Three heterotetranuclear complexes, [{Ru II (bpy) 2 (L n )} 3 Mn II ] 8+ (bpy = 2,2′-bipyridine, n = 2, 4, 6), in which a Mn II -tris-bipyridine-like centre is covalently linked to three Ru II –tris-bipyridine-like moieties using bridging bis-bipyridine L n ligands, have been synthesised and characterised. The electrochemical, photophysical and photochemical properties of these complexes have been investigated in CH 3 CN. The cyclic voltammograms of the three complexes exhibit two successive very close one-electron metal-centred oxidation processes in the positive potential region. The first, which is irreversible, corresponds to the Mn II /Mn III redox system ( E pa ≈0.82 V vs Ag/Ag + 0.01 M in CH 3 CN–0.1 M Bu 4 NClO 4 ), whereas the second which is, reversible, is associated with the Ru II /Ru III redox couple ( E 1/2 ≈0.91 V). In the negative potential region, three successive reversible four electron systems are observed, corresponding to ligand-based reduction processes. The three stable dimeric oxidized forms of the complexes, [Mn 2 III,IV O 2 {Ru II (bpy) 2 (L n )} 4 ] 11+ , [Mn 2 IV,IV O 2 {Ru II (bpy) 2 (L n )} 4 ] 12+ and [Mn 2 IV,IV O 2 {Ru III (bpy) 2 (L n )} 4 ] 16+ are obtained in fairly good yields by sequential electrolyses after consumption of respectively 1.5, 0.5 and 3 electrons per molecule of initial tetranuclear complexes. The formation of the di-µ-oxo binuclear complexes are the result of the instability of the {[Ru II (bpy) 2 (L n )] 3 Mn III } 9+ species, which react with residual water, via a disproportionation reaction and the release of one ligand, [Ru II (bpy) 2 (L n )] 2+ . A quantitative yield can be obtained for these reactions if the electrochemical oxidations are performed in the presence of an added external base like 2,6-dimethylpyridine. Photophysical properties of these compounds have been investigated showing that the luminescence of the Ru II -tris-bipyridine-like moieties is little affected by the presence of manganese within the tetranuclear complexes. A slight quenching of the excited states of the ruthenium moieties, which occurs by an intramolecular process, has been observed. Measurements made at low concentration (