ORBITAL SPECIFIC CHARGE-TRANSFER DISTANCES, SOLVENT REORGANIZATION ENERGIES, AND ELECTRONIC COUPLING ENERGIES - ELECTRONIC STARK-EFFECT STUDIES OF PARALLEL AND ORTHOGONAL INTERVALENCE TRANSFER IN (NC)(5)OS-II-CN-RU-III(NH3)(5)(-)

For the mixed-valent chromophore, (NC)(5)Os-II-CN-Ru-III(NH3)(5)(-), s pin-orbit coupling and ligand-field asymmetry effects lead to multiple visible region intervalence (metal-to-metal) charge transfer transiti ons (Forlando et al. Inorg. Chim. Acta 1994, 223, 37). The higher ener gy transition is associated with transfer from an Os 5d pi orbital tha t is nominally orthogonal to the charge transfer axis. The lower energ y transition, on the other hand, involves a degenerate pair of Os 5d p i donor orbitals directed along the charge transfer axis, Low-temperat ure electronic Stark effect measurements of the partially resolved tra nsitions permit donor-orbital-specific one-electron-transfer distances to be directly evaluated. The distances, R, are remarkably dependent upon donor orbital orientation (R(parallel) = 2.8 +/- 0.2 Angstrom; R( orthogonal) = 4.0 +/- 0.4 Angstrom) and significantly shorter than sim ple geometric estimates (5.0 Angstrom). From the distance information, donor-orbital-specific coupling energies and solvent reorganization e nergies can also be estimated. These also differ substantially from th ose obtained by equating the charge transfer distance with the geometr ic donor/acceptor separation distance.