Length-Dependence of Intramolecular Electron Transfer in Sigma-Bonded Rigid Molecular Rods: An ab initio Molecular Orbital Study

摘要

The dependence of electron transfer (ET) coupling element, V(question mark)sub AB(exclamation point), on the length of rigid-rod-like systems consisting of bicyclo1.1.1pentane (BCP), cubane (CUB), and bicyclo2.2.2octane (BCO) monomers, has been investigated with the use of ab initio Hartree-Fock (HF) method employing Marcus-Hush two-state (TS) model. The value of V(question mark)sub AB(exclamation point) decreases exponentially with increase in the number of the cage units of the sigma-bonded molecules. The calculated decay constant, beta, shows good agreement with previously reported data. For molecular length >or=15 AA, the value of V(question mark)sub AB(exclamation point) becomes negligibly small, suggesting complete suppression of the through bond direct tunneling contribution to ET process.