%0 Journal Article %1 Poppe.1993 %A Poppe, Juergen %A Moscherosch, Michael %A Kaim, Wolfgang. %D 1993 %J Inorganic Chemistry %K ESR ammine complex complex;UV complex;redox complex;ruthenium electronic factor g potential pyridyl ruthenium spectrum structure tetrazine %N 12 %P 2640--2643 %R 10.1021/ic00064a012 %T An unusually weak intervalence transition in a very stable bis chelate analog of the ruthenium mixed-valent Creutz-Taube ion. UV/visible/near-IR and EPR spectroelectrochemistry of (NH3)4Ru(m-bptz)Ru(NH3)4n+ (bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; n = 3 - 5) %V 32 %X The pentacationic form 25+ of the title complex, which exhibits an electrochem. stability const. Kc of 1015 in MeCN, shows much formal similarity to the mixed-valent (RuII/RuIII) pyrazine-bridged Creutz-Taube ion 15+. However, the flanking of the central p-accepting tetrazine ring of the bridging ligand bptz by 2 coordinating pyridyl groups results in a rigid chelate arrangement with the Ru-ammine bonds situated parallel and perpendicular to the p system of bptz. This conformation is essentially different from the staggered arrangement in 15+, the difference being reflected not by the shape or max. of the band due to the intervalence transition (IT) at 1450 nm but by a decrease of its intensity by 1 order of magnitude from e 5000 (15+) to 500 M-1 cm-1 for 25+. While the IT band max. is essentially solvent insensitive, the near-IR spectrum in D2O/DCl reveals some structuring of the IT band with a spacing of $\sim$900 cm-1. In addn. to UV/visible/near-IR spectroelectrochem., the EPR data confirm the metal-based spin in the 5+ form (g1 = 2.019, g2 = 2.418, g3 = 2.913) and a predominantly ligand-centered unpaired electron in the 3+ state (g‖ = 2.022, g$\bot$ = 1.989), which is accessible here due to the good p-acceptor properties of bptz. Nevertheless, the observation of the EPR signal only \textless70 K indicates a stronger metal contribution in 23+ than in the related radical complex (bpy)2Ru(m-bptz)Ru(bpy)23+. on SciFinder(R)

@article{Poppe.1993, abstract = {The pentacationic form 25+ of the title complex, which exhibits an electrochem. stability const. Kc of 1015 in MeCN, shows much formal similarity to the mixed-valent (RuII/RuIII) pyrazine-bridged Creutz-Taube ion 15+. However, the flanking of the central \textgreek{p}-accepting tetrazine ring of the bridging ligand bptz by 2 coordinating pyridyl groups results in a rigid chelate arrangement with the Ru-ammine bonds situated parallel and perpendicular to the \textgreek{p} system of bptz. This conformation is essentially different from the staggered arrangement in 15+, the difference being reflected not by the shape or max. of the band due to the intervalence transition (IT) at 1450 nm but by a decrease of its intensity by 1 order of magnitude from \textgreek{e} 5000 (15+) to 500 M-1 cm-1 for 25+. While the IT band max. is essentially solvent insensitive, the near-IR spectrum in D2O/DCl reveals some structuring of the IT band with a spacing of $\sim$900 cm-1. In addn. to UV/visible/near-IR spectroelectrochem., the EPR data confirm the metal-based spin in the 5+ form (g1 = 2.019, g2 = 2.418, g3 = 2.913) and a predominantly ligand-centered unpaired electron in the 3+ state (g‖ = 2.022, g$\bot$ = 1.989), which is accessible here due to the good \textgreek{p}-acceptor properties of bptz. Nevertheless, the observation of the EPR signal only {\textless}70 K indicates a stronger metal contribution in 23+ than in the related radical complex [(bpy)2Ru(\textgreek{m}-bptz)Ru(bpy)2]3+. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Poppe, Juergen and Moscherosch, Michael and Kaim, Wolfgang.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2604fd63cdbd44189f502b5c1f27a2883/huebleriac}, doi = {10.1021/ic00064a012}, interhash = {aff854329962a1f9d0b06d2d2f4c301b}, intrahash = {604fd63cdbd44189f502b5c1f27a2883}, issn = {0020-1669}, journal = {Inorganic Chemistry}, keywords = {ESR ammine complex complex;UV complex;redox complex;ruthenium electronic factor g potential pyridyl ruthenium spectrum structure tetrazine}, number = 12, pages = {2640--2643}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {An unusually weak intervalence transition in a very stable bis chelate analog of the ruthenium mixed-valent Creutz-Taube ion. UV/visible/near-IR and EPR spectroelectrochemistry of [(NH3)4Ru(\textgreek{m}-bptz)Ru(NH3)4]n+ (bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; n = 3 - 5)}, volume = 32, year = 1993 }