SOLVENT MEDIATED ELECTRON TRANSFER IN C-CLAMP SHAPED MOLECULES

The role of solvent in mediating the electronic coupling between an electron donor and acceptor is investigated. The temperature dependent electron transfer rate constants in two C-clamp shaped Donor-Bridge-Acceptor (DBA) molecules are used to evaluate the electronic coupling between the donor and acceptor sites. By varying the solvent, it is demonstrated that the donor-acceptor electronic couping is strongly dependent on both the electronic nature and the position of the intervening medium. An experimental strategy that utilizes the semiclassical treatment of electron transfer together with a molecular based solvation model is introduced and shown to be a reliable way of determining the magnitude of the electronic coupling. The results demonstrate a strong dependence of the electronic coupling on the relative energy between the donor excited state energy and the intervening structure's LUMO energy. An observation consistent with electron mediated 'superexchange.' In addition, the dependence of the electron transfer rate on solvent position is evaluated. These results are consistent with a temperature dependent electronic coupling mechanism