Carotenoids as electron or excited-state energy donors in artificial photosynthesis: An ultrafast investigation of a carotenoporphyrin and a carotenofullerene dyad

Smitha Pillai, Janneke Ravensbergen, Antaeres Antoniuk-Pablant, Benjamin D. Sherman, Rienk Van Grondelle, Raoul N. Frese, Thomas Moore, Devens Gust, Ana Moore, John T M Kennis

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Photophysical investigations of molecular donor-acceptor systems have helped elucidate many details of natural photosynthesis and revealed design principles for artificial photosynthetic systems. To obtain insights into the factors that govern the partition between excited-state energy transfer (EET) and electron transfer (ET) processes among carotenoids and tetrapyrroles and fullerenes, we have designed artificial photosynthetic dyads that are thermodynamically poised to favor ET over EET processes. The dyads were studied using transient absorption spectroscopy with ∼100 femtosecond time resolution. For dyad 1, a carotenoporphyrin, excitation to the carotenoid S 2 state induces ultrafast ET, competing with internal conversion (IC) to the carotenoid S1 state. In addition, the carotenoid S 1 state gives rise to ET. In contrast with biological photosynthesis and many artificial photosynthetic systems, no EET at all was detected for this dyad upon carotenoid S2 excitation. Recombination of the charge separated state takes place in hundreds of picoseconds and yields a triplet state, which is interpreted as a triplet delocalized between the porphyrin and carotenoid moieties. In dyad 2, a carotenofullerene, excitation of the carotenoid in the S2 band results in internal conversion to the S1 state, ET and probably EET to fullerene on ultrafast timescales. From the carotenoid S1 state EET to fullerene occurs. Subsequently, the excited-state fullerene gives rise to ET from the carotenoid to the fullerene. Again, the charge separated state recombines in hundreds of picoseconds. The results illustrate that for a given rate of EET, the ratio of ET to EET can be controlled by adjusting the driving force for electron transfer.

Original languageEnglish (US)
Pages (from-to)4775-4784
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume15
Issue number13
DOIs
StatePublished - Apr 7 2013

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry

Fingerprint

Dive into the research topics of 'Carotenoids as electron or excited-state energy donors in artificial photosynthesis: An ultrafast investigation of a carotenoporphyrin and a carotenofullerene dyad'. Together they form a unique fingerprint.

Cite this