Electronic Structural Studies Of The Ru-3(Iii,Ii,Ii) Mixed-Valent State Of Oxo-Centered Triruthenium Clusters

The anionic state of basic ruthenium acetate complexes of the type [Ru3O(OAc)(6)](CO)(L-1)(L-2) (L = 4-cyanopyridine, pyridine, and N,N-dimethylamino-pyridine) feature pronounced optical transitions in the near-infrared region indicative of strongly coupled mixed-valence states. A series of these clusters was prepared and studied spectroscopically in tandem with density functional theory (DFT) computational results to construct an orbital structure-function description of how the electron density is shared between the ruthenium centers in this mixed-valent state. The mixed-valency manifests itself as a combination of the nonbonding atomic orbitals of the equivalent ruthenium centers, with increased energetic splitting between the orbitals with symmetries appropriate for more efficient electronic communication. This DFT-based model agrees with the Marcus-Hush description of mixed-valency, with the added knowledge that specific orbitals contribute to different degrees in the electronic coupling between two redox centers.