Single-electron reductions of linked triruthenium clusters of the gene
ral type Ru-3-pyrazine-Ru-3 produced mixed valence systems showing spe
ctroscopic characteristics of rapid intramolecular electron transfer.
Reflectance infrared spectroelectrochemistry was used to characterize
the vibrational spectra of mixed valence systems that contained one ca
rbon monoxide ligand on each Ru-3 cluster. Infrared spectra in the CO
stretching region showed two resolved, partially coalesced, and coales
ced nu(CO) bands for clusters with rate constants for intramolecular e
lectron transfer k(e) increasing from = 1 x 10(9) s(-1) up to 5 x 10(1
1) and 9 x 10(11) s(-1), respectively. These data provide a strong cor
relation between rates of intramolecular electron transfer and infrare
d spectral bandshape.