Ion pairing in aqueous solutions: An investigation using molecular simulations

PHYS 323

Christopher J. Fennell, cfennell@maxwell.compbio.ucsf.edu, Department of Pharmaceutical Chemistry, University of California, San Francisco, MC 2240, San Francisco, CA 94158-2517, Alan Bizjak, University of Ljubljana, Slovenia, V Vlachy, University of Llubljana, Slovenia, and Ken A. Dill, dill@maxwell.compbio.ucsf.edu, Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, CA 94143.
We present a comprehensive look at ion pairing in water using classical molecular dynamics simulations. In this study, we consider the full set of alkali-halide ion pairs with several ion parameter sets and water models. We utilize the potential of mean force (PMF) to explore the features and trends in ion pairing and to calculate association constants between the different possible ion pairs. We find that ion association is quite dependent on the chosen parameters, often showing significant differences among parameter sets developed to model the same system. We also use the PMF to show and explain properties of the solvent, such as its asymmetric electrostatic response, and map out key ion separation distances where the structuring of the first shell solvent molecules gives rise to particularly favorable and unfavorable interactions.
 

PHYS Poster Session - Water Mediated Interactions
7:30 PM-10:00 PM, Wednesday, August 20, 2008 Pennsylvania Convention Center -- Hall C, Poster

Division of Physical Chemistry

The 236th ACS National Meeting, Philadelphia, PA, August 17-21, 2008