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Mixed-Valence Properties of an Acetate-Bridged Dinuclear Ruthenium (II,III) Complex

Lomoth, Reiner; Magnusson, Ann LU ; Xu, Yunhua and Sun, Licheng (2003) In The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory 107(22). p.4373-4380
Abstract
The mixed-valence dinuclear ruthenium complex [Ru2(bpmp)(-OAc)2]2+ (where bpmp is the phenolate anion of 2,6-bis[bis(2-pyridylmethyl) aminomethyl]-4-methylphenol, H-bpmp) has been studied by UV-Vis-NIR, IR, and EPR spectroscopic and electrochemical techniques. The Ru2II,III complex undergoes reversible one-electron reduction (E1/2 = -0.61 V vs Fc+/0) and oxidation (E1/2 = 0.09 V vs Fc+/0), resulting in the Ru2II,II and Ru2III,III complexes, respectively. A comproportionation constant of Kc = 1.10 × 1012 (Gc = -68 kJ mol-1) indicates considerable stability of the mixed-valence state. The paramagnetic complex displays a rhombic EPR spectrum (g1 = 2.492; g2 = 2.242; g3 = 1.855) arising from a ground state in a S = 1/2 low spin system in a low... (More)
The mixed-valence dinuclear ruthenium complex [Ru2(bpmp)(-OAc)2]2+ (where bpmp is the phenolate anion of 2,6-bis[bis(2-pyridylmethyl) aminomethyl]-4-methylphenol, H-bpmp) has been studied by UV-Vis-NIR, IR, and EPR spectroscopic and electrochemical techniques. The Ru2II,III complex undergoes reversible one-electron reduction (E1/2 = -0.61 V vs Fc+/0) and oxidation (E1/2 = 0.09 V vs Fc+/0), resulting in the Ru2II,II and Ru2III,III complexes, respectively. A comproportionation constant of Kc = 1.10 × 1012 (Gc = -68 kJ mol-1) indicates considerable stability of the mixed-valence state. The paramagnetic complex displays a rhombic EPR spectrum (g1 = 2.492; g2 = 2.242; g3 = 1.855) arising from a ground state in a S = 1/2 low spin system in a low symmetry environment. Three intense, distinguishable intervalence bands are observed in the NIR to mid-IR spectrum of [Ru2(bpmp)(-OAc)2]2+ at 3765 cm-1 ( = 1840 M-1cm-1), 5615 cm-1 ( = 10590 M-1cm-1 ), and 7735 cm-1 ( = 3410 M-1cm-1). All intervalence bands are symmetric but more narrow than predicted for the classical limit and independent of solvent polarity. The results of the spectroscopic and electrochemical characterization indicate that [Ru2(bpmp)(-OAc)2]2+ is either electronically delocalized (class III, Hab = 1880 cm-1) or at the borderline between localization and delocalization (class II-III, Hab 590 cm-1) with rapid electron transfer (kET > 4 × 1012 s-1) decoupled from solvent reorientation but with a residual activation barrier (Ea 440 cm-1) from inner reorganization. (Less)
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Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
volume
107
issue
22
pages
4373 - 4380
publisher
The American Chemical Society
external identifiers
  • wos:000183223300007
  • scopus:0038511085
ISSN
1520-5215
DOI
10.1021/jp022563y
language
English
LU publication?
yes
id
c76dcbf4-8d39-4d67-8e7e-c3821e3bdb35 (old id 124683)
date added to LUP
2007-07-06 09:55:39
date last changed
2018-05-29 11:21:04
@article{c76dcbf4-8d39-4d67-8e7e-c3821e3bdb35,
  abstract     = {The mixed-valence dinuclear ruthenium complex [Ru2(bpmp)(-OAc)2]2+ (where bpmp is the phenolate anion of 2,6-bis[bis(2-pyridylmethyl) aminomethyl]-4-methylphenol, H-bpmp) has been studied by UV-Vis-NIR, IR, and EPR spectroscopic and electrochemical techniques. The Ru2II,III complex undergoes reversible one-electron reduction (E1/2 = -0.61 V vs Fc+/0) and oxidation (E1/2 = 0.09 V vs Fc+/0), resulting in the Ru2II,II and Ru2III,III complexes, respectively. A comproportionation constant of Kc = 1.10 × 1012 (Gc = -68 kJ mol-1) indicates considerable stability of the mixed-valence state. The paramagnetic complex displays a rhombic EPR spectrum (g1 = 2.492; g2 = 2.242; g3 = 1.855) arising from a ground state in a S = 1/2 low spin system in a low symmetry environment. Three intense, distinguishable intervalence bands are observed in the NIR to mid-IR spectrum of [Ru2(bpmp)(-OAc)2]2+ at 3765 cm-1 ( = 1840 M-1cm-1), 5615 cm-1 ( = 10590 M-1cm-1 ), and 7735 cm-1 ( = 3410 M-1cm-1). All intervalence bands are symmetric but more narrow than predicted for the classical limit and independent of solvent polarity. The results of the spectroscopic and electrochemical characterization indicate that [Ru2(bpmp)(-OAc)2]2+ is either electronically delocalized (class III, Hab = 1880 cm-1) or at the borderline between localization and delocalization (class II-III, Hab 590 cm-1) with rapid electron transfer (kET > 4 × 1012 s-1) decoupled from solvent reorientation but with a residual activation barrier (Ea 440 cm-1) from inner reorganization.},
  author       = {Lomoth, Reiner and Magnusson, Ann and Xu, Yunhua and Sun, Licheng},
  issn         = {1520-5215},
  language     = {eng},
  number       = {22},
  pages        = {4373--4380},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory},
  title        = {Mixed-Valence Properties of an Acetate-Bridged Dinuclear Ruthenium (II,III) Complex},
  url          = {http://dx.doi.org/10.1021/jp022563y},
  volume       = {107},
  year         = {2003},
}