Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System
The pyrazine-bridged diosmium(II) complex {(μ-C4H4N2)[Os(CN)5] 2}6- has been synthesized as the hexapotassium salt and was converted to the hexakis(tetrabutylammonium) compound by ion exchange. Its stepwise oxidation to the Os2IIIOsII and Os2IIIOsIII states was monitored spectroelectrochemically in...
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todo:paper_00201669_v37_n2_p311_Hornung2023-10-03T14:16:48Z Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System Hornung, F.M. Baumann, F. Kaim, W. Olabe, J.A. Slep, L.D. Fiedler, J. The pyrazine-bridged diosmium(II) complex {(μ-C4H4N2)[Os(CN)5] 2}6- has been synthesized as the hexapotassium salt and was converted to the hexakis(tetrabutylammonium) compound by ion exchange. Its stepwise oxidation to the Os2IIIOsII and Os2IIIOsIII states was monitored spectroelectrochemically in acetonitrile/0.1 M Bu4NPF6 in the UV-vis-NIR and IR regions and by EPR. The OsII2 species exhibits long-wavelength solvatochromic MLCT bands at 14 800 and 18 480 cm-1. The pentaanionic mixed-valent ion has a comproportionation constant Kc of 105.8 and is distinguished by several electronic absorptions in the IR region. The bands at 1972, 2480, 4000, 5000, 7170, and 11 900 cm-1 are similar but appreciably lower in energy than those reported for the analogous complex {(μ-C4H4N2)[Os(NH3) 5]2}5+. In addition to CN vibrational stretching features shifted on electron transfer there is an additional sharp band only for the 5- ion at 1582 cm-1 which is attributed to a pyrazine ring vibration. The intensity of this band suggests an unsymmetrical situation and thus valence localization on the vibrational time scale. The EPR signals at g⊥ = 2.0563 and gpar; = 1.761 point toward excited states lying close to the doublet ground state and to significant metal/cyanide interaction. Compared to the Creutz-Taube ion {(μ-C4H4N2)[Ru-(NH3) 5]2}5+ and its osmium homologue, the 5- ion described here exhibits a lower degree of metal-metal coupling. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00201669_v37_n2_p311_Hornung |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
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R-134 |
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| description |
The pyrazine-bridged diosmium(II) complex {(μ-C4H4N2)[Os(CN)5] 2}6- has been synthesized as the hexapotassium salt and was converted to the hexakis(tetrabutylammonium) compound by ion exchange. Its stepwise oxidation to the Os2IIIOsII and Os2IIIOsIII states was monitored spectroelectrochemically in acetonitrile/0.1 M Bu4NPF6 in the UV-vis-NIR and IR regions and by EPR. The OsII2 species exhibits long-wavelength solvatochromic MLCT bands at 14 800 and 18 480 cm-1. The pentaanionic mixed-valent ion has a comproportionation constant Kc of 105.8 and is distinguished by several electronic absorptions in the IR region. The bands at 1972, 2480, 4000, 5000, 7170, and 11 900 cm-1 are similar but appreciably lower in energy than those reported for the analogous complex {(μ-C4H4N2)[Os(NH3) 5]2}5+. In addition to CN vibrational stretching features shifted on electron transfer there is an additional sharp band only for the 5- ion at 1582 cm-1 which is attributed to a pyrazine ring vibration. The intensity of this band suggests an unsymmetrical situation and thus valence localization on the vibrational time scale. The EPR signals at g⊥ = 2.0563 and gpar; = 1.761 point toward excited states lying close to the doublet ground state and to significant metal/cyanide interaction. Compared to the Creutz-Taube ion {(μ-C4H4N2)[Ru-(NH3) 5]2}5+ and its osmium homologue, the 5- ion described here exhibits a lower degree of metal-metal coupling. |
| format |
JOUR |
| author |
Hornung, F.M. Baumann, F. Kaim, W. Olabe, J.A. Slep, L.D. Fiedler, J. |
| spellingShingle |
Hornung, F.M. Baumann, F. Kaim, W. Olabe, J.A. Slep, L.D. Fiedler, J. Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System |
| author_facet |
Hornung, F.M. Baumann, F. Kaim, W. Olabe, J.A. Slep, L.D. Fiedler, J. |
| author_sort |
Hornung, F.M. |
| title |
Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System |
| title_short |
Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System |
| title_full |
Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System |
| title_fullStr |
Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System |
| title_full_unstemmed |
Spectroelectrochemical Characterization of the Two-Step Redox System {(μ-pz)[Os(CN)5]2}n- (n = 4, 5, 6; pz = Pyrazine). Similarities and Differences in Relation to the Creutz-Taube System |
| title_sort |
spectroelectrochemical characterization of the two-step redox system {(μ-pz)[os(cn)5]2}n- (n = 4, 5, 6; pz = pyrazine). similarities and differences in relation to the creutz-taube system |
| url |
http://hdl.handle.net/20.500.12110/paper_00201669_v37_n2_p311_Hornung |
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