THE DYNAMICS OF SOME METAL-ORGANIC AND ORGANIC-MOLECULES IN WATER SOLUTION STUDIED BY MOLECULAR MECHANICAL AND MOLECULAR DYNAMICAL METHODS

A force field is developed to reproduce geometries and vibration spectra of rutheniumhexaamine(III) and rutheniumhexaamine(II) complexes. The force constants for ruthenium were then used in molecular dynamics simulation of a Ru2+ ion, a Ru3+ ion and Ru(NH3)5-pyrazine2+ in water solution. Simulations of pyrazine and 1,3-dimethyluracile in water solution were also performed. A comparison of different ways of how to include solvation effects in quantum chemical calculations is discussed using the results from the simulations. The MD simulations show that the solvent surrounding a small charged ion, such as a Ru2+ ion, have a pronounced shell structure and the first layer of solvent molecules is stable during a 61 ps simulation. For a metal-organic molecule as Ru(NH3)5-pyrazine the solvent shows shell structure, but the water molecules are exchanged frequently. In the relatively charge-symmetric pyrazine the solvent is not polarized around the molecule. In a molecule like 1,3-dimethyluracile, which is non-symmetric in the charge distribution, the water is strongly polarized.