Mimicry of carotenoid photoprotection in artificial photosynthetic reaction centers

Triplet-triplet energy transfer by a relay mechanism

John Devens Gust, Thomas A Moore, Ana L Moore, Darius Kuciauskas, Paul A. Liddell, Brian D. Halbert

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69 Citations (Scopus)

Abstract

Two artificial photosynthetic reaction centers consisting of a porphyrin (P) covalently linked to both a carotenoid polyene (C) and a fullerene derivative (C60) have been prepared and found to transfer triplet excitation energy from the fullerene moiety of C-P-3C60 to the carotenoid polyene, yielding 3C-P-C60. The transfer has been studied both in toluene at ambient temperatures and in 2-methyltetrahydrofuran at lower temperatures. The energy transfer is an activated process, with E(a) = 0.17 eV. This is consistent with transfer by a triplet energy transfer relay, whereby energy first migrates from C-P-3C60 to the porphyrin, yielding C-3P-C60 in a slow, thermally activated step. Rapid energy transfer from the porphyrin triplet to the carotenoid gives the final state. Triplet relays of this sort have been observed in photosynthetic reaction centers, and are part of the system that protects the organism from damage by singlet oxygen, whose production is sensitized by chlorophyll triplet states. The fullerene-containing triads can also demonstrate stepwise photoinduced electron transfer to yield long-lived C.+-P-C60.- charge-separated states. Electron transfer occurs even at 8 K. Charge recombination of C.+-P-C60.- yields 3C-P-C60, rather than the molecular ground state. These photochemical events are reminiscent of photoinduced electron transfer in photosynthetic reaction centers.

Original languageEnglish
Pages (from-to)209-216
Number of pages8
JournalJournal of Photochemistry and Photobiology B: Biology
Volume43
Issue number3
DOIs
Publication statusPublished - Jun 1 1998

Fingerprint

fullerene
photosynthetic reaction centers
Photosynthetic Reaction Center Complex Proteins
Fullerenes
carotenoids
porphyrins
photostability
Energy Transfer
Porphyrins
relay
Carotenoids
energy transfer
Energy transfer
electron transfer
fullerenes
Polyenes
Electrons
atomic energy levels
oxygen production
Singlet Oxygen

Keywords

  • Carotene
  • Energy transfer
  • Photosynthesis
  • Porphyrin
  • Triplet

ASJC Scopus subject areas

  • Plant Science
  • Bioengineering
  • Physical and Theoretical Chemistry

Cite this

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title = "Mimicry of carotenoid photoprotection in artificial photosynthetic reaction centers: Triplet-triplet energy transfer by a relay mechanism",
abstract = "Two artificial photosynthetic reaction centers consisting of a porphyrin (P) covalently linked to both a carotenoid polyene (C) and a fullerene derivative (C60) have been prepared and found to transfer triplet excitation energy from the fullerene moiety of C-P-3C60 to the carotenoid polyene, yielding 3C-P-C60. The transfer has been studied both in toluene at ambient temperatures and in 2-methyltetrahydrofuran at lower temperatures. The energy transfer is an activated process, with E(a) = 0.17 eV. This is consistent with transfer by a triplet energy transfer relay, whereby energy first migrates from C-P-3C60 to the porphyrin, yielding C-3P-C60 in a slow, thermally activated step. Rapid energy transfer from the porphyrin triplet to the carotenoid gives the final state. Triplet relays of this sort have been observed in photosynthetic reaction centers, and are part of the system that protects the organism from damage by singlet oxygen, whose production is sensitized by chlorophyll triplet states. The fullerene-containing triads can also demonstrate stepwise photoinduced electron transfer to yield long-lived C.+-P-C60.- charge-separated states. Electron transfer occurs even at 8 K. Charge recombination of C.+-P-C60.- yields 3C-P-C60, rather than the molecular ground state. These photochemical events are reminiscent of photoinduced electron transfer in photosynthetic reaction centers.",
keywords = "Carotene, Energy transfer, Photosynthesis, Porphyrin, Triplet",
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T2 - Triplet-triplet energy transfer by a relay mechanism

AU - Gust, John Devens

AU - Moore, Thomas A

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AU - Kuciauskas, Darius

AU - Liddell, Paul A.

AU - Halbert, Brian D.

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N2 - Two artificial photosynthetic reaction centers consisting of a porphyrin (P) covalently linked to both a carotenoid polyene (C) and a fullerene derivative (C60) have been prepared and found to transfer triplet excitation energy from the fullerene moiety of C-P-3C60 to the carotenoid polyene, yielding 3C-P-C60. The transfer has been studied both in toluene at ambient temperatures and in 2-methyltetrahydrofuran at lower temperatures. The energy transfer is an activated process, with E(a) = 0.17 eV. This is consistent with transfer by a triplet energy transfer relay, whereby energy first migrates from C-P-3C60 to the porphyrin, yielding C-3P-C60 in a slow, thermally activated step. Rapid energy transfer from the porphyrin triplet to the carotenoid gives the final state. Triplet relays of this sort have been observed in photosynthetic reaction centers, and are part of the system that protects the organism from damage by singlet oxygen, whose production is sensitized by chlorophyll triplet states. The fullerene-containing triads can also demonstrate stepwise photoinduced electron transfer to yield long-lived C.+-P-C60.- charge-separated states. Electron transfer occurs even at 8 K. Charge recombination of C.+-P-C60.- yields 3C-P-C60, rather than the molecular ground state. These photochemical events are reminiscent of photoinduced electron transfer in photosynthetic reaction centers.

AB - Two artificial photosynthetic reaction centers consisting of a porphyrin (P) covalently linked to both a carotenoid polyene (C) and a fullerene derivative (C60) have been prepared and found to transfer triplet excitation energy from the fullerene moiety of C-P-3C60 to the carotenoid polyene, yielding 3C-P-C60. The transfer has been studied both in toluene at ambient temperatures and in 2-methyltetrahydrofuran at lower temperatures. The energy transfer is an activated process, with E(a) = 0.17 eV. This is consistent with transfer by a triplet energy transfer relay, whereby energy first migrates from C-P-3C60 to the porphyrin, yielding C-3P-C60 in a slow, thermally activated step. Rapid energy transfer from the porphyrin triplet to the carotenoid gives the final state. Triplet relays of this sort have been observed in photosynthetic reaction centers, and are part of the system that protects the organism from damage by singlet oxygen, whose production is sensitized by chlorophyll triplet states. The fullerene-containing triads can also demonstrate stepwise photoinduced electron transfer to yield long-lived C.+-P-C60.- charge-separated states. Electron transfer occurs even at 8 K. Charge recombination of C.+-P-C60.- yields 3C-P-C60, rather than the molecular ground state. These photochemical events are reminiscent of photoinduced electron transfer in photosynthetic reaction centers.

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