INVESTIGATION OF THE REDOX STATES OF [RU(BPY)2CN]2CN+ - EVIDENCE FOR VALENCE DELOCALIZATION OF THE SINGLY OXIDIZED COMPLEX

A spectroelectrochemical study of both the oxidized and reduced forms of [Ru(bpy)2CN]2CN+ is reported. Th UV-vis spectra of the parent and reduced species indicate that the complex consists of two identical chromophores, which are nearly identical with the Ru(bpy)2(CN)2 chromophore, even though one ruthenium is bound to the carbon of the bridging CN while the other is nitrogen bound. Only the shift in the bridging CN stretching frequency with reduction offers any distinction between the two metal centers. The one-electron oxidation product of the bimetallic species is assigned as valence delocalized on the basis of the following observations: (1) only two CN stretches are observed in the oxidized form, (2) the shift to higher energy of the terminal CN stretches for the bimetallic species is half of that observed upon oxidation of the monometallic complex, (3) the sharpness and solvent independence of the near-IR band is not consistent with Hush predictions for the IVT band, and (4) the separation of the oxidation waves implies a comproportionation constant for the bimetallic species of 1.38 x 10(10) (assuming no difference in metal centers) comparable in magnitude to other delocalized systems.