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(NH3)(5)pyz}(2)Ru(NH3)(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(SO4)(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(NH3)(5)(pyz)](2+) and trans-[Ru(NH3)(4)(pyz)(2)](2+).