Intervalence transfer properties of the binuclear μ-benzotriazolate- and μ-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 benzimidazolate) have been prepared in aqueous solution and characterized by means of electrochemical and spectroelectrochemical methods. Contrasting intervalence transfer properties have been observed for the mixed valence complexes: while the benzimidazole derivative behaves as a valence trapped system (class II), the analogous benzotriazole is better described as a class III system, exhibiting significant electronic delocalization. The distinct behavior for the last one has been attributed to a stronger interaction between the metal centers promoted by the fluxional coordination properties of the bridging ligand. The results have been discussed in the light of ZINDO semi-empirical molecular orbital calculations. (C) 1999 Elsevier Science S.A. All rights reserved.