Microscopic Solvation Structure of Glucose in 1-Ethyl-3-methylimidazolium Methylphosphonate Ionic Liquid

Abstract

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.

Room Temperature Ionic Liquids Meet Biomolecules: A Microscopic View of Structure and Dynamics

“…Moreover, NMR data collected on the same samples confirm the validity of MD estimates for the diffusion coefficient, while 2D nuclear Overhauser effect spectroscopy shows that H-bonding consists only of donations from glucose to the anion, while the protons in the cation and anion do not interact significantly with the glucose hydroxyl groups, at least in this RTIL compounds. Similar results were obtained in ref , mutually reinforcing the confidence in each of these two studies.…”

“…A general conclusion that might be of interest for all RTIL/biomolecules investigations is the confirmation by refs and that conventional nonpolarizable force fields represent a reliable tool to predict structures and to some extent linear transport coefficients.…”

“…Two studies arguably represent the state of the art of investigating microscopic properties of carbohydrates in RTIL systems. , To simplify their task, both studies focused on monosaccharides and used a combination of diffraction experiments and computer modeling. Both neutron and X-ray diffraction, in principle, are powerful techniques to investigate structural properties, but in molecular fluid systems, the interpretation of the data is hampered by the variety of different correlations to be determined by a single diffraction pattern.…”

“…Solvation structure of glucose in [C 2 mim] + [CH 3 (H)­PO 3 ] − ionic liquid investigated by high-energy X-ray diffraction experiments and molecular dynamics (MD) simulations . The radial distribution function r 2 [ G ( r ) – 1], together with (inset) a schematic illustration of the chemical structure.…”

“…The first of these benchmark experiments 208 uses highenergy X-ray diffraction and molecular dynamics to investigate the solvation of the same monosaccharide (glucose) unit into [C 2 mim][CH 3 (H)PO 3 ], i.e, the RTIL that dissolves the highest proportion of cellulose (see Figure 9). Glucose concentrations up to 30 wt % have been considered, with measurements carried out at ambient conditions.…”