Synthesis, Characterization, and Electrochemical Properties of Diruthenium Complexes Bridged by Anthraquinones

We have prepared four isomeric binuclear ruthenium complexes, in which two ruthenium units have been attached to the 1,4- ( 4a ), 1,5- ( 4b ), 1,8- ( 4c ), or 2,6-positions ( 4d ) of a central anthraquinone (Aq) moiety, leading to packed ( 4c ) or extended ( 4a, b, d ) topologies. All of these bimetallic complexes were fully characterized by elemental analysis, 1 H, 13 C{ 1 H}, and 31 P NMR{ 1 H} spectrometry, and UV/vis spectrophotometry. Moreover, the structures of 4a, b were established by X-ray crystallography. The electrochemical properties of the stable binuclear ruthenium complexes 4a − d were investigated, revealing that the two metal centers in 4a − c could interact with each other through an anthraquinone bridge, suggesting that the electron-withdrawing carbonyl chain actually functions as an effective bridge.