The new compounds Rbpy)(2)Os-II(mu-L-1(2-))Os-II(bpy)(2)](ClO4)(2) ([1]-(ClO4)(2)) and [(pap)(2)Os-II(mu-L,2)Os-II(pap)(2)] (ClO4)(2) ([2](ClO4)(2)) (H(2)L1 = 1,4dihydroxy-9,10-anthraquinone, bpy = 2,2/-bipyridine, and pap = 2-phenylazopyridine) and Rbpy)(2)Os-II(mu-L-2(center dot-))Os-II(bpy)(2)] (ClO4)(3) ([3] (ClO4)(3)) and Rpap)(2)Os-II(itL22-)Os-11(pap)(2)] (ClO4)(2) ([4] (ClO4)(2)) (H2L2 = 1,4-diamino-9,10-anthraquinone) have been analytically identified as the meso and rac diastereoisomers, respectively. The paramagnetic [3] (ClO4)(3) was also characterized by crystal structure determination. In CD3CN solution, [3] (ClO4)(3) displays rather narrow but widely split (13 > 5> 8 ppm) resonances in the 11-1 NMR spectrum, yet no EPR signal was observed down to 120 K Cyclic voltammetry and differential pulse voltammetry reveal several accessible redox states on oxidation and reduction, showing that the replacement of 1,4-oxido by imido donors causes cathodic shifts and that the substitution of bpy by the stronger 2T-accept ng pap ligands leads to a strong increase of redox potentials. Accordingly, system 3" with the lowest (2+13+) potential was synthetically obtained in the mono-oxidized (3+) form. The (3+) intermediates display small comproportionation constants lc of about 103 and long-wavelength near-infrared absorptions; an EPR signal with appreciable g splitting (1.84, 1.96, and 2.03) was only observed for 43+, which exhibits the smallest spin density on the osmium centers. An oxidation state formulation [Os-III(y1.73-)Os-III]3+ with some [Osii(mu-L2-)Os3+ contribution was found to best describe the electronic structures. UV-vis NIR absorption spectra were recorded for all accessible states by OTTLE spectroelectrochemistry and assigned on the basis of TDDFT calculations. These results and additional EPR measurements suggest rather variegated oxidation state situations, e.g., the pap ligands competing with the bridge L for electrons, while the oxidation produces mixed spin systems with variable metal/ ligand contributions.