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, H-1, C-13{H-1}, and P-31 NMR{H-1} 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.