%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