Collect. Czech. Chem. Commun. 2003, 68, 1677-1686

Electronic Absorption Spectrum and Reduction Behavior of a Multicomponent, Trinuclear Ru(II) Species Containing 2,3-Bis(2'-pyridyl)pyrazine Bridging Ligands and 2,2'-Biquinoline Peripheral Ligands

Frédérique Loiseau*, Scolastica Serroni* and Sebastiano Campagna*

Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Via Sperone 31, 98166 Messina, Italy


Electronic absorption spectrum and reduction pattern of a trinuclear Ru(II) species containing 2,3-bis(2'-pyridyl)pyrazine bridging ligands and 2,2'-biquinoline peripheral ligands have been studied and compared with other multinuclear metal complexes of the same family of systems. The structural formula of the compound investigated is [RuCl2{Ru(biq)2(μ-2,3-dpp)}2]4+ (1; biq = 2,2'-biquinoline, 2,3-dpp = 2,3-bis(2'-pyridyl)pyrazine). The electronic absorption spectrum of 1 (in acetonitrile) is dominated by intense spin-allowed ligand-centred bands in the UV region and by moderately intense spin-allowed metal-to-ligand charge-transfer bands in the visible. The studied compound undergoes several quasireversible reduction processes in the potential window investigated (up to -1.20 V vs SCE in DMF): two successive one-electron reductions at -0.52 and -0.61 V, followed by two processes involving two closely-spaced one-electron reductions each. Extensive comparison with reduction patterns of closely related species allows to assign each process to specific subunits of the multicomponent array. The effect of the peripheral biq ligands on the electronic interaction between inner subunits is evidenced.

Keywords: Ruthenium complexes; Redox behavior; Reductions; Multinuclear complexes; Polypyridine ligands; Bipyridines; UV spectroscopy; Voltammetry; Electrochemistry.

References: 27 live references.