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

Chanda, Nripen ; Sarkar, Biprajit ; Kar, Sanjib ; Fiedler, Jan ; Kaim, Wolfgang ; Lahiri, Goutam Kumar (2004) 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 Inorganic Chemistry, 43 (16). pp. 5128-5133. ISSN 0020-1669

Full text not available from this repository.

Official URL: http://pubs.acs.org/doi/abs/10.1021/ic049605c

Related URL: http://dx.doi.org/10.1021/ic049605c

Abstract

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 κ, 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.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:88398
Deposited On:28 Mar 2012 10:02
Last Modified:28 Mar 2012 10:02

Repository Staff Only: item control page