Superexchange effects on the electronic coupling element for electron transfer are investigated using water dimers and atomic donors and acceptors. We compare the electronic coupling elements obtained with H-bonded dimers to those obtained for other water dimer geometries at given donor−acceptor and oxygen−oxygen distances. The H-bonded orientation does not yield significantly different coupling elements from non-H-bonded orientations at a given oxygen−oxygen distance. In addition, the distance dependence of the coupling mediated by H-bonds is not significantly different from that for other dimer geometries. It is found that protonation of the intervening waters has a significant effect on coupling elements for donor/acceptor pairs with low ionization potentials. The implications of these results are discussed for condensed-phase ground- and excited-state electron transfers.
© 2002 American Chemical Society
Cukier, E.; Daniels, S.; Vinson, E.; Cave, R.J. “Are Hydrogen Bonds Unique Among Weak Interactions in Their Ability to Mediate Electronic Coupling?,” J. Phys. Chem. A 2002, 106, 11240. DOI: 10.1021/jp026230c