The Electron Transfer Process in Mixed Valence Compounds with a Low-lying Energy Bridge in Different Oxidation States.

Mixed-valence compounds with the iso-cyanidometal-ligand bridge in different oxidation states are used as models for the investigation of the electron-transfer process. We synthesized a series of trimetallic isocyanidometal-bridged compounds with [Fe-CN-Ru-NC-Fe]n+ (n=2-4), in which the one-electron oxidation product (N3+ ) and two-electron oxidation product (N4+ ) compounds possess an isocyanidometal bridge whose energy is, respectively lower and slightly higher than the terminal metal centers energies. For the N3+ compounds, the bridge state (FeII -RuIII -FeII ) and mixed-valence states (FeIII -RuII -FeII or FeII -RuII -FeIII ) could be simultaneously observed on the IR timescale. For the N4+ compounds, as the donor becomes stronger the electron transfer bridge excited state (FeIII -RuII -FeIII ) becomes more and more stable, and even becomes ground state due to the strong electronic coupling between Fe and Ru.