Another look at the structure of the (H 2 O) n •־ system: water anion vs. hydrated electron

Quantum chemical computations using both density functional theory and coupled-cluster theory methods, in conjunction with a polarizable continuum model for treatment of structures in solution, were carried out on a series of small water anions [(H 2 O) n ]•־, n = 2, 3, 4, 5, and 16. Location of the excess electron was probed from a partition of electron densities using ELF and AIM techniques. For each size n of the [(H 2 O) n ]•־ system, two distinct structural motifs are identified: a classical water radical anion formed by hydrogen bonds and a hydrated electron in which the excess electron is directly interacting with H atoms. Both motifs have comparable energy content and likely coexist in aqueous solution.