%0 Journal Article %1 Heilmann.2006 %A Heilmann, Martina %A Frantz, Stephanie %A Kaim, Wolfgang %A Fiedler, Jan %A Duboc, Carole. %D 2006 %J Inorganica Chimica Acta %K EPR azobispyridine bridge complex complex;electron complex;hole complex;mixed cyclic electrochem heterobinuclear;osmium homobinuclear osmium prepn redox ruthenium spectroelectrochem;radical transfer valence voltammetry %N 3 %P 821--829 %R 10.1016/j.ica.2005.04.044 %T Mixed-valent and radical states of complexes (bpy)2M(m-abpy)M'(bpy)2n+, M,M' = Ru or Os, abpy = 2,2'-azobispyridine: Electron transfer vs. hole transfer mechanism in azo ligand-bridged complexes %V 359 %X The title complexes were obtained as MIIM'II species (bpy)2M(m-abpy)M'(bpy)2(PF6)4 (M,M' = Ru or Os, abpy = 2,2'-azobispyridine, bpy = 2,2'-bipyridine) using the new mononuclear precursor (bpy)2Os(abpy)(PF6)2 for the Os-contg. dinuclear complexes. One-electron redn. produces radical complexes (bpy)2M(m-abpy)M'(bpy)2.bul.3+ and (bpy)2M(abpy).bul.+ with significant contributions from the metals, as evident from the EPR effects on successive replacement of Ru by Os with its much higher spin-orbit coupling const. The diruthenium and diosmium radical complexes were also studied by EPR at high-frequency (285 GHz), the latter shows an unusually large g anisotropy g1 - g3 = 0.25 in frozen soln. Further redn. was monitored by UV/visible spectroelectrochem. Oxidn. produced OsIII EPR signals for (bpy)2Os(abpy)3+ and (bpy)2Os(m-abpy)Ru(bpy)25+, indicating a RuIIOsIII species for the latter. The diosmium(III,II) and diruthenium(III,II) mixed-valent species remained EPR silent at 4 K, however, they exhibit weak inter-valence charge transfer (IVCT) bands at $\sim$1460 nm. Whereas the cyclic voltammetric response towards redn. is only marginally different for the three dinuclear complexes, successive replacement of Ru by Os causes the first oxidn. potential to decrease. The much higher comproportionation const. Kc for the mixed valent diosmium(III,II) state (Kc \textgreater 1015) in comparison to the diruthenium(III,II) analog with Kc = 1010 confirms the electron transfer alternative for the valence exchange mechanism, in contrast to the hole transfer established for analogous dinuclear complexes with the formally related diacylhydrazido(2-) bridging ligands. on SciFinder(R)

@article{Heilmann.2006, abstract = {The title complexes were obtained as MIIM'II species [(bpy)2M(\textgreek{m}-abpy)M'(bpy)2](PF6)4 (M,M' = Ru or Os, abpy = 2,2'-azobispyridine, bpy = 2,2'-bipyridine) using the new mononuclear precursor [(bpy)2Os(abpy)](PF6)2 for the Os-contg. dinuclear complexes. One-electron redn. produces radical complexes [(bpy)2M(\textgreek{m}-abpy)M'(bpy)2].bul.3+ and [(bpy)2M(abpy)].bul.+ with significant contributions from the metals, as evident from the EPR effects on successive replacement of Ru by Os with its much higher spin-orbit coupling const. The diruthenium and diosmium radical complexes were also studied by EPR at high-frequency (285 GHz), the latter shows an unusually large g anisotropy g1 - g3 = 0.25 in frozen soln. Further redn. was monitored by UV/visible spectroelectrochem. Oxidn. produced OsIII EPR signals for [(bpy)2Os(abpy)]3+ and [(bpy)2Os(\textgreek{m}-abpy)Ru(bpy)2]5+, indicating a RuIIOsIII species for the latter. The diosmium(III,II) and diruthenium(III,II) mixed-valent species remained EPR silent at 4 K, however, they exhibit weak inter-valence charge transfer (IVCT) bands at $\sim$1460 nm. Whereas the cyclic voltammetric response towards redn. is only marginally different for the three dinuclear complexes, successive replacement of Ru by Os causes the first oxidn. potential to decrease. The much higher comproportionation const. Kc for the mixed valent diosmium(III,II) state (Kc {\textgreater} 1015) in comparison to the diruthenium(III,II) analog with Kc = 1010 confirms the electron transfer alternative for the valence exchange mechanism, in contrast to the hole transfer established for analogous dinuclear complexes with the formally related diacylhydrazido(2-) bridging ligands. [on SciFinder(R)]}, added-at = {2019-07-15T13:41:23.000+0200}, author = {Heilmann, Martina and Frantz, Stephanie and Kaim, Wolfgang and Fiedler, Jan and Duboc, Carole.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/25d27c98a16a54e45f3b3435359826a36/b_schwederski}, doi = {10.1016/j.ica.2005.04.044}, interhash = {0eb51d05c6ae17d96f92572ecf443255}, intrahash = {5d27c98a16a54e45f3b3435359826a36}, issn = {0020-1693}, journal = {Inorganica Chimica Acta}, keywords = {EPR azobispyridine bridge complex complex;electron complex;hole complex;mixed cyclic electrochem heterobinuclear;osmium homobinuclear osmium prepn redox ruthenium spectroelectrochem;radical transfer valence voltammetry}, number = 3, pages = {821--829}, timestamp = {2019-07-15T11:42:10.000+0200}, title = {Mixed-valent and radical states of complexes [(bpy)2M(\textgreek{m}-abpy)M'(bpy)2]n+, M,M' = Ru or Os, abpy = 2,2'-azobispyridine: Electron transfer vs. hole transfer mechanism in azo ligand-bridged complexes}, volume = 359, year = 2006 }