Kennis

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Abstract

We present results from transient absorption spectroscopy on a series of artificial light-harvesting dyads made up of a zinc phthalocyanine (Pc) covalently linked to carotenoids with 9, 10, or 11 conjugated carbon-carbon double bonds, referred to as dyads 1, 2, and 3, respectively. We assessed the energy transfer and excited-state deactivation pathways following excitation of the strongly allowed carotenoid 82 state as a function of the conjugation length. The 82 state rapidly relaxes to the S* and Si states. In all systems we detected a new pathway of energy deactivation within the carotenoid manifold in which the S* state acts as an intermediate state in the 8 2 → S1 internal conversion pathway on a sub-picosecond time scale. In dyad 3, a novel type of collective carotenoid-Pc electronic state is observed that may correspond to a carotenoid excited state(s)-Pc Q exciplex. The exciplex is only observed upon direct carotenoid excitation and is nonfluorescent. In dyad 1, two carotenoid singlet excited states, S2 and S1, contribute to singlet-singlet energy transfer to Pc, making the process very efficient (>90%) while for dyads 2 and 3 the Si energy transfer channel is precluded and only S2 is capable of transferring energy to Pc. In the latter two systems, the lifetime of the first singlet excited state of Pc is dramatically shortened compared to the 9 double-bond dyad and model Pc, indicating that the carotenoid acts as a strong quencher of the phthalocyanine excited-state energy.

Original languageEnglish (US)
Pages (from-to)6868-6877
Number of pages10
JournalJournal of Physical Chemistry B
Volume111
Issue number24
DOIs
StatePublished - Jun 21 2007

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Berera, R., Van Stokkum, I. H. M., Kodis, G., Keirstead, A. E., Pillai, S., Herrero, C., Palacios, R. E., Vengris, M., Van Grondelle, R., Gust, D., Moore, T., Moore, A., & Kennis, J. T. M. (2007). Energy transfer, excited-state deactivation, and exciplex formation in artificial caroteno-phthalocyanine light-harvesting antennas. Journal of Physical Chemistry B, 111(24), 6868-6877. https://doi.org/10.1021/jp071010q