Microscopic solvation structure of glucose in 1-ethyl-3-methylimidazolium methylphosphonate ionic liquid

The solvation structure of glucose in 1-ethyl-3-methylimidazolium methylphosphonate, [C2mIm(+)][CH3(H)PO3(-)] ionic liquid and the liquid structure of the neat [C2mIm(+)][CH3(H)PO3(-)] were investigated by high-energy X-ray diffraction (HEXRD) experiments with the aid of molecular dynamics (MD) simulations. In neat [C2mIm(+)][CH3(H)PO3(-)], a specific interaction between the cation and anion is found, that is, the oxygen atoms within CH3(H)PO3(-) are hydrogen bonded with the hydrogen of the C2 position within C2mIm(+). In glucose/[C2mIm(+)][CH3(H)PO3(-)] solutions, a significant peak is observed at 2.6 Å in experimental radial distribution functions and is enhanced with increasing glucose concentration. It is found from MD simulations that the peak originated from the nearest-neighbor intermolecular interaction between glucose and the anion in [C2mIm(+)][CH3(H)PO3(-)]. The atom-atom pair correlation function derived from MD results shows that hydroxyl groups of glucose interact with oxygen atoms within CH3(H)PO3(-) through the hydrogen bonds. The intermolecular hydrogen bonds coexist with the intramolecular hydrogen bond in a glucose molecule. We conclude that glucose is easy to form a hydrogen bond with a polar CH3(H)PO3 anion; however, rupture of intramolecular hydrogen bonds within glucose is not enough in the ionic liquid.