Modeling platinum group metal complexes in aqueous solution

We construct force fields suited for the study of three platinum group meta ls (PCM) as chloranions in aqueous solution from quantum chemical computati ons and report experimental data. Density functional theory (DFT) using the local density approximation (LDA), as well as extended basis sets that inc orporate relativistic corrections for the transition metal atoms, has been used to obtain equilibrium geometrics. harmonic vibrational frequencies, an d atomic charges for the complexes. We found that DFT calculations of [PtCl 6](2-). 3H(2)O, [PdCl4](2-). 2H(2)O, and [RhCl6](3-). 3H(2)O water clusters compared well with molecular mechanics (MM) calculations using the specifi c force field developed here. The force field performed equally well in con densed phase simulations. A 500 ps molecular dynamics (MD) simulation of [P tCl6](2-) in water was used to study the structure of the solvation Shell a round the anion. The resulting data were compared to an experimental radial distribution function derived from X-ray diffraction experiments. We found the calculated pair correlation functions (PCF) for hexachloroplatinate to be in good agreement with experiment and were able to use the simulation r esults to identify and resolve two water-anion peaks in the experimental sp ectrum.