Ultrafast energy transfer in binuclear ruthenium-osmium complexes as models for light-harvesting antennas

Helena Berglund Baudin, Jan Davidsson, Scolastica Serroni, Alberto Juris, Vincenzo Balzani, Sebastiano Campagna, Leif Hammarström

Research output: Contribution to journalArticle

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Abstract

The binuclear complexes [(bpy)2Ru(μ-2,3-dpp)Ru(bpy)2]4+, [(bpy)2Ru(μ-2,5-dpp)Ru(bpy)2]4+, [(bpy)2Ru(μ-2,3-dpp)Os(bpy)2]4+, [(bpy)2Ru(μ-2,5-dpp)Os(biq)2]4+, and [(bpy)2Os(μ-2,3-dpp)Os(bpy)2]4+ (dpp = bis(2-pyridyl)pyrazine, bpy = 2,2-bipyridine, biq = 2,2-biquinoline) have been studied with femtosecond pump-probe spectroscopy. Excitation energy transfer from the Ru to the Os center in the heterometallic binuclear complexes occurs within 200 fs. This is a time scale comparable to the singlet-triplet conversion and vibrational relaxation of the lowest metal-to-ligand charge transfer (MLCT) state in this type of complexes. Thus, energy transfer probably involves nonthermalized initial states, which may be an explanation for the fast transfer rate. Small spectral changes with time constants of ca. 400-800 fs were observed for all complexes examined, and are attributed to relaxation (vibrational and/or spin) of the MLCT state localized on the lowest energy unit. Energy transfer seems to occur within 200 fs also in the symmetric RuII-RuII and OsII-OsII complexes although the reaction driving force is zero. The results suggest that very large antennas or photonic wires could be constructed based on these metal complexes, in which energy transfer can occur in several steps over long distances, with only very small losses.

Original languageEnglish
Pages (from-to)4312-4319
Number of pages8
JournalJournal of Physical Chemistry A
Volume106
Issue number17
DOIs
Publication statusPublished - May 2 2002

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Osmium
Ruthenium
osmium
Energy transfer
ruthenium
antennas
energy transfer
Antennas
molecular relaxation
Charge transfer
Metals
charge transfer
metals
Ligands
Pyrazines
ligands
Excitation energy
pyrazines
Coordination Complexes
Photonics

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Ultrafast energy transfer in binuclear ruthenium-osmium complexes as models for light-harvesting antennas. / Baudin, Helena Berglund; Davidsson, Jan; Serroni, Scolastica; Juris, Alberto; Balzani, Vincenzo; Campagna, Sebastiano; Hammarström, Leif.

In: Journal of Physical Chemistry A, Vol. 106, No. 17, 02.05.2002, p. 4312-4319.

Research output: Contribution to journalArticle

Baudin, Helena Berglund ; Davidsson, Jan ; Serroni, Scolastica ; Juris, Alberto ; Balzani, Vincenzo ; Campagna, Sebastiano ; Hammarström, Leif. / Ultrafast energy transfer in binuclear ruthenium-osmium complexes as models for light-harvesting antennas. In: Journal of Physical Chemistry A. 2002 ; Vol. 106, No. 17. pp. 4312-4319.
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abstract = "The binuclear complexes [(bpy)2Ru(μ-2,3-dpp)Ru(bpy)2]4+, [(bpy)2Ru(μ-2,5-dpp)Ru(bpy)2]4+, [(bpy)2Ru(μ-2,3-dpp)Os(bpy)2]4+, [(bpy)2Ru(μ-2,5-dpp)Os(biq)2]4+, and [(bpy)2Os(μ-2,3-dpp)Os(bpy)2]4+ (dpp = bis(2-pyridyl)pyrazine, bpy = 2,2-bipyridine, biq = 2,2-biquinoline) have been studied with femtosecond pump-probe spectroscopy. Excitation energy transfer from the Ru to the Os center in the heterometallic binuclear complexes occurs within 200 fs. This is a time scale comparable to the singlet-triplet conversion and vibrational relaxation of the lowest metal-to-ligand charge transfer (MLCT) state in this type of complexes. Thus, energy transfer probably involves nonthermalized initial states, which may be an explanation for the fast transfer rate. Small spectral changes with time constants of ca. 400-800 fs were observed for all complexes examined, and are attributed to relaxation (vibrational and/or spin) of the MLCT state localized on the lowest energy unit. Energy transfer seems to occur within 200 fs also in the symmetric RuII-RuII and OsII-OsII complexes although the reaction driving force is zero. The results suggest that very large antennas or photonic wires could be constructed based on these metal complexes, in which energy transfer can occur in several steps over long distances, with only very small losses.",
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AB - The binuclear complexes [(bpy)2Ru(μ-2,3-dpp)Ru(bpy)2]4+, [(bpy)2Ru(μ-2,5-dpp)Ru(bpy)2]4+, [(bpy)2Ru(μ-2,3-dpp)Os(bpy)2]4+, [(bpy)2Ru(μ-2,5-dpp)Os(biq)2]4+, and [(bpy)2Os(μ-2,3-dpp)Os(bpy)2]4+ (dpp = bis(2-pyridyl)pyrazine, bpy = 2,2-bipyridine, biq = 2,2-biquinoline) have been studied with femtosecond pump-probe spectroscopy. Excitation energy transfer from the Ru to the Os center in the heterometallic binuclear complexes occurs within 200 fs. This is a time scale comparable to the singlet-triplet conversion and vibrational relaxation of the lowest metal-to-ligand charge transfer (MLCT) state in this type of complexes. Thus, energy transfer probably involves nonthermalized initial states, which may be an explanation for the fast transfer rate. Small spectral changes with time constants of ca. 400-800 fs were observed for all complexes examined, and are attributed to relaxation (vibrational and/or spin) of the MLCT state localized on the lowest energy unit. Energy transfer seems to occur within 200 fs also in the symmetric RuII-RuII and OsII-OsII complexes although the reaction driving force is zero. The results suggest that very large antennas or photonic wires could be constructed based on these metal complexes, in which energy transfer can occur in several steps over long distances, with only very small losses.

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