Anomalous dynamic behavior of ions and water molecules in dilute aqueous solution of 1-butyl-3-methylimidazolium bromide studied by NMR

Proton-deuterium exchange of acetone catalyzed in imidazolium-based ionic liquid-D2O mixtures

The reaction of the proton–deuterium exchange of acetone in imidazolium-based ionic liquid (IL)–deuterium oxide mixtures was studied in detail via NMR spectroscopy. Certain ILs exhibit considerable catalytic properties and contribute to the course of reaction up to the complete deuteration. The efficiency of deuterium exchange crucially depends on the features of ILs; the type of anion and chain length of cation. The linear secondary isotope effects on the NMR chemical shifts of the ¹³C atoms in acetone were observed depending on the deuteration level of the molecule.

The reaction of the proton–deuterium exchange of acetone in imidazolium-based ionic liquid (IL)–deuterium oxide mixtures was studied in detail via NMR spectroscopy.

NMR spectroscopy in ionic liquds

Today, NMR spectroscopy is the most important analytical tool for synthetically working chemists. This review describes the development of NMR spectroscopic methods for use in ionic liquid media and the state-of-the art in terms of routine analytics as well as modern advanced techniques.

Thermal dynamics of lithium salt mixtures of ionic liquid in water by PGSE NMR spectroscopy

The dynamics of ionic liquid–H₂O–Li⁺ salt mixtures have been studied through PGSE NMR spectroscopy.

Unusual linear dependency of viscosity with temperature in ionic liquid/water mixtures

The unusual linear scaling of the self-diffusion coefficient and viscosity leads to the violation of the SE and FSE equations and shows dynamic heterogeneity.

Properties of water confined in ionic liquids

The varying states of water confined in the nano-domain structures of typical room temperature ionic liquids (ILs) were investigated by ¹H NMR and by measurements of self-diffusion coefficients while systematically varying the IL cations and anions. The NMR peaks for water in BF₄-based ILs were clearly split, indicating the presence of two discrete states of confined water (H₂O and HOD). Proton and/or deuterium exchange rate among the water molecules was very slowly in the water-pocket. Notably, no significant changes were observed in the chemical shifts of the ILs. Self-diffusion coefficient results showed that water molecules exhibit a similar degree of mobility, although their diffusion rate is one order of magnitude faster than that of the IL cations and anions. These findings provide information on a completely new type of confinement, that of liquid water in soft matter.

Structures of ionic liquid–water mixtures investigated by IR and NMR spectroscopy

Imidazolium-based ionic liquids having different anions 1-butyl-3-methylimidazolium ([BMIM]X: X = Cl⁻, Br⁻, I⁻, and BF₄⁻) and their aqueous mixtures were investigated by IR absorption and proton NMR spectroscopy.

State of hydrophobic and hydrophilic ionic liquids in aqueous solutions: are the ions fully dissociated?

Molecular dynamics simulations were performed for aqueous solutions of five ionic liquids (ILs): 1-ethyl-3-methylimidazolium ([C2mim]) bis(trifluoromethanesulfonyl) imide ([NTf2]), 1-n-butyl-3-methylimidazolium ([C4mim]) [NTf2], 1-n-hexyl-3-methylimidazolium ([C6mim]) [NTf2], [C2mim] ethylsulfate ([C2H5SO4]), and [C2mim] chloride (Cl) to determine whether the ions of these ILs are associated at relatively high dilutions and whether the association is governed by hydrophobicity/hydrophilicity of the ILs. The adaptive biasing force technique was applied to calculate the potential of mean force (PMF) for each IL ion pair. For all of the ILs, the PMF is characterized by two distinct contact minima in which the ions have different relative conformations. The hydrophobic ILs bearing the anion [NTf2](-) exist predominantly in the associative state; the strength of the association of these ILs increases with increase in the alkyl chain length. The most hydrophilic IL [C2mim] Cl was determined to be almost fully dissociated at the concentration examined in the study. [C2mim] [C2H5SO4] showed hydration behavior that was intermediate between that exhibited by the ILs in which the anion is substituted with either Cl(-) or [NTf2](-) paired with [C2mim](+). Association constants for these ILs were also computed. Radial distribution functions calculated by constraining the ions at the contact minima showed that hydration of the anion plays the dominant role in determining the microscopic behavior of these ILs in aqueous solutions.