Is seven the minimum number of water molecules per ion pair for assured biological activity in ionic liquid–water mixtures?

Abstract

Ionic liquids (ILs) containing small amounts of water are called hydrated ILs and they show diverse physico-chemical properties that are strongly dependent on their water content. Some properties of hydrated ILs, such as biological activity and phase transition behaviour, were found to change non-linearly, with an inflection at a water molecule to ion pair ratio of around 7 : 1. This critical hydration number of ILs has been discussed in this paper with respect to the state of solvated water molecules.