A series of ligand-bridged cluster dimers of the type [(py)2Ru3O(CH3C02)6(L)Ru3O(CH3CO2)6(py)2]2+ (L = pyrazine(pyr), 4, 4ʹ-bipyridine (4, 4ʹ-bpy), trans-1, 2-bis(4-pyridyl)ethylene (BPE), l, 2-bis(4-pyridyl)ethane (BPA); pyridine (py))has been prepared. As shown by cyclic voltammetry, the extensive reversible redoxchemistry of the individual clusters, e.g., [Ru3O(CH3C02)6](py)2(pyr)]3+/2+/+/0-/2-, appears in the dimers but is even more complex. In the individual clusters, electrons are gained or lost from a scries of delocalized, intracluster levels and it is concluded that in the dimers the cluster units can be treated as single “super” redox sites with regard to electronic interactions through the bridging ligands. Theextent of intercluster interaction depends both on the bridging ligand and on the electron content of the clusters. In the201C;mixed-valence” dimers [(py)2Ru3O(CH3CO2)6(pyr)Ru3O(CH3CO2)6(py)2]m+ (m = 1, 3), there appear to be discrete(Ru3O+-Ru03O or Ru2+3O—Ru+) cluster sites and difference spectra in the near-infrared region provide evidence for low-energy cluster-cluster charge transfer (CCCT) or intervalence transfer (CCIT) absorption bands. Intercluster electronic coupling appears to increase with electron content and in the 1—mixed-valence dimer may be sufficient that the dimer is delocalized. © 1979, American Chemical Society. All rights reserved.
