Is Iodate a Strongly Hydrated Cation?

Abstract

We show, through a combination of density function theory-based molecular dynamics simulations (DFT-MD) and experimental X-ray absorption fine structure spectroscopy (XAFS) studies, that the iodate ion (IO3–) contains a local region that is strongly hydrated as a cation. The local region adjoining the I atom is sufficiently electropositive that three hydrating waters are oriented with their O atoms directly interacting with the iodine atom at an I–OH2O distance of 2.94 Å. This is the orientation of water hydrating a cation. Further, approximately 2–3 water molecules hydrate each O of IO3– through their H atoms in an orientation of the water that is expected for an anion at an I–OH2O distance of 3.83 Å. We predict that this structure persists, although to a much lesser degree, for BrO3–, and ClO3–. This type of local microstructure profoundly affects the behavior of the “anion” at interfaces and how it interacts with other ionic species in solution.