A step towards the a priori design of ionic liquids

Abstract

A range of methods for the computational prediction of experimentally derived α and β Kamlet–Taft parameters, indicators of hydrogen bond (H-bond) acidity and basicity for ionic liquids (ILs) have been explored. Most usefully, a good correlation has been established between several simple and easily computed quantities which allow for a “quick bench-top” evaluation. More accurate, but also more sophisticated methods employing TD-DFT calculations involving the Kamlet–Taft dyes have been examined and evaluated. Importantly, these techniques open up the opportunity for pre-screening and a priori prediction of properties for ILs not yet synthesised. A key fundamental insight into IL H-bonds has been the determination of an estimate for the energy associated with replacing both neutral molecules in a H-bond with ionic molecules, thus forming the “doubly ionic” H-bond found in ILs.