%0 Journal Article %A Chanda, Nripen %A Sarkar, Biprajit %A Kar, Sanjib %A Fiedler, Jan %A Kaim, Wolfgang %A Lahiri, Goutam Kumar %D 2004 %T Mixed Valence Aspects of Diruthenium Complexes [{(L)ClRu}2(μ-tppz)]n+ Incorporating 2-(2-Pyridyl)azoles (L) as Ancillary Functions and 2,3,5,6-Tetrakis(2-pyridyl)pyrazine (Tppz) as Bis-Tridentate Bridging Ligand %U https://acs.figshare.com/articles/journal_contribution/Mixed_Valence_Aspects_of_Diruthenium_Complexes_L_ClRu_sub_2_sub_i_i_tppz_i_sup_n_sup_i_sup_sup_Incorporating_2_2_Pyridyl_azoles_L_as_Ancillary_Functions_and_2_3_5_6_Tetrakis_2_pyridyl_pyrazine_Tppz_as_Bis_Tridentate_Bridging_Ligand/3329422 %R 10.1021/ic049605c.s001 %2 https://acs.figshare.com/ndownloader/files/5168632 %K EPR %K Tppz %K ligand %K valent %K comproportionation constants 10 4 %K pyridyl %K Mixed Valence Aspects %K L 2 %K L 1 %K L 3 %K tppz %K oxidation %K UV %K L 3 exhibit %K Intervalence charge transfer %K sequence L 1 %K complex %K IVCT %X Tppz [2,3,5,6-tetrakis(2-pyridyl)pyrazine]-bridged complexes [{(L)ClRu}2(μ-tppz)]n+ with structurally similar but electronically different ancillary ligands, 2-(2-pyridyl)azoles (L), were synthesized as diruthenium(II) species. Cyclic voltammetry, EPR of paramagnetic states, and UV−vis−NIR spectroelectrochemistry show that the first two reduction processes occur at the tppz bridge and that oxidation involves mainly the metal centers. The mixed valent intermediates from one-electron oxidation exhibit moderate comproportionation constants 104 < Kc < 105 but appear to be valence-averaged according to the Hush criterion. Redox potentials, EPR, and UV−vis−NIR results show the effect of increasing donor strength of the ancillary ligands along the sequence L1 < L2 < L4 ≪ L3, L1 = 2-(2-pyridyl)benzoxazole, L2 = 2-(2-pyridyl)benzthiazole, L3 = 2-(2-pyridyl)benzimidazolate, L4 = 1-methyl-2-(2-pyridyl)-1H-benzimidazole. Whereas the mixed valent complexes with L1 and L2 remain EPR silent at 4 K, the analogues with L4 and L3 exhibit typical ruthenium(III) EPR signals, albeit with some noticeable ligand contribution in the case of the L3-containing complex. Intervalence charge transfer (IVCT) bands were found in the visible spectrum for the complex with L3 but in the near-infrared range (at ca. 1500 nm) for the other systems. %I ACS Publications