Is Solute Rotation in an Ionic Liquid Influenced by the Addition of Glucose?

Abstract

Fluorescence anisotropy measurements and molecular dynamics (MD) simulations have been performed to understand the specific interactions of two structurally similar nondipolar solutes, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP), with neat 1-butyl-3-methylimidazolium dicyanamide ([BMIM][N(CN)]) and also in the presence of glucose. It has been observed that the measured reorientation times of DMDPP in neat [BMIM][N(CN)] follow the predictions of the Stokes-Einstein-Debye hydrodynamic theory with slip boundary condition. Addition of glucose (0.075 and 0.15 mole fraction) has no bearing on the rotational diffusion of the solute apart from the viscosity related effects. In contrast, the reorientation times of DPP in neat [BMIM][N(CN)] obey stick boundary condition as the hydrogen bond donating solute experiences specific interactions with the dicyanamide anion. No influence of the additive can be noticed on the rotational diffusion of DPP at 0.075 mole fraction of glucose. However, at 0.15 mole fraction of glucose, the reorientation times of the solute at a given viscosity and temperature decrease by 15-40% compared to those obtained in the neat ionic liquid. MD simulations indicate that each DPP molecule hydrogen bonds with two dicyanamide anions in neat ionic liquid. The simulations also reveal that, at 0.15 mole fraction of glucose, the concentration of anions hydrogen bonded to glucose increases significantly; therefore, the percentage of solute molecules that can form hydrogen bonds with two dicyanamide anions decreases to 84, which leads to faster rotation of DPP.

Unveiling the Structural and Dynamic Characteristics of Concentrated LiNO3 Aqueous Solutions through Ultrafast Infrared Spectroscopy and Molecular Dynamics Simulations

“…For LiNO 3 solutions, the value of p using the equation presented above is determined to be 0.68 ± 0.06. The significant deviation of the p value for SCN – from the uniform value suggests greater dynamic heterogeneity with an increase in the concentration of a LiNO 3 solution. , In our previous studies, a larger p value of 0.74 ± 0.03 was observed in a LiCl solution, while a LiTFSI aqueous solution with a larger molecular volume had a p value of 0.60 ± 0.02, as shown in Figure S4 . The change in the p value indicates that the structure of anions significantly influences the local microscopic heterogeneity of WIS electrolytes.…”

Comparing Rotational and Translational Diffusion to Evaluate Heterogeneity in Binary Solvent Systems

“…The glycerol–water binary solvent system is of great interest due to its use in cryopreservation, in industrial formulations, and as an environmentally friendly “green” solvent system . In addition, glycerol–water serves as an excellent model system because of its inherently high viscosity, molecular-scale heterogeneity, , and potential relevance to many systems of interest, such as ionic liquids, , deep eutectic solvents, solvents in the glassy state, − and confined solvation environments. , Theoretical, computational, and experimental approaches have been utilized to better understand dynamics and heterogeneity in binary solvent systems. − Previous studies have examined computationally the temperature dependent rotational or translational diffusion behavior of molecular species in binary solvents, focusing on changes in interaction energies at the solute–solvent “boundary”. , Unfortunately, changes in temperature likely result in transformation(s) to the molecular-scale organization of the solvating environment. , Recent work by our group has utilized the relationship between rotational and translational diffusion as expressed through DSE and SES models to determine the interaction energy of a tethered chromophore at the solid–liquid interface . In this study, we utilize the relationship between rotational and translational diffusion to evaluate the solute–solvent system interfacial boundary behavior at constant temperature to minimize thermal perturbation of the microscale heterogeneous environment that characterizes the glycerol–water binary solvent system.…”

“…1−11 The glycerol−water binary solvent system is of great interest due to its use in cryopreservation, 12 in industrial formulations, 13 and as an environmentally friendly "green" solvent system. 14 In addition, glycerol−water serves as an excellent model system because of its inherently high viscosity, molecular-scale heterogeneity, 15,16 and potential relevance to many systems of interest, such as ionic liquids, 17,18 deep eutectic solvents, 19 solvents in the glassy state, 20−22 and confined solvation environments. 23,24 Theoretical, computational, and experimental approaches have been utilized to better understand dynamics and heterogeneity in binary solvent systems.…”