Photoinduced energy transfer coupled to charge separation in a Ru(II)-Ru(II)-acceptor triad

Magnus Borgström, Sascha Ott, Reiner Lomoth, Jonas Bergquist, Leif Hammarström, Olof Johansson

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Abstract

The bichromophoric system Ru-Ruc-Pl ([(bpy)3Ru-Ph- Ru(dpb)(Metpy-Pl)][PF6]3, where bpy is 2,2′-bipyridine, Hdpb is 1,3-di(2-pyridyl)-benzene, Metpy is 4′-methyl-2,2′:6′,2″-terpyridine and Pl is pyromellitimide) containing two Ru(II) polypyridyl chromophores with a N 6 and a N5C ligand set, respectively, was synthesized and characterized. Its photophysical properties were investigated and compared to those of the monochromophoric cyclometalated complexes Ruc-Pl ([Ru(dpb)(Metpy-Pl)][PF6]), Ruc-φ-Pl ([Ru(dpb)(ttpy-Pl)][PF6], ttpy is 4′-p-tolyl-2,2′: 6′,2″-terpyridine), Ruc-φ ([Ru(dpb)(ttpy)][PF 6]), and Ruc ([Ru(dpb)(Metpy)][PF6]). Excitation of the Ruc-unit in the dyads leads to oxidative quenching, forming the Ruc III-φ-Pl•- and Ru c III-Pl•- charge-separated (CS) states with kf ET = 7.7 × 107 s-1 (CH3CN, 298 K) in the tolyl-linked Ruc-φ-Pl and k f ET = 4.4 × 109 s-1 (CH 2Cl2, 298 K) in the methylene-linked Ruc-Pl. In the Ru-Ruc-Pl triad, excitation of the Ruc chromophore leads to dynamics similar to those in the Ruc-Pl dyad, generating the RuII-Ruc III-Pl•- CS state, whereas excitation of the Ru unit results in an initial energy transfer (k EnT = 4.7 × 1011 s-1) to the cyclometalated Ruc unit. Subsequent electron transfer to the Pl acceptor results in the formation of the same RuII-Ru c III-Pl•- CS state with kf ET = 5.6 × 109 s-1 that undergoes rapid recombination with kb ET = 1 × 1010 s -1 (CH2Cl2, 298 K). The fate of the Ru II-Ruc III-Pl•- CS state upon a second photoexcitation was studied by pump-pump-probe experiments in an attempt to detect the fully charge-separated RuIII-Ruc II-Pl•- state.

Original languageEnglish
Pages (from-to)4820-4829
Number of pages10
JournalInorganic Chemistry
Volume45
Issue number12
DOIs
Publication statusPublished - Jun 12 2006

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polarization (charge separation)
Chromophores
Energy transfer
energy transfer
Pumps
chromophores
Photoexcitation
Benzene
pumps
excitation
Quenching
Ligands
photoexcitation
methylene
Electrons
electron transfer
quenching
benzene
methylidyne
ligands

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Photoinduced energy transfer coupled to charge separation in a Ru(II)-Ru(II)-acceptor triad. / Borgström, Magnus; Ott, Sascha; Lomoth, Reiner; Bergquist, Jonas; Hammarström, Leif; Johansson, Olof.

In: Inorganic Chemistry, Vol. 45, No. 12, 12.06.2006, p. 4820-4829.

Research output: Contribution to journalArticle

Borgström, Magnus ; Ott, Sascha ; Lomoth, Reiner ; Bergquist, Jonas ; Hammarström, Leif ; Johansson, Olof. / Photoinduced energy transfer coupled to charge separation in a Ru(II)-Ru(II)-acceptor triad. In: Inorganic Chemistry. 2006 ; Vol. 45, No. 12. pp. 4820-4829.
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title = "Photoinduced energy transfer coupled to charge separation in a Ru(II)-Ru(II)-acceptor triad",
abstract = "The bichromophoric system Ru-Ruc-Pl ([(bpy)3Ru-Ph- Ru(dpb)(Metpy-Pl)][PF6]3, where bpy is 2,2′-bipyridine, Hdpb is 1,3-di(2-pyridyl)-benzene, Metpy is 4′-methyl-2,2′:6′,2″-terpyridine and Pl is pyromellitimide) containing two Ru(II) polypyridyl chromophores with a N 6 and a N5C ligand set, respectively, was synthesized and characterized. Its photophysical properties were investigated and compared to those of the monochromophoric cyclometalated complexes Ruc-Pl ([Ru(dpb)(Metpy-Pl)][PF6]), Ruc-φ-Pl ([Ru(dpb)(ttpy-Pl)][PF6], ttpy is 4′-p-tolyl-2,2′: 6′,2″-terpyridine), Ruc-φ ([Ru(dpb)(ttpy)][PF 6]), and Ruc ([Ru(dpb)(Metpy)][PF6]). Excitation of the Ruc-unit in the dyads leads to oxidative quenching, forming the Ruc III-φ-Pl•- and Ru c III-Pl•- charge-separated (CS) states with kf ET = 7.7 × 107 s-1 (CH3CN, 298 K) in the tolyl-linked Ruc-φ-Pl and k f ET = 4.4 × 109 s-1 (CH 2Cl2, 298 K) in the methylene-linked Ruc-Pl. In the Ru-Ruc-Pl triad, excitation of the Ruc chromophore leads to dynamics similar to those in the Ruc-Pl dyad, generating the RuII-Ruc III-Pl•- CS state, whereas excitation of the Ru unit results in an initial energy transfer (k EnT = 4.7 × 1011 s-1) to the cyclometalated Ruc unit. Subsequent electron transfer to the Pl acceptor results in the formation of the same RuII-Ru c III-Pl•- CS state with kf ET = 5.6 × 109 s-1 that undergoes rapid recombination with kb ET = 1 × 1010 s -1 (CH2Cl2, 298 K). The fate of the Ru II-Ruc III-Pl•- CS state upon a second photoexcitation was studied by pump-pump-probe experiments in an attempt to detect the fully charge-separated RuIII-Ruc II-Pl•- state.",
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T1 - Photoinduced energy transfer coupled to charge separation in a Ru(II)-Ru(II)-acceptor triad

AU - Borgström, Magnus

AU - Ott, Sascha

AU - Lomoth, Reiner

AU - Bergquist, Jonas

AU - Hammarström, Leif

AU - Johansson, Olof

PY - 2006/6/12

Y1 - 2006/6/12

N2 - The bichromophoric system Ru-Ruc-Pl ([(bpy)3Ru-Ph- Ru(dpb)(Metpy-Pl)][PF6]3, where bpy is 2,2′-bipyridine, Hdpb is 1,3-di(2-pyridyl)-benzene, Metpy is 4′-methyl-2,2′:6′,2″-terpyridine and Pl is pyromellitimide) containing two Ru(II) polypyridyl chromophores with a N 6 and a N5C ligand set, respectively, was synthesized and characterized. Its photophysical properties were investigated and compared to those of the monochromophoric cyclometalated complexes Ruc-Pl ([Ru(dpb)(Metpy-Pl)][PF6]), Ruc-φ-Pl ([Ru(dpb)(ttpy-Pl)][PF6], ttpy is 4′-p-tolyl-2,2′: 6′,2″-terpyridine), Ruc-φ ([Ru(dpb)(ttpy)][PF 6]), and Ruc ([Ru(dpb)(Metpy)][PF6]). Excitation of the Ruc-unit in the dyads leads to oxidative quenching, forming the Ruc III-φ-Pl•- and Ru c III-Pl•- charge-separated (CS) states with kf ET = 7.7 × 107 s-1 (CH3CN, 298 K) in the tolyl-linked Ruc-φ-Pl and k f ET = 4.4 × 109 s-1 (CH 2Cl2, 298 K) in the methylene-linked Ruc-Pl. In the Ru-Ruc-Pl triad, excitation of the Ruc chromophore leads to dynamics similar to those in the Ruc-Pl dyad, generating the RuII-Ruc III-Pl•- CS state, whereas excitation of the Ru unit results in an initial energy transfer (k EnT = 4.7 × 1011 s-1) to the cyclometalated Ruc unit. Subsequent electron transfer to the Pl acceptor results in the formation of the same RuII-Ru c III-Pl•- CS state with kf ET = 5.6 × 109 s-1 that undergoes rapid recombination with kb ET = 1 × 1010 s -1 (CH2Cl2, 298 K). The fate of the Ru II-Ruc III-Pl•- CS state upon a second photoexcitation was studied by pump-pump-probe experiments in an attempt to detect the fully charge-separated RuIII-Ruc II-Pl•- state.

AB - The bichromophoric system Ru-Ruc-Pl ([(bpy)3Ru-Ph- Ru(dpb)(Metpy-Pl)][PF6]3, where bpy is 2,2′-bipyridine, Hdpb is 1,3-di(2-pyridyl)-benzene, Metpy is 4′-methyl-2,2′:6′,2″-terpyridine and Pl is pyromellitimide) containing two Ru(II) polypyridyl chromophores with a N 6 and a N5C ligand set, respectively, was synthesized and characterized. Its photophysical properties were investigated and compared to those of the monochromophoric cyclometalated complexes Ruc-Pl ([Ru(dpb)(Metpy-Pl)][PF6]), Ruc-φ-Pl ([Ru(dpb)(ttpy-Pl)][PF6], ttpy is 4′-p-tolyl-2,2′: 6′,2″-terpyridine), Ruc-φ ([Ru(dpb)(ttpy)][PF 6]), and Ruc ([Ru(dpb)(Metpy)][PF6]). Excitation of the Ruc-unit in the dyads leads to oxidative quenching, forming the Ruc III-φ-Pl•- and Ru c III-Pl•- charge-separated (CS) states with kf ET = 7.7 × 107 s-1 (CH3CN, 298 K) in the tolyl-linked Ruc-φ-Pl and k f ET = 4.4 × 109 s-1 (CH 2Cl2, 298 K) in the methylene-linked Ruc-Pl. In the Ru-Ruc-Pl triad, excitation of the Ruc chromophore leads to dynamics similar to those in the Ruc-Pl dyad, generating the RuII-Ruc III-Pl•- CS state, whereas excitation of the Ru unit results in an initial energy transfer (k EnT = 4.7 × 1011 s-1) to the cyclometalated Ruc unit. Subsequent electron transfer to the Pl acceptor results in the formation of the same RuII-Ru c III-Pl•- CS state with kf ET = 5.6 × 109 s-1 that undergoes rapid recombination with kb ET = 1 × 1010 s -1 (CH2Cl2, 298 K). The fate of the Ru II-Ruc III-Pl•- CS state upon a second photoexcitation was studied by pump-pump-probe experiments in an attempt to detect the fully charge-separated RuIII-Ruc II-Pl•- state.

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