Structure of the hydrated electron

Abstract

An intuitive 4-water structure of the hydrated electron based on recent threshold photoionization studies is analyzed in light of past kinetic, thermodymamic, and spectroscopic measurements. It is concluded that the equilibrium state of the hydrated electron may actually be the complex (OH ...H3O)(aq). The central feature is an H2O anion with a large distortion of one OH bond caused by the presence of the localized excess electron. A structure for the hydrated dielectron is also suggested. In these structures, thermodynamic stability is gained through hydration of the hydroxyl ion, while spectroscopic properties mainly arise from the oxonium radical. In order to examine these structures more extensively, quantum theoretical computations using Gaussian 82 have been carried out on (H2O)/sub N/ with N = 1 and 4. The computations do suggest a propensity to form a single stretched OH bond when a localized excess electron is present. This feature is similar to conclusions reached by Bettendorff, Buenker, and Peyerimhoff from extensive CI calculations on the isoelectronic monomeric species HF , where two structures participate in an in-out dual stability: (1) a delocalized electron with a localized hydrogen atom (normal H-F bond), or (2) a localized electron with a delocalized hydrogen atom (distendedmore » H-F bond). In solution, solvent interactions are expected to lower the energy of the localized electron structure compared with the delocalized one.« less