Intervalence transfer properties of the binuclear mu-benzotriazolate- and mu-benzimidazolate-bis{ruthenium(II)/(III)-edta} complexes

Symmetric binuclear complexes of the type [(edta)Ru-L-Ru(edta)(n-) (n = 3, 4, 5; edta = ethylenedinitrilotetraacetate; L = benzotriazolate or benzimid azolate) have been prepared in aqueous solution and characterized by means of electrochemical and spectroelectrochemical methods. Contrasting interval ence transfer properties have been observed for the mixed valence complexes : while the benzimidazole derivative behaves as a valence trapped system (c lass II), the analogous benzotriazole is better described as a class III sy stem, exhibiting significant electronic delocalization. The distinct behavi or for the last one has been attributed to a stronger interaction between t he metal centers promoted by the fluxional coordination properties of the b ridging ligand. The results have been discussed in the light of ZINDO semi- empirical molecular orbital calculations. (C) 1999 Elsevier Science S.A. Al l rights reserved.