Solvent and barrier effects on electron transfer

Electron transfer in the liquid phase can be greatly affected by environmental considerations such as solvent polarity, distance of transfer, and composition of the intervening media. This thesis explores various aspects of these factors. First, electron capture and intramolecular transfer is studied in binary solvents containing both a major nonpolar solvent component and a minor polar solvent component. A model is proposed which accounts for the observed capture and transfer rates, which are shown to be strongly dependent on the polar solvent concentration. Next, the radical anion of benzene and a few of its analogs are shown to exist in equilibrium with the solvated electron at room temperature in tetrahydrofuran (THF). Equilibrium constants, and free energy changes are determined over the temperature range of --80C° to +40C°. In the third project, the reduction potential of the solvated electron in THF is tied to the electrochemical scale. Pulse radiolysis was utilized to reach into a region of the electrochemical scale not accessible to traditional electrochemistry. The equilibrium constants between various molecular species whose reduction potentials lie in this region were measured providing a reduction potential ladder between the solvated electron and those compounds whose electrochemical potentials are known through electrochemical means. Finally, experiments were performed in which solvated electrons were transferred to a molecular system which was not expected to form a radical anion. The molecular system is unique in that it is a host-guest system where the guest molecule is incarcerated within but not covalently linked to the host's spherical cage-like structure. The system captures solvated electrons and forms a radical anion like species. It is shown through careful experimentation that none of the components of the molecular system forms radical anions. Evidence is presented which argues that the electron resides not on any of the molecular moieties of the system, but inside the cavity between the host and guest molecule.