Ricerc@Sapienza

Regardless of its actual synthetic procedure, a protic ionic liquid (PIL) can be thought as stemming from a simple acid/base reaction: AH + B --> A- + BH+ where, in order to form a true PIL, the ensuing product has to be a fully ionized liquid.
From basic chemistry, it is well-known that the above reaction is an equilibrium process that can be more or less shifted to the right depending on the propensity of the acid/base pair to share the proton. At the moment, a straightforward relation between the position of said equilibrium in PILs and the nature of the constituent molecules and ions seems to have eluded the research community.
A crucial question therefore arises and part of its solution consists in assessing via first principle calculations the propensity for the involved ions to exchange the proton when in the bulk phase. This apparently trivial question has no simple answer: molecular indicators such as proton affinities or pKa are often not sufficient to predict the extent of the proton transfer equilibrium and complex many body effects due to the self-solvation properties of the liquid come into play.
The focus of this project is attempting to elucidate the features of proton transfer equilibria in several prototype (biocompatible) PILs, using accurate ab initio and molecular dynamics methods. Given the complexity of these materials and the fact that chemical bond breaking and formation is taking place during their equilibrium dynamics, the use ab-initio molecular dynamics would be mandatory. However, performance considerations, and our previous experience suggest that a semiempirical approach based on the DFTB (density functional tight binding) method is often sufficient to achieve a reliable description of the materials with the advantage of making this project feasible in a reasonable time span.