Effect of Solvent Polarity on the Potential of Mean Force between Two Molecular Ions: MD Simulation

MD simulations with the two-constraint umbrella sampling method have been applied in calculations of the potential of mean force (PMF) between N,N-dimethylaniline cation (DMA⁺) and anthracene anion (AN^-) in solvents of high and low polarity (acetonitrile and cyclohexane) at room temperature. Relation between quenching of the photoexcited AN^* via electron transfer from DMA and the exciplex formation for solvents of different polarity has been considered by comparing the two PMFs. Applicability of the primitive model of ions and the dielectric continuum model of the solvent, usually employed in calculations of the interaction energy between two solutes, is discussed.