Observation of Mixed-Valence Isomers

Cyclic voltammetry of 5 and 6, in a 0.1 M tetrabutylammonium hexa-fluorophosphate solution in methylene chloride V5. the ferrocene/ferrocenium reference, reveals two two-electron oxidations ( 1/2 = 200 mV, 1000 mV) and two one-electron reductions ( 1/2 = —H60mV, —ISOOmV). The splitting in the reduction waves, A , is 340 mV, and corresponds to a comproportionation equilibrium constant of 5.6 x 10. The total electrochemical splitting reflects both the electronic interactions typical of a strongly electronically coupled 

State of 5, the spectral pattern (from higher to lower energy) corresponds to contributions from the minor, major, major, and minor isomers, while in the mixed-valence state of 6, the spectral pattern is reversed to major, minor, minor, major. This is the expected result of reversing the side of the asymmetric mixed-valence complex that contains the ligand. On account of the N-atom 

Analysis of the spectral lineshapes of 5 and 6 gave an uphill rate for charge transfer of 6.5 x lO s (Table 5.2), and an equilibrium constant of 2.2 for the charge distribution, which compares well with previously reported rate constants for similar mixed-valence dimers of trinuclear ruthenium clusters. 

The dilferent case studies presented here show how a variable-temperature reflectance spectroelectrochemical cell provides the versatility to carry out studies of UV-Vis electronic spectra, IR spectra, and resonance Raman spectra of inorganic and organic compounds in a multiplicity of different redox states. A key finding is that when rates of intramolecular electron transfer in mixed-valence states approach the ultrafast timescale of IR line- 

Spectroelectrochemical Investigations on Carbon-Rich Organometallic Complexes 

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