SPECIFIC AND NONSPECIFIC SOLVATION CONTRIBUTIONS TO INTERVALENCE ELECTRON-TRANSFER TRANSITIONS AND REDOX POTENTIALS IN RUTHENIUM AMMINE COMPLEXES

A series of binuclear complexes of general formula L(m)Ru-BL-RuL'(n+)( m) where L and L' are monodentate or bidentate ligands bound to one me tal center and BL is a bridging ligand are analyzed with the recently reported unified solvation model (USM). The solvent dependence of Delt a E(1/2) and E(IT) data are analyzed for cases where L is the same as L' and where L and L' differ. Data for the change in E(1/2) and E(IT) as the Lewis base, B, is varied in (bpy)(2)ClRupyz Ru(NH3)(4)B (where bpy is 2,2'-bipyridine and pyz is pyrazine) are also correlated. The U SM provides the relative contributions of specific and nonspecific sol vation to the solvent dependence of the physicochemical property. The factoring of the solvent dependence permits the construction of potent ial energy surfaces providing unprecedented detail concerning the infl uence of solvent donor-acceptor and solvation contributions to these m easurements. The ability of USM to correlate Franck-Condon energies an d the failure of donor numbers (DN) to do so emphasizes the need for a dual parameter treatment of the specific interaction. In contrast to nonsymmetrical binuclear complexes, the solvent dependence of the E(IT ) bands for symmetrical complexes is not correlated by solvent donor a nd polarity parameters but is fit to the dielectric constants and refr active indices of the Marcus-Hush dielectric continuum model. A ration ale for this disparate behavior of symmetrical and unsymmetrical binuc lear complexes is given.