title: Trinuclear pyrazine-bridged ruthenium complexes: syntheses, electrochemistry, NIR-Vis spectra, and their interpretation in terms of a 5-orbital-3-parameter model.
abstract: A study of absorption spectra in the near-infrared (NIR) and visible (vis) regions of trinuclear Ru complexes containing pyrazine (pyz) as bridging ligand, trans-[(Ru(NH(3))(5)pyz)(2)Ru(NH(3))(4)](m+)(m = 6-9), is reported. The spectra were recorded on aqueous solutions containing the described species formed in situ by stoichiometric additions of a standard solution of Ce(SO(4))(2). They were interpreted in terms of a simple 5-orbital-3-parameter model which includes the effects of d-pi interaction and electronic correlation. The model is shown to account for the observed NIR-vis spectra of the complex ions. The 6+ parent species was synthesized by an improved literature method and fully characterized. The novel 8+ complex was also prepared and characterized. The 9+ ion was established to be slowly reduced by water, with dioxygen formation. Electrochemical (CV and DPV) studies were performed on the trinuclear 6+ complex, as well as on its constituent fragments [Ru(NH(3))(5)(pyz)](2+) and trans-[Ru(NH(3))(4)(pyz)(2)](2+).
authors.affiliation: Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa, Via del Borghetto 80, I-56124 Pisa, Italy.
authors.forename: Milena
authors.initials: M
authors.lastname: Sommovigo
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ferretti
authors.forename: Margherita
authors.initials: M
authors.lastname: Venturi
authors.forename: Paola
authors.initials: P
authors.lastname: Ceroni
authors.forename: Cecilia
authors.initials: C
authors.lastname: Giardi
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Denti