ESR study on solvated electrons in water and alcohols: Difference in the g factor and related analysis of the electronic state by MO calculation

An induction-detecting ESR spectrometer system, capable of μs time resolution, has been set up, and measurements were made on the radiolytically produced solvated electrons in water, methanol, ethanol, and mixtures of water and these alcohols. The spectrum of the solvated electron was a singlet in all these solvents. The g factor of the hydrated electron was measured to be 2.000 47 +- 0.000 07 at 22 0C in reasonable agreement with the reported data. While this value is significantly smaller than the free electron g factor, the corresponding g factors in methanol and in ethanol, respectively 2.002 05 +- 0.000 07 and 2.001 97 +- 0.000 07 at 22 0C, were found much closer to it. In both methanol--water and ethanol--water mixtures the g factor of the solvated electron varied approximately in proportion to the mole fraction. The g shift of the hydrated electron was interpreted as arising from spin density in the proximity of oxygen nuclei of water molecules. Ab initio MO calculations were performed for an anionic cluster of water and that of methanol, assuming a cavity-like structure. The result showed that while in a water cluster the spin population on oxygen 2p atomic orbitals was in fact significant, the corresponding orbital spin population was smaller in a methanol cluster especially with a dipole-oriented model. The difference was considered to be related to increased diffuseness of the half-occupied orbital in the latter cluster