Ancillary ligand determination of the spin location in both oxidised and reduced forms of diruthenium complexes bridged by bis-bidentate 1,4-bis(2-phenolato)-1,4-diazabutadiene

Kar, Sanjib ; Sarkar, Biprajit ; Ghumaan, Sandeep ; Leboschka, Markus ; Fiedler, Jan ; Kaim, Wolfgang ; Lahiri, Goutam Kumar (2007) Ancillary ligand determination of the spin location in both oxidised and reduced forms of diruthenium complexes bridged by bis-bidentate 1,4-bis(2-phenolato)-1,4-diazabutadiene Dalton Transactions (19). pp. 1934-1938. ISSN 0300-9246

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Official URL: http://pubs.rsc.org/en/Content/ArticleLanding/2007...

Related URL: http://dx.doi.org/10.1039/B617468J

Abstract

The rare bridging mode of 1,4-bis(2-phenolato)-1,4-diazabutadiene = glyoxalbis(2-hydroxyanil) (L2-) is adopted in {(μ -L2-)[RuII(bpy)2]2}2+ (12+), obtained as bis-perchlorate. Four well accessible redox forms of 1n (n = 4+, 3+, 2+, +) have been characterised by UV-VIS-NIR spectroelectrochemistry. The (3+) and (+) intermediates have also been investigated by EPR, both showing radical-type signals close to g = 2. This observation stands in stark contrast to EPR results previously obtained for the related {(μ -L)[Ru(acac)2]2}n, n = + and -, both of which exhibit metal-centred spin. In combination with the UV-VIS-NIR spectra these results suggest the preferential involvement of the multistep ligand redox system Ln- in the electron transfer processes. The relative stabilisation of RuII by π-accepting bpy is made responsible for the oxidation of the ligand L2- instead of the metal.

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