Binding of Pentaammineruthenium(II) Residues to the Tris(bipyrazine)ruthenium(II) Cation.

Abstract : A series of (NH3)5Ru) (bpz))2n+ (n=1,2) and (Ru(bpz) 3 (Ru(NH3)n)2+2n (n = 1,3,6, bpz = bipyrazine) complexes has been synthesized and characterized by means of electronic spectra, 1H NMR, cyclic voltammetry and spectroelectrochemistry. The complexes are very stable and inert in aqueous solution. The peripheral pentaammineruthenium(II) groups in the tris(bipyrazine) series exhibit strong absorption bands in the visible, around 490 and 660 nm, ascribed to metal-to-ligand charge-transfer transitions. The attached ions can be reversibly oxidized, with formal potentials of approximately 0.65 V versus NHE, in comparison to 0.52 V for the ((NH3)5Ru) n (bpz)2n+ complexes. (Keywords: Pentaammineruthenium, Tris(bipyrazine) ruthenium cation, Peripheral binding, Electronic spectra, Charge transfer spectra, Electrochemistry, Ruthenium.