Interactions of alkali- and alkaline earth-halides with carbohydrates in the crystalline state – the overlooked salt and sugar cocrystals

Ionic cocrystals have recently gained attention as multi-component pharmaceutical materials capable of improving the physicochemical properties of the respective pharmaceutically active compound. Contrastingly, ionic cocrystals between common carbohydrates and alkali or alkaline earth halides have been investigated since the beginning of chemistry. This is well reflected in the multitude of denominations attached to this class of crystalline species over the years, e.g. adducts, binary compounds, complexes, cocrystals, ionic cocrystals or metal–organic frameworks. Throughout several centuries, these compounds have been inspected with the specific perspective of contemporary interest. In most cases, they can conveniently be prepared from the ionic salt and the respective neutral carbohydrate via solution crystallization or mechanochemical approaches and therefore offer an opportunity for fundamental studies in the fields of crystal engineering and solid state chemistry, bridging traditional organic and inorganic chemistry. Certainly ionic cocrystals remain an underexplored class of compounds and this review gives an in-depth overview of the work that has been performed until today, hoping to elicit further contributions in the discipline.