Electron transfer on the infrared vibrational time scale in the mixed valence state of 1,4-pyrazine- and 4,4'-bipyridine-bridged ruthenium cluster complexes

Tasuku Ito, Tomohiko Hamaguchi, Haruko Nagino, Tadashi Yamaguchi, Hiroaki Kido, Igor S. Zavarine, Todd Richmond, John Washington, Clifford P. Kubiak

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Abstract

Intramolecular electron transfers within the mixed valence states of the ligand bridged hexaruthenium clusters Ru33-O)(μ-CH3CO2)6(CO)(L)(μ- L')Ru33-O)(μ-CH3CO2)6(CO)(L) (L' = 1,4-pyrazine; L = 4- dimethylaminopyridine (1), pyridine (2), 4-cyanopyridine (3), or L' = 4,4'- bipyridine; L = 4-dimethylaminopyridine (4), pyridine (5), 4-cyanopyridine (6)) were examined. Two discrete and reversible single electron reductions are evident by cyclic voltammetry in the redox chemistry of 1-5, and the intercluster charge-transfer complexes are well-defined. The splitting of the reduction waves, ΔE, is related to the electronic coupling H(AB) between the triruthenium clusters, and varies from 80 mV for 5 to 440 mV for 1. In the case of 6, the splitting of the reduction waves, ΔE, is <50 mV and the intercluster charge-transfer complex is not defined. The mixed valence states of 1-3 also exhibit intervalence charge transfer (ICT) bands in the region 12 100 (1) to 10 800 cm-1 (3) which provide spectroscopic estimates of H(AB) in the range 2180 (1) to 1310 cm-1 (3). The magnitude of the electronic coupling H(AB) is found to strongly influence the IR spectra of the singly reduced (-1) mixed valence states of 1-6 in the v(CO) region. In the case of relatively weak electronic coupling (4-6), two v(CO) bands are clearly resolved. In the cases of strong electronic coupling (1-3), these bands broaden to a single v(CO) absorption band. These data allow the rate constants, k(e), for electron transfer in the mixed valence states of 1, 2, and 3 to be estimated by simulating dynamical effects (Bloch-type equations) on v(CO) absorption band shape at 9 x 1011, 5 x 1011, and ca. 1 x 1011 s-1, respectively. The less strongly coupled 4,4'-bipyridine-bridged complexes 4-6 exhibit IR line shapes in the -1 mixed valence states that are not as strongly affected by electron-transfer dynamics. The rate constant for the -1 mixed valence state of 4 is close to the lower limit that can be estimated by this approach, between 1 x 1010 and 1 x 1011 s-1.

Original languageEnglish
Pages (from-to)4625-4632
Number of pages8
JournalJournal of the American Chemical Society
Volume121
Issue number19
DOIs
Publication statusPublished - 1999 May 19
Externally publishedYes

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Pyrazines
Ruthenium
Electrons
Infrared radiation
Charge transfer
Pyridine
Absorption spectra
Rate constants
Cyclic voltammetry
Oxidation-Reduction
Ligands
4,4'-bipyridyl
pyridine
4-cyanopyridine
4-dimethylaminopyridine

ASJC Scopus subject areas

  • Chemistry(all)

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Electron transfer on the infrared vibrational time scale in the mixed valence state of 1,4-pyrazine- and 4,4'-bipyridine-bridged ruthenium cluster complexes. / Ito, Tasuku; Hamaguchi, Tomohiko; Nagino, Haruko; Yamaguchi, Tadashi; Kido, Hiroaki; Zavarine, Igor S.; Richmond, Todd; Washington, John; Kubiak, Clifford P.

In: Journal of the American Chemical Society, Vol. 121, No. 19, 19.05.1999, p. 4625-4632.

Research output: Contribution to journalArticle

Ito, Tasuku ; Hamaguchi, Tomohiko ; Nagino, Haruko ; Yamaguchi, Tadashi ; Kido, Hiroaki ; Zavarine, Igor S. ; Richmond, Todd ; Washington, John ; Kubiak, Clifford P. / Electron transfer on the infrared vibrational time scale in the mixed valence state of 1,4-pyrazine- and 4,4'-bipyridine-bridged ruthenium cluster complexes. In: Journal of the American Chemical Society. 1999 ; Vol. 121, No. 19. pp. 4625-4632.
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title = "Electron transfer on the infrared vibrational time scale in the mixed valence state of 1,4-pyrazine- and 4,4'-bipyridine-bridged ruthenium cluster complexes",
abstract = "Intramolecular electron transfers within the mixed valence states of the ligand bridged hexaruthenium clusters Ru3(μ3-O)(μ-CH3CO2)6(CO)(L)(μ- L')Ru3(μ3-O)(μ-CH3CO2)6(CO)(L) (L' = 1,4-pyrazine; L = 4- dimethylaminopyridine (1), pyridine (2), 4-cyanopyridine (3), or L' = 4,4'- bipyridine; L = 4-dimethylaminopyridine (4), pyridine (5), 4-cyanopyridine (6)) were examined. Two discrete and reversible single electron reductions are evident by cyclic voltammetry in the redox chemistry of 1-5, and the intercluster charge-transfer complexes are well-defined. The splitting of the reduction waves, ΔE, is related to the electronic coupling H(AB) between the triruthenium clusters, and varies from 80 mV for 5 to 440 mV for 1. In the case of 6, the splitting of the reduction waves, ΔE, is <50 mV and the intercluster charge-transfer complex is not defined. The mixed valence states of 1-3 also exhibit intervalence charge transfer (ICT) bands in the region 12 100 (1) to 10 800 cm-1 (3) which provide spectroscopic estimates of H(AB) in the range 2180 (1) to 1310 cm-1 (3). The magnitude of the electronic coupling H(AB) is found to strongly influence the IR spectra of the singly reduced (-1) mixed valence states of 1-6 in the v(CO) region. In the case of relatively weak electronic coupling (4-6), two v(CO) bands are clearly resolved. In the cases of strong electronic coupling (1-3), these bands broaden to a single v(CO) absorption band. These data allow the rate constants, k(e), for electron transfer in the mixed valence states of 1, 2, and 3 to be estimated by simulating dynamical effects (Bloch-type equations) on v(CO) absorption band shape at 9 x 1011, 5 x 1011, and ca. 1 x 1011 s-1, respectively. The less strongly coupled 4,4'-bipyridine-bridged complexes 4-6 exhibit IR line shapes in the -1 mixed valence states that are not as strongly affected by electron-transfer dynamics. The rate constant for the -1 mixed valence state of 4 is close to the lower limit that can be estimated by this approach, between 1 x 1010 and 1 x 1011 s-1.",
author = "Tasuku Ito and Tomohiko Hamaguchi and Haruko Nagino and Tadashi Yamaguchi and Hiroaki Kido and Zavarine, {Igor S.} and Todd Richmond and John Washington and Kubiak, {Clifford P.}",
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T1 - Electron transfer on the infrared vibrational time scale in the mixed valence state of 1,4-pyrazine- and 4,4'-bipyridine-bridged ruthenium cluster complexes

AU - Ito, Tasuku

AU - Hamaguchi, Tomohiko

AU - Nagino, Haruko

AU - Yamaguchi, Tadashi

AU - Kido, Hiroaki

AU - Zavarine, Igor S.

AU - Richmond, Todd

AU - Washington, John

AU - Kubiak, Clifford P.

PY - 1999/5/19

Y1 - 1999/5/19

N2 - Intramolecular electron transfers within the mixed valence states of the ligand bridged hexaruthenium clusters Ru3(μ3-O)(μ-CH3CO2)6(CO)(L)(μ- L')Ru3(μ3-O)(μ-CH3CO2)6(CO)(L) (L' = 1,4-pyrazine; L = 4- dimethylaminopyridine (1), pyridine (2), 4-cyanopyridine (3), or L' = 4,4'- bipyridine; L = 4-dimethylaminopyridine (4), pyridine (5), 4-cyanopyridine (6)) were examined. Two discrete and reversible single electron reductions are evident by cyclic voltammetry in the redox chemistry of 1-5, and the intercluster charge-transfer complexes are well-defined. The splitting of the reduction waves, ΔE, is related to the electronic coupling H(AB) between the triruthenium clusters, and varies from 80 mV for 5 to 440 mV for 1. In the case of 6, the splitting of the reduction waves, ΔE, is <50 mV and the intercluster charge-transfer complex is not defined. The mixed valence states of 1-3 also exhibit intervalence charge transfer (ICT) bands in the region 12 100 (1) to 10 800 cm-1 (3) which provide spectroscopic estimates of H(AB) in the range 2180 (1) to 1310 cm-1 (3). The magnitude of the electronic coupling H(AB) is found to strongly influence the IR spectra of the singly reduced (-1) mixed valence states of 1-6 in the v(CO) region. In the case of relatively weak electronic coupling (4-6), two v(CO) bands are clearly resolved. In the cases of strong electronic coupling (1-3), these bands broaden to a single v(CO) absorption band. These data allow the rate constants, k(e), for electron transfer in the mixed valence states of 1, 2, and 3 to be estimated by simulating dynamical effects (Bloch-type equations) on v(CO) absorption band shape at 9 x 1011, 5 x 1011, and ca. 1 x 1011 s-1, respectively. The less strongly coupled 4,4'-bipyridine-bridged complexes 4-6 exhibit IR line shapes in the -1 mixed valence states that are not as strongly affected by electron-transfer dynamics. The rate constant for the -1 mixed valence state of 4 is close to the lower limit that can be estimated by this approach, between 1 x 1010 and 1 x 1011 s-1.

AB - Intramolecular electron transfers within the mixed valence states of the ligand bridged hexaruthenium clusters Ru3(μ3-O)(μ-CH3CO2)6(CO)(L)(μ- L')Ru3(μ3-O)(μ-CH3CO2)6(CO)(L) (L' = 1,4-pyrazine; L = 4- dimethylaminopyridine (1), pyridine (2), 4-cyanopyridine (3), or L' = 4,4'- bipyridine; L = 4-dimethylaminopyridine (4), pyridine (5), 4-cyanopyridine (6)) were examined. Two discrete and reversible single electron reductions are evident by cyclic voltammetry in the redox chemistry of 1-5, and the intercluster charge-transfer complexes are well-defined. The splitting of the reduction waves, ΔE, is related to the electronic coupling H(AB) between the triruthenium clusters, and varies from 80 mV for 5 to 440 mV for 1. In the case of 6, the splitting of the reduction waves, ΔE, is <50 mV and the intercluster charge-transfer complex is not defined. The mixed valence states of 1-3 also exhibit intervalence charge transfer (ICT) bands in the region 12 100 (1) to 10 800 cm-1 (3) which provide spectroscopic estimates of H(AB) in the range 2180 (1) to 1310 cm-1 (3). The magnitude of the electronic coupling H(AB) is found to strongly influence the IR spectra of the singly reduced (-1) mixed valence states of 1-6 in the v(CO) region. In the case of relatively weak electronic coupling (4-6), two v(CO) bands are clearly resolved. In the cases of strong electronic coupling (1-3), these bands broaden to a single v(CO) absorption band. These data allow the rate constants, k(e), for electron transfer in the mixed valence states of 1, 2, and 3 to be estimated by simulating dynamical effects (Bloch-type equations) on v(CO) absorption band shape at 9 x 1011, 5 x 1011, and ca. 1 x 1011 s-1, respectively. The less strongly coupled 4,4'-bipyridine-bridged complexes 4-6 exhibit IR line shapes in the -1 mixed valence states that are not as strongly affected by electron-transfer dynamics. The rate constant for the -1 mixed valence state of 4 is close to the lower limit that can be estimated by this approach, between 1 x 1010 and 1 x 1011 s-1.

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