Hydration structure and water exchange dynamics of Fe(II) ion in aqueous solution

Computer simulation studies of the hydration structure and water exchange dynamics in the first hydration shell for Fe(II) in water are presented. The structure of the hydrated ion is discussed in terms of radial distribution functions, coordination numbers, and angular distributions. The average first-shell hydration structure is a 6-coordinate octahedron, in agreement with experimental results. The water exchange reaction around the Fe(II) ion in water was investigated using classical umbrella-sampling molecular dynamic simulations. The water exchange mechanism, estimates for reaction rate, as well as structural changes during the activation process are discussed. The water exchange mechanism proceeds via the Id mechanism. The water exchange rate constant at 298 K is estimated by the transition state theory to be 2.1 x 107 s-1, assuming a transmission coefficient of unity. KEY WORDS: Hydration, Water exchange, Umbrella sampling, Rate constant, Iron(II) ion Bull. Chem. Soc. Ethiop. 2010, 24(2), 239-250.