Probing Mixed Valence in a New tppz-Bridged Diruthenium(III,II) Complex (μ-tppz)Ru(bik)Cl23+ (tppz = 2,3,5,6-Tetrakis(2-pyridyl)pyrazine, bik = 2,2'-Bis(1-methylimidazolyl)ketone): EPR Silence, Intervalence Absorption, and nCO Line Broadening
The complex dication of the diruthenium(II) compd. (μ-tppz)Ru(bik)Cl2(ClO4)2 can be oxidized and reduced in two 1-electron steps each. In MeCN/0.1 M Bu4NPF6, the odd-electron intermediates(μ-tppz)Ru(bik)Cl2n+, n = 1 and 3, have comproportionation consts. of 7 $\times$ 108 and 1 $\times$ 105, resp. Both exhibit near-IR absorptions, in the case of n = 3 the 1640 nm band (e = 1200 M-1 cm-1, Dn1/2 = 1560 cm-1) is attributed to an intervalence charge-transfer transition. While the mixed-valent intermediate (n = 3) is EPR silent even at 4 K, the n = 1 form shows g(‖) 2.005 and g($\bot$) 1.994 at that temp., signifying a diruthenium(II) complex of the tppz.bul.- radical anion. The variation of energy and intensity of nCO and of the ring vibration band around 1590 cm-1 was monitored not only for (μ-tppz)Ru(bik)Cl2n+, n = 0-4, but also for the mononuclear (tppz)Ru(bik)Cln+, n = 0-2. In the dinuclear complex the carbonyl stretching bands of the spectator ligand bik are shifted by $\sim$15 cm-1 on each 1-electron-transfer step, increasing with the pos. charge. The mixed-valent (μ-tppz)Ru(bik)Cl23+ shows a perceptibly broader nCO band, suggesting incomplete valence averaging (partial localization). on SciFinder(R)
%0 Journal Article
%1 Koley.2007
%A Koley, Moumita
%A Sarkar, Biprajit
%A Ghumaan, Sandeep
%A Bulak, Ece
%A Fiedler, Jan
%A Kaim, Wolfgang
%A Lahiri, Goutam Kumar.
%D 2007
%J Inorganic Chemistry
%K ESR IR UV charge electrochem methylimidazolylketone methylimidazolylketone;intervalence methylimidazolylketone;ruthenium mixed oxidn prepn pyridylpyrazine redn ruthenium transfer transition valent
%N 9
%P 3736--3742
%R 10.1021/ic0700102
%T Probing Mixed Valence in a New tppz-Bridged Diruthenium(III,II) Complex (μ-tppz)Ru(bik)Cl23+ (tppz = 2,3,5,6-Tetrakis(2-pyridyl)pyrazine, bik = 2,2'-Bis(1-methylimidazolyl)ketone): EPR Silence, Intervalence Absorption, and nCO Line Broadening
%V 46
%X The complex dication of the diruthenium(II) compd. (μ-tppz)Ru(bik)Cl2(ClO4)2 can be oxidized and reduced in two 1-electron steps each. In MeCN/0.1 M Bu4NPF6, the odd-electron intermediates(μ-tppz)Ru(bik)Cl2n+, n = 1 and 3, have comproportionation consts. of 7 $\times$ 108 and 1 $\times$ 105, resp. Both exhibit near-IR absorptions, in the case of n = 3 the 1640 nm band (e = 1200 M-1 cm-1, Dn1/2 = 1560 cm-1) is attributed to an intervalence charge-transfer transition. While the mixed-valent intermediate (n = 3) is EPR silent even at 4 K, the n = 1 form shows g(‖) 2.005 and g($\bot$) 1.994 at that temp., signifying a diruthenium(II) complex of the tppz.bul.- radical anion. The variation of energy and intensity of nCO and of the ring vibration band around 1590 cm-1 was monitored not only for (μ-tppz)Ru(bik)Cl2n+, n = 0-4, but also for the mononuclear (tppz)Ru(bik)Cln+, n = 0-2. In the dinuclear complex the carbonyl stretching bands of the spectator ligand bik are shifted by $\sim$15 cm-1 on each 1-electron-transfer step, increasing with the pos. charge. The mixed-valent (μ-tppz)Ru(bik)Cl23+ shows a perceptibly broader nCO band, suggesting incomplete valence averaging (partial localization). on SciFinder(R)
@article{Koley.2007,
abstract = {The complex dication of the diruthenium(II) compd. {(μ-tppz)[Ru(bik)Cl]2}(ClO4)2 can be oxidized and reduced in two 1-electron steps each. In MeCN/0.1 M Bu4NPF6, the odd-electron intermediates{(μ-tppz)[Ru(bik)Cl]2}n+, n = 1 and 3, have comproportionation consts. of 7 $\times$ 108 and 1 $\times$ 105, resp. Both exhibit near-IR absorptions, in the case of n = 3 the 1640 nm band (\textgreek{e} = 1200 M-1 cm-1, \textgreek{Dn}1/2 = 1560 cm-1) is attributed to an intervalence charge-transfer transition. While the mixed-valent intermediate (n = 3) is EPR silent even at 4 K, the n = 1 form shows g(‖) 2.005 and g($\bot$) 1.994 at that temp., signifying a diruthenium(II) complex of the tppz.bul.- radical anion. The variation of energy and intensity of \textgreek{n}CO and of the ring vibration band around 1590 cm-1 was monitored not only for {(μ-tppz)[Ru(bik)Cl]2}n+, n = 0-4, but also for the mononuclear {(tppz)Ru(bik)Cl}n+, n = 0-2. In the dinuclear complex the carbonyl stretching bands of the spectator ligand bik are shifted by $\sim$15 cm-1 on each 1-electron-transfer step, increasing with the pos. charge. The mixed-valent {(μ-tppz)[Ru(bik)Cl]2}3+ shows a perceptibly broader \textgreek{n}CO band, suggesting incomplete valence averaging (partial localization). [on SciFinder(R)]},
added-at = {2022-06-15T11:26:56.000+0200},
author = {Koley, Moumita and Sarkar, Biprajit and Ghumaan, Sandeep and Bulak, Ece and Fiedler, Jan and Kaim, Wolfgang and Lahiri, Goutam Kumar.},
biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2c41133118aa0b9c23b8cd30ea2ceac86/huebleriac},
doi = {10.1021/ic0700102},
interhash = {824c1221f56dc19adb48da1837f4f0bf},
intrahash = {c41133118aa0b9c23b8cd30ea2ceac86},
issn = {0020-1669},
journal = {Inorganic Chemistry},
keywords = {ESR IR UV charge electrochem methylimidazolylketone methylimidazolylketone;intervalence methylimidazolylketone;ruthenium mixed oxidn prepn pyridylpyrazine redn ruthenium transfer transition valent},
number = 9,
pages = {3736--3742},
timestamp = {2022-06-15T09:26:56.000+0200},
title = {Probing Mixed Valence in a New tppz-Bridged Diruthenium(III,II) Complex {(μ-tppz)[Ru(bik)Cl]2}3+ (tppz = 2,3,5,6-Tetrakis(2-pyridyl)pyrazine, bik = 2,2'-Bis(1-methylimidazolyl)ketone): EPR Silence, Intervalence Absorption, and \textgreek{n}CO Line Broadening},
volume = 46,
year = 2007
}