Is Iodate a Strongly Hydrated Cation?

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-O-H2O distance of 2.94 angstrom. 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-O-H2O distance of 3.83 angstrom. 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.