Using solvent binding and dielectric friction to interpret the hydration behavior of complex anions.

We investigate the hydration structure and water/ion dynamics about complex anions using a revised platinum group metal chloro-anion force field. Nanosecond atomistic molecular dynamics simulations were performed for the platinum group metal chloro-anion complexes. This investigation makes the first attempt at describing diffusion trends of polyatomic complex anions with counterions such as these using both hydrodynamic and dielectric friction properties of the anion solution. The transition metal anion complex diffusion rates are shown to be correlated to their first solvent shell radial distribution function peaks, their mean water residence times, and their solvation volumes as calculated by Voronoi tessellation of the simulation cell. The general trend is for slower diffusion rates to result from larger hydration shell volumes. This diffusion rate trend calculated from Stokes' law is best described using the solventberg approach with well-chosen effective solvated radii. However, to improve the diffusion constant estimates when they are compared with those calculated from computer simulations, the dielectric friction is required.