The complex ions [L3Ru(μ,η3:η3-BL)RuL3] n+ (1 n+, L3 = 4,4',4″-tri- tert-butyl-2,6,2',6″-terpyridine and H2BL2- = 1,2-bis(salicyloyl)hydrazide(2-)) were isolated with PF6- or ClO4- counterions ( n = 1) and as bis(hexafluorophosphate) ( n = 2). Structural, electrochemical, and spectroscopic characterization reveals the monocation as intermediate ( Kc = 108.2) in the three-step reversible redox system 10/+/2+/3+. The 1+ ion has the molecule-bridged (Ru- - -Ru 4.727 Å) ruthenium centers involved in five- and six-membered chelate rings, and it exhibits long-wavelength absorptions at λmax 2240, 1660, and 1530 nm (εmax = 1000, 3000, and 8000 M-1 cm-1, respectively), which would be compatible with a RuIIIRuII mixed-valent situation or with a coordinated radical ion bridge. In fact, EPR and DFT analysis of 1+ reveals that the spin is equally distributed over the ligand bridge and over both metals. The oxidized paramagnetic ions 12+ and 13+ have been studied by 1H NMR and EPR and by TD-DFT supported UV-vis-NIR and MIR (mid-IR) spectroelectrochemistry. The capacity of various kinds of bis( mer-tridentate) bridging ligands (π donors or π acceptors, cyclometalated or noncyclometalated) for mediating metal-metal interactions is discussed.