Tetraarylethanediols: Surprisingly Low Energy Requirements for Electron Transfer in Solution and in the Gas Phase

Article abstract of DOI:10.1021/ja00003a039

A number of methyl-substituted tetraarylethanediols 1 have been found to undergo facile electron transfer (et) to tris(1,10-phenanthroline)iron(III) complexes (Fe^IIIL3).The products of this reaction are the corresponding benzophenones when an appropriate base is added to the reaction solution.The electron-transfer rate constants (k_et) for the reaction of 1 and Fe^IIIL3 have been measured as a function of temperature and are higher than anticipated, based on the energetic predictions derived from model arenes.The oxidation potential, derived from the measured ΔG_et^*, is in good agreement with the solution-phase ΔG_et^o, which can be calculated from the gas-phase ionization potential.Control experiments demonstrate that the reaction proceeds through a normal outer-sphere electron-transfer reaction.The surprisingly low oxidation potentials can only be explained by through-space phenyl-phenyl interactions.