A priori evaluation of the solvent contribution to the reorganization energy accompanying intramolecular electron transfer: Predicting the nature of the Creutz-Taube ion

作者：Reimers JR^*; Cai ZL; Hush NS

来源：Chemical Physics, 2005, 319(1-3): 39-51.

DOI：10.1016/j.chemphys.2005.06.039

• solvent reorganization energy
• multi-reference
• intervalence charge transfer
• Creutz-Taube ion
• non-Condon effects
• symmetric modes

The solvent contribution to the reorganization energy is one of the key physical properties controlling electron-transfer processes. A priori computational schemes have been developed that can predict realistic values for all other properties controlling charge transfer such as electronic couplings, vibronic couplings for intramolecular modes, the effects of asymmetry, and the effects of symmetric modes, but robust schemes for treating solvation remain elusive. In recent years, excited-state quantum chemical electronic-structure packages have gained the ability to calculate non-equilibrium solvation effects without the need to treat solvent explicitly, establishing the core of the required technology. While quantum chemical schemes involving excited-states represented as perturbed ground states can readily be applied in such calculations, they in general fail to include sufficient inactive-electron correlation to properly describe the excited-state manifold of charge transfer states, states for which only multi-reference procedures may robustly be applied. We develop computational procedures by which complete-active-space self-consistent-field (CASSCF) and related multi-reference calculations may be applied to electron-transfer systems whose energetics are controlled by the solvent-solute interaction. This is tested through the evaluation of the reorganization energy for electron-transfer in the bis-pentaammineruthenium complexes of alpha,omega-dipyridyl trans-polyenes in aqueous solution. Predictions are then made for the Creutz-Taube ion that place it clearly in the region of maximum breakdown of the Born-Oppenheimer approximation for which both the localized and delocalized diabatic descriptions of its electronic structure become inappropriate. This result is in qualitative agreement with conclusions drawn over the last four years based on a number of sources.

• 出版日期2005-12-7