A series of water-soluble Ru-2(5+) complexes of the type Ru-2(O2CCH3)(3)(L)Cl where L = 2,3,4,5,6-F(5)ap, 2,4,6-F(3)ap, 2-Fap, ap, 2-Meap, 2,6-Me(2)ap, or 2,4,6-Me(3)ap, where ap is the anilinopyridinate anion, have been characterized as to their structural and physicochemical properties in H2O and DMSO. Five of the newly synthesized complexes were structurally characterized, and the Ru-Cl bond lengths range from 2.477 to 2.544 angstrom while the Ru-Ru bond lengths range from 2.2838 to 2.2935 angstrom. The UV-vis spectra of each compound are characterized by three absorption bands in both H2O and DMSO, the intensity and position of which vary with both the type of bridging ligand and the solvent. The seven examined Ru-2(5+) complexes exist as 1:1 electrolytes in water, and each undergoes a reversible one-electron reduction assigned to Ru-2(5 +)/Ru-2(4 +) in both investigated solvents. A second irreversible reduction attributed to Ru-2(4+)/Ru-2(3+) is also observed for each compound at more negative potentials in DMSO. A linear free energy relationship exists between the sum of the Hammett substituent constants (Sigma sigma) on the ap-type bridging ligand and the wavenumber of an absorption band for the Ru-2(5+) complexes. A linear relationship is also seen between Sigma sigma and measured E-1/2 values for the Ru-2(5+)/Ru-2(4+) process in water containing 0.1 M KCl, but little to no effect is seen between the specific bridging ligand and the structural features of the investigated compounds.