An electronic model for donor-bridge-acceptor systems is discussed for the specific cases of [(NH3)(5)Ru-pyz-Ru(NH3)(5)](m+) and [(NH3)(5)Ru-(4,4'-bpy)-Ru(NH3)(5)](m+) (m = 4, 5, 6) as well as for their longer chain analogues. The model accounts for the optical properties observed in the near-IR-vis and provides an explanation of their dependence upon the oxidation state of the metals as well as of the effect of changing the bridging ligand. The results obtained suggest that this model contains the essential ingredients for being considered a basic minimal model for the study of electron transfer in donor-bridge-acceptor systems.